IPAC2021 - List of Keywords (electron)

Paper	Title	Other Keywords	Page
MOXB02	First Results of the IOTA Ring Research at Fermilab	experiment, optics, lattice, octupole	19
	A. Valishev, D.R. Broemmelsiek, A.V. Burov, K. Carlson, B.L. Cathey, S. Chattopadhyay, N. Eddy, D.R. Edstrom, J.D. Jarvis, V.A. Lebedev, S. Nagaitsev, H. Piekarz, A.L. Romanov, J. Ruan, J.K. Santucci, V.D. Shiltsev, G. Stancari Fermilab, Batavia, Illinois, USA A. Arodzero, A.Y. Murokh, M. Ruelas RadiaBeam, Santa Monica, California, USA D.L. Bruhwiler, J.P. Edelen, C.C. Hall RadiaSoft LLC, Boulder, Colorado, USA S. Chattopadhyay, S. Szustkowski Northern Illinois University, DeKalb, Illinois, USA A. Halavanau, Z. Huang, V. Yakimenko SLAC, Menlo Park, California, USA M. Hofer TU Vienna, Wien, Austria M. Hofer, R. Tomás García CERN, Geneva, Switzerland K. Hwang, C.E. Mitchell, R.D. Ryne LBNL, Berkeley, California, USA K.-J. Kim ANL, Lemont, Illinois, USA K.-J. Kim, Y.K. Kim, N. Kuklev, I. Lobach University of Chicago, Chicago, Illinois, USA T.V. Shaftan BNL, Upton, New York, USA
	Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. The IOTA ring at Fermilab is a unique machine exclusively dedicated to accelerator beam physics R&D. The research conducted at IOTA includes topics such as nonlinear integrable optics, suppression of coherent beam instabilities, optical stochastic cooling and quantum science experiments. In this talk we report on the first results of experiments with implementations of nonlinear integrable beam optics. The first of its kind practical realization of a two-dimensional integrable system in a strongly-focusing storage ring was demonstrated allowing among other things for stable beam circulation near or at the integer resonance. Also presented will be the highlights of the world’s first demonstration of optical stochastic beam cooling and other selected results of IOTA’s broad experimental program.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOXB02
About •	paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 19 August 2021
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MOXC02	Improved Lifetime of a High Spin Polarization Superlattice Photocathode	cathode, polarization, gun, vacuum	31
	L. Cultrera BNL, Upton, New York, USA
	Funding: Department of Energy under grant DE-SC0012704 Highly spin polarized electron beams are required for the operation of a wide range of accelerators and instruments. The production of such electrons requires the use of Negative Electron Affinity (NEA) activated GaAs-based cathodes operated in photoelectron guns. Because of their extreme sensitivity to poor vacuum conditions the degradation of the photoemission process is so strong that NEA activated GaAs-based photocathodes can only survive in the extreme vacuums typical of DC gun. State-of-the-art on photocathode technology for spin polarized beam productions are summarized. Recent results on the use of robust NEA coating based on the Cs-Te and Cs-Sb leading to improved operational lifetime of a high spin polarization photocathode are reviewed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOXC02
About •	paper received ※ 20 May 2021 paper accepted ※ 19 July 2021 issue date ※ 11 August 2021
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MOPAB003	Machine Learning Analysis of Electron Cooler Operation for RHIC	luminosity, operation, scattering, GUI	45
	X. Gu, A.V. Fedotov, D. Kayran BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. A regression machine learning algorithm was applied to analyze the operation data of RHIC with electron cooler LEReC during the 2020 physics run. After constructing a black-box surrogate model from the XGBoost algorithm and plotting their partial dependency plots for different operation parameters, we can find the effects of an individual parameter on the RHIC luminosity and optimize it accordingly offline.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB003
About •	paper received ※ 14 May 2021 paper accepted ※ 25 May 2021 issue date ※ 11 August 2021
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MOPAB004	JSPEC - A Simulation Program for IBS and Electron Cooling	simulation, experiment, emittance, scattering	49
	H. Zhang, S.V. Benson, M.W. Bruker, Y. Zhang JLab, Newport News, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. Intrabeam scattering is an important collective effect that can deteriorate the properties of a high-intensity beam, and electron cooling is a method to mitigate the IBS effect. JSPEC (JLab Simulation Package for Electron Cooling) is an open-source program developed at Jefferson Lab, which simulates the evolution of the ion beam under the IBS and/or the electron cooling effect. JSPEC has been benchmarked with BETACOOL and experimental data. In this report, we will introduce the features of JSPEC, including the friction force calculation, the IBS expansion rate and electron cooling rate calculation, and the beam-dynamic simulations for the electron cooling process; explain how to set up the simulations in JSPEC; and demonstrate the benchmarking results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB004
About •	paper received ※ 19 May 2021 paper accepted ※ 21 May 2021 issue date ※ 13 August 2021
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MOPAB010	RHIC Beam Energy Scan Operation with Electron Cooling in 2020	operation, luminosity, emittance, experiment	72
	C. Liu, P. Adams, E.N. Beebe, S. Binello, I. Blackler, M. Blaskiewicz, K.A. Brown, D. Bruno, B.D. Coe, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, C.E. Giorgio, X. Gu, T. Hayes, K. Hock, H. Huang, R.L. Hulsart, T. Kanesue, D. Kayran, N.A. Kling, B. Lepore, Y. Luo, D. Maffei, G.J. Marr, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty, J. Morris, C. Naylor, S. Nemesure, M. Okamura, I. Pinayev, S. Polizzo, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, P. Thieberger, M. Valette, A. Zaltsman, I. Zane, K. Zeno, W. Zhang BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. RHIC provided Au-Au collisions at beam energies of 5.75 and 4.59 GeV/nucleon for the physics program in 2020 as a part of the Beam Energy Scan II experiment. The operational experience at these energies will be reported with emphasis on their unique features. These unique features include the addition of a third harmonic RF system to enable a large longitudinal acceptance at 5.75 GeV/nucleon, the application of additional lower frequency cavities for alleviating space charge effects, and the world-first operation of cooling with an RF-accelerated bunched electron beam.
	Poster MOPAB010 [3.523 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB010
About •	paper received ※ 17 May 2021 paper accepted ※ 29 July 2021 issue date ※ 30 August 2021
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MOPAB013	Radiation to Electronics Impact on CERN LHC Operation: Run 2 Overview and HL-LHC Outlook	radiation, operation, luminosity, target	80
	Y.Q. Aguiar, A. Apollonio, F. Cerutti, S. Danzeca, R. García Alía, G. Lerner, D. Prelipcean, M. Sabaté-Gilarte CERN, Geneva 23, Switzerland
	Funding: Research supported by the HL-LHC project After the mitigation measures implemented during Run 1 (2010-2012) and Long Shutdown 1 (LS1, 2013-2014), the number of equipment failures due to radiation effects on electronics (R2E) leading to LHC beam dumps and/or machine downtime has been sufficiently low as to yield a minor impact on the accelerator performance. During Run 2 (2015-2018) the R2E related failures per unit of integrated luminosity remained below the target value of 0.5 events/fb-1, with the sole exception of the 2015 run during which the machine commissioning took place. However, during 2018, an increase in the failure rate was observed, linked to the increased radiation levels in the dispersion suppressors of the ATLAS and CMS experimental insertions, significantly affecting the Quench Protection System located underneath the superconducting magnets in the tunnel. This work provides an overview of the Run 2 R2E events during LHC proton-proton operation, putting them in the context of the related radiation levels and equipment sensitivity, and providing an outlook for Run 3 and HL-LHC operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB013
About •	paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 15 August 2021
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MOPAB017	Influence of Injection Kicker Post-pulses on Storage of Ion Stack in NICA Collider	kicker, injection, collider, betatron	93
	E. Syresin, A. Tuzikov, N.O. Zagibin JINR, Dubna, Moscow Region, Russia
	The peculiarity of the injection kicker power supply in NICA collider is related to same post pulse of the magnetic field which is appeared after a regular injection pulse. The magnetic field of this post pulse became to an increase of the stack ion angle spread during each injection cycle. When the stack ion angles reaches the acceptance angle the ions are lost in the collider. Influence of the injection kicker post pulse on the storage of the ion stack is considered in this paper in presence of the electron cooling and ion electron recombination losses.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB017
About •	paper received ※ 17 May 2021 paper accepted ※ 20 May 2021 issue date ※ 12 August 2021
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MOPAB019	Possible Application of Round-to-Flat Hadron Beam Creation Using 3rd Order Coupling Resonances for the Electron-Ion Collider	resonance, emittance, sextupole, coupling	99
	J. Kallestrup PSI, Villigen PSI, Switzerland X. Gu BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. An Electron-Ion Collider (EIC) is planned to be built in Brookhaven National Laboratory with the contribution from Jefferson National Laboratory. To have a high luminosity, both the EIC ion bunch and the EIC electron bunch are designed to be flat during their collision. The existing injector source provides a round beam of width 2.5 um rad transverse emittances. In this paper we investigate the option of dynamically crossing the 2Qx-Qy coupling resonance in order to create a flat-beam with emittance ratio Ex/Ey of up to 4. Furthermore, we explore the possibility of using a pulsed- or AC skew sextupole magnets to achieve a similar effect. Using one of these methods for flat beam creation will help lower the ion beam cooling time.
	Poster MOPAB019 [0.323 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB019
About •	paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 26 August 2021
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MOPAB025	First Experiments with Accelerated Ion Beams in the Booster of NICA Accelerator Complex	booster, injection, power-supply, heavy-ion	123
	A.V. Butenko, V. Andreev, A.M. Bazanov, O.I. Brovko, D.E. Donets, A.V. Eliseev, I.V. Gorelyshev, A.V. Konstantinov, S.A. Kostromin, O.S. Kozlov, K.A. Levterov, A. Nesterov, A.V. Philippov, D.O. Ponkin, G.S. Sedykh, I.V. Shirikov, A.O. Sidorin, E. Syresin, A. Tuzikov, V. Volkov JINR/VBLHEP, Dubna, Moscow region, Russia N.N. Agapov, A.V. Alfeev, A.A. Baldin, A.A. Fateev, A.R. Galimov, B.V. Golovenskiy, E.V. Gorbachev, A. Govorov, E.V. Ivanov, V. Karpinsky, V.D. Kekelidze, H.G. Khodzhibagiyan, A. Kirichenko, A.G. Kobets, S.A. Korovkin, V. Kosachev, A.D. Kovalenko, G. Kunchenko, I.N. Meshkov, V.A. Mikhailov, V.A. Monchinsky, D. Nikiforov, R.V. Pivin, S. Romanov, A.A. Shurygin, A.I. Sidorov, A.N. Svidetelev, G.V. Trubnikov, B. Vasilishin JINR, Dubna, Moscow Region, Russia G.A. Fatkin Cosylab Siberia, Novosibirsk, Russia
	The NICA accelerator complex in JINR consist of two linear injector chains, a 578 MeV/u superconducting (SC) Booster synchrotron, the existing SC synchrotron Nuclotron, and a new SC collider that has two storage rings. The construction of the facility is based on the Nuclotron technology of SC magnets with an iron yoke and hollow SC cable. Assembly of the Booster synchrotron was finished in autumn of 2020 and first machine Run and experiments with ion beams were successfully done in December 2020. The results of this Run are discussed in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB025
About •	paper received ※ 16 May 2021 paper accepted ※ 24 August 2021 issue date ※ 07 September 2021
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MOPAB030	Research and Development Progress of CEPC RF Shield Bellows	vacuum, positron, impedance, controls	142
	J.M. Liu, Y.H. Guan, S.M. Liu, B. Tan, P.C. Wang DNSC, Dongguan, People’s Republic of China H. Dong, Y. Ma IHEP, Beijing, People’s Republic of China H.Y. He, T. Huang IHEP CSNS, Guangdong Province, People’s Republic of China
	The circular electron positron collider (CEPC) is a candidate for the next-generation electron positron collider, which can be used to accurately measure the Higgs and electroweak bosons. The RF shield bellow is a vacuum component necessary for the construction of CEPC. Therefore, a RF shield bellow model machine with an elliptical cross-section was designed and processed for technical verification. Based on the traditional interdigital structure, a special contact force testing device was also designed to reduce measurement errors. The on-off status of the circuit was used by the device to determine whether the spring finger was pulled up, thus reducing the influences of human factors in the measurement process. It can be known from the measurement results of the model machine that the contact force of the spring finger is between 120g and 130g, which can satisfy the technical requirements.
	Poster MOPAB030 [1.467 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB030
About •	paper received ※ 19 May 2021 paper accepted ※ 20 May 2021 issue date ※ 28 August 2021
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MOPAB032	Estimates of Collective Effects for the FCC-e⁺e⁻ Pre-Booster Ring	impedance, injection, emittance, collective-effects	148
	O. Etisken, F. Antoniou, K. Oide, Y. Papaphilippou, F. Zimmermann CERN, Geneva, Switzerland A.K. Çiftçi Izmir University of Economics, Balçova/Izmir, Turkey
	The FCC-e⁺e⁻ injector complex needs to produce and to transport high-intensity e⁺ and e^- beams at a fast repetition rate for topping up the collider at its collision energy. Two different options are under consideration as pre-accelerator before the bunches are transferred to the high-energy booster: either using the existing SPS machine or designing a completely new ring. The purpose of this paper is to present the studies of collective effects with analytical estimates for both the pre-booster ring design options including space charge (SC), longitudinal micro-wave instability (LMI), transverse mode coupling instability (TMCI), ion effects, electron cloud (e-cloud), coherent synchrotron radiation (CSR), and intra-beam scattering (IBS).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB032
About •	paper received ※ 17 May 2021 paper accepted ※ 27 May 2021 issue date ※ 12 August 2021
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MOPAB034	VEPP-4M Collider Operation at High Energy	collider, experiment, luminosity, positron	155
	P.A. Piminov, G.N. Baranov, A.V. Bogomyagkov, V.M. Borin, V.L. Dorokhov, S.E. Karnaev, K.Yu. Karyukina, V.A. Kiselev, E.B. Levichev, O.I. Meshkov, S.I. Mishnev, I.A. Morozov, I.N. Okunev, E.A. Simonov, S.V. Sinyatkin, E.V. Starostina, A.N. Zhuravlev BINP SB RAS, Novosibirsk, Russia
	VEPP-4M is an electron positron collider equipped with the universal KEDR detector for HEP experiments in the beam energy range from 1 GeV to 6 GeV. A unique feature of VEPP-4M is the high precision beam energy calibration by resonant polarization technique which allows conducting of interesting experiments despite the low luminosity of the collider. Recently we have started new luminosity acquisition run above 2 GeV. The hadron cross section was measured from 2.3 GeV to 3.5 GeV has been done. The luminosity run for gamma-gamma physics has been started. The luminosity at ψ(1S)-meson has been obtained. For the beam energy calibration the laser polarimeter is used. The paper discusses recent results from VEPP-4M collider.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB034
About •	paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 23 August 2021
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MOPAB036	Different Operation Regimes at the KIT Storage Ring KARA (Karlsruhe Research Accelerator)	operation, optics, lattice, storage-ring	163
	A.I. Papash, M. Brosi, E. Huttel, A. Mochihashi, A.-S. Müller, R. Ruprecht, P. Schreiber, M. Schuh, N.J. Smale KIT, Karlsruhe, Germany
	The KIT storage ring KARA operates in a wide energy range from 0.5 to 2.5 GeV. Different operation modes have been implemented at KARA, so far, the double-bend achromat (DBA) lattice with non-dispersive straight sections, the theoretical minimum emittance (TME) lattice with distributed dispersion, different versions of low-compaction factor optics with highly stretched dispersion function. Short bunches of a few ps pulse width are available at KARA. Low-alpha optics has been simulated, tested and implemented in a wide operational range of the storage ring and is now routinely used at 1.3 GeV for studies of beam bursting effects caused by coherent synchrotron radiation in the THz frequency range. Different non-linear effects, in particular residual high-order components of the magnetic field, generated in high-field superconducting wigglers have been studied and cured. Based on good agreement between computer simulations and experiments, a new operation mode at high vertical tune was implemented. The beam performance during user operation as well as at low-alpha regimes has been improved. A specific optic with negative compaction factor was simulated, tested and is in operation.
	Poster MOPAB036 [1.477 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB036
About •	paper received ※ 13 May 2021 paper accepted ※ 08 June 2021 issue date ※ 30 August 2021
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MOPAB037	On Possibility of Alpha-buckets Detecting at the KIT Storage Ring KARA (Karlsruhe Research Accelerator)	storage-ring, operation, optics, synchrotron	167
	A.I. Papash, T. Boltz, M. Brosi, A.-S. Müller, R. Ruprecht, P. Schreiber, M. Schuh, N.J. Smale KIT, Karlsruhe, Germany
	Computer studies of longitudinal motion have been performed with the objective to estimate the possibility of detection of alpha-buckets at the KIT storage ring KARA (Karlsruhe Research Accelerator). The longitudinal equations of motion and the Hamiltonian were expanded to high order terms of the energy deviation of particles in a beam. Roots of third order equation for three leading terms of momentum compaction factor and free energy independent term were derived in a form suitable for analytical estimations. Averaged quadratic terms of closed orbit distortions caused by misalignment of magnetic elements in a ring lead to orbit lengthening independent of particle energy deviation. Particle transverse excursions were estimated and are taken into account. Simulations have been bench-marked on existing experiments at Metrology Light Source (MLS) in Berlin (Germany) and SOLEIL (France). Parameters of three simultaneous beams and alpha buckets at MLS and SOLEIL have been reproduced with high accuracy. A computer model of KARA was used to predict behavior and the dynamics of possible simultaneous beams in the ring.
	Poster MOPAB037 [1.269 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB037
About •	paper received ※ 11 May 2021 paper accepted ※ 28 May 2021 issue date ※ 28 August 2021
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MOPAB040	Gain of Hard X-Ray Fel at 3 GeV and Required Parameters	FEL, undulator, laser, focusing	178
	L.H. Yu BNL, Upton, New York, USA
	We develop a tool for the calculation to study the conditions for a hard x-ray FEL oscillator based on an electron beam in the medium energy range from 3 to 4.5 GeV. We show that the approach developed by K.J. Kim et al. for the small-signal low gain formula can be modified so that the gain can be derived without taking the "no focusing approximation" adopted in the approach so that a strong focusing can be applied. We also derive the formula to allow for the gain calculation of harmonic lasing. The gain in this formula can be cast in the form of a product of two factors with one of them only depends on the harmonic number, undulator period, and gap. Thus this factor can be used to show that it is favorable to use harmonic lasing to achieve hard x-ray FEL working in the medium energy range and in the small-signal low gain regime.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB040
About •	paper received ※ 09 May 2021 paper accepted ※ 26 May 2021 issue date ※ 22 August 2021
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MOPAB042	Beam Dynamics Investigation for a New Project of Compton Back Scattering Photon Source at NRNU MEPhI	linac, photon, scattering, laser	186
	V.S. Dyubkov, I.A. Ashanin, M. Gusarova, Yu.D. Kliuchevskaia, M.V. Lalayan, S.M. Polozov, A.I. Pronikov, V.I. Rashchikov MEPhI, Moscow, Russia
	Funding: This project is supported by Russian Foundation for Basic Research, Grant no. 19-29-12036. The activities on physical models design of a compact monochromatic radiation source in the x-ray range based on inverse Compton scattering are started at NRNU MEPhI. There are comparison of two schemes of the photon source here: one of them is considered to be based on linac with variable energy of 20-60 MeV only and the other one is considered as accelerator complex where linac is supposed to be used as injector to medium size storage ring (energy up to 60 MeV). Preliminary results of linac structures and storage ring design as well as electron dynamics simulation are discussed
	Poster MOPAB042 [0.962 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB042
About •	paper received ※ 13 May 2021 paper accepted ※ 20 May 2021 issue date ※ 27 August 2021
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MOPAB049	Gyroresonant Acceleration of Electrons by an Axisymmetric Transverse Electric Field	resonance, acceleration, cyclotron, plasma	213
	E.A. Orozco, O. Otero Olarte UIS, Bucaramanga, Colombia
	The acceleration of electrons using gyromagnetic autoresonance consist on the sustaint of the electron cyclotron resonant condition through of a magnetic field which increase on time, this scheme was propose by K. S. Golovanivsky. In this work, we considerer the gyroresonant acceleration of electrons using an axisymmetric transverse electric field and its limitations. The 2D acceleration of electrons by a TE011 cylindrical mode is studied numerically. The trajectory, energy and phase-shift between the electron transverse velocity and the electric field are determined by the numerical solution of the relativistic Newton-Lorentz equation using a finite difference scheme. The growth rate of the magnetic field obtained is such that it maintains the phase difference within the acceleration band. The study includes the evolution of the energy for electrons initially ubicated in diferents initial points. For an electron that starts from rest and located at the radial midpoint of the transverse central plane of the cavity, it is reaches an energy close to 560 keV in 625 cycles of the microwave field using an electric field amplitude of 1 kV/cm and a frequency of 2.45 GHz.
	Poster MOPAB049 [3.541 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB049
About •	paper received ※ 17 May 2021 paper accepted ※ 14 June 2021 issue date ※ 13 August 2021
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MOPAB050	Spatial Autoresonant Acceleration of Electrons by an Axysimmetric Transverse Electric Field	resonance, acceleration, cyclotron, cavity	217
	E.A. Orozco, O. Otero Olarte UIS, Bucaramanga, Colombia
	In this research, The autoresonance acceleration of electrons by an axisymmetric transverse electric field in presence of a stationary inhomogeneous magnetic field is studied. The dynamics of electrons is determined by the numerical solution of the relativistic Newton-Lorentz equation using a finite difference scheme. The inhomogeneous external magnetic field is generated with a three-coil system and calculated using the Biot-Savart law. The electrons move along a TE011 cylinder cavity in a stationary magnetic field whose axis coincides with the cavity axis. The magnetic field profile obtained is such that it keeps the phase difference between the electric field vector of the microwave mode and the velocity vector of the particle within the acceleration band. For an electron injected longitudinally with an energy of 1 keV and that starts at the radial midpoint of the cavity, it is accelerated up to an energy of about 185 keV using an electric field amplitude of 14 kV/cm and a frequency of 2.45 GHz at a distance of 14 cm.
	Poster MOPAB050 [3.298 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB050
About •	paper received ※ 17 May 2021 paper accepted ※ 15 June 2021 issue date ※ 30 August 2021
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MOPAB054	Start-to-End Simulation of a Free-Electron Laser Driven by a Laser-Plasma Wakefield Accelerator	plasma, laser, bunching, radiation	233
	W. Liu, Y. Jiao, S. Wang IHEP, Beijing, People’s Republic of China
	The rapid development of laser-plasma wakefield accelerator (LPA) has opened up a new possible way to achieve ultra-compact free-electron laser (FEL). To this end, LPA experts have made many efforts to generate electron beams with sub-micrometer emittance and low energy spread. Recently, a new laser modulation method was proposed for generating EUV coherent pulse in an LPA-driven FEL. The simulation demonstration of this scheme is based on the Gaussian beam. However, the distribution of the LPA beam is not Gaussian. To further verify the feasibility of the method mentioned above, a start-to-end simulation is required.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB054
About •	paper received ※ 18 May 2021 paper accepted ※ 27 May 2021 issue date ※ 30 August 2021
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MOPAB055	Generation of Coherent Attosecond X-ray Pulses in the Southern Advanced Photon Source	laser, storage-ring, emittance, photon	237
	W. Liu, Y. Zhao IHEP CSNS, Guangdong Province, People’s Republic of China Y. Jiao, S. Wang IHEP, Beijing, People’s Republic of China
	Southern Advanced Photon Source (SAPS) is a fourth-generation storage ring light source that has been considered for construction in Guangdong province of China, adjacent to the China Spallation Neutron Source. As a low-emittance storage ring, the natural emittance of SAPS is below 100 pm. One of the benefits is that the brightness is about 2 orders high than 3rd generation light sources. However, like many other storage ring-based light sources, the time resolution is limited by the electron bunch length in the range of picoseconds. In this work, we propose a new scheme for the generation of coherent attoseconds X-ray pulses with a high repetition rate in SAPS. A numerical demonstration of the scheme is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB055
About •	paper received ※ 17 May 2021 paper accepted ※ 26 May 2021 issue date ※ 12 August 2021
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MOPAB058	Swap-Out Safety Tracking for the Advanced Photon Source Upgrade	photon, dipole, simulation, power-supply	249
	M. Borland, J.S. Downey, M.S. Jaski ANL, Lemont, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source upgrade will operate in swap-out mode, which is similar to top-up but involves complete replacement of individual depleted bunches in a single shot. As with top-up, safety is a concern given that this process will take place with beamline shutters open. We describe the methods used to model swap-out safety, including creation and validation of a full ring lattice based on 3D field maps. We also describe a new method of implementing complex, intersecting channels for electron beams and photon beams, as well as a method of easily identifying potentially dangerous stray particles. Numerous potential errors (e.g., magnet shorts) were modeled, giving a reliable indication of performance of proposed stored beam and magnet interlocks.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB058
About •	paper received ※ 14 May 2021 paper accepted ※ 28 May 2021 issue date ※ 23 August 2021
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MOPAB093	Operational Status of Photon Factory Light Sources	injection, operation, radiation, vacuum	350
	T. Honda, Y. Kobayashi, C. Mitsuda, S. Nagahashi, R. Takai, H. Takaki KEK, Ibaraki, Japan
	One of the recent topics of Photon Factory light sources, PF-ring and PF-AR, is a construction of a GeV-class beamline for testing detectors at the PF-AR. The bremsstrahlung photons generated by a thin carbon wire are brought to a copper target to generate e⁺e⁻ pairs. Sufficient count rates can be expected when the thin wire touching halo of the stored beam, and the test beamline can be used without disturbing the synchrotron radiation experiments. In addition to the usual 6.5-GeV operation, a low-energy operation at 5-GeV was started recently at PF-AR to secure operation time by saving electricity costs. At the PF-ring, the injection section has been upgraded with the septum-magnet replacement. By the top-up injection and improved bunch feedback, the hybrid-fill mode operation has become convenient for both single-bunch users and multi-bunch users, and about 30% or 40% of the user time is scheduled as the hybrid-fill mode now.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB093
About •	paper received ※ 21 May 2021 paper accepted ※ 25 May 2021 issue date ※ 01 September 2021
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MOPAB095	Concept Design for the CLS2 Accelerator Complex	emittance, storage-ring, synchrotron, lattice	354
	M.J. Boland, P.J. Hunchak University of Saskatchewan, Saskatoon, Canada C.K. Baribeau, D. Bertwistle, J.M. Patel, H. Shaker, X. Shen, M.J. Sigrist CLS, Saskatoon, Saskatchewan, Canada F. Le Pimpec EuXFEL, Schenefeld, Germany E.J. Wallén LBNL, Berkeley, California, USA
	The Canadian Light Source has been in operation since 2005 and is now looking at a design concept to upgrade to a fourth generation storage ring. A brief overview is given of a possible accelerator complex layout, including some details on the lattice design and injection system. A full energy linac is being explored as an option for top-up injection and to future proof the facility for a potential FEL upgrade in the future.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB095
About •	paper received ※ 23 May 2021 paper accepted ※ 28 July 2021 issue date ※ 29 August 2021
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MOPAB097	Two Color Grating design for Soft X-Ray Self-Seeding at LCLS-II	FEL, simulation, laser, photon	361
	A. Halavanau, D. Cocco, E. Hemsing, G. Marcus, D.S. Morton SLAC, Menlo Park, California, USA G.R. Wilcox Cornell University, Ithaca, New York, USA
	A new grating design is examined for the soft x-ray self-seeding system (SXRSS) at LCLS-II to ultimately produce stable two-color XFEL pulses. The grating performance is analyzed with Fourier optics methods. The final XFEL performance is assessed via full numerical XFEL simulations that substantiate the feasibility of the proposed design.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB097
About •	paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 01 September 2021
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MOPAB098	LCLS Multi-Bunch Improvement Plan	laser, FEL, linac, experiment	365
	A. Halavanau, S. Carbajo, F.-J. Decker, A.K. Krasnykh, A.A. Lutman, A. Marinelli, C.E. Mayes, D.C. Nguyen SLAC, Menlo Park, California, USA
	Current and future experiments at LCLS require XFEL pulse trains of variable time separation. The cavity based XFEL (CBXFEL) project requires multiple pulses separated by 220 ns, the X-ray Laser Oscillator (XLO) uses 15 ns spaced pulse trains and Matter under Extreme Conditions (MEC) experiments need a shortly spaced (less than 5 ns) pulse trains. In this proceeding, we discuss the LCLS multi-bunch improvement plan and report on its recently status and progress.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB098
About •	paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 13 August 2021
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MOPAB099	Intensity Fluctuations Reduction in the Double-Bunch FEL at LCLS	FEL, laser, free-electron-laser, undulator	369
	G. Zhou, A. Halavanau, C. Pellegrini SLAC, Menlo Park, California, USA
	In this paper we explore the possibility of reducing the intensity fluctuations of a hard X-ray double-bunch free-electron laser (DBFEL) by using an ultra-short, high peak current electron bunch to generate the seed signal, as studied recently for soft X-ray single bunch self-seeding. The ultra-short, nearly single-spike, SASE pulse is amplified to saturation, where a four-crystal monochromator selects a narrow bandwidth seed for the second bunch. Start-to-end simulation results for 7 keV photon energy are presented here for a DBFEL already studied for LCLS using the HXR undulator. We show that using this enhanced DBFEL (EDBFEL) system; the seed signal intensity fluctuations can be reduced from 85% to about 30%, and the second bunch intensity fluctuation at saturation to about 15%.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB099
About •	paper received ※ 24 May 2021 paper accepted ※ 16 July 2021 issue date ※ 02 September 2021
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MOPAB100	Progress Report on Population Inversion-Based X-Ray Laser Oscillator	FEL, laser, experiment, radiation	373
	A. Halavanau, R. Alonso-Mori, A. Aquila, U. Bergmann, D. DePonte, F.-J. Decker, F. Fuller, M. Liang, A.A. Lutman, C. Pellegrini SLAC, Menlo Park, California, USA M. Doyle UCB, Berkeley, USA
	The population inversion X-ray Laser Oscillator (XLO) is a fully coherent, transform limited hard X-ray source. It operates by repetitively pumping inner-shell atomic transitions with an XFEL, in a closed Bragg cavity. XLO will produce very bright monochromatic X-ray pulses for applications in quantum optics, X-ray interferometry and metrology. We report the progress to build the first XLO operating at the copper alpha line, using LCLS 9 keV SASE X-ray pulses as a pump.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB100
About •	paper received ※ 20 May 2021 paper accepted ※ 29 July 2021 issue date ※ 27 August 2021
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MOPAB101	Hollow and Flat Electron Beam Generation at FACET-II	emittance, wakefield, quadrupole, experiment	376
	A. Halavanau, S.J. Gessner, C.E. Mayes SLAC, Menlo Park, California, USA J.B. Rosenzweig UCLA, Los Angeles, California, USA
	In this proceeding, we investigate hollow and flat electron beam generation at FACET-II facility. We focus on the case of a circular beamlet arrangement, also known as ’necklace’ beams. We study, via numerical simulations, the resulting e-beam dynamics in the FACET-II photoinjector, beam propagation through the high energy section, as well as possible experimental applications of the ’necklace’ beams. Finally, we evaluate the feasibility of high charge flat beam generation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB101
About •	paper received ※ 23 May 2021 paper accepted ※ 27 July 2021 issue date ※ 24 August 2021
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MOPAB118	The Impact of Short-Range Wakes on Injection Into the ALS-U Accumulator Ring	injection, wakefield, kicker, booster	429
	G. Penn, M.P. Ehrlichman, T. Hellert, C. Steier, C. Sun, M. Venturini, D. Wang LBNL, Berkeley, California, USA
	Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DEAC02-05CH11231. As part of the ALS-U design, bunches with small charge will be added to the accumulator ring in a manner that initially leaves both the stored and injected bunches displaced from the nominal orbit. While the beam current is below instability thresholds, transient effects due to the combination of short-range wake fields and large initial displacements can have an impact on injection efficiency. In this paper, the impact of wake fields on the two bunches is detailed using the elegant simulation code, and different techniques to optimize the injection efficiency are explored.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB118
About •	paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 01 September 2021
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MOPAB137	Interaction Region Design for DWA Experiments at FACET-II	experiment, radiation, alignment, diagnostics	478
	O. Williams, G. Andonian, A. Fukasawa, W.J. Lynn, N. Majernik, P. Manwani, B. Naranjo, J.B. Rosenzweig, Y. Sakai, M. Yadav, Y. Zhuang UCLA, Los Angeles, California, USA C.I. Clarke, M.J. Hogan, B.D. O’Shea, D.W. Storey, V. Yakimenko SLAC, Menlo Park, California, USA M. Ruelas RadiaBeam, Santa Monica, California, USA M. Yadav The University of Liverpool, Liverpool, United Kingdom
	Funding: DOE HEP Grant DE-SC0009914 The extremely intense beam generated at FACET-II provides the unique opportunity to investigate the effects of beam-driven GV/m fields in dielectrics exceeding meter-long interaction lengths. The diverse range of phenomena to be explored, such as material response in the terahertz regime, suppression of high-field pulse damping effects, advanced geometry structures, and methods for beam break up (BBU) mitigation, all within a single UHV vacuum vessel, requires flexibility and precision in the experimental layout. We present here details of the experimental design for the dielectric program at FACET-II. Specifically, consideration is given to the alignment of the dielectric structures due to the extreme fields associated with the electron beam, as well as implementation of electron beam and Cherenkov radiation-based diagnostics.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB137
About •	paper received ※ 19 May 2021 paper accepted ※ 17 August 2021 issue date ※ 21 August 2021
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MOPAB139	High Resolution Imaging Design Using Permanent Magnet Quadrupoles at BNL UEM	experiment, focusing, quadrupole, target	485
	G. Andonian, T.J. Campese, I.I. Gadjev, M. Ruelas RadiaBeam, Marina del Rey, California, USA M.G. Fedurin, K. Kusche, X. Yang, Y. Zhu BNL, Upton, New York, USA C.C. Hall RadiaSoft LLC, Boulder, Colorado, USA
	Ultrafast electron microscopy techniques have demonstrated the potential to reach very high combined spatio-temporal resolution. In order to achieve high resolution, strong focusing magnets must be used as the objective and projector lenses. In this paper, we discuss the design and development of a high-resolution objective lens for use in the BNL UEM. The objective lens is a quintuplet array of permanent magnet quadrupoles, which in sum, provide symmetric focusing, high magnification, and control of higher order aberration terms. The application and design for a proof-of-concept experiment using a calibrated slit for imaging are presented. The image resolution is monitored as a function of beam parameters (energy, energy spread, charge, bunch length, spot size), and quintuplet lens parameters (drifts between lenses).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB139
About •	paper received ※ 26 May 2021 paper accepted ※ 28 May 2021 issue date ※ 02 September 2021
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MOPAB140	Gas Sheet Ionization Diagnostic for High Intensity Electron Beams	diagnostics, detector, operation, vacuum	489
	N.P. Norvell, G. Andonian, T.J. Campese, A.-L.M.S. Lamure, M. Ruelas, A.Yu. Smirnov RadiaBeam, Santa Monica, California, USA N.M. Cook RadiaSoft LLC, Boulder, Colorado, USA J.K. Penney UCLA, Los Angeles, California, USA C.P. Welsch The University of Liverpool, Liverpool, United Kingdom
	Funding: Work supported by DOE grant DE-SC0019717 The characterization of high intensity charged particle beams in a minimally interceptive, and non-destructive manner is performed using an ionization diagnostic. In this application, a neutral gas is tailored into a thin sheet, or curtain-like, distribution at the interaction point with an electron beam. The electron beam ionizes the neutral gas in localized space, leaving a footprint of the beam transverse distribution. The ion cloud is subseqeuntly imaged with a series of electrostatic lenses to a detector plane. The resultant image is used in a reconstruction algorithm to reconstruct the beam profile at the interaction point. In this paper, we present progress on the development of this diagnostic for the characterization of high charge, 10GeV electron beams with small transverse distributions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB140
About •	paper received ※ 20 May 2021 paper accepted ※ 10 June 2021 issue date ※ 18 August 2021
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MOPAB141	Terahertz Driven Compression and Time-Stamping Technique for Single-Shot Ultrafast Electron Diffraction	laser, FEM, radiation, resonance	492
	M.A.K. Othman, A.E. Gabriel, M.C. Hoffmann, F. Ji, E.A. Nanni, X. Shen, E.J.C. Snively, X.J. Wang SLAC, Menlo Park, California, USA
	Funding: This research has been supported by the U.S. Department of Energy (DOE) under Contract No. DE-AC02-76SF00515 and DE-AC02-05-CH11231. Ultrafast structural dynamics are well understood through pump-probe characterization using ultrafast electron diffraction (UED). Advancements in electron diffraction and spectroscopy techniques open new frontiers for scientific discovery through interrogation of ultrafast phenomena, such as quantum phase transitions. Previously, we have demonstrated that strong-field THz radiation can be utilized to efficiently manipulate and compress ultrafast electron probes , and also offer temporal diagnostics with sub-femtosecond resolution * enabled by the inherent phase locking of THz radiation to the photoemission optical drive. In this work, we demonstrate a novel THz compression and time-stamping technique to probe solid-state materials at time scales previously inaccessible with standard UED. A high-frequency THz generation method using the organic OH-1 crystals is employed to enable a threefold reduction in the electron probes length and overall timing jitter. These time-stamped probes are used to demonstrate a substantial enhancement in the UED temporal resolution using pump-probe measurement in both photoexcited single crystal and polycrystalline samples. * E. C. Snively et al., Phys. Rev. Lett, vol. 124, no. 6, p. 054801, 2020. ** R. K. Li et al., Phys. Rev. Accel. Beams, vol. 22, no. 1, p. 012803, Jan. 2019.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB141
About •	paper received ※ 20 May 2021 paper accepted ※ 21 June 2021 issue date ※ 30 August 2021
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MOPAB143	Simulations for MeV Energy Gain in Multi-Micron Vacuum Channel Dielectric Structures Driven by a CO₂ Laser	laser, simulation, vacuum, acceleration	499
	G. Yadav, O. Apsimon, Y. Wei, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom O. Apsimon, C.P. Welsch, G.X. Xia Cockcroft Institute, Warrington, Cheshire, United Kingdom G.X. Xia The University of Manchester, Manchester, United Kingdom
	Funding: This work was supported by STFC LIV. DAT under grant agreement ST/P006752/1. This research used the resources of the Supercomputing Laboratory at KAUST in Thuwal, Saudi Arabia. Dielectric Laser Accelerators (DLAs) have been demonstrated as a novel scheme for producing high acceleration gradients (~1 GV/m) within the damage threshold of the dielectric. The compactness of the DLAs and the low emittance of the output electron beam make it an attractive candidate for future endoscopic devices to be used in tumor irradiation. However, due to the small accelerating distances(sub-mm), the total energy gain is limited to sub-MeV which remains an obstacle for its realistic applications. Also, these DLAs operate under solid-state lasers with wavelengths near IR (800 nm to 2 um), where required sub-micron vacuum channel at such wavelengths imposes major aperture restrictions for the amount of charge to be accelerated. Here, we present numerical simulation results for a dielectric structure excited by a CO₂ laser with a wavelength of 10.6 um. Upon injecting a 50 MeV electron bunch through a 5.3 um diameter of vacuum channel width, our simulation suggests an energy gain beyond 1 MeV. These results are the initial steps for the realization of an mm-scale DLA capable of producing MeV energy electron beams.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB143
About •	paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 20 August 2021
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MOPAB145	Acceleration and Focusing of Positron Bunch by Electron Bunch Wakefield in the Dielectric Waveguide Filled with Plasma	plasma, positron, focusing, wakefield	505
	G.V. Sotnikov, R.R. Kniaziev, P.I. Markov NSC/KIPT, Kharkov, Ukraine
	Funding: The National Research Foundation of Ukraine, program "Leading and Young Scientists Research Support" (project # 2020.02/0299) The results of the numerical PIC-simulation of accelerated positron bunch focusing in the plasma dielectric wakefield accelerator unit, filled with radially inhomogeneous plasma that has vacuum channel inside are presented. The Wakefield was created by drive electron bunch in quartz dielectric tube with external and internal diameters of 1.2 mm and 1.0 mm, respectively. The tube was embedded in cylindrical metal waveguide. The internal area of dielectric tube has been filled with different transverse density profiles of plasma: homogeneous density and inhomogeneous density created in capillary discharge. Drive bunch electrons energy was 5 GeV, drive bunch charge was 3 nC. The test positron bunch had the same parameters as the drive bunch except for the charge of 0.05 nC. Results of numerical PIC simulation have shown the possibility of simultaneous acceleration and focusing of test positron bunch in the wakefield excited by drive electron bunch. The dependence of transport and acceleration of positron bunch on size of vacuum channel is studied.
	Poster MOPAB145 [2.003 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB145
About •	paper received ※ 19 May 2021 paper accepted ※ 20 May 2021 issue date ※ 27 August 2021
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MOPAB147	Efficient, High Power Terahertz Radiation Outcoupling From a Beam Driven Dielectric Wakefield Accelerator	radiation, wakefield, acceleration, GUI	513
	M. Yadav, G. Andonian, C.E. Hansel, W.J. Lynn, N. Majernik, B. Naranjo, J.B. Rosenzweig, O. Williams UCLA, Los Angeles, California, USA G. Andonian RadiaBeam, Santa Monica, California, USA C.P. Welsch The University of Liverpool, Liverpool, United Kingdom C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work was supported by DE-SC0009914 (UCLA) and the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1. Wakefields in dielectric structures are a useful tool for beam diagnostics and manipulation with applications including acceleration, shaping, chirping, and THz radiation generation. It is possible to use the produced THz radiation to diagnose the fields produced during the DWA interaction but, to do so, it is necessary to effectively out-couple this radiation to free space for transport to diagnostics such as a bolometer or interferometer. To this end, simulations have been conducted using CST Studio for a 10 GeV beam with FACET-II parameters in a slab-symmetric, dielectric waveguide. Various termination geometries were studied including flat cuts, metal horns, and the "Vlasov antenna". Simulations indicate that the Vlasov antenna geometry is optimal and detailed studies were conducted on a variety of dielectrics including quartz, diamond, and silicon. Multiple modes were excited and coherent Cherenkov radiation (CCR) was computationally generated for both symmetric and asymmetric beams. Finally, we include witness beams to study transport and acceleration dynamics as well as the achievable field gradients.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB147
About •	paper received ※ 24 May 2021 paper accepted ※ 27 August 2021 issue date ※ 29 August 2021
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MOPAB149	Ion Motion in Flat Beam Plasma Accelerators	plasma, emittance, collider, linear-collider	521
	M. Yadav, C.E. Hansel, J.B. Rosenzweig UCLA, Los Angeles, California, USA O. Apsimon, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom O. Apsimon, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work was supported by UCLA and the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1. This work is done on SCARF Cluster. Intense beams, such as those in proposed plasma based linear colliders, can not only blow out electrons to form a bubble but can also attract ions towards the beam. This violates the assumption that the ions are stationary on the timescale of the beam, which is a common assumption for shorter and less intense beams. While some research has been done on understanding the physics of ion motion in blowout Plasma Wakefield Accelerators (PWFAs), this research has almost exclusively focused on cylindrically symmetric beams, rather than flat asymmetric emittance beams which are often used in linear colliders in order to minimize beamstrahlung at the final focus. This contribution investigates both analytically and computationally ion motion of a flat beam scenario in order to understand the basic physics as well as how to mitigate emittance growth, beam hosing and quadrupole.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB149
About •	paper received ※ 24 May 2021 paper accepted ※ 17 June 2021 issue date ※ 10 August 2021
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MOPAB150	Optimization of the Gain Medium Delivery System for an X-Ray Laser Oscillator	laser, target, free-electron-laser, FEL	524
	M. Yadav, N. Majernik, P. Manwani, B. Naranjo, C. Pellegrini, J.B. Rosenzweig UCLA, Los Angeles, California, USA E.C. Galtier, A. Halavanau, C. Pellegrini SLAC, Menlo Park, California, USA A. Malinouski ASC HMTI, Minsk, Belarus
	Funding: This work was supported by DE-SC0009914. X-ray laser oscillator, dubbed XLO, is a recently proposed project at SLAC to build the first population inversion X-ray laser. XLO utilizes a train of XFEL SASE pulses to pump atomic core-states. The resulting amplified spontaneous emission radiation is recirculated in a backscattering Bragg cavity and subsequently amplified. XLO could provide fully coherent, transform-limited X-ray pulses with 50 meV bandwidth and 1e10 photons. Currently, XLO is being considered for operation at the copper K-alpha line at 8048 eV. In this work, we focus on the optimization of gain medium delivery in the XLO cavity. We consider a fast, subsonic jet of copper nitrate solution, moving through a cylindrical nozzle. We focus on the nozzle geometry optimization and possible diagnostics of the jet-XFEL interaction point.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB150
About •	paper received ※ 24 May 2021 paper accepted ※ 18 June 2021 issue date ※ 23 August 2021
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MOPAB154	Multi-Cell Accelerating Structure Driven by a Lens-Focused Picosecond THz Pulse	laser, focusing, timing, acceleration	537
	S.P. Antipov, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia
	Recently, gradients on the order of 1 GV/m level have been obtained in a form of a single cycle (~1 ps) THz pulses produced by conversion of a high peak power laser radiation in nonlinear crystals (~1 mJ, 1 ps, up to 3% conversion efficiency). Such high-intensity radiation can be utilized for charged particle acceleration. However, these pulses are short in time (~1ps) and broadband, therefore a new accelerating structure type is required. In this paper, we propose a novel structure based on focusing of THz radiation in accelerating cell and stacking such cells to achieve a long-range interaction required for an efficient acceleration process. We present an example in which a 100 microJoule THz pulse produces a 600 keV energy gain in 5 mm long 10 cell accelerating structure for an ultra-relativistic electron. This design can be readily extended to non-relativistic particles. Such structure had been laser microfabricated and appropriate dimensions were achieved.
	Poster MOPAB154 [1.283 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB154
About •	paper received ※ 27 May 2021 paper accepted ※ 05 July 2021 issue date ※ 14 August 2021
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MOPAB156	Wakefields and Transverse Bunch Dynamics Studies of a Plasma-Dielectric Accelerating Structure	plasma, wakefield, GUI, focusing	542
	K. Galaydych, I.N. Onishchenko, G.V. Sotnikov NSC/KIPT, Kharkov, Ukraine
	Funding: The National Research Foundation of Ukraine, programme "Leading and Young Scientists Research Support" (grant agreement n. 2020.02/0299). A theoretical investigation of a wakefield excitation in a plasma-dielectric accelerating structure by a drive electron bunch in the case of an off-axis bunch injection is carried out. The structure under investigation is a round dielectric-loaded metal waveguide with channel for the charged particles, filled with homogeneous cold plasma. In this paper we focus on the spatial distribution of the bunch-excited wakefield components, which act on both the drive and test bunches, and on transverse bunch dynamics. Dependence of the drive bunch propagation distance on its offset is studied.
	Poster MOPAB156 [2.042 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB156
About •	paper received ※ 19 May 2021 paper accepted ※ 18 June 2021 issue date ※ 31 August 2021
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MOPAB163	First Synchronous Measurement of Single-Bunched Electron and Positron Beams with a Wideband Feedthrough-BPM at the Positron Capture Section of the SuperKEKB Injector Linac	positron, solenoid, wakefield, linac	557
	M.A. Rehman, F. Miyahara, T. Suwada KEK, Ibaraki, Japan
	The SuperKEKB is an asymmetric e⁻/e⁺ collider with 40 times higher luminosity than the KEKB project, to explore the new physics beyond the standard model. For the SuperKEKB, the positrons are created by striking the accelerated electrons at a tungsten target. The secondary electrons are also produced during the positron creation process and accelerated in the capture section. Because of phase slipping in the capture section, the secondary electron bunch is only ∼ 180 ps away from the positron. Conventional stripline-type BPM cannot detect such closely spaced and opposite polarity signals due to slow frequency response and high cable losses. Therefore, a new wideband feedthrough-type beam position monitor was developed. It was successfully employed at the positron capture section of the SuperKEKB injector linac for the first synchronous measurement of the electron and positron beams. The cable losses effect also has been de-embedded to reveal correct signal properties. This paper describes the initial results of synchronous measurement of e⁻/e⁺ transverse position.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB163
About •	paper received ※ 20 May 2021 paper accepted ※ 27 May 2021 issue date ※ 19 August 2021
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MOPAB164	Miniature, High Strength Transport Line Design for Laser Plasma Accelerator-Driven FELs	laser, quadrupole, plasma, undulator	561
	S. Fatehi, A. Bernhard, A.-S. Müller, M.S. Ning KIT, Karlsruhe, Germany
	Funding: This work is supported by the BMBF project 05K19VKA PlasmaFEL (Federal Ministry of Education and Research). Laser-plasma acceleration is an outstanding candidate to drive the next-generation compact light sources and FELs. To compensate large chromatic effects using novel compact beam optic elements in the beam transport line is required. We aim at designing miniature, high strength, normal conducting and superconducting transport line magnets and optics for capturing and matching LPA-generated electron bunches to given applications. Our primary application case is a demonstration experiment for transverse gradient undulator (TGU) FELs, to be performed at the JETI laser facility, Jena, Germany. In this contribution, we present the current design of the beam transport line magnets and the beam optics calculations. Laser Plasma Accelerators, FELs, Magnets, Beam Dynamics, Superconductivity, transverse gradient undulator
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB164
About •	paper received ※ 19 May 2021 paper accepted ※ 25 May 2021 issue date ※ 24 August 2021
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MOPAB165	Identical Focusing of Train of Relativistic Positron Gaussian Bunches in Plasma	plasma, focusing, positron, wakefield	565
	D.S. Bondar KhNU, Kharkov, Ukraine V.I. Maslov, I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine
	Funding: The study is supported by the National Research Fundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299). Focusing of both electron and positron bunches in an electron-positron collider is necessary. The focusing mechanism in the plasma, in which all electron bunches are focused identically, has been proposed earlier. This mechanism is considered for positron bunches by using simulation with LCODE. Three types of lenses with different trains of cosine profile positron bunches are considered depending on the bunch length, the distance between bunches, and their charge. It has been shown that all positron bunches are focused identically at special parameters of the first positron bunch, wherein the middle of bunches are focused weaker than their fronts. V. I. Maslov et al. PAST. 3(2012) 159. ** K. V. Lotov, Phys. Plas. 5 (1998) 785.
	Poster MOPAB165 [2.272 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB165
About •	paper received ※ 17 May 2021 paper accepted ※ 20 May 2021 issue date ※ 14 August 2021
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MOPAB167	Wakefield Excitation in Plasma of Metallic Density by a Laser Pulse	laser, plasma, wakefield, acceleration	571
	D.S. Bondar KhNU, Kharkov, Ukraine V.I. Maslov, I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine
	Funding: The study is supported by the National Research Foundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299). Recently the proposal to use X-ray Exawatt pulse for particle acceleration in a crystal has been declared . Short X-ray high-power pulse excites wakefield in electron plasma of metallic density which can be used for high gradient acceleration of charged particles. This wakefield is suited for laser wakefield acceleration. In this paper there are simulated with PIC code UMKA: excitation of the large wakefield amplitude up to several TV/m in electron plasma of metallic density by a powerful X-ray laser pulse; laser-plasma wakefield acceleration of self-injected electron bunch in such setup; combined acceleration by plasma wakefield driven by a laser pulse (LPWA) and by self-injected electron bunch (PWFA). T.Tajima. Eur. Phys. J. Special Topics 223 (2014) 1037.
	Poster MOPAB167 [2.054 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB167
About •	paper received ※ 17 May 2021 paper accepted ※ 21 May 2021 issue date ※ 02 September 2021
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MOPAB168	Nanoplasmonic Accelerators Towards Tens of TeraVolts per Meter Gradients Using Nanomaterials	plasma, wakefield, experiment, focusing	574
	A.A. Sahai, M. Golkowski, V. Harid CU Denver, Denver, Colorado, USA C. Joshi UCLA, Los Angeles, California, USA T.C. Katsouleas Duke ECE, Durham, North Carolina, USA A. Latina, F. Zimmermann CERN, Geneva, Switzerland J. Resta-López Cockcroft Institute, Warrington, Cheshire, United Kingdom P. Taborek UCI, Irvine, California, USA A.G.R. Thomas University of Michigan, Ann Arbor, Michigan, USA
	Funding: University of Colorado Denver Ultra-high gradients which are critical for future advances in high-energy physics, have so far relied on plasma and dielectric accelerating structures. While bulk crystals were predicted to offer unparalleled TV/m gradients that are at least two orders of magnitude higher than gaseous plasmas, crystal-based acceleration has not been realized in practice. We have developed the concept of nanoplasmonic crunch-in surface modes which utilizes the tunability of collective oscillations in nanomaterials to open up unprecedented tens of TV/m gradients. Particle beams interacting with nanomaterials that have vacuum-like core regions, experience minimal disruptive effects such as filamentation and collisions, while the beam-driven crunch-in modes sustain tens of TV/m gradients. Moreover, as the effective apertures for transverse and longitudinal crunch-in wakes are different, the limitation of traditional scaling of structure wakefields to smaller dimensions is significantly relaxed. The SLAC FACET-II experiment of the nano2WA collaboration will utilize ultra-short, high-current electron beams to excite nonlinear plasmonic modes and demonstrate this possibility. * doi:10.1109/ACCESS.2021.3070798 doi:10.1142/S0217751X19430097 * indico.fnal.gov/event/19478/contributions/52561 **** indico.cern.ch/event/867535/contributions/3716404
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB168
About •	paper received ※ 11 May 2021 paper accepted ※ 08 June 2021 issue date ※ 17 August 2021
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MOPAB169	Generating 510 MW of X-Band Power for Structure-Based Wakefield Acceleration Using a Metamaterial-Based Power Extractor	experiment, wakefield, acceleration, simulation	578
	J.F. Picard, I. Mastovsky, M.A. Shapiro, R.J. Temkin MIT/PSFC, Cambridge, Massachusetts, USA M.E. Conde, D.S. Doran, J.G. Power, J.H. Shao, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing Euclid TechLabs, Solon, Ohio, USA X. Lu Northern Illinois University, DeKalb, Illinois, USA
	Funding: Research sponsored under Award No. DE-SC0015566 by U.S. Department of Energy, Office of Science, Office of High Energy Physics and Contract No. DE-AC02-06CH11357 by the Office of Science. We present our recent results generating 510 MW of power at 11.7 GHz using a metamaterial-based metallic power-extractor for application in structure-based wakefield acceleration (SWFA). SWFA is a novel acceleration scheme in which high-charge electron bunches are passed through a power extractor structure to produce a high-intensity wakefield. This wakefield can then be used to accelerate a witness bunch in the same beamline or passed to a separate acceleration beamline. MIT’s approach uses a specialized metamaterial for the power extractor design. By using a metamaterial, we can overcome some of the challenges faced by other SWFA techniques. Here, we discuss the Stage 3 experiment. The Stage 1 and Stage 2 experiments successfully demonstrated the functionality of the metamaterial approach by generating high power RF pulses using the 65 MeV electron beam at the Argonne Wakefield Accelerator (AWA) facility. The 510 MW result from Stage 3 experiment is the highest power generated to-date for SWFA at AWA, and was enable by significant design improvements, including an all-copper structure, fully-symmetric coupler design, and breakdown risk-reduction treatment.
	Poster MOPAB169 [8.882 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB169
About •	paper received ※ 08 May 2021 paper accepted ※ 16 July 2021 issue date ※ 12 August 2021
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MOPAB171	Numerical Simulation on Plasma-Based Beam Dumps Using Smilei	plasma, laser, wakefield, acceleration	582
	S. Kumar, C. Davut, G.X. Xia UMAN, Manchester, United Kingdom A. Bonatto, C. Davut, L. Liang The University of Manchester, Manchester, United Kingdom A. Bonatto Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil B.S. Nunes IF-UFRGS, Porto Alegre, Brazil R.P. Nunes UFRGS, Porto Alegre, Brazil
	The active plasma beam dump utilizes a laser to generate a plasma wakefield and decelerate an externally injected beam to low energy. We use the particle-in-cell code "Smi-lei" for the investigation of electron beam energy loss in plasma. In this research work, we optimize the laser and plasma parameters to investigate the active plasma beam dump scheme. In doing so, most of the beam energy will be deposited in the plasma. The optimization strategy for the beam energy loss in plasma is presented. A. Bonatto, C. B. Schroeder et al., Physics of Plasmas 22 (8) 083106 (2015). G. Xia, A. Bonatto et al., Instruments 4 (2) 10 (2020). *A Bonatto et al., J. Phys.: Conf. Ser. 1596 012058, 2020.
	Poster MOPAB171 [0.756 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB171
About •	paper received ※ 15 May 2021 paper accepted ※ 24 May 2021 issue date ※ 31 August 2021
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MOPAB173	Physics Program and Experimental for AWAKE Run 2	plasma, wakefield, proton, experiment	586
	P. Muggli MPI, Muenchen, Germany
	Run 1 experimental results demonstrate many characteristics of the self-modulation (SM) in plasma of a long, 400GeV SPS proton bunch. Externally injected, 19MeV electrons were accelerated to 2GeV. Based on these results, we are assembling a physics and experiment program aiming at producing a multi-GeV electron bunch with emittance and energy spread sufficiently low for possible early applications to high-energy physics experiments. Plans include two plasmas, the first for SM, the second for acceleration, and of scalable length, separated by an injection region. The first plasma includes a density step to maintain large-amplitude wakefields after saturation of the SM process. Seeding of the SM process may be obtained from an electron bunch. The 150MeV witness electron bunch from an S-band gun, X-band linac has parameters that produce plasma electron blow out and loading of the wakefields in order to minimize final energy spread and emittance*. We are studying the possibility of using a helicon plasma source for the accelerator, a source that can in principle be very long (100s of m). AWAKE, PRL 122, 054802 (2019), Turner, PRL 122, 054801 (2019), Turner, PRAB 23, 081302, (2020), Braunmueller PRL 125, 264801 (2020) AWAKE, Nature 561, 363 (2018) *Olsen, PRAB 21, 011301 (2018)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB173
About •	paper received ※ 18 May 2021 paper accepted ※ 28 May 2021 issue date ※ 26 August 2021
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MOPAB175	Advanced Concepts and Technologies for Heavy Ion Synchrotrons	laser, synchrotron, heavy-ion, space-charge	594
	P.J. Spiller, O. Boine-Frankenheim, L.H.J. Bozyk, S. Klammes, H. Kollmus, D. Ondreka, I. Pongrac, N. Pyka, C. Roux, K. Sugita, St. Wilfert, T. Winkler, D.F.A. Winters GSI, Darmstadt, Germany
	New concepts and technologies are developed to advance the performance of heavy ion synchrotrons. Besides fast ramping of superconducting magnets, extreme UHV technologies to stabilize dynamic vacuum and charge related loss, broad band MA cavities, space charge compensation by means of electron lenses and new cooling technologies, e.g. laser cooling, show great promise to advance the forefront of beam parameters. Several of these technologies and concepts are developed and tested at GSI/FAIR. Progress and plans will be reported.
	Poster MOPAB175 [1.367 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB175
About •	paper received ※ 11 May 2021 paper accepted ※ 21 May 2021 issue date ※ 01 September 2021
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MOPAB177	ELENA Commissioning and Status	proton, antiproton, experiment, MMI	598
	C. Carli, M.E. Angoletta, W. Bartmann, L. Bojtár, F. Butin, B. Dupuy, Y. Dutheil, M.A. Fraser, P. Freyermuth, D. Gamba, L.V. Jørgensen, B. Lefort, O. Marqversen, M. McLean, S. Ogur, S. Pasinelli, L. Ponce, G. Tranquille CERN, Geneva, Switzerland
	The Extra Low ENergy Antiproton ring ELENA is a small synchrotron recently constructed and commissioned to decelerate antiprotons injected from the Antiproton Decelerator AD with a kinetic energy of 5.3 MeV down to 100 keV. Controlled deceleration in the synchrotron, equipped with an electron cooler to reduce losses and generate dense bunches, allows the experiments, typically capturing the antiprotons in traps and manipulating them further, to improve the trapping efficiency by one to two orders of magnitude. During 2018, bunches with an energy of 100 keV with parameters close to nominal have been demonstrated, and first beams have been provided to an experiment in a new experimental zone. The magnetic transfer lines from the AD to the experiments have been replaced by electrostatic lines from ELENA. Commissioning of the new transfer lines and, in parallel, studies to better understand the ring with H⁻ beams from a dedicated source, have started in autumn 2020. The first 100 keV antiproton physics run using ELENA will start in late summer 2021.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB177
About •	paper received ※ 18 May 2021 paper accepted ※ 14 June 2021 issue date ※ 01 September 2021
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MOPAB212	3-D Quantum Lifetime	simulation, damping, radiation, emittance	700
	H. Zhao, M. Blaskiewicz BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The quantum lifetime of electron beam in storage rings is defined by the particle loss that caused by the aperture limitation. Based on the equilibrium beam distribution produced by radiation damping and quantum excitation, the 1-d quantum lifetime has been well studied by A. Piwinski. In this paper, we give the derivation of the 3-d quantum lifetime, which can be applied to the machines with elliptical aperture and momentum acceptance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB212
About •	paper received ※ 04 June 2021 paper accepted ※ 21 June 2021 issue date ※ 14 August 2021
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MOPAB232	Observation of Polarization-Dependent Changes in Higher-Order Mode Responses as a Function of Transverse Beam Position in Tesla-Type Cavities at FAST	cavity, HOM, dipole, cryomodule	756
	R.M. Thurman-Keup, D.R. Edstrom, A.H. Lumpkin, P.S. Prieto, J. Ruan Fermilab, Batavia, Illinois, USA J.A. Diaz Cruz UNM-ECE, Albuquerque, USA J.A. Diaz Cruz, B.T. Jacobson, J.P. Sikora, F. Zhou SLAC, Menlo Park, California, USA
	Funding: FNAL supported by U.S. Department of Energy, Office of Science, under contract DE-AC02-07CH11359. SLAC supported by U.S. Department of Energy, Office of Science, under contract DE-AC02-76SF00515. Higher-order modes (HOMs) in superconducting rf cavities present problems for an electron bunch traversing the cavity in the form of long-range wakefields from previous bunches. These may dilute the emittance of the macropulse average, especially with low emittance beams at facilities such as the European X-ray Free-electron Laser (XFEL) and the upgraded Linac Coherent Light Source (LCLS-II). Here we present observations of HOMs driven by the beam at the Fermilab Accelerator Science and Technology (FAST) facility. The FAST facility features two independent TESLA-type cavities (CC1 and CC2) after a photocathode rf gun followed by an 8-cavity cryomodule. The HOM signals were acquired from cavities using bandpass filters of 1.75 ± 0.15 GHz, 2.5 ± 0.2 GHz, and 3.25 ± 0.2 GHz and recorded using an 8-GHz, 20 GSa/s oscilloscope. The frequency resolution obtained is sufficient to separate polarization components of many of the HOMs. These HOM signals were captured from CC1 and cavities 1 and 8 of the cryomodule for various initial trajectories through the cavities, and we observe correlations between trajectory, HOM signals, and which polarization component of a mode is affected.
	Poster MOPAB232 [2.144 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB232
About •	paper received ※ 20 May 2021 paper accepted ※ 25 May 2021 issue date ※ 28 August 2021
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MOPAB235	Transverse 2d Phase-Space Tomography Using Beam Position Monitor Data of Kicked Beams	emittance, optics, betatron, storage-ring	763
	K. Hwang, C.E. Mitchell, R.D. Ryne LBNL, Berkeley, California, USA
	Funding: U.S. Department of Energy under Contract No. DE-AC02-05CH11231 The time-series Beam Position Monitor (BPM) data of kicked beam is a function of lattice parameters and beam parameters including phase-space density. The decoherence model using the first-order detuning parameter has an exact solution when the beam is Gaussian. We parameterize the beam phase-space density by multiple Gaussian kernels of different weights, means, and sizes to formulate the inverse problem for 2D phase-space tomography. Numerical optimization and Bayesian inference are used to infer the beam density.
	Poster MOPAB235 [1.253 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB235
About •	paper received ※ 20 May 2021 paper accepted ※ 02 June 2021 issue date ※ 10 August 2021
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MOPAB241	Design of the Proton and Electron Transfer Lines for AWAKE Run 2c	plasma, proton, acceleration, experiment	778
	R.L. Ramjiawan JAI, Oxford, United Kingdom S. Döbert, E. Gschwendtner, P. Muggli, F.M. Velotti, L. Verra CERN, Meyrin, Switzerland J.P. Farmer MPI-P, München, Germany P. Muggli MPI, Muenchen, Germany
	The AWAKE Run 1 experiment achieved electron acceleration to 2 GeV using plasma wakefield acceleration driven by 400 GeV, self-modulated proton bunches from the CERN SPS. The Run 2c phase of the experiment aims to build on these results by demonstrating acceleration to ~10 GeV while preserving the quality of the accelerated electron beam. To realize this, there will be an additional plasma cell, to separate the proton bunch self-modulation and the electron acceleration. A new 150 MeV beamline is required to transport and focus the witness electron beam to a beam size of several microns at the injection point. This specification is designed to preserve the beam emittance during acceleration, also requiring micron-level stability between the driver and witness beams. To facilitate these changes, the Run 1 proton transfer line will be reconfigured to shift the first plasma cell 40 m downstream. The Run 1 electron beamline will be adapted and used to inject electron bunches into the first plasma cell to seed the proton bunch self-modulation. Proposed adjustments to the proton transfer line and studies for the designs of the two electron transfer lines are detailed in this contribution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB241
About •	paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 12 August 2021
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MOPAB247	Multipacting Studies for the JAEA-ADS Five-Cell Elliptical Superconducting RF Cavities	multipactoring, cavity, SRF, simulation	793
	B. Yee-Rendón, Y. Kondo, F.M. Maekawa, S.I. Meigo, J. Tamura JAEA/J-PARC, Tokai-mura, Japan E. Cicek KEK, Ibaraki, Japan
	The Five-cell Elliptical Superconducting Radio-Frequency Cavities (SRFC) provide the final acceleration in the JAEA-ADS linac (from 208 MeV to 1.5 GeV); thus, their performance is essential for the success of the JAEA-ADS project. After their optimization of the cavity geometry to achieve a high acceleration gradient with lower electromagnetic peaks, the next step in the R&D strategy is the accurate estimation of beam-cavity effects which can affect the performance of the cavities. To this end, multipacting studies were developed to investigate its effect in the cavity operation regimen and find countermeasures. The results of this study will help in the development of the SRFC models and in the consolidation of the JAEA-ADS project.
	Poster MOPAB247 [0.599 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB247
About •	paper received ※ 10 May 2021 paper accepted ※ 07 June 2021 issue date ※ 02 September 2021
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MOPAB255	Demonstration of a Novel Longitudinal Phase Space Linearization Method without Higher Harmonics	cavity, gun, simulation, laser	805
	R. Stark University of Hamburg, Hamburg, Germany K. Flöttmann, M. Hachmann DESY, Hamburg, Germany F.J. Grüner Center for Free-Electron Laser Science, Universität Hamburg, Hamburg, Germany B. Zeitler CFEL, Hamburg, Germany
	Nonlinear correlations in the longitudinal phase space of electron bunches can be a decisive limitation to the achievable bunch length compression and attainability of small energy spreads. To overcome the restrictions imposed by nonlinear distortions, the longitudinal phase space distribution must be linearized. Previously, a novel linearization procedure based on the controlled expansion of the bunch between two radio frequency cavities operated at the same fundamental frequency has been presented in . A demonstration of this linearization method is presented in this work. B. Zeitler, K. Floettmann, and F. Grüner, "Linearization of the longitudinal phase space without higher harmonic field," Phys. Rev. ST Accel. Beams, vol. 18, p. 120102, 2015.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB255
About •	paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 12 August 2021
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MOPAB257	Effects of Mode Launcher on Beam Dynamics in Next Generation High Brightness C-Band Guns	gun, emittance, simulation, cathode	813
	A. Giribono, D. Alesini, F. Cardelli, G. Di Raddo, M. Ferrario, A. Gallo, J. Scifo, C. Vaccarezza, A. Vannozzi INFN/LNF, Frascati (Roma), Italy G. Castorina AVO-ADAM, Meyrin, Switzerland L. Ficcadenti INFN-Roma, Roma, Italy G. Muti Sapienza University of Rome, Rome, Italy G. Pedrocchi SBAI, Roma, Italy
	High-brightness RF photo-injectors plays nowadays a crucial role in the fields of radiation generation and advanced acceleration schemes. A high gradient C-band photoinjector consisting of a 2.5 cell gun followed by TW sections is here proposed as an electron source for radiation user facilities. The paper reports on beam dynamics studies in the RF injector and illustrates the effects on the beam quality of the mode launcher with a focus on the compensation of the quadrupole RF components.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB257
About •	paper received ※ 19 May 2021 paper accepted ※ 08 June 2021 issue date ※ 12 August 2021
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MOPAB267	End to End Simulations of Antiproton Transport and Degradation	simulation, proton, antiproton, experiment	847
	S. Padden, E. Kukstas, P. Pusa, V. Rodin, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom K. Nordlund HIP, University of Helsinki, Finland V. Rodin, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The ELENA ring decelerates anti-protons to 100 keV down from 5.3 MeV with transport to experiments handled by electrostatic transfer lines. Even at 100 keV antiprotons are still too high in energy for direct injection into an ion trap, and this is why degrader foils are used to further lower the energy. This contribution presents full end-to-end simulations from the point of extraction until passing through the foil using realistic beam transport simulations coupled with accurate simulations of degrader foils via the use of density functional theory and molecular dynamics. Particles are tracked from the point of extraction until their injection into the trap with full physical modeling at all time steps. The results of this study provide a versatile platform for the optimization of low energy ion experiments towards specific targets.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB267
About •	paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 02 September 2021
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MOPAB270	Beam Dynamics Studies in a Standing Wave Ka-band Linearizer	emittance, bunching, operation, simulation	857
	J. Scifo, M. Behtouei, L. Faillace, M. Ferrario, A. Giribono, B. Spataro, C. Vaccarezza INFN/LNF, Frascati, Italy M. Migliorati INFN-Roma1, Rome, Italy M. Migliorati Sapienza University of Rome, Rome, Italy G. Torrisi INFN/LNS, Catania, Italy
	Next-generation FEL user facilities require high-quality electron beams with kA peak current. The combination of a high brightness RF injector and a magnetic compression stage represents a very performant solution in terms of electron beam emittance and peak current. One of the important issues is the design of a proper device that acts as a linearizer for the beam longitudinal phase space. Recently, the design of a SW Ka band RF accelerating structure has been proposed with promising results. The paper reports on electron beam dynamics studies in the described RF structure.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB270
About •	paper received ※ 19 May 2021 paper accepted ※ 15 August 2021 issue date ※ 29 August 2021
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MOPAB272	Consideration the Prospects of Beam Diagnostic System Upgrade in the Transport Channels of Injection Complex VEPP-5	positron, injection, diagnostics, operation	860
	K.V. Astrelina, F.A. Emanov BINP SB RAS, Novosibirsk, Russia F.A. Emanov NSU, Novosibirsk, Russia
	Transport electron and positron channels from linear accelerator to storage ring of Injection Complex VEPP-5 (BINP, Novosibirsk) have complicated 3D configuration and equipped only with luminophore screens as a beam test. For the regular machine operations the non-destructive beam diagnostic system is required to adjust the electron and positron beam trajectories and minimize the beam losses. The proposal of new beam position monitors (BPM) assembling is considered. Newly added BPMs allow one to control the beam trajectory during operations. Collecting beam position data in several points makes it possible to calculate and correct the beamline parameters: Twiss parameters, dispersion, beam energy variations. The possible configuration of the new BPMs placing is suggested and the rate of beam loss reducing due the additional diagnostics is estimated.
	Poster MOPAB272 [1.164 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB272
About •	paper received ※ 20 May 2021 paper accepted ※ 02 June 2021 issue date ※ 22 August 2021
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MOPAB278	Prototype of the Bunch Arrival Time Monitor for SHINE	pick-up, laser, FEL, controls	881
	X.Q. Liu, L.W. Lai SARI-CAS, Pudong, Shanghai, People’s Republic of China Y.B. Leng, R.X. Yuan, N. Zhang, Y.M. Zhou SSRF, Shanghai, People’s Republic of China
	Funding: Youth Innovation Promotion Association, CAS (Grant No. 2019290) Bunch arrival time monitor (BAM) is an important tool to investigate the temporal characteristic of electron bunch in free electron lasers (FEL). Since the timing jitter of electron bunch will affect the FEL’s stability and the resolution of time-resolved experiment at FELs, it is nec-essary to precisely measure the electron bunch’s arrival time information to stabilize the electron bunch’s timing jitter using beam-based feedback. The BAM based on electro-optic modulator (EOM) is currently being devel-oping for Shanghai high-repetition-rate XFEL and Ex-treme light facility (SHINE). And the first BAM prototype has been installed on SXFEL for beam test. The beam test result shows that the estimated resolution of the pro-totype is about 27.5 fs rms.
	Poster MOPAB278 [1.166 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB278
About •	paper received ※ 20 May 2021 paper accepted ※ 23 June 2021 issue date ※ 28 August 2021
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MOPAB279	Non-Invasive Beam Profile Monitoring for the HL-LHC Hollow Electron Lens	photon, proton, background, luminosity	884
	A. Salehilashkajani, N. Kumar, O. Sedláček, C.P. Welsch, H.D. Zhang The University of Liverpool, Liverpool, United Kingdom M. Ady, N.S. Chritin, N. Jens, O.R. Jones, R. Kersevan, T. Lefèvre, S. Mazzoni, G. Papazoglou, A. Rossi, G. Schneider, R. Veness CERN, Geneva, Switzerland P. Forck, S. Udrea GSI, Darmstadt, Germany N. Kumar, O. Sedláček, C.P. Welsch, H.D. Zhang Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work was supported by the HL-LHC-UK phase II project funded by STFC under Grant Ref: ST/T001925/1 and the STFC Cockcroft core grant No. ST/G008248/1. A Hollow Electron Lens (HEL) is currently under development for the High-Luminosity upgrade of the Large Hadron Collider (HL-LHC). In this device, a hollow electron beam co-propagates with a central proton beam and provides active halo control in the LHC. To ensure the concentricity of the two beams, a non-invasive diagnostic instrument is currently being commissioned. This instrument is a compact version of an existing prototype that leverages beam induced fluorescence with supersonic gas curtain technology. This contribution includes the design features of this version of the monitor, recent progress, and future plans for tests at the Cockcroft Institute and the electron lens test stand at CERN.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB279
About •	paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 14 August 2021
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MOPAB280	Split Ring Resonator Experiment - Simulation Results	simulation, laser, experiment, solenoid	888
	J. Schäfer, B. Härer, A. Malygin, A.-S. Müller, M. Nabinger, M.J. Nasse, T. Schmelzer, M. Schuh, T. Windbichler KIT, Karlsruhe, Germany
	Funding: Supported by "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology (KSETA)" and European Union’s Horizon 2020 Research and Innovation programme. FLUTE (Ferninfrarot Linac- Und Test-Experiment) is a compact linac-based test facility for accelerator and diagnostics R&D. An example for a new accelerator diagnostics tool currently studied at FLUTE is the split-ring-resonator (SRR) experiment, which aims to measure the longitudinal bunch profile of fs-scale electron bunches. Laser-generated THz radiation is used to excite a high frequency oscillating electromagnetic field in the SRR. Particles passing through the SRR gap are time-dependently deflected in the vertical plane, which allows a vertical streaking of an electron bunch. This principle allows a diagnosis of the longitudinal bunch profile in the femtosecond time domain and will be tested at FLUTE. This contribution presents an overview of the SRR experiment and the results of various tracking simulations for different scenarios as a function of laser pulse length and bunch charge. Based on these results possible working points for the experiments at FLUTE will be proposed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB280
About •	paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 16 August 2021
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MOPAB281	Research on Resolution Evaluation of Stripline BPM at SXFEL-UF	FEL, network, linac, experiment	892
	B. Gao, J. Chen, Y.B. Leng SSRF, Shanghai, People’s Republic of China
	48 stripline BPMs are installed in the injection section and linear acceleration section of Shanghai X-ray Free Electron Laser (SXFEL) for electron beam position measurement. These two sections require resolution of 20 µm@100pC. Resolution evaluation is an important step in BPM installation and commissioning. This paper presents BPM resolution evaluation methods based on correlation analysis. Experimental methods, data processing and result analysis will be discussed
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB281
About •	paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 15 August 2021
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MOPAB283	Simulations of Space-Charge and Guiding Fields Effects on the Performance of Gas Jet Profile Monitoring	simulation, HOM, collimation, GUI	898
	O. Sedláček, N. Kumar, A. Salehilashkajani, C.P. Welsch, H.D. Zhang The University of Liverpool, Liverpool, United Kingdom P. Forck, S. Udrea GSI, Darmstadt, Germany N. Kumar, A. Salehilashkajani, O. Sedláček, C.P. Welsch, H.D. Zhang Cockcroft Institute, Warrington, Cheshire, United Kingdom S. Mazzoni, O. Sedláček CERN, Geneva, Switzerland
	Gas jet based profile monitors inject a usually curtain shaped gas jet across a charged particle beam and exploit the results of the minimally invasive beam-gas interaction to provide information about the beam’s transversal profile. Such monitor will be installed as part of the High Luminosity LHC upgrade at CERN in the Hollow Electron Lens (HEL). The HEL represents a new collimation stage increasing the diffusion rate of halo particles by placing a high intensity hollow electron beam concentrically around the LHC beam. The gas jet monitor will use the fluorescence radiation resulting due to the beam-gas interaction to create an image of the profiles of both hollow electron and LHC beams However, the high beam space-charge and strong guiding magnetic field of the electron beam cause significant displacements of the excited molecules, as they are also ionized, and thus image distortions. This work presents preliminary simulation results showing expected fluorescence images of the hollow electron profile as affected by space-charge and guiding fields using simulation tools such as IPMsim. The influence of the estimated electron beam and gas jet curtain parameters are investigated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB283
About •	paper received ※ 18 May 2021 paper accepted ※ 28 July 2021 issue date ※ 30 August 2021
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MOPAB284	Status of the Dedicated Electron Diagnostic Beamline at AXSIS	diagnostics, MMI, dipole, controls	902
	H. Dinter, R.W. Aßmann, F. Burkart, M.J. Kellermeier DESY, Hamburg, Germany C. Lechner EuXFEL, Schenefeld, Germany
	Funding: The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 609920. AXSIS (Attosecond X-ray Science: Imaging and Spectroscopy) is a compact, accelerator-driven X-ray source currently under construction at DESY Hamburg. It comprises a THz-powered electron gun and THz-driven linac for all-optical electron extraction and acceleration to several MeV with the goal of providing X-rays generated by inverse Compton scattering for photon science experiments. For the commissioning and characterisation of the THz gun and linac the facility includes a dedicated accelerator testing area, for which an electron diagnostic beamline has been designed and is currently under construction. The challenges imposed by the AXSIS project on the development of the diagnostics beamline are the wide ranges of bunch charge (15 fC to 3 pC) and energy (5 MeV to 20 MeV) expected from the THz-driven accelerator as well as the limited available space of only ca. 2.5 metres length. In this contribution we present an overview of the design and the current commissioning status of the electron diagnostic beamline as well as plans for future steps.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB284
About •	paper received ※ 19 May 2021 paper accepted ※ 18 June 2021 issue date ※ 13 August 2021
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MOPAB286	Towards a Data Science Enabled MeV Ultrafast Electron Diffraction System	network, experiment, real-time, laser	906
	M.A. Fazio, S. Biedron, M. Martínez-Ramón, D.J. Monk, S.I. Sosa Guitron UNM-ECE, Albuquerque, USA M. Babzien, K.A. Brown, M.G. Fedurin, J.J. Li, M.A. Palmer, J. Tao BNL, Upton, New York, USA S. Biedron, T. Talbott UNM-ME, Albuquerque, New Mexico, USA J. Chen, A.J. Hurd, N.A. Moody, R. Prasankumar, C. Sweeney LANL, Los Alamos, New Mexico, USA D. Martin, M.E. Papka ANL, Lemont, Illinois, USA
	Funding: US DOE, SC, BES, MSE, award DE-SC0021365 and DOE NNSA award 89233218CNA000001 through DOE’s EPSCoR program in Office of BES with resources of DOE SC User Facilities BNL’s ATF and ALCF. A MeV ultrafast electron diffraction (MUED) instrument is a unique characterization technique to study ultrafast processes in materials by a pump-probe technique. This relatively young technology can be advanced further into a turn-key instrument by using data science and artificial intelligence (AI) mechanisms in conjunctions with high-performance computing. This can facilitate automated operation, data acquisition and real time or near- real time processing. AI based system controls can provide real time feedback on the electron beam which is currently not possible due to the use of destructive diagnostics. Deep learning can be applied to the MUED diffraction patterns to recover valuable information on subtle lattice variations that can lead to a greater understanding of a wide range of material systems. A data science enabled MUED facility will also facilitate the application of this technique, expand its user base, and provide a fully automated state-of-the-art instrument. We will discuss the progress made on the MUED instrument in the Accelerator Test Facility of Brookhaven National Laboratory.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB286
About •	paper received ※ 20 May 2021 paper accepted ※ 09 June 2021 issue date ※ 24 August 2021
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MOPAB287	The Development of Single Pulse High Dynamic Range BPM Signal Detector Design at AWA	detector, pick-up, experiment, electronics	909
	E.M. Siebert, S. Baturin Northern Illinois University, DeKalb, Illinois, USA D.S. Doran, G. Ha, W. Liu, P. Piot, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA
	Funding: the US Department of Energy, Office of Science Single pulse high dynamic range BPM signal detector has been on the most wanted list of Argonne Wakefield Accelerator (AWA) Test Facility for many years. Unique capabilities of AWA beamline require BPM instrumentation with an unprecedented dynamic range, thus cost effective solution could be challenging to design and prototype. Our most recent design, and the results of our quest for a solution, are shared in this paper.
	Poster MOPAB287 [1.372 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB287
About •	paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 21 August 2021
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MOPAB289	Machine Learning Training for HOM reduction and Emittance Preservation in a TESLA-type Cryomodule at FAST	HOM, cavity, emittance, controls	916
	J.A. Diaz Cruz UNM-ECE, Albuquerque, USA J.A. Diaz Cruz, A.L. Edelen, B.T. Jacobson, J.P. Sikora SLAC, Menlo Park, California, USA D.R. Edstrom, A.H. Lumpkin, R.M. Thurman-Keup Fermilab, Batavia, Illinois, USA

Paper

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MOXB02

First Results of the IOTA Ring Research at Fermilab

experiment, optics, lattice, octupole

19

A. Valishev, D.R. Broemmelsiek, A.V. Burov, K. Carlson, B.L. Cathey, S. Chattopadhyay, N. Eddy, D.R. Edstrom, J.D. Jarvis, V.A. Lebedev, S. Nagaitsev, H. Piekarz, A.L. Romanov, J. Ruan, J.K. Santucci, V.D. Shiltsev, G. Stancari
Fermilab, Batavia, Illinois, USA
A. Arodzero, A.Y. Murokh, M. Ruelas
RadiaBeam, Santa Monica, California, USA
D.L. Bruhwiler, J.P. Edelen, C.C. Hall
RadiaSoft LLC, Boulder, Colorado, USA
S. Chattopadhyay, S. Szustkowski
Northern Illinois University, DeKalb, Illinois, USA
A. Halavanau, Z. Huang, V. Yakimenko
SLAC, Menlo Park, California, USA
M. Hofer
TU Vienna, Wien, Austria
M. Hofer, R. Tomás García
CERN, Geneva, Switzerland
K. Hwang, C.E. Mitchell, R.D. Ryne
LBNL, Berkeley, California, USA
K.-J. Kim
ANL, Lemont, Illinois, USA
K.-J. Kim, Y.K. Kim, N. Kuklev, I. Lobach
University of Chicago, Chicago, Illinois, USA
T.V. Shaftan
BNL, Upton, New York, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The IOTA ring at Fermilab is a unique machine exclusively dedicated to accelerator beam physics R&D. The research conducted at IOTA includes topics such as nonlinear integrable optics, suppression of coherent beam instabilities, optical stochastic cooling and quantum science experiments. In this talk we report on the first results of experiments with implementations of nonlinear integrable beam optics. The first of its kind practical realization of a two-dimensional integrable system in a strongly-focusing storage ring was demonstrated allowing among other things for stable beam circulation near or at the integer resonance. Also presented will be the highlights of the world’s first demonstration of optical stochastic beam cooling and other selected results of IOTA’s broad experimental program.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOXB02

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paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 19 August 2021

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MOXC02

Improved Lifetime of a High Spin Polarization Superlattice Photocathode

cathode, polarization, gun, vacuum

31

L. Cultrera
BNL, Upton, New York, USA

Funding: Department of Energy under grant DE-SC0012704
Highly spin polarized electron beams are required for the operation of a wide range of accelerators and instruments. The production of such electrons requires the use of Negative Electron Affinity (NEA) activated GaAs-based cathodes operated in photoelectron guns. Because of their extreme sensitivity to poor vacuum conditions the degradation of the photoemission process is so strong that NEA activated GaAs-based photocathodes can only survive in the extreme vacuums typical of DC gun. State-of-the-art on photocathode technology for spin polarized beam productions are summarized. Recent results on the use of robust NEA coating based on the Cs-Te and Cs-Sb leading to improved operational lifetime of a high spin polarization photocathode are reviewed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOXC02

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paper received ※ 20 May 2021 paper accepted ※ 19 July 2021 issue date ※ 11 August 2021

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MOPAB003

Machine Learning Analysis of Electron Cooler Operation for RHIC

luminosity, operation, scattering, GUI

45

X. Gu, A.V. Fedotov, D. Kayran
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
A regression machine learning algorithm was applied to analyze the operation data of RHIC with electron cooler LEReC during the 2020 physics run. After constructing a black-box surrogate model from the XGBoost algorithm and plotting their partial dependency plots for different operation parameters, we can find the effects of an individual parameter on the RHIC luminosity and optimize it accordingly offline.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB003

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paper received ※ 14 May 2021 paper accepted ※ 25 May 2021 issue date ※ 11 August 2021

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MOPAB004

JSPEC - A Simulation Program for IBS and Electron Cooling

simulation, experiment, emittance, scattering

49

H. Zhang, S.V. Benson, M.W. Bruker, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Intrabeam scattering is an important collective effect that can deteriorate the properties of a high-intensity beam, and electron cooling is a method to mitigate the IBS effect. JSPEC (JLab Simulation Package for Electron Cooling) is an open-source program developed at Jefferson Lab, which simulates the evolution of the ion beam under the IBS and/or the electron cooling effect. JSPEC has been benchmarked with BETACOOL and experimental data. In this report, we will introduce the features of JSPEC, including the friction force calculation, the IBS expansion rate and electron cooling rate calculation, and the beam-dynamic simulations for the electron cooling process; explain how to set up the simulations in JSPEC; and demonstrate the benchmarking results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB004

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paper received ※ 19 May 2021 paper accepted ※ 21 May 2021 issue date ※ 13 August 2021

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MOPAB010

RHIC Beam Energy Scan Operation with Electron Cooling in 2020

operation, luminosity, emittance, experiment

72

C. Liu, P. Adams, E.N. Beebe, S. Binello, I. Blackler, M. Blaskiewicz, K.A. Brown, D. Bruno, B.D. Coe, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, C.E. Giorgio, X. Gu, T. Hayes, K. Hock, H. Huang, R.L. Hulsart, T. Kanesue, D. Kayran, N.A. Kling, B. Lepore, Y. Luo, D. Maffei, G.J. Marr, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty, J. Morris, C. Naylor, S. Nemesure, M. Okamura, I. Pinayev, S. Polizzo, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, P. Thieberger, M. Valette, A. Zaltsman, I. Zane, K. Zeno, W. Zhang
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
RHIC provided Au-Au collisions at beam energies of 5.75 and 4.59 GeV/nucleon for the physics program in 2020 as a part of the Beam Energy Scan II experiment. The operational experience at these energies will be reported with emphasis on their unique features. These unique features include the addition of a third harmonic RF system to enable a large longitudinal acceptance at 5.75 GeV/nucleon, the application of additional lower frequency cavities for alleviating space charge effects, and the world-first operation of cooling with an RF-accelerated bunched electron beam.

Poster MOPAB010 [3.523 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB010

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paper received ※ 17 May 2021 paper accepted ※ 29 July 2021 issue date ※ 30 August 2021

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MOPAB013

Radiation to Electronics Impact on CERN LHC Operation: Run 2 Overview and HL-LHC Outlook

radiation, operation, luminosity, target

80

Y.Q. Aguiar, A. Apollonio, F. Cerutti, S. Danzeca, R. García Alía, G. Lerner, D. Prelipcean, M. Sabaté-Gilarte
CERN, Geneva 23, Switzerland

Funding: Research supported by the HL-LHC project
After the mitigation measures implemented during Run 1 (2010-2012) and Long Shutdown 1 (LS1, 2013-2014), the number of equipment failures due to radiation effects on electronics (R2E) leading to LHC beam dumps and/or machine downtime has been sufficiently low as to yield a minor impact on the accelerator performance. During Run 2 (2015-2018) the R2E related failures per unit of integrated luminosity remained below the target value of 0.5 events/fb-1, with the sole exception of the 2015 run during which the machine commissioning took place. However, during 2018, an increase in the failure rate was observed, linked to the increased radiation levels in the dispersion suppressors of the ATLAS and CMS experimental insertions, significantly affecting the Quench Protection System located underneath the superconducting magnets in the tunnel. This work provides an overview of the Run 2 R2E events during LHC proton-proton operation, putting them in the context of the related radiation levels and equipment sensitivity, and providing an outlook for Run 3 and HL-LHC operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB013

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paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 15 August 2021

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MOPAB017

Influence of Injection Kicker Post-pulses on Storage of Ion Stack in NICA Collider

kicker, injection, collider, betatron

93

E. Syresin, A. Tuzikov, N.O. Zagibin
JINR, Dubna, Moscow Region, Russia

The peculiarity of the injection kicker power supply in NICA collider is related to same post pulse of the magnetic field which is appeared after a regular injection pulse. The magnetic field of this post pulse became to an increase of the stack ion angle spread during each injection cycle. When the stack ion angles reaches the acceptance angle the ions are lost in the collider. Influence of the injection kicker post pulse on the storage of the ion stack is considered in this paper in presence of the electron cooling and ion electron recombination losses.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB017

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paper received ※ 17 May 2021 paper accepted ※ 20 May 2021 issue date ※ 12 August 2021

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MOPAB019

Possible Application of Round-to-Flat Hadron Beam Creation Using 3rd Order Coupling Resonances for the Electron-Ion Collider

resonance, emittance, sextupole, coupling

99

J. Kallestrup
PSI, Villigen PSI, Switzerland
X. Gu
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
An Electron-Ion Collider (EIC) is planned to be built in Brookhaven National Laboratory with the contribution from Jefferson National Laboratory. To have a high luminosity, both the EIC ion bunch and the EIC electron bunch are designed to be flat during their collision. The existing injector source provides a round beam of width 2.5 um rad transverse emittances. In this paper we investigate the option of dynamically crossing the 2Qx-Qy coupling resonance in order to create a flat-beam with emittance ratio Ex/Ey of up to 4. Furthermore, we explore the possibility of using a pulsed- or AC skew sextupole magnets to achieve a similar effect. Using one of these methods for flat beam creation will help lower the ion beam cooling time.

Poster MOPAB019 [0.323 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB019

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 26 August 2021

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MOPAB025

First Experiments with Accelerated Ion Beams in the Booster of NICA Accelerator Complex

booster, injection, power-supply, heavy-ion

123

A.V. Butenko, V. Andreev, A.M. Bazanov, O.I. Brovko, D.E. Donets, A.V. Eliseev, I.V. Gorelyshev, A.V. Konstantinov, S.A. Kostromin, O.S. Kozlov, K.A. Levterov, A. Nesterov, A.V. Philippov, D.O. Ponkin, G.S. Sedykh, I.V. Shirikov, A.O. Sidorin, E. Syresin, A. Tuzikov, V. Volkov
JINR/VBLHEP, Dubna, Moscow region, Russia
N.N. Agapov, A.V. Alfeev, A.A. Baldin, A.A. Fateev, A.R. Galimov, B.V. Golovenskiy, E.V. Gorbachev, A. Govorov, E.V. Ivanov, V. Karpinsky, V.D. Kekelidze, H.G. Khodzhibagiyan, A. Kirichenko, A.G. Kobets, S.A. Korovkin, V. Kosachev, A.D. Kovalenko, G. Kunchenko, I.N. Meshkov, V.A. Mikhailov, V.A. Monchinsky, D. Nikiforov, R.V. Pivin, S. Romanov, A.A. Shurygin, A.I. Sidorov, A.N. Svidetelev, G.V. Trubnikov, B. Vasilishin
JINR, Dubna, Moscow Region, Russia
G.A. Fatkin
Cosylab Siberia, Novosibirsk, Russia

The NICA accelerator complex in JINR consist of two linear injector chains, a 578 MeV/u superconducting (SC) Booster synchrotron, the existing SC synchrotron Nuclotron, and a new SC collider that has two storage rings. The construction of the facility is based on the Nuclotron technology of SC magnets with an iron yoke and hollow SC cable. Assembly of the Booster synchrotron was finished in autumn of 2020 and first machine Run and experiments with ion beams were successfully done in December 2020. The results of this Run are discussed in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB025

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paper received ※ 16 May 2021 paper accepted ※ 24 August 2021 issue date ※ 07 September 2021

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MOPAB030

Research and Development Progress of CEPC RF Shield Bellows

vacuum, positron, impedance, controls

142

J.M. Liu, Y.H. Guan, S.M. Liu, B. Tan, P.C. Wang
DNSC, Dongguan, People’s Republic of China
H. Dong, Y. Ma
IHEP, Beijing, People’s Republic of China
H.Y. He, T. Huang
IHEP CSNS, Guangdong Province, People’s Republic of China

The circular electron positron collider (CEPC) is a candidate for the next-generation electron positron collider, which can be used to accurately measure the Higgs and electroweak bosons. The RF shield bellow is a vacuum component necessary for the construction of CEPC. Therefore, a RF shield bellow model machine with an elliptical cross-section was designed and processed for technical verification. Based on the traditional interdigital structure, a special contact force testing device was also designed to reduce measurement errors. The on-off status of the circuit was used by the device to determine whether the spring finger was pulled up, thus reducing the influences of human factors in the measurement process. It can be known from the measurement results of the model machine that the contact force of the spring finger is between 120g and 130g, which can satisfy the technical requirements.

Poster MOPAB030 [1.467 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB030

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paper received ※ 19 May 2021 paper accepted ※ 20 May 2021 issue date ※ 28 August 2021

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MOPAB032

Estimates of Collective Effects for the FCC-e⁺e⁻ Pre-Booster Ring

impedance, injection, emittance, collective-effects

148

O. Etisken, F. Antoniou, K. Oide, Y. Papaphilippou, F. Zimmermann
CERN, Geneva, Switzerland
A.K. Çiftçi
Izmir University of Economics, Balçova/Izmir, Turkey

The FCC-e⁺e⁻ injector complex needs to produce and to transport high-intensity e⁺ and e^- beams at a fast repetition rate for topping up the collider at its collision energy. Two different options are under consideration as pre-accelerator before the bunches are transferred to the high-energy booster: either using the existing SPS machine or designing a completely new ring. The purpose of this paper is to present the studies of collective effects with analytical estimates for both the pre-booster ring design options including space charge (SC), longitudinal micro-wave instability (LMI), transverse mode coupling instability (TMCI), ion effects, electron cloud (e-cloud), coherent synchrotron radiation (CSR), and intra-beam scattering (IBS).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB032

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paper received ※ 17 May 2021 paper accepted ※ 27 May 2021 issue date ※ 12 August 2021

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MOPAB034

VEPP-4M Collider Operation at High Energy

collider, experiment, luminosity, positron

155

P.A. Piminov, G.N. Baranov, A.V. Bogomyagkov, V.M. Borin, V.L. Dorokhov, S.E. Karnaev, K.Yu. Karyukina, V.A. Kiselev, E.B. Levichev, O.I. Meshkov, S.I. Mishnev, I.A. Morozov, I.N. Okunev, E.A. Simonov, S.V. Sinyatkin, E.V. Starostina, A.N. Zhuravlev
BINP SB RAS, Novosibirsk, Russia

VEPP-4M is an electron positron collider equipped with the universal KEDR detector for HEP experiments in the beam energy range from 1 GeV to 6 GeV. A unique feature of VEPP-4M is the high precision beam energy calibration by resonant polarization technique which allows conducting of interesting experiments despite the low luminosity of the collider. Recently we have started new luminosity acquisition run above 2 GeV. The hadron cross section was measured from 2.3 GeV to 3.5 GeV has been done. The luminosity run for gamma-gamma physics has been started. The luminosity at ψ(1S)-meson has been obtained. For the beam energy calibration the laser polarimeter is used. The paper discusses recent results from VEPP-4M collider.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB034

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paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 23 August 2021

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MOPAB036

Different Operation Regimes at the KIT Storage Ring KARA (Karlsruhe Research Accelerator)

operation, optics, lattice, storage-ring

163

A.I. Papash, M. Brosi, E. Huttel, A. Mochihashi, A.-S. Müller, R. Ruprecht, P. Schreiber, M. Schuh, N.J. Smale
KIT, Karlsruhe, Germany

The KIT storage ring KARA operates in a wide energy range from 0.5 to 2.5 GeV. Different operation modes have been implemented at KARA, so far, the double-bend achromat (DBA) lattice with non-dispersive straight sections, the theoretical minimum emittance (TME) lattice with distributed dispersion, different versions of low-compaction factor optics with highly stretched dispersion function. Short bunches of a few ps pulse width are available at KARA. Low-alpha optics has been simulated, tested and implemented in a wide operational range of the storage ring and is now routinely used at 1.3 GeV for studies of beam bursting effects caused by coherent synchrotron radiation in the THz frequency range. Different non-linear effects, in particular residual high-order components of the magnetic field, generated in high-field superconducting wigglers have been studied and cured. Based on good agreement between computer simulations and experiments, a new operation mode at high vertical tune was implemented. The beam performance during user operation as well as at low-alpha regimes has been improved. A specific optic with negative compaction factor was simulated, tested and is in operation.

Poster MOPAB036 [1.477 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB036

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paper received ※ 13 May 2021 paper accepted ※ 08 June 2021 issue date ※ 30 August 2021

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MOPAB037

On Possibility of Alpha-buckets Detecting at the KIT Storage Ring KARA (Karlsruhe Research Accelerator)

storage-ring, operation, optics, synchrotron

167

A.I. Papash, T. Boltz, M. Brosi, A.-S. Müller, R. Ruprecht, P. Schreiber, M. Schuh, N.J. Smale
KIT, Karlsruhe, Germany

Computer studies of longitudinal motion have been performed with the objective to estimate the possibility of detection of alpha-buckets at the KIT storage ring KARA (Karlsruhe Research Accelerator). The longitudinal equations of motion and the Hamiltonian were expanded to high order terms of the energy deviation of particles in a beam. Roots of third order equation for three leading terms of momentum compaction factor and free energy independent term were derived in a form suitable for analytical estimations. Averaged quadratic terms of closed orbit distortions caused by misalignment of magnetic elements in a ring lead to orbit lengthening independent of particle energy deviation. Particle transverse excursions were estimated and are taken into account. Simulations have been bench-marked on existing experiments at Metrology Light Source (MLS) in Berlin (Germany) and SOLEIL (France). Parameters of three simultaneous beams and alpha buckets at MLS and SOLEIL have been reproduced with high accuracy. A computer model of KARA was used to predict behavior and the dynamics of possible simultaneous beams in the ring.

Poster MOPAB037 [1.269 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB037

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paper received ※ 11 May 2021 paper accepted ※ 28 May 2021 issue date ※ 28 August 2021

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MOPAB040

Gain of Hard X-Ray Fel at 3 GeV and Required Parameters

FEL, undulator, laser, focusing

178

L.H. Yu
BNL, Upton, New York, USA

We develop a tool for the calculation to study the conditions for a hard x-ray FEL oscillator based on an electron beam in the medium energy range from 3 to 4.5 GeV. We show that the approach developed by K.J. Kim et al. for the small-signal low gain formula can be modified so that the gain can be derived without taking the "no focusing approximation" adopted in the approach so that a strong focusing can be applied. We also derive the formula to allow for the gain calculation of harmonic lasing. The gain in this formula can be cast in the form of a product of two factors with one of them only depends on the harmonic number, undulator period, and gap. Thus this factor can be used to show that it is favorable to use harmonic lasing to achieve hard x-ray FEL working in the medium energy range and in the small-signal low gain regime.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB040

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paper received ※ 09 May 2021 paper accepted ※ 26 May 2021 issue date ※ 22 August 2021

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MOPAB042

Beam Dynamics Investigation for a New Project of Compton Back Scattering Photon Source at NRNU MEPhI

linac, photon, scattering, laser

186

V.S. Dyubkov, I.A. Ashanin, M. Gusarova, Yu.D. Kliuchevskaia, M.V. Lalayan, S.M. Polozov, A.I. Pronikov, V.I. Rashchikov
MEPhI, Moscow, Russia

Funding: This project is supported by Russian Foundation for Basic Research, Grant no. 19-29-12036.
The activities on physical models design of a compact monochromatic radiation source in the x-ray range based on inverse Compton scattering are started at NRNU MEPhI. There are comparison of two schemes of the photon source here: one of them is considered to be based on linac with variable energy of 20-60 MeV only and the other one is considered as accelerator complex where linac is supposed to be used as injector to medium size storage ring (energy up to 60 MeV). Preliminary results of linac structures and storage ring design as well as electron dynamics simulation are discussed

Poster MOPAB042 [0.962 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB042

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paper received ※ 13 May 2021 paper accepted ※ 20 May 2021 issue date ※ 27 August 2021

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MOPAB049

Gyroresonant Acceleration of Electrons by an Axisymmetric Transverse Electric Field

resonance, acceleration, cyclotron, plasma

213

E.A. Orozco, O. Otero Olarte
UIS, Bucaramanga, Colombia

The acceleration of electrons using gyromagnetic autoresonance consist on the sustaint of the electron cyclotron resonant condition through of a magnetic field which increase on time, this scheme was propose by K. S. Golovanivsky. In this work, we considerer the gyroresonant acceleration of electrons using an axisymmetric transverse electric field and its limitations. The 2D acceleration of electrons by a TE011 cylindrical mode is studied numerically. The trajectory, energy and phase-shift between the electron transverse velocity and the electric field are determined by the numerical solution of the relativistic Newton-Lorentz equation using a finite difference scheme. The growth rate of the magnetic field obtained is such that it maintains the phase difference within the acceleration band. The study includes the evolution of the energy for electrons initially ubicated in diferents initial points. For an electron that starts from rest and located at the radial midpoint of the transverse central plane of the cavity, it is reaches an energy close to 560 keV in 625 cycles of the microwave field using an electric field amplitude of 1 kV/cm and a frequency of 2.45 GHz.

Poster MOPAB049 [3.541 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB049

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paper received ※ 17 May 2021 paper accepted ※ 14 June 2021 issue date ※ 13 August 2021

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MOPAB050

Spatial Autoresonant Acceleration of Electrons by an Axysimmetric Transverse Electric Field

resonance, acceleration, cyclotron, cavity

217

E.A. Orozco, O. Otero Olarte
UIS, Bucaramanga, Colombia

In this research, The autoresonance acceleration of electrons by an axisymmetric transverse electric field in presence of a stationary inhomogeneous magnetic field is studied. The dynamics of electrons is determined by the numerical solution of the relativistic Newton-Lorentz equation using a finite difference scheme. The inhomogeneous external magnetic field is generated with a three-coil system and calculated using the Biot-Savart law. The electrons move along a TE011 cylinder cavity in a stationary magnetic field whose axis coincides with the cavity axis. The magnetic field profile obtained is such that it keeps the phase difference between the electric field vector of the microwave mode and the velocity vector of the particle within the acceleration band. For an electron injected longitudinally with an energy of 1 keV and that starts at the radial midpoint of the cavity, it is accelerated up to an energy of about 185 keV using an electric field amplitude of 14 kV/cm and a frequency of 2.45 GHz at a distance of 14 cm.

Poster MOPAB050 [3.298 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB050

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paper received ※ 17 May 2021 paper accepted ※ 15 June 2021 issue date ※ 30 August 2021

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MOPAB054

Start-to-End Simulation of a Free-Electron Laser Driven by a Laser-Plasma Wakefield Accelerator

plasma, laser, bunching, radiation

233

W. Liu, Y. Jiao, S. Wang
IHEP, Beijing, People’s Republic of China

The rapid development of laser-plasma wakefield accelerator (LPA) has opened up a new possible way to achieve ultra-compact free-electron laser (FEL). To this end, LPA experts have made many efforts to generate electron beams with sub-micrometer emittance and low energy spread. Recently, a new laser modulation method was proposed for generating EUV coherent pulse in an LPA-driven FEL. The simulation demonstration of this scheme is based on the Gaussian beam. However, the distribution of the LPA beam is not Gaussian. To further verify the feasibility of the method mentioned above, a start-to-end simulation is required.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB054

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paper received ※ 18 May 2021 paper accepted ※ 27 May 2021 issue date ※ 30 August 2021

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MOPAB055

Generation of Coherent Attosecond X-ray Pulses in the Southern Advanced Photon Source

laser, storage-ring, emittance, photon

237

W. Liu, Y. Zhao
IHEP CSNS, Guangdong Province, People’s Republic of China
Y. Jiao, S. Wang
IHEP, Beijing, People’s Republic of China

Southern Advanced Photon Source (SAPS) is a fourth-generation storage ring light source that has been considered for construction in Guangdong province of China, adjacent to the China Spallation Neutron Source. As a low-emittance storage ring, the natural emittance of SAPS is below 100 pm. One of the benefits is that the brightness is about 2 orders high than 3rd generation light sources. However, like many other storage ring-based light sources, the time resolution is limited by the electron bunch length in the range of picoseconds. In this work, we propose a new scheme for the generation of coherent attoseconds X-ray pulses with a high repetition rate in SAPS. A numerical demonstration of the scheme is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB055

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paper received ※ 17 May 2021 paper accepted ※ 26 May 2021 issue date ※ 12 August 2021

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MOPAB058

Swap-Out Safety Tracking for the Advanced Photon Source Upgrade

photon, dipole, simulation, power-supply

249

M. Borland, J.S. Downey, M.S. Jaski
ANL, Lemont, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source upgrade will operate in swap-out mode, which is similar to top-up but involves complete replacement of individual depleted bunches in a single shot. As with top-up, safety is a concern given that this process will take place with beamline shutters open. We describe the methods used to model swap-out safety, including creation and validation of a full ring lattice based on 3D field maps. We also describe a new method of implementing complex, intersecting channels for electron beams and photon beams, as well as a method of easily identifying potentially dangerous stray particles. Numerous potential errors (e.g., magnet shorts) were modeled, giving a reliable indication of performance of proposed stored beam and magnet interlocks.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB058

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paper received ※ 14 May 2021 paper accepted ※ 28 May 2021 issue date ※ 23 August 2021

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MOPAB093

Operational Status of Photon Factory Light Sources

injection, operation, radiation, vacuum

350

T. Honda, Y. Kobayashi, C. Mitsuda, S. Nagahashi, R. Takai, H. Takaki
KEK, Ibaraki, Japan

One of the recent topics of Photon Factory light sources, PF-ring and PF-AR, is a construction of a GeV-class beamline for testing detectors at the PF-AR. The bremsstrahlung photons generated by a thin carbon wire are brought to a copper target to generate e⁺e⁻ pairs. Sufficient count rates can be expected when the thin wire touching halo of the stored beam, and the test beamline can be used without disturbing the synchrotron radiation experiments. In addition to the usual 6.5-GeV operation, a low-energy operation at 5-GeV was started recently at PF-AR to secure operation time by saving electricity costs. At the PF-ring, the injection section has been upgraded with the septum-magnet replacement. By the top-up injection and improved bunch feedback, the hybrid-fill mode operation has become convenient for both single-bunch users and multi-bunch users, and about 30% or 40% of the user time is scheduled as the hybrid-fill mode now.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB093

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paper received ※ 21 May 2021 paper accepted ※ 25 May 2021 issue date ※ 01 September 2021

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MOPAB095

Concept Design for the CLS2 Accelerator Complex

emittance, storage-ring, synchrotron, lattice

354

M.J. Boland, P.J. Hunchak
University of Saskatchewan, Saskatoon, Canada
C.K. Baribeau, D. Bertwistle, J.M. Patel, H. Shaker, X. Shen, M.J. Sigrist
CLS, Saskatoon, Saskatchewan, Canada
F. Le Pimpec
EuXFEL, Schenefeld, Germany
E.J. Wallén
LBNL, Berkeley, California, USA

The Canadian Light Source has been in operation since 2005 and is now looking at a design concept to upgrade to a fourth generation storage ring. A brief overview is given of a possible accelerator complex layout, including some details on the lattice design and injection system. A full energy linac is being explored as an option for top-up injection and to future proof the facility for a potential FEL upgrade in the future.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB095

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paper received ※ 23 May 2021 paper accepted ※ 28 July 2021 issue date ※ 29 August 2021

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MOPAB097

Two Color Grating design for Soft X-Ray Self-Seeding at LCLS-II

FEL, simulation, laser, photon

361

A. Halavanau, D. Cocco, E. Hemsing, G. Marcus, D.S. Morton
SLAC, Menlo Park, California, USA
G.R. Wilcox
Cornell University, Ithaca, New York, USA

A new grating design is examined for the soft x-ray self-seeding system (SXRSS) at LCLS-II to ultimately produce stable two-color XFEL pulses. The grating performance is analyzed with Fourier optics methods. The final XFEL performance is assessed via full numerical XFEL simulations that substantiate the feasibility of the proposed design.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB097

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paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 01 September 2021

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MOPAB098

LCLS Multi-Bunch Improvement Plan

laser, FEL, linac, experiment

365

A. Halavanau, S. Carbajo, F.-J. Decker, A.K. Krasnykh, A.A. Lutman, A. Marinelli, C.E. Mayes, D.C. Nguyen
SLAC, Menlo Park, California, USA

Current and future experiments at LCLS require XFEL pulse trains of variable time separation. The cavity based XFEL (CBXFEL) project requires multiple pulses separated by 220 ns, the X-ray Laser Oscillator (XLO) uses 15 ns spaced pulse trains and Matter under Extreme Conditions (MEC) experiments need a shortly spaced (less than 5 ns) pulse trains. In this proceeding, we discuss the LCLS multi-bunch improvement plan and report on its recently status and progress.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB098

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paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 13 August 2021

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MOPAB099

Intensity Fluctuations Reduction in the Double-Bunch FEL at LCLS

FEL, laser, free-electron-laser, undulator

369

G. Zhou, A. Halavanau, C. Pellegrini
SLAC, Menlo Park, California, USA

In this paper we explore the possibility of reducing the intensity fluctuations of a hard X-ray double-bunch free-electron laser (DBFEL) by using an ultra-short, high peak current electron bunch to generate the seed signal, as studied recently for soft X-ray single bunch self-seeding. The ultra-short, nearly single-spike, SASE pulse is amplified to saturation, where a four-crystal monochromator selects a narrow bandwidth seed for the second bunch. Start-to-end simulation results for 7 keV photon energy are presented here for a DBFEL already studied for LCLS using the HXR undulator. We show that using this enhanced DBFEL (EDBFEL) system; the seed signal intensity fluctuations can be reduced from 85% to about 30%, and the second bunch intensity fluctuation at saturation to about 15%.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB099

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paper received ※ 24 May 2021 paper accepted ※ 16 July 2021 issue date ※ 02 September 2021

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MOPAB100

Progress Report on Population Inversion-Based X-Ray Laser Oscillator

FEL, laser, experiment, radiation

373

A. Halavanau, R. Alonso-Mori, A. Aquila, U. Bergmann, D. DePonte, F.-J. Decker, F. Fuller, M. Liang, A.A. Lutman, C. Pellegrini
SLAC, Menlo Park, California, USA
M. Doyle
UCB, Berkeley, USA

The population inversion X-ray Laser Oscillator (XLO) is a fully coherent, transform limited hard X-ray source. It operates by repetitively pumping inner-shell atomic transitions with an XFEL, in a closed Bragg cavity. XLO will produce very bright monochromatic X-ray pulses for applications in quantum optics, X-ray interferometry and metrology. We report the progress to build the first XLO operating at the copper alpha line, using LCLS 9 keV SASE X-ray pulses as a pump.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB100

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paper received ※ 20 May 2021 paper accepted ※ 29 July 2021 issue date ※ 27 August 2021

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MOPAB101

Hollow and Flat Electron Beam Generation at FACET-II

emittance, wakefield, quadrupole, experiment

376

A. Halavanau, S.J. Gessner, C.E. Mayes
SLAC, Menlo Park, California, USA
J.B. Rosenzweig
UCLA, Los Angeles, California, USA

In this proceeding, we investigate hollow and flat electron beam generation at FACET-II facility. We focus on the case of a circular beamlet arrangement, also known as ’necklace’ beams. We study, via numerical simulations, the resulting e-beam dynamics in the FACET-II photoinjector, beam propagation through the high energy section, as well as possible experimental applications of the ’necklace’ beams. Finally, we evaluate the feasibility of high charge flat beam generation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB101

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paper received ※ 23 May 2021 paper accepted ※ 27 July 2021 issue date ※ 24 August 2021

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MOPAB118

The Impact of Short-Range Wakes on Injection Into the ALS-U Accumulator Ring

injection, wakefield, kicker, booster

429

G. Penn, M.P. Ehrlichman, T. Hellert, C. Steier, C. Sun, M. Venturini, D. Wang
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DEAC02-05CH11231.
As part of the ALS-U design, bunches with small charge will be added to the accumulator ring in a manner that initially leaves both the stored and injected bunches displaced from the nominal orbit. While the beam current is below instability thresholds, transient effects due to the combination of short-range wake fields and large initial displacements can have an impact on injection efficiency. In this paper, the impact of wake fields on the two bunches is detailed using the elegant simulation code, and different techniques to optimize the injection efficiency are explored.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB118

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paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 01 September 2021

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MOPAB137

Interaction Region Design for DWA Experiments at FACET-II

experiment, radiation, alignment, diagnostics

478

O. Williams, G. Andonian, A. Fukasawa, W.J. Lynn, N. Majernik, P. Manwani, B. Naranjo, J.B. Rosenzweig, Y. Sakai, M. Yadav, Y. Zhuang
UCLA, Los Angeles, California, USA
C.I. Clarke, M.J. Hogan, B.D. O’Shea, D.W. Storey, V. Yakimenko
SLAC, Menlo Park, California, USA
M. Ruelas
RadiaBeam, Santa Monica, California, USA
M. Yadav
The University of Liverpool, Liverpool, United Kingdom

Funding: DOE HEP Grant DE-SC0009914
The extremely intense beam generated at FACET-II provides the unique opportunity to investigate the effects of beam-driven GV/m fields in dielectrics exceeding meter-long interaction lengths. The diverse range of phenomena to be explored, such as material response in the terahertz regime, suppression of high-field pulse damping effects, advanced geometry structures, and methods for beam break up (BBU) mitigation, all within a single UHV vacuum vessel, requires flexibility and precision in the experimental layout. We present here details of the experimental design for the dielectric program at FACET-II. Specifically, consideration is given to the alignment of the dielectric structures due to the extreme fields associated with the electron beam, as well as implementation of electron beam and Cherenkov radiation-based diagnostics.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB137

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paper received ※ 19 May 2021 paper accepted ※ 17 August 2021 issue date ※ 21 August 2021

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MOPAB139

High Resolution Imaging Design Using Permanent Magnet Quadrupoles at BNL UEM

experiment, focusing, quadrupole, target

485

G. Andonian, T.J. Campese, I.I. Gadjev, M. Ruelas
RadiaBeam, Marina del Rey, California, USA
M.G. Fedurin, K. Kusche, X. Yang, Y. Zhu
BNL, Upton, New York, USA
C.C. Hall
RadiaSoft LLC, Boulder, Colorado, USA

Ultrafast electron microscopy techniques have demonstrated the potential to reach very high combined spatio-temporal resolution. In order to achieve high resolution, strong focusing magnets must be used as the objective and projector lenses. In this paper, we discuss the design and development of a high-resolution objective lens for use in the BNL UEM. The objective lens is a quintuplet array of permanent magnet quadrupoles, which in sum, provide symmetric focusing, high magnification, and control of higher order aberration terms. The application and design for a proof-of-concept experiment using a calibrated slit for imaging are presented. The image resolution is monitored as a function of beam parameters (energy, energy spread, charge, bunch length, spot size), and quintuplet lens parameters (drifts between lenses).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB139

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paper received ※ 26 May 2021 paper accepted ※ 28 May 2021 issue date ※ 02 September 2021

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MOPAB140

Gas Sheet Ionization Diagnostic for High Intensity Electron Beams

diagnostics, detector, operation, vacuum

489

N.P. Norvell, G. Andonian, T.J. Campese, A.-L.M.S. Lamure, M. Ruelas, A.Yu. Smirnov
RadiaBeam, Santa Monica, California, USA
N.M. Cook
RadiaSoft LLC, Boulder, Colorado, USA
J.K. Penney
UCLA, Los Angeles, California, USA
C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: Work supported by DOE grant DE-SC0019717
The characterization of high intensity charged particle beams in a minimally interceptive, and non-destructive manner is performed using an ionization diagnostic. In this application, a neutral gas is tailored into a thin sheet, or curtain-like, distribution at the interaction point with an electron beam. The electron beam ionizes the neutral gas in localized space, leaving a footprint of the beam transverse distribution. The ion cloud is subseqeuntly imaged with a series of electrostatic lenses to a detector plane. The resultant image is used in a reconstruction algorithm to reconstruct the beam profile at the interaction point. In this paper, we present progress on the development of this diagnostic for the characterization of high charge, 10GeV electron beams with small transverse distributions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB140

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paper received ※ 20 May 2021 paper accepted ※ 10 June 2021 issue date ※ 18 August 2021

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MOPAB141

Terahertz Driven Compression and Time-Stamping Technique for Single-Shot Ultrafast Electron Diffraction

laser, FEM, radiation, resonance

492

M.A.K. Othman, A.E. Gabriel, M.C. Hoffmann, F. Ji, E.A. Nanni, X. Shen, E.J.C. Snively, X.J. Wang
SLAC, Menlo Park, California, USA

Funding: This research has been supported by the U.S. Department of Energy (DOE) under Contract No. DE-AC02-76SF00515 and DE-AC02-05-CH11231.
Ultrafast structural dynamics are well understood through pump-probe characterization using ultrafast electron diffraction (UED). Advancements in electron diffraction and spectroscopy techniques open new frontiers for scientific discovery through interrogation of ultrafast phenomena, such as quantum phase transitions. Previously, we have demonstrated that strong-field THz radiation can be utilized to efficiently manipulate and compress ultrafast electron probes *, and also offer temporal diagnostics with sub-femtosecond resolution ** enabled by the inherent phase locking of THz radiation to the photoemission optical drive. In this work, we demonstrate a novel THz compression and time-stamping technique to probe solid-state materials at time scales previously inaccessible with standard UED. A high-frequency THz generation method using the organic OH-1 crystals is employed to enable a threefold reduction in the electron probes length and overall timing jitter. These time-stamped probes are used to demonstrate a substantial enhancement in the UED temporal resolution using pump-probe measurement in both photoexcited single crystal and polycrystalline samples.
* E. C. Snively et al., Phys. Rev. Lett, vol. 124, no. 6, p. 054801, 2020.
** R. K. Li et al., Phys. Rev. Accel. Beams, vol. 22, no. 1, p. 012803, Jan. 2019.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB141

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paper received ※ 20 May 2021 paper accepted ※ 21 June 2021 issue date ※ 30 August 2021

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MOPAB143

Simulations for MeV Energy Gain in Multi-Micron Vacuum Channel Dielectric Structures Driven by a CO₂ Laser

laser, simulation, vacuum, acceleration

499

G. Yadav, O. Apsimon, Y. Wei, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
O. Apsimon, C.P. Welsch, G.X. Xia
Cockcroft Institute, Warrington, Cheshire, United Kingdom
G.X. Xia
The University of Manchester, Manchester, United Kingdom

Funding: This work was supported by STFC LIV. DAT under grant agreement ST/P006752/1. This research used the resources of the Supercomputing Laboratory at KAUST in Thuwal, Saudi Arabia.
Dielectric Laser Accelerators (DLAs) have been demonstrated as a novel scheme for producing high acceleration gradients (~1 GV/m) within the damage threshold of the dielectric. The compactness of the DLAs and the low emittance of the output electron beam make it an attractive candidate for future endoscopic devices to be used in tumor irradiation. However, due to the small accelerating distances(sub-mm), the total energy gain is limited to sub-MeV which remains an obstacle for its realistic applications. Also, these DLAs operate under solid-state lasers with wavelengths near IR (800 nm to 2 um), where required sub-micron vacuum channel at such wavelengths imposes major aperture restrictions for the amount of charge to be accelerated. Here, we present numerical simulation results for a dielectric structure excited by a CO₂ laser with a wavelength of 10.6 um. Upon injecting a 50 MeV electron bunch through a 5.3 um diameter of vacuum channel width, our simulation suggests an energy gain beyond 1 MeV. These results are the initial steps for the realization of an mm-scale DLA capable of producing MeV energy electron beams.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB143

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paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 20 August 2021

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MOPAB145

Acceleration and Focusing of Positron Bunch by Electron Bunch Wakefield in the Dielectric Waveguide Filled with Plasma

plasma, positron, focusing, wakefield

505

G.V. Sotnikov, R.R. Kniaziev, P.I. Markov
NSC/KIPT, Kharkov, Ukraine

Funding: The National Research Foundation of Ukraine, program "Leading and Young Scientists Research Support" (project # 2020.02/0299)
The results of the numerical PIC-simulation of accelerated positron bunch focusing in the plasma dielectric wakefield accelerator unit, filled with radially inhomogeneous plasma that has vacuum channel inside are presented. The Wakefield was created by drive electron bunch in quartz dielectric tube with external and internal diameters of 1.2 mm and 1.0 mm, respectively. The tube was embedded in cylindrical metal waveguide. The internal area of dielectric tube has been filled with different transverse density profiles of plasma: homogeneous density and inhomogeneous density created in capillary discharge. Drive bunch electrons energy was 5 GeV, drive bunch charge was 3 nC. The test positron bunch had the same parameters as the drive bunch except for the charge of 0.05 nC. Results of numerical PIC simulation have shown the possibility of simultaneous acceleration and focusing of test positron bunch in the wakefield excited by drive electron bunch. The dependence of transport and acceleration of positron bunch on size of vacuum channel is studied.

Poster MOPAB145 [2.003 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB145

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paper received ※ 19 May 2021 paper accepted ※ 20 May 2021 issue date ※ 27 August 2021

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MOPAB147

Efficient, High Power Terahertz Radiation Outcoupling From a Beam Driven Dielectric Wakefield Accelerator

radiation, wakefield, acceleration, GUI

513

M. Yadav, G. Andonian, C.E. Hansel, W.J. Lynn, N. Majernik, B. Naranjo, J.B. Rosenzweig, O. Williams
UCLA, Los Angeles, California, USA
G. Andonian
RadiaBeam, Santa Monica, California, USA
C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was supported by DE-SC0009914 (UCLA) and the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1.
Wakefields in dielectric structures are a useful tool for beam diagnostics and manipulation with applications including acceleration, shaping, chirping, and THz radiation generation. It is possible to use the produced THz radiation to diagnose the fields produced during the DWA interaction but, to do so, it is necessary to effectively out-couple this radiation to free space for transport to diagnostics such as a bolometer or interferometer. To this end, simulations have been conducted using CST Studio for a 10 GeV beam with FACET-II parameters in a slab-symmetric, dielectric waveguide. Various termination geometries were studied including flat cuts, metal horns, and the "Vlasov antenna". Simulations indicate that the Vlasov antenna geometry is optimal and detailed studies were conducted on a variety of dielectrics including quartz, diamond, and silicon. Multiple modes were excited and coherent Cherenkov radiation (CCR) was computationally generated for both symmetric and asymmetric beams. Finally, we include witness beams to study transport and acceleration dynamics as well as the achievable field gradients.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB147

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paper received ※ 24 May 2021 paper accepted ※ 27 August 2021 issue date ※ 29 August 2021

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MOPAB149

Ion Motion in Flat Beam Plasma Accelerators

plasma, emittance, collider, linear-collider

521

M. Yadav, C.E. Hansel, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
O. Apsimon, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
O. Apsimon, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was supported by UCLA and the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1. This work is done on SCARF Cluster.
Intense beams, such as those in proposed plasma based linear colliders, can not only blow out electrons to form a bubble but can also attract ions towards the beam. This violates the assumption that the ions are stationary on the timescale of the beam, which is a common assumption for shorter and less intense beams. While some research has been done on understanding the physics of ion motion in blowout Plasma Wakefield Accelerators (PWFAs), this research has almost exclusively focused on cylindrically symmetric beams, rather than flat asymmetric emittance beams which are often used in linear colliders in order to minimize beamstrahlung at the final focus. This contribution investigates both analytically and computationally ion motion of a flat beam scenario in order to understand the basic physics as well as how to mitigate emittance growth, beam hosing and quadrupole.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB149

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paper received ※ 24 May 2021 paper accepted ※ 17 June 2021 issue date ※ 10 August 2021

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MOPAB150

Optimization of the Gain Medium Delivery System for an X-Ray Laser Oscillator

laser, target, free-electron-laser, FEL

524

M. Yadav, N. Majernik, P. Manwani, B. Naranjo, C. Pellegrini, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
E.C. Galtier, A. Halavanau, C. Pellegrini
SLAC, Menlo Park, California, USA
A. Malinouski
ASC HMTI, Minsk, Belarus

Funding: This work was supported by DE-SC0009914.
X-ray laser oscillator, dubbed XLO, is a recently proposed project at SLAC to build the first population inversion X-ray laser. XLO utilizes a train of XFEL SASE pulses to pump atomic core-states. The resulting amplified spontaneous emission radiation is recirculated in a backscattering Bragg cavity and subsequently amplified. XLO could provide fully coherent, transform-limited X-ray pulses with 50 meV bandwidth and 1e10 photons. Currently, XLO is being considered for operation at the copper K-alpha line at 8048 eV. In this work, we focus on the optimization of gain medium delivery in the XLO cavity. We consider a fast, subsonic jet of copper nitrate solution, moving through a cylindrical nozzle. We focus on the nozzle geometry optimization and possible diagnostics of the jet-XFEL interaction point.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB150

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paper received ※ 24 May 2021 paper accepted ※ 18 June 2021 issue date ※ 23 August 2021

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MOPAB154

Multi-Cell Accelerating Structure Driven by a Lens-Focused Picosecond THz Pulse

laser, focusing, timing, acceleration

537

S.P. Antipov, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

Recently, gradients on the order of 1 GV/m level have been obtained in a form of a single cycle (~1 ps) THz pulses produced by conversion of a high peak power laser radiation in nonlinear crystals (~1 mJ, 1 ps, up to 3% conversion efficiency). Such high-intensity radiation can be utilized for charged particle acceleration. However, these pulses are short in time (~1ps) and broadband, therefore a new accelerating structure type is required. In this paper, we propose a novel structure based on focusing of THz radiation in accelerating cell and stacking such cells to achieve a long-range interaction required for an efficient acceleration process. We present an example in which a 100 microJoule THz pulse produces a 600 keV energy gain in 5 mm long 10 cell accelerating structure for an ultra-relativistic electron. This design can be readily extended to non-relativistic particles. Such structure had been laser microfabricated and appropriate dimensions were achieved.

Poster MOPAB154 [1.283 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB154

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paper received ※ 27 May 2021 paper accepted ※ 05 July 2021 issue date ※ 14 August 2021

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MOPAB156

Wakefields and Transverse Bunch Dynamics Studies of a Plasma-Dielectric Accelerating Structure

plasma, wakefield, GUI, focusing

542

K. Galaydych, I.N. Onishchenko, G.V. Sotnikov
NSC/KIPT, Kharkov, Ukraine

Funding: The National Research Foundation of Ukraine, programme "Leading and Young Scientists Research Support" (grant agreement n. 2020.02/0299).
A theoretical investigation of a wakefield excitation in a plasma-dielectric accelerating structure by a drive electron bunch in the case of an off-axis bunch injection is carried out. The structure under investigation is a round dielectric-loaded metal waveguide with channel for the charged particles, filled with homogeneous cold plasma. In this paper we focus on the spatial distribution of the bunch-excited wakefield components, which act on both the drive and test bunches, and on transverse bunch dynamics. Dependence of the drive bunch propagation distance on its offset is studied.

Poster MOPAB156 [2.042 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB156

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paper received ※ 19 May 2021 paper accepted ※ 18 June 2021 issue date ※ 31 August 2021

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MOPAB163

First Synchronous Measurement of Single-Bunched Electron and Positron Beams with a Wideband Feedthrough-BPM at the Positron Capture Section of the SuperKEKB Injector Linac

positron, solenoid, wakefield, linac

557

M.A. Rehman, F. Miyahara, T. Suwada
KEK, Ibaraki, Japan

The SuperKEKB is an asymmetric e⁻/e⁺ collider with 40 times higher luminosity than the KEKB project, to explore the new physics beyond the standard model. For the SuperKEKB, the positrons are created by striking the accelerated electrons at a tungsten target. The secondary electrons are also produced during the positron creation process and accelerated in the capture section. Because of phase slipping in the capture section, the secondary electron bunch is only ∼ 180 ps away from the positron. Conventional stripline-type BPM cannot detect such closely spaced and opposite polarity signals due to slow frequency response and high cable losses. Therefore, a new wideband feedthrough-type beam position monitor was developed. It was successfully employed at the positron capture section of the SuperKEKB injector linac for the first synchronous measurement of the electron and positron beams. The cable losses effect also has been de-embedded to reveal correct signal properties. This paper describes the initial results of synchronous measurement of e⁻/e⁺ transverse position.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB163

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paper received ※ 20 May 2021 paper accepted ※ 27 May 2021 issue date ※ 19 August 2021

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MOPAB164

Miniature, High Strength Transport Line Design for Laser Plasma Accelerator-Driven FELs

laser, quadrupole, plasma, undulator

561

S. Fatehi, A. Bernhard, A.-S. Müller, M.S. Ning
KIT, Karlsruhe, Germany

Funding: This work is supported by the BMBF project 05K19VKA PlasmaFEL (Federal Ministry of Education and Research).
Laser-plasma acceleration is an outstanding candidate to drive the next-generation compact light sources and FELs. To compensate large chromatic effects using novel compact beam optic elements in the beam transport line is required. We aim at designing miniature, high strength, normal conducting and superconducting transport line magnets and optics for capturing and matching LPA-generated electron bunches to given applications. Our primary application case is a demonstration experiment for transverse gradient undulator (TGU) FELs, to be performed at the JETI laser facility, Jena, Germany. In this contribution, we present the current design of the beam transport line magnets and the beam optics calculations.
Laser Plasma Accelerators, FELs, Magnets, Beam Dynamics, Superconductivity, transverse gradient undulator

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB164

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paper received ※ 19 May 2021 paper accepted ※ 25 May 2021 issue date ※ 24 August 2021

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MOPAB165

Identical Focusing of Train of Relativistic Positron Gaussian Bunches in Plasma

plasma, focusing, positron, wakefield

565

D.S. Bondar
KhNU, Kharkov, Ukraine
V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

Funding: The study is supported by the National Research Fundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299).
Focusing of both electron and positron bunches in an electron-positron collider is necessary. The focusing mechanism in the plasma, in which all electron bunches are focused identically, has been proposed earlier*. This mechanism is considered for positron bunches by using simulation with LCODE**. Three types of lenses with different trains of cosine profile positron bunches are considered depending on the bunch length, the distance between bunches, and their charge. It has been shown that all positron bunches are focused identically at special parameters of the first positron bunch, wherein the middle of bunches are focused weaker than their fronts.
* V. I. Maslov et al. PAST. 3(2012) 159.
** K. V. Lotov, Phys. Plas. 5 (1998) 785.

Poster MOPAB165 [2.272 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB165

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paper received ※ 17 May 2021 paper accepted ※ 20 May 2021 issue date ※ 14 August 2021

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MOPAB167

Wakefield Excitation in Plasma of Metallic Density by a Laser Pulse

laser, plasma, wakefield, acceleration

571

D.S. Bondar
KhNU, Kharkov, Ukraine
V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

Funding: The study is supported by the National Research Foundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299).
Recently the proposal to use X-ray Exawatt pulse for particle acceleration in a crystal has been declared *. Short X-ray high-power pulse excites wakefield in electron plasma of metallic density which can be used for high gradient acceleration of charged particles. This wakefield is suited for laser wakefield acceleration. In this paper there are simulated with PIC code UMKA: excitation of the large wakefield amplitude up to several TV/m in electron plasma of metallic density by a powerful X-ray laser pulse; laser-plasma wakefield acceleration of self-injected electron bunch in such setup; combined acceleration by plasma wakefield driven by a laser pulse (LPWA) and by self-injected electron bunch (PWFA).
* T.Tajima. Eur. Phys. J. Special Topics 223 (2014) 1037.

Poster MOPAB167 [2.054 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB167

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paper received ※ 17 May 2021 paper accepted ※ 21 May 2021 issue date ※ 02 September 2021

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MOPAB168

Nanoplasmonic Accelerators Towards Tens of TeraVolts per Meter Gradients Using Nanomaterials

plasma, wakefield, experiment, focusing

574

A.A. Sahai, M. Golkowski, V. Harid
CU Denver, Denver, Colorado, USA
C. Joshi
UCLA, Los Angeles, California, USA
T.C. Katsouleas
Duke ECE, Durham, North Carolina, USA
A. Latina, F. Zimmermann
CERN, Geneva, Switzerland
J. Resta-López
Cockcroft Institute, Warrington, Cheshire, United Kingdom
P. Taborek
UCI, Irvine, California, USA
A.G.R. Thomas
University of Michigan, Ann Arbor, Michigan, USA

Funding: University of Colorado Denver
Ultra-high gradients which are critical for future advances in high-energy physics, have so far relied on plasma and dielectric accelerating structures. While bulk crystals were predicted to offer unparalleled TV/m gradients that are at least two orders of magnitude higher than gaseous plasmas, crystal-based acceleration has not been realized in practice. We have developed the concept of nanoplasmonic crunch-in surface modes which utilizes the tunability of collective oscillations in nanomaterials to open up unprecedented tens of TV/m gradients. Particle beams interacting with nanomaterials that have vacuum-like core regions, experience minimal disruptive effects such as filamentation and collisions, while the beam-driven crunch-in modes sustain tens of TV/m gradients. Moreover, as the effective apertures for transverse and longitudinal crunch-in wakes are different, the limitation of traditional scaling of structure wakefields to smaller dimensions is significantly relaxed. The SLAC FACET-II experiment of the nano2WA collaboration will utilize ultra-short, high-current electron beams to excite nonlinear plasmonic modes and demonstrate this possibility.
* doi:10.1109/ACCESS.2021.3070798
** doi:10.1142/S0217751X19430097
*** indico.fnal.gov/event/19478/contributions/52561
**** indico.cern.ch/event/867535/contributions/3716404

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB168

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paper received ※ 11 May 2021 paper accepted ※ 08 June 2021 issue date ※ 17 August 2021

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MOPAB169

Generating 510 MW of X-Band Power for Structure-Based Wakefield Acceleration Using a Metamaterial-Based Power Extractor

experiment, wakefield, acceleration, simulation

578

J.F. Picard, I. Mastovsky, M.A. Shapiro, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA
M.E. Conde, D.S. Doran, J.G. Power, J.H. Shao, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing
Euclid TechLabs, Solon, Ohio, USA
X. Lu
Northern Illinois University, DeKalb, Illinois, USA

Funding: Research sponsored under Award No. DE-SC0015566 by U.S. Department of Energy, Office of Science, Office of High Energy Physics and Contract No. DE-AC02-06CH11357 by the Office of Science.
We present our recent results generating 510 MW of power at 11.7 GHz using a metamaterial-based metallic power-extractor for application in structure-based wakefield acceleration (SWFA). SWFA is a novel acceleration scheme in which high-charge electron bunches are passed through a power extractor structure to produce a high-intensity wakefield. This wakefield can then be used to accelerate a witness bunch in the same beamline or passed to a separate acceleration beamline. MIT’s approach uses a specialized metamaterial for the power extractor design. By using a metamaterial, we can overcome some of the challenges faced by other SWFA techniques. Here, we discuss the Stage 3 experiment. The Stage 1 and Stage 2 experiments successfully demonstrated the functionality of the metamaterial approach by generating high power RF pulses using the 65 MeV electron beam at the Argonne Wakefield Accelerator (AWA) facility. The 510 MW result from Stage 3 experiment is the highest power generated to-date for SWFA at AWA, and was enable by significant design improvements, including an all-copper structure, fully-symmetric coupler design, and breakdown risk-reduction treatment.

Poster MOPAB169 [8.882 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB169

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paper received ※ 08 May 2021 paper accepted ※ 16 July 2021 issue date ※ 12 August 2021

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MOPAB171

Numerical Simulation on Plasma-Based Beam Dumps Using Smilei

plasma, laser, wakefield, acceleration

582

S. Kumar, C. Davut, G.X. Xia
UMAN, Manchester, United Kingdom
A. Bonatto, C. Davut, L. Liang
The University of Manchester, Manchester, United Kingdom
A. Bonatto
Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
B.S. Nunes
IF-UFRGS, Porto Alegre, Brazil
R.P. Nunes
UFRGS, Porto Alegre, Brazil

The active plasma beam dump utilizes a laser to generate a plasma wakefield and decelerate an externally injected beam to low energy. We use the particle-in-cell code "Smi-lei" for the investigation of electron beam energy loss in plasma. In this research work, we optimize the laser and plasma parameters to investigate the active plasma beam dump scheme. In doing so, most of the beam energy will be deposited in the plasma. The optimization strategy for the beam energy loss in plasma is presented.
*A. Bonatto, C. B. Schroeder et al., Physics of Plasmas 22 (8) 083106 (2015).
*G. Xia, A. Bonatto et al., Instruments 4 (2) 10 (2020).
*A Bonatto et al., J. Phys.: Conf. Ser. 1596 012058, 2020.

Poster MOPAB171 [0.756 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB171

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paper received ※ 15 May 2021 paper accepted ※ 24 May 2021 issue date ※ 31 August 2021

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MOPAB173

Physics Program and Experimental for AWAKE Run 2

plasma, wakefield, proton, experiment

586

P. Muggli
MPI, Muenchen, Germany

Run 1 experimental results demonstrate many characteristics of the self-modulation (SM) in plasma of a long, 400GeV SPS proton bunch*. Externally injected, 19MeV electrons were accelerated to 2GeV**. Based on these results, we are assembling a physics and experiment program aiming at producing a multi-GeV electron bunch with emittance and energy spread sufficiently low for possible early applications to high-energy physics experiments. Plans include two plasmas, the first for SM, the second for acceleration, and of scalable length, separated by an injection region. The first plasma includes a density step to maintain large-amplitude wakefields after saturation of the SM process. Seeding of the SM process may be obtained from an electron bunch. The 150MeV witness electron bunch from an S-band gun, X-band linac has parameters that produce plasma electron blow out and loading of the wakefields in order to minimize final energy spread and emittance***. We are studying the possibility of using a helicon plasma source for the accelerator, a source that can in principle be very long (100s of m).
*AWAKE, PRL 122, 054802 (2019), Turner, PRL 122, 054801 (2019), Turner, PRAB 23, 081302, (2020), Braunmueller PRL 125, 264801 (2020)
**AWAKE, Nature 561, 363 (2018)
***Olsen, PRAB 21, 011301 (2018)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB173

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paper received ※ 18 May 2021 paper accepted ※ 28 May 2021 issue date ※ 26 August 2021

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MOPAB175

Advanced Concepts and Technologies for Heavy Ion Synchrotrons

laser, synchrotron, heavy-ion, space-charge

594

P.J. Spiller, O. Boine-Frankenheim, L.H.J. Bozyk, S. Klammes, H. Kollmus, D. Ondreka, I. Pongrac, N. Pyka, C. Roux, K. Sugita, St. Wilfert, T. Winkler, D.F.A. Winters
GSI, Darmstadt, Germany

New concepts and technologies are developed to advance the performance of heavy ion synchrotrons. Besides fast ramping of superconducting magnets, extreme UHV technologies to stabilize dynamic vacuum and charge related loss, broad band MA cavities, space charge compensation by means of electron lenses and new cooling technologies, e.g. laser cooling, show great promise to advance the forefront of beam parameters. Several of these technologies and concepts are developed and tested at GSI/FAIR. Progress and plans will be reported.

Poster MOPAB175 [1.367 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB175

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paper received ※ 11 May 2021 paper accepted ※ 21 May 2021 issue date ※ 01 September 2021

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MOPAB177

ELENA Commissioning and Status

proton, antiproton, experiment, MMI

598

C. Carli, M.E. Angoletta, W. Bartmann, L. Bojtár, F. Butin, B. Dupuy, Y. Dutheil, M.A. Fraser, P. Freyermuth, D. Gamba, L.V. Jørgensen, B. Lefort, O. Marqversen, M. McLean, S. Ogur, S. Pasinelli, L. Ponce, G. Tranquille
CERN, Geneva, Switzerland

The Extra Low ENergy Antiproton ring ELENA is a small synchrotron recently constructed and commissioned to decelerate antiprotons injected from the Antiproton Decelerator AD with a kinetic energy of 5.3 MeV down to 100 keV. Controlled deceleration in the synchrotron, equipped with an electron cooler to reduce losses and generate dense bunches, allows the experiments, typically capturing the antiprotons in traps and manipulating them further, to improve the trapping efficiency by one to two orders of magnitude. During 2018, bunches with an energy of 100 keV with parameters close to nominal have been demonstrated, and first beams have been provided to an experiment in a new experimental zone. The magnetic transfer lines from the AD to the experiments have been replaced by electrostatic lines from ELENA. Commissioning of the new transfer lines and, in parallel, studies to better understand the ring with H⁻ beams from a dedicated source, have started in autumn 2020. The first 100 keV antiproton physics run using ELENA will start in late summer 2021.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB177

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paper received ※ 18 May 2021 paper accepted ※ 14 June 2021 issue date ※ 01 September 2021

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MOPAB212

3-D Quantum Lifetime

simulation, damping, radiation, emittance

700

H. Zhao, M. Blaskiewicz
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The quantum lifetime of electron beam in storage rings is defined by the particle loss that caused by the aperture limitation. Based on the equilibrium beam distribution produced by radiation damping and quantum excitation, the 1-d quantum lifetime has been well studied by A. Piwinski. In this paper, we give the derivation of the 3-d quantum lifetime, which can be applied to the machines with elliptical aperture and momentum acceptance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB212

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paper received ※ 04 June 2021 paper accepted ※ 21 June 2021 issue date ※ 14 August 2021

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MOPAB232

Observation of Polarization-Dependent Changes in Higher-Order Mode Responses as a Function of Transverse Beam Position in Tesla-Type Cavities at FAST

cavity, HOM, dipole, cryomodule

756

R.M. Thurman-Keup, D.R. Edstrom, A.H. Lumpkin, P.S. Prieto, J. Ruan
Fermilab, Batavia, Illinois, USA
J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz, B.T. Jacobson, J.P. Sikora, F. Zhou
SLAC, Menlo Park, California, USA

Funding: FNAL supported by U.S. Department of Energy, Office of Science, under contract DE-AC02-07CH11359. SLAC supported by U.S. Department of Energy, Office of Science, under contract DE-AC02-76SF00515.
Higher-order modes (HOMs) in superconducting rf cavities present problems for an electron bunch traversing the cavity in the form of long-range wakefields from previous bunches. These may dilute the emittance of the macropulse average, especially with low emittance beams at facilities such as the European X-ray Free-electron Laser (XFEL) and the upgraded Linac Coherent Light Source (LCLS-II). Here we present observations of HOMs driven by the beam at the Fermilab Accelerator Science and Technology (FAST) facility. The FAST facility features two independent TESLA-type cavities (CC1 and CC2) after a photocathode rf gun followed by an 8-cavity cryomodule. The HOM signals were acquired from cavities using bandpass filters of 1.75 ± 0.15 GHz, 2.5 ± 0.2 GHz, and 3.25 ± 0.2 GHz and recorded using an 8-GHz, 20 GSa/s oscilloscope. The frequency resolution obtained is sufficient to separate polarization components of many of the HOMs. These HOM signals were captured from CC1 and cavities 1 and 8 of the cryomodule for various initial trajectories through the cavities, and we observe correlations between trajectory, HOM signals, and which polarization component of a mode is affected.

Poster MOPAB232 [2.144 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB232

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paper received ※ 20 May 2021 paper accepted ※ 25 May 2021 issue date ※ 28 August 2021

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MOPAB235

Transverse 2d Phase-Space Tomography Using Beam Position Monitor Data of Kicked Beams

emittance, optics, betatron, storage-ring

763

K. Hwang, C.E. Mitchell, R.D. Ryne
LBNL, Berkeley, California, USA

Funding: U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The time-series Beam Position Monitor (BPM) data of kicked beam is a function of lattice parameters and beam parameters including phase-space density. The decoherence model using the first-order detuning parameter has an exact solution when the beam is Gaussian. We parameterize the beam phase-space density by multiple Gaussian kernels of different weights, means, and sizes to formulate the inverse problem for 2D phase-space tomography. Numerical optimization and Bayesian inference are used to infer the beam density.

Poster MOPAB235 [1.253 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB235

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paper received ※ 20 May 2021 paper accepted ※ 02 June 2021 issue date ※ 10 August 2021

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MOPAB241

Design of the Proton and Electron Transfer Lines for AWAKE Run 2c

plasma, proton, acceleration, experiment

778

R.L. Ramjiawan
JAI, Oxford, United Kingdom
S. Döbert, E. Gschwendtner, P. Muggli, F.M. Velotti, L. Verra
CERN, Meyrin, Switzerland
J.P. Farmer
MPI-P, München, Germany
P. Muggli
MPI, Muenchen, Germany

The AWAKE Run 1 experiment achieved electron acceleration to 2 GeV using plasma wakefield acceleration driven by 400 GeV, self-modulated proton bunches from the CERN SPS. The Run 2c phase of the experiment aims to build on these results by demonstrating acceleration to ~10 GeV while preserving the quality of the accelerated electron beam. To realize this, there will be an additional plasma cell, to separate the proton bunch self-modulation and the electron acceleration. A new 150 MeV beamline is required to transport and focus the witness electron beam to a beam size of several microns at the injection point. This specification is designed to preserve the beam emittance during acceleration, also requiring micron-level stability between the driver and witness beams. To facilitate these changes, the Run 1 proton transfer line will be reconfigured to shift the first plasma cell 40 m downstream. The Run 1 electron beamline will be adapted and used to inject electron bunches into the first plasma cell to seed the proton bunch self-modulation. Proposed adjustments to the proton transfer line and studies for the designs of the two electron transfer lines are detailed in this contribution.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB241

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paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 12 August 2021

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MOPAB247

Multipacting Studies for the JAEA-ADS Five-Cell Elliptical Superconducting RF Cavities

multipactoring, cavity, SRF, simulation

793

B. Yee-Rendón, Y. Kondo, F.M. Maekawa, S.I. Meigo, J. Tamura
JAEA/J-PARC, Tokai-mura, Japan
E. Cicek
KEK, Ibaraki, Japan

The Five-cell Elliptical Superconducting Radio-Frequency Cavities (SRFC) provide the final acceleration in the JAEA-ADS linac (from 208 MeV to 1.5 GeV); thus, their performance is essential for the success of the JAEA-ADS project. After their optimization of the cavity geometry to achieve a high acceleration gradient with lower electromagnetic peaks, the next step in the R&D strategy is the accurate estimation of beam-cavity effects which can affect the performance of the cavities. To this end, multipacting studies were developed to investigate its effect in the cavity operation regimen and find countermeasures. The results of this study will help in the development of the SRFC models and in the consolidation of the JAEA-ADS project.

Poster MOPAB247 [0.599 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB247

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paper received ※ 10 May 2021 paper accepted ※ 07 June 2021 issue date ※ 02 September 2021

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MOPAB255

Demonstration of a Novel Longitudinal Phase Space Linearization Method without Higher Harmonics

cavity, gun, simulation, laser

805

R. Stark
University of Hamburg, Hamburg, Germany
K. Flöttmann, M. Hachmann
DESY, Hamburg, Germany
F.J. Grüner
Center for Free-Electron Laser Science, Universität Hamburg, Hamburg, Germany
B. Zeitler
CFEL, Hamburg, Germany

Nonlinear correlations in the longitudinal phase space of electron bunches can be a decisive limitation to the achievable bunch length compression and attainability of small energy spreads. To overcome the restrictions imposed by nonlinear distortions, the longitudinal phase space distribution must be linearized. Previously, a novel linearization procedure based on the controlled expansion of the bunch between two radio frequency cavities operated at the same fundamental frequency has been presented in *. A demonstration of this linearization method is presented in this work.
*B. Zeitler, K. Floettmann, and F. Grüner, "Linearization of the longitudinal phase space without higher harmonic field," Phys. Rev. ST Accel. Beams, vol. 18, p. 120102, 2015.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB255

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paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 12 August 2021

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MOPAB257

Effects of Mode Launcher on Beam Dynamics in Next Generation High Brightness C-Band Guns

gun, emittance, simulation, cathode

813

A. Giribono, D. Alesini, F. Cardelli, G. Di Raddo, M. Ferrario, A. Gallo, J. Scifo, C. Vaccarezza, A. Vannozzi
INFN/LNF, Frascati (Roma), Italy
G. Castorina
AVO-ADAM, Meyrin, Switzerland
L. Ficcadenti
INFN-Roma, Roma, Italy
G. Muti
Sapienza University of Rome, Rome, Italy
G. Pedrocchi
SBAI, Roma, Italy

High-brightness RF photo-injectors plays nowadays a crucial role in the fields of radiation generation and advanced acceleration schemes. A high gradient C-band photoinjector consisting of a 2.5 cell gun followed by TW sections is here proposed as an electron source for radiation user facilities. The paper reports on beam dynamics studies in the RF injector and illustrates the effects on the beam quality of the mode launcher with a focus on the compensation of the quadrupole RF components.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB257

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paper received ※ 19 May 2021 paper accepted ※ 08 June 2021 issue date ※ 12 August 2021

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MOPAB267

End to End Simulations of Antiproton Transport and Degradation

simulation, proton, antiproton, experiment

847

S. Padden, E. Kukstas, P. Pusa, V. Rodin, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
K. Nordlund
HIP, University of Helsinki, Finland
V. Rodin, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The ELENA ring decelerates anti-protons to 100 keV down from 5.3 MeV with transport to experiments handled by electrostatic transfer lines. Even at 100 keV antiprotons are still too high in energy for direct injection into an ion trap, and this is why degrader foils are used to further lower the energy. This contribution presents full end-to-end simulations from the point of extraction until passing through the foil using realistic beam transport simulations coupled with accurate simulations of degrader foils via the use of density functional theory and molecular dynamics. Particles are tracked from the point of extraction until their injection into the trap with full physical modeling at all time steps. The results of this study provide a versatile platform for the optimization of low energy ion experiments towards specific targets.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB267

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 02 September 2021

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MOPAB270

Beam Dynamics Studies in a Standing Wave Ka-band Linearizer

emittance, bunching, operation, simulation

857

J. Scifo, M. Behtouei, L. Faillace, M. Ferrario, A. Giribono, B. Spataro, C. Vaccarezza
INFN/LNF, Frascati, Italy
M. Migliorati
INFN-Roma1, Rome, Italy
M. Migliorati
Sapienza University of Rome, Rome, Italy
G. Torrisi
INFN/LNS, Catania, Italy

Next-generation FEL user facilities require high-quality electron beams with kA peak current. The combination of a high brightness RF injector and a magnetic compression stage represents a very performant solution in terms of electron beam emittance and peak current. One of the important issues is the design of a proper device that acts as a linearizer for the beam longitudinal phase space. Recently, the design of a SW Ka band RF accelerating structure has been proposed with promising results. The paper reports on electron beam dynamics studies in the described RF structure.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB270

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paper received ※ 19 May 2021 paper accepted ※ 15 August 2021 issue date ※ 29 August 2021

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MOPAB272

Consideration the Prospects of Beam Diagnostic System Upgrade in the Transport Channels of Injection Complex VEPP-5

positron, injection, diagnostics, operation

860

K.V. Astrelina, F.A. Emanov
BINP SB RAS, Novosibirsk, Russia
F.A. Emanov
NSU, Novosibirsk, Russia

Transport electron and positron channels from linear accelerator to storage ring of Injection Complex VEPP-5 (BINP, Novosibirsk) have complicated 3D configuration and equipped only with luminophore screens as a beam test. For the regular machine operations the non-destructive beam diagnostic system is required to adjust the electron and positron beam trajectories and minimize the beam losses. The proposal of new beam position monitors (BPM) assembling is considered. Newly added BPMs allow one to control the beam trajectory during operations. Collecting beam position data in several points makes it possible to calculate and correct the beamline parameters: Twiss parameters, dispersion, beam energy variations. The possible configuration of the new BPMs placing is suggested and the rate of beam loss reducing due the additional diagnostics is estimated.

Poster MOPAB272 [1.164 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB272

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paper received ※ 20 May 2021 paper accepted ※ 02 June 2021 issue date ※ 22 August 2021

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MOPAB278

Prototype of the Bunch Arrival Time Monitor for SHINE

pick-up, laser, FEL, controls

881

X.Q. Liu, L.W. Lai
SARI-CAS, Pudong, Shanghai, People’s Republic of China
Y.B. Leng, R.X. Yuan, N. Zhang, Y.M. Zhou
SSRF, Shanghai, People’s Republic of China

Funding: Youth Innovation Promotion Association, CAS (Grant No. 2019290)
Bunch arrival time monitor (BAM) is an important tool to investigate the temporal characteristic of electron bunch in free electron lasers (FEL). Since the timing jitter of electron bunch will affect the FEL’s stability and the resolution of time-resolved experiment at FELs, it is nec-essary to precisely measure the electron bunch’s arrival time information to stabilize the electron bunch’s timing jitter using beam-based feedback. The BAM based on electro-optic modulator (EOM) is currently being devel-oping for Shanghai high-repetition-rate XFEL and Ex-treme light facility (SHINE). And the first BAM prototype has been installed on SXFEL for beam test. The beam test result shows that the estimated resolution of the pro-totype is about 27.5 fs rms.

Poster MOPAB278 [1.166 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB278

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paper received ※ 20 May 2021 paper accepted ※ 23 June 2021 issue date ※ 28 August 2021

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MOPAB279

Non-Invasive Beam Profile Monitoring for the HL-LHC Hollow Electron Lens

photon, proton, background, luminosity

884

A. Salehilashkajani, N. Kumar, O. Sedláček, C.P. Welsch, H.D. Zhang
The University of Liverpool, Liverpool, United Kingdom
M. Ady, N.S. Chritin, N. Jens, O.R. Jones, R. Kersevan, T. Lefèvre, S. Mazzoni, G. Papazoglou, A. Rossi, G. Schneider, R. Veness
CERN, Geneva, Switzerland
P. Forck, S. Udrea
GSI, Darmstadt, Germany
N. Kumar, O. Sedláček, C.P. Welsch, H.D. Zhang
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was supported by the HL-LHC-UK phase II project funded by STFC under Grant Ref: ST/T001925/1 and the STFC Cockcroft core grant No. ST/G008248/1.
A Hollow Electron Lens (HEL) is currently under development for the High-Luminosity upgrade of the Large Hadron Collider (HL-LHC). In this device, a hollow electron beam co-propagates with a central proton beam and provides active halo control in the LHC. To ensure the concentricity of the two beams, a non-invasive diagnostic instrument is currently being commissioned. This instrument is a compact version of an existing prototype that leverages beam induced fluorescence with supersonic gas curtain technology. This contribution includes the design features of this version of the monitor, recent progress, and future plans for tests at the Cockcroft Institute and the electron lens test stand at CERN.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB279

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paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 14 August 2021

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MOPAB280

Split Ring Resonator Experiment - Simulation Results

simulation, laser, experiment, solenoid

888

J. Schäfer, B. Härer, A. Malygin, A.-S. Müller, M. Nabinger, M.J. Nasse, T. Schmelzer, M. Schuh, T. Windbichler
KIT, Karlsruhe, Germany

Funding: Supported by "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology (KSETA)" and European Union’s Horizon 2020 Research and Innovation programme.
FLUTE (Ferninfrarot Linac- Und Test-Experiment) is a compact linac-based test facility for accelerator and diagnostics R&D. An example for a new accelerator diagnostics tool currently studied at FLUTE is the split-ring-resonator (SRR) experiment, which aims to measure the longitudinal bunch profile of fs-scale electron bunches. Laser-generated THz radiation is used to excite a high frequency oscillating electromagnetic field in the SRR. Particles passing through the SRR gap are time-dependently deflected in the vertical plane, which allows a vertical streaking of an electron bunch. This principle allows a diagnosis of the longitudinal bunch profile in the femtosecond time domain and will be tested at FLUTE. This contribution presents an overview of the SRR experiment and the results of various tracking simulations for different scenarios as a function of laser pulse length and bunch charge. Based on these results possible working points for the experiments at FLUTE will be proposed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB280

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 16 August 2021

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MOPAB281

Research on Resolution Evaluation of Stripline BPM at SXFEL-UF

FEL, network, linac, experiment

892

B. Gao, J. Chen, Y.B. Leng
SSRF, Shanghai, People’s Republic of China

48 stripline BPMs are installed in the injection section and linear acceleration section of Shanghai X-ray Free Electron Laser (SXFEL) for electron beam position measurement. These two sections require resolution of 20 µm@100pC. Resolution evaluation is an important step in BPM installation and commissioning. This paper presents BPM resolution evaluation methods based on correlation analysis. Experimental methods, data processing and result analysis will be discussed

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB281

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paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 15 August 2021

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MOPAB283

Simulations of Space-Charge and Guiding Fields Effects on the Performance of Gas Jet Profile Monitoring

simulation, HOM, collimation, GUI

898

O. Sedláček, N. Kumar, A. Salehilashkajani, C.P. Welsch, H.D. Zhang
The University of Liverpool, Liverpool, United Kingdom
P. Forck, S. Udrea
GSI, Darmstadt, Germany
N. Kumar, A. Salehilashkajani, O. Sedláček, C.P. Welsch, H.D. Zhang
Cockcroft Institute, Warrington, Cheshire, United Kingdom
S. Mazzoni, O. Sedláček
CERN, Geneva, Switzerland

Gas jet based profile monitors inject a usually curtain shaped gas jet across a charged particle beam and exploit the results of the minimally invasive beam-gas interaction to provide information about the beam’s transversal profile. Such monitor will be installed as part of the High Luminosity LHC upgrade at CERN in the Hollow Electron Lens (HEL). The HEL represents a new collimation stage increasing the diffusion rate of halo particles by placing a high intensity hollow electron beam concentrically around the LHC beam. The gas jet monitor will use the fluorescence radiation resulting due to the beam-gas interaction to create an image of the profiles of both hollow electron and LHC beams However, the high beam space-charge and strong guiding magnetic field of the electron beam cause significant displacements of the excited molecules, as they are also ionized, and thus image distortions. This work presents preliminary simulation results showing expected fluorescence images of the hollow electron profile as affected by space-charge and guiding fields using simulation tools such as IPMsim. The influence of the estimated electron beam and gas jet curtain parameters are investigated.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB283

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paper received ※ 18 May 2021 paper accepted ※ 28 July 2021 issue date ※ 30 August 2021

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MOPAB284

Status of the Dedicated Electron Diagnostic Beamline at AXSIS

diagnostics, MMI, dipole, controls

902

H. Dinter, R.W. Aßmann, F. Burkart, M.J. Kellermeier
DESY, Hamburg, Germany
C. Lechner
EuXFEL, Schenefeld, Germany

Funding: The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 609920.
AXSIS (Attosecond X-ray Science: Imaging and Spectroscopy) is a compact, accelerator-driven X-ray source currently under construction at DESY Hamburg. It comprises a THz-powered electron gun and THz-driven linac for all-optical electron extraction and acceleration to several MeV with the goal of providing X-rays generated by inverse Compton scattering for photon science experiments. For the commissioning and characterisation of the THz gun and linac the facility includes a dedicated accelerator testing area, for which an electron diagnostic beamline has been designed and is currently under construction. The challenges imposed by the AXSIS project on the development of the diagnostics beamline are the wide ranges of bunch charge (15 fC to 3 pC) and energy (5 MeV to 20 MeV) expected from the THz-driven accelerator as well as the limited available space of only ca. 2.5 metres length. In this contribution we present an overview of the design and the current commissioning status of the electron diagnostic beamline as well as plans for future steps.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB284

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paper received ※ 19 May 2021 paper accepted ※ 18 June 2021 issue date ※ 13 August 2021

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MOPAB286

Towards a Data Science Enabled MeV Ultrafast Electron Diffraction System

network, experiment, real-time, laser

906

M.A. Fazio, S. Biedron, M. Martínez-Ramón, D.J. Monk, S.I. Sosa Guitron
UNM-ECE, Albuquerque, USA
M. Babzien, K.A. Brown, M.G. Fedurin, J.J. Li, M.A. Palmer, J. Tao
BNL, Upton, New York, USA
S. Biedron, T. Talbott
UNM-ME, Albuquerque, New Mexico, USA
J. Chen, A.J. Hurd, N.A. Moody, R. Prasankumar, C. Sweeney
LANL, Los Alamos, New Mexico, USA
D. Martin, M.E. Papka
ANL, Lemont, Illinois, USA

Funding: US DOE, SC, BES, MSE, award DE-SC0021365 and DOE NNSA award 89233218CNA000001 through DOE’s EPSCoR program in Office of BES with resources of DOE SC User Facilities BNL’s ATF and ALCF.
A MeV ultrafast electron diffraction (MUED) instrument is a unique characterization technique to study ultrafast processes in materials by a pump-probe technique. This relatively young technology can be advanced further into a turn-key instrument by using data science and artificial intelligence (AI) mechanisms in conjunctions with high-performance computing. This can facilitate automated operation, data acquisition and real time or near- real time processing. AI based system controls can provide real time feedback on the electron beam which is currently not possible due to the use of destructive diagnostics. Deep learning can be applied to the MUED diffraction patterns to recover valuable information on subtle lattice variations that can lead to a greater understanding of a wide range of material systems. A data science enabled MUED facility will also facilitate the application of this technique, expand its user base, and provide a fully automated state-of-the-art instrument. We will discuss the progress made on the MUED instrument in the Accelerator Test Facility of Brookhaven National Laboratory.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB286

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paper received ※ 20 May 2021 paper accepted ※ 09 June 2021 issue date ※ 24 August 2021

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MOPAB287

The Development of Single Pulse High Dynamic Range BPM Signal Detector Design at AWA

detector, pick-up, experiment, electronics

909

E.M. Siebert, S. Baturin
Northern Illinois University, DeKalb, Illinois, USA
D.S. Doran, G. Ha, W. Liu, P. Piot, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA

Funding: the US Department of Energy, Office of Science
Single pulse high dynamic range BPM signal detector has been on the most wanted list of Argonne Wakefield Accelerator (AWA) Test Facility for many years. Unique capabilities of AWA beamline require BPM instrumentation with an unprecedented dynamic range, thus cost effective solution could be challenging to design and prototype. Our most recent design, and the results of our quest for a solution, are shared in this paper.

Poster MOPAB287 [1.372 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB287

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 21 August 2021

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MOPAB289

Machine Learning Training for HOM reduction and Emittance Preservation in a TESLA-type Cryomodule at FAST

HOM, cavity, emittance, controls

916

J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz, A.L. Edelen, B.T. Jacobson, J.P. Sikora
SLAC, Menlo Park, California, USA
D.R. Edstrom, A.H. Lumpkin, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA

Low emittance electron beams are of high importance at facilities like the LCLS-II at SLAC. Emittance dilution effects due to off-axis beam transport for a TESLA-type cryomodule (CM) have been shown at the Fermilab Accelerator Science and Technology facility. The results showed the correlation between the electron beam-induced cavity high-order modes (HOMs) and submacropulse centroid slewing and oscillation downstream of the CM. Mitigation of emittance dilution can be achieved by reducing the HOM signals and the variances in the submacropulse beam positions downstream of the CM. Here we present a Machine Learning based optimization and model construction for HOM signal level reduction using Neural Networks and Gaussian Processes. To gather training data we performed experiments using single bunch and 50 bunch electron beams with charges up to 125 pC/b. We measured HOM signals of all cavities and beam position with a set of BPMs downstream of the CM. The beam trajectory was changed using V/H125 corrector set located upstream of the CM. The results presented here will inform the LCLS-II injector commissioning and will serve as a prototype for HOM reduction and emittance preservation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB289

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 24 August 2021

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MOPAB293

Electro-Optical Diagnostics at KARA and FLUTE - Results and Prospects

diagnostics, laser, storage-ring, experiment

927

G. Niehues, E. Bründermann, M. Caselle, S. Funkner, A.-S. Müller, M.J. Nasse, M.M. Patil, R. Ruprecht, M. Schuh, M. Weber, C. Widmann
KIT, Karlsruhe, Germany

Funding: S.F. was funded by BMBF contract No. 05K16VKA, C. W. by BMBF contract number 05K19VKD. G.N. and E.B. acknowledge support by the Helmholtz President’s strategic fund IVF "Plasma Accelerators".
Electro-optical (EO) methods are nowadays well-proven diagnostic tools, which are utilized to detect THz fields in countless experiments. The world’s first near-field EO sampling monitor at an electron storage ring was developed and installed at the KIT storage ring KARA (Karlsruhe Research Accelerator) and optimized to detect longitudinal bunch profiles. This experiment with other diagnostic techniques builds a distributed, synchronized sensor network to gain comprehensive data about the phase-space of electron bunches as well as the produced coherent synchrotron radiation (CSR). These measurements facilitate studies of physical conditions to provide, at the end, intense and stable CSR in the THz range. At KIT, we also operate FLUTE (Ferninfrarot Linac- und Test-Experiment), a new compact versatile linear accelerator as a test facility for novel techniques and diagnostics. There, EO diagnostics will be implemented to open up possibilities to evaluate and compare new techniques for longitudinal bunch diagnostics. In this contribution, we will give an overview of results achieved, the current status of the EO diagnostic setups at KARA and FLUTE and discuss future prospects.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB293

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paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 29 August 2021

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MOPAB301

A Concept for Reconstruction of the Capsulated Microchip Structure Using Its Interaction with High-Energy Ion Beams of the NICA Accelerator Complex

detector, radiation, simulation, electronics

949

A. Slivin, A.V. Butenko, G.A. Filatov, E. Syresin, A. Tuzikov, A. Zhemchugov
JINR, Dubna, Moscow Region, Russia

Within the framework of the NICA project an applied research station for irradiation by long-range ions (SODIT) is being constructed for testing radiation hardness of semiconductor micro- and nanoelectronics products in the energy range of 150-350 MeV/n. Calculations for the interaction of high-energy gold ions with the microchip and strip detector structures are performed using the GEANT4 simulation toolkit. A concept was developed for reconstruction of the capsulated microchip structure in terms of depth and in terms of cross-section using interaction with high-energy ions at the technical station for irradiation by long-range ions. The possibility of localizing the radiation-vulnerable area of the microchip is evaluated.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB301

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paper received ※ 19 May 2021 paper accepted ※ 20 May 2021 issue date ※ 11 August 2021

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MOPAB302

Characterization of the Full Transverse Phase Space of Electron Bunches at ARES

simulation, experiment, quadrupole, linac

952

S. Jaster-Merz, R.W. Aßmann, R. Brinkmann, F. Burkart, H. Dinter, W. Kuropka, F. Mayet, T. Vinatier
DESY, Hamburg, Germany
R.W. Aßmann
INFN/LNF, Frascati, Italy
S. Jaster-Merz
University of Hamburg, Hamburg, Germany

The ARES linear accelerator at the SINBAD facility (DESY) is dedicated to perform accelerator R&D studies with sub-fs short electron bunches to test novel acceleration techniques and diagnostics devices. Currently, the commissioning of the linac is ongoing and first experiments are being performed. For this, the knowledge of the full phase space of the particle beams is of high interest to, for example, optimize the accelerator performance and identify possible errors in the beam line. Tomographic methods can be used to gain insight into the full 4D transverse phase space and its correlations. Here, simulation results and first experimental preparations of a 4D transverse phase-space tomography of electron bunches at ARES are presented and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB302

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paper received ※ 17 May 2021 paper accepted ※ 16 June 2021 issue date ※ 21 August 2021

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MOPAB303

Design of the X-Ray Beam Size Monitor for the Advanced Photon Source Upgrade

emittance, photon, detector, storage-ring

956

K.P. Wootton, F.K. Anthony, K. Belcher, J.S. Budz, J. Carwardine, W.X. Cheng, S. Chitra, G. Decker, S.J. Izzo, S.H. Lee, J. Lenner, Z. Liu, P. McNamara, H.V. Nguyen, F.S. Rafael, C. Roehrig, J. Runchey, N. Sereno, G. Shen, J.B. Stevens, B.X. Yang
ANL, Lemont, Illinois, USA

Funding: This research used resources of the Advanced Photon Source, operated for the U.S. Department of Energy Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
A beam size monitor provides an intuitive display of the status of the beam profile and motion in an accelerator. In the present work, we outline the design of the X-ray electron beam size monitor for the Advanced Photon Source Upgrade. Components and anticipated performance characteristics of the beam size monitor are outlined.

Poster MOPAB303 [0.577 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB303

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paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 01 September 2021

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MOPAB310

Vertical Phase Space Measurement Progress at Canadian Light Source

emittance, lattice, synchrotron, experiment

963

Y. Yousefi Sigari, D. Bertwistle, M.J. Boland
CLS, Saskatoon, Saskatchewan, Canada
M.J. Boland
University of Saskatchewan, Saskatoon, Canada

A key feature of third-generation light sources is their small vertical opening angle, which is difficult to measure experimentally. To reconstruct the vertical phase space, one can scan the beam’s position using X-ray synchrotron radiation (XSR) and a pinhole camera. The XSR diagnostic beamline, operational in the wavelength region of 0.05 - 0.15 nm, in Canadian Light Source (CLS) is qualified to measure the beam position with X-ray radiation. Using the corrector magnets in CLS lattice made of 12 identical double-bend achromats (DBA) cells, vertical iterations can be executed parallel to the beam’s original orbit. The outcomes of this experiment are: 1) the vertical beam positions that are monitored by BPMs, and 2) the X-ray image of the beam that is projected through the pinhole. The bumps were simulated using Matlab Middle Layer (MML) for Accelerator control systems to get an insight of the source point’s position in the XSR’s bending magnet. The simulation shows the position of the source point depends on which corrector sets are chosen.

Poster MOPAB310 [0.328 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB310

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paper received ※ 19 May 2021 paper accepted ※ 28 July 2021 issue date ※ 11 August 2021

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MOPAB313

Argonaut - A Robotic System for Cryogenic Environments

detector, diagnostics, operation, cryogenics

966

W. Pellico, N.M. Curfman, M. Wong-Squires
Fermilab, Batavia, Illinois, USA

Funding: Department of Energy
Fermilab and the HEP community invest significant resources into liquid argon detectors. The largest and most expensive of these detectors will be located in the Deep Underground Neutrino Experiment (DUNE). However, recent experiences have shown that there are limited avenues of monitoring, intervention, and interaction in the internal liquid environment. This proposal shows a technological path that could provide a valuable tool to ensure or at least improve the management of these HEP detectors. The development of a robotic system named Argonaut will demonstrate several technologies including 1) demonstration of suitable mobility of a small robotic device at liquid argon temperatures, 2) demonstration of wireless communication, 3) demonstration of improved diagnostics capabilities - such as tunable optics with motion control, 4) demonstration of interconnectivity of a robotic system with hardware residing within the detector. This initial research will be a seed for extended development in cold robotics and associated technologies. This work will allow FNAL to contribute a significant technology capability to recent efforts to cryogenic detector operations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB313

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paper received ※ 19 May 2021 paper accepted ※ 21 May 2021 issue date ※ 11 August 2021

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MOPAB314

Surrogate Modeling for MUED with Neural Networks

experiment, gun, network, operation

970

D.J. Monk, S. Biedron, M.A. Fazio, M. Martínez-Ramón, S.I. Sosa Guitron
UNM-ECE, Albuquerque, USA
M. Babzien, K.A. Brown, M.A. Palmer, J. Tao
BNL, Upton, New York, USA
D. Martin, M.E. Papka
ANL, Lemont, Illinois, USA
T. Talbott
UNM-ME, Albuquerque, New Mexico, USA

Electron diffraction is among the most complex and influential inventions of the last century and contributes to research in many areas of physics and engineering. Not only does it aid in problems like materials and plasma research, electron diffraction systems like the MeV ultra-fast electron diffraction(MUED) instrument at the Brookhaven National Lab(BNL) also present opportunities to explore/implement surrogate modeling methods using artificial intelligence/machine learning/deep learning algorithms. Running the MUED system requires extended periods of uninterrupted runtime, skilled operators, and many varying parameters that depend on the desired output. These problems lend themselves to techniques based on neural networks(NNs), which are suited to modeling, system controls, and analysis of time-varying/multi-parameter systems. NNs can be deployed in model-based control areas and can be used simulate control designs, planned experiments, and to simulate employment of new components. Surrogate models based on NNs provide fast and accurate results, ideal for real-time control systems during continuous operation and may be used to identify irregular beam behavior as they develop.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB314

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paper received ※ 20 May 2021 paper accepted ※ 07 June 2021 issue date ※ 15 August 2021

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MOPAB316

Commissioning the New CERN Beam Instrumentation Following the Upgrade of the LHC Injector Chain

linac, MMI, diagnostics, instrumentation

976

F. Roncarolo, S. Bart Pedersen, J.M. Belleman, D. Belohrad, M. Bozzolan, C. Bracco, S. Di Carlo, J. Emery, A. Goldblatt, A. Guerrero, S. Levasseur, A. Navarro Fernandez, E. Renner, H.S. Sandberg, J.W. Storey, J. Tan, J. Tassan-Viol
CERN, Geneva, Switzerland
A. Navarro Fernandez
UPC, Barcelona, Spain
E. Renner
TU Vienna, Wien, Austria

The LHC injectors Upgrade (LIU) program has been fully implemented during the second long shutdown (LS2), which took place in 2019-20. In this context, new or upgraded beam instrumentation was developed to cope with H⁻ beam in LINAC4 and the new Proton Synchrotron Booster (PSB) injection systems which would provide high brightness proton beams in the rest of the injector complex. After a short overview of the newly installed diagnostics, the main focus of this paper will move to the instruments already commissioned with the beam. This will include LINAC4 diagnostics, the PSB H⁰/H⁻ monitor, the PSB Trajectory Measurement System, and the PS beam gas ionization monitor. In addition, particular emphasis will be given to the first operational experience with the new generation of fast wire scanners installed in all injector synchronous.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB316

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 20 August 2021

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MOPAB323

Commissioning of the LCLS-II Prototype HOM Detectors with Tesla-Type Cavities at Fast

cavity, HOM, cryomodule, detector

996

J.P. Sikora, J.A. Diaz Cruz, B.T. Jacobson
SLAC, Menlo Park, California, USA
J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
D.R. Edstrom, A.H. Lumpkin, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA

Funding: *Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. **Work supported by the U.S. Department of Energy, contract DE-AC02-76SF00515.
Experiments at the Fermilab Accelerator Science and Technology* (FAST) facility detected electron beam-induced high order mode (HOM) signals from Tesla superconducting cavities. This paper describes some of the signal detection hardware used in this experiment, as well as measurements of the HOM signal magnitude versus beam trajectory. These measurements were made both with a single bunch and with a train of 50 bunches at bunch charges from 400 pC/b down to 10 pC/b. The detection hardware is designed for use with the Tesla superconducting cavities of LCLS-II at SLAC** and is based on a prototype already in use at Fermilab. The HOM signal passes through a bandpass filter that is centered on several cavity dipole modes and a zero bias Schottky diode detects its magnitude. Direct comparisons were made between the FNAL chassis and the SLAC prototype for identical beam steering conditions. To support measurements with bunch charges as low as 10 pC, the SLAC detector has RF amplification between the bandpass filter and the diode detector. With this hardware, usable HOM signal measurements are obtained with a single bunch of 10 pC in cryomodule cavities as will be needed for LCLS-II.

Poster MOPAB323 [2.076 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB323

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paper received ※ 17 May 2021 paper accepted ※ 07 June 2021 issue date ※ 25 August 2021

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MOPAB324

High Voltage Design and Evaluation of Wien Filters for the CEBAF 200 keV Injector Upgrade

vacuum, high-voltage, GUI, simulation

1000

G.G. Palacios Serrano, P.A. Adderley, J.F. Benesch, D.B. Bullard, J.M. Grames, C. Hernandez-Garcia, A.S. Hofler, D. Machie, M. Poelker, M.L. Stutzman, R. Suleiman
JLab, Newport News, Virginia, USA
H. Baumgart, G.G. Palacios Serrano
ODU, Norfolk, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
High-energy nuclear physics experiments at the Jefferson Lab Continuous Electron Beam Accelerator Facility (CEBAF) require highly spin-polarization electron beams, produced from strained super-lattice GaAs photocathodes, activated to negative electron affinity in a photogun operating at 130 kV dc. A pair of Wien filter spin rotators in the injector defines the orientation of the electron beam polarization at the end station target. An upgrade of the CEBAF injector to better support the upcoming MOLLER experiment requires increasing the electron beam energy to 200 keV, to reduce unwanted helicity correlated intensity and position systematics and provide precise control of the polarization orientation. Our contribution describes design, fabrication and testing of the high voltage system to upgrade the Wien spin rotator to be compatible with the 200 keV beam. This required Solidworks modeling, CST and Opera electro- and magnetostatic simulations, upgrading HV vacuum feedthroughs, and assembly techniques for improving electrode alignment. The electric and magnetic fields required by the Wien condition and the successful HV characterization under vacuum conditions are also presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB324

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paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 18 August 2021

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MOPAB327

Beam Loss Diagnostics System for SKIF Synchrotron Light Source

simulation, storage-ring, diagnostics, synchrotron

1012

X.C. Ma
BINP, Novosibirsk, Russia
S.V. Ivanenko, E.A. Puryga
Budker Institute of Nuclear Physics, Novosibirsk, Russia
A.D. Khilchenko, Yu.I. Maltseva, O.I. Meshkov
BINP SB RAS, Novosibirsk, Russia
Yu.I. Maltseva, O.I. Meshkov
NSU, Novosibirsk, Russia

The Siberian ring photon source (SKIF) is a new generation synchrotron light source designed and built by the Budker Institute of Nuclear Physics. The beam loss diagnostics system is a tool for monitoring beam loss information. It is widely used in modern large accelerators to provide a basis for diagnosing and locating machine faults, optimizing and debugging working beam parameters, and improving beam lifetime. Two types of beam loss monitor (BLM) will be applied on SKIF: fiber-based Cherenkov beam loss monitor (CBLM) and scintillator-based BLM (SBLM). Multi-mode silica fibers CBLM will be installed on linear accelerator and transfer lines. 128 SBLMs will be placed around the storage ring, dynamic ranges and sophisticated electronic equipment are employed to cover different SKIF operating modes. This article represents the details of design of beam loss diagnostics of SKIF, introduces the simulation and experimental studies of CBLM and SBLM.

Poster MOPAB327 [4.893 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB327

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paper received ※ 19 May 2021 paper accepted ※ 26 May 2021 issue date ※ 26 August 2021

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MOPAB328

Beam Instrumentation for Linear Accelerator of SKIF Synchrotron Light Source

diagnostics, photon, radiation, simulation

1016

X.C. Ma
BINP, Novosibirsk, Russia
M.V. Arsentyeva, E.A. Bekhtenev, V.M. Borin, G.V. Karpov, Yu.I. Maltseva, O.I. Meshkov, D.A. Nikiforov, O.A. Pavlov, V.G. Tcheskidov, V. Volkov
BINP SB RAS, Novosibirsk, Russia
M.V. Arsentyeva, E.A. Bekhtenev, V.M. Borin, Yu.I. Maltseva, O.I. Meshkov, D.A. Nikiforov
NSU, Novosibirsk, Russia
V.M. Borin
NSTU, Novosibirsk, Russia

A new synchrotron light source SKIF of the 4th generation is under construction at BINP SB RAS (Novosibirsk, Russia). The linear accelerator is SKIF’s injector to provide 200 MeV electron beam. The set of diagnostics will be applied for tuning of the linear accelerator and measurements of beam parameters from electron RF gun to output of the accelerator. It includes 8 fluorescent screens for the beam transverse dimensions measurement, 2 Cherenkov probes for the beam duration measurement, magnetic spectrometer with range from 0.6 to 200 MeV, and some beam charge and current measurement devices, as Faraday cup, FCT, BPM along linear accelerator. Numerical simulations of diagnostics elements and results of beam dynamics simulations are introduced in paper. Brief description of the design and parameters of each diagnostics system is presented. Possible scenarios of linear accelerator tuning are also discussed.

Poster MOPAB328 [2.324 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB328

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paper received ※ 19 May 2021 paper accepted ※ 21 May 2021 issue date ※ 20 August 2021

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MOPAB339

Design Of An X-band 3MeV Standing-wave Accelerating Structure with Nose-cone Structure Made From Two Halves

coupling, impedance, cavity, bunching

1051

F. Liu, H.B. Chen, J. Shi, C.-X. Tang, H. Zha
TUB, Beijing, People’s Republic of China

This work presents an X-band 3MeV standing-wave accelerating structure with nose cones made from two halves. Milling two longitudinally split halves is one economic method to manufacture accelerating structure for decrease of welding, with increasing the difficulty in machining. This linear accelerator includes 4 buncher cavities and 4 accelerating cavities, and nose cone is applied to achieve high shunt impedance. A technical prototype is under fabrication to bring two milled halves manufacture way into practical application.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB339

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paper received ※ 19 May 2021 paper accepted ※ 26 May 2021 issue date ※ 17 August 2021

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MOPAB346

Broadband Frequency Electromagnetic Characterisation of Coating Materials

GUI, experiment, vacuum, site

1076

A. Passarelli, C. Koral, M.R. Masullo
INFN-Napoli, Napoli, Italy
A. Andreone
Naples University Federico II, Napoli, Italy
M. De Stefano
University of Naples, Naples, Italy
V.G. Vaccaro
Naples University Federico II and INFN, Napoli, Italy

In the new generation of particle accelerators and storage rings, collective effects have to be carefully analyzed. In particular, the finite conductivity of the beam pipe walls is a major source of impedance and instabilities. A reliable electromagnetic (EM) characterisation of different coating materials is required up to hundreds of GHz due to very short bunches. We propose two different measurement techniques for an extended frequency characterization: (i) a THz time domain setup based on the signal transmission response of a tailored waveguide to infer the coating EM properties from 100 to 300 GHz or even further*.**. This technique has been tested both on NEG and amorphous Carbon films. (ii) a resonant method, based on dielectric cavities, to evaluate the surface resistance Rs of thin conducting samples at low (GHz) frequencies***. Due to its high sensitivity, Rs values can be obtained for very thin (nanometric) coatings or for copper samples with a laser treated surface, since they have an expected conductivity very close to bulk copper.
*A. Passarelli et al., Phys. Rev. Accel. Beams, v.21, p.103101, 2018
**A. Passarelli et al., Cond. Matter, v.5, p.9, 2020
***A. Andreone et al., Applied Physics Letters, v.91, n.7, p.072512, 2007

Poster MOPAB346 [2.613 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB346

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 22 August 2021

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MOPAB358

Design and Measurement of the 1.4 GHz Cavity for LEReC Linac

cavity, resonance, GUI, HOM

1113

B.P. Xiao, J.C. Brutus, J.M. Fite, K. Hamdi, D. Holmes, K. Mernick, K.S. Smith, J.E. Tuozzolo, T. Xin, A. Zaltsman
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The Low Energy RHIC electron Cooler (LEReC) is the first electron cooler based on rf acceleration of electron bunches. To further improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, a normal conducting RF cavity at 1.4 GHz was designed and fabricated for the LINAC that will provide longer electron bunches for the LEReC. It is a single-cell cavity with an effective cavity length shorter than half of the 1.4 GHz wavelength. This cavity was fabricated and tested on-site at BNL to verify RF properties, i.e. the resonance frequency, FPC coupling strength, tuner system performance, and high power tests. In this paper, we report the RF test results for this cavity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB358

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paper received ※ 17 May 2021 paper accepted ※ 25 June 2021 issue date ※ 10 August 2021

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MOPAB359

Operational Experience and Redesign of the Tuner without Spring Fingers for the LEReC Warm Cavity

cavity, operation, vacuum, SRF

1116

B.P. Xiao, J.M. Brennan, J.C. Brutus, K. Mernick, S. Polizzo, S.K. Seberg, F. Severino, K.S. Smith, A. Zaltsman
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
A folded coaxial tuner without spring fingers was designed for the Low Energy RHIC electron Cooler (LEReC) 2.1 GHz warm cavity. During RHIC run 2019, this tuner was found to cause cavity trips via different failure modes. After analyzing these failure modes, a new straight coaxial tuner without spring fingers was proposed and was installed. We show the operational experience of the new tuner in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB359

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paper received ※ 17 May 2021 paper accepted ※ 25 June 2021 issue date ※ 12 August 2021

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MOPAB361

Threshold in Filling Failure of RF Cavity Caused by Beam Loading in Multipactor

multipactoring, cavity, simulation, experiment

1122

J. Pang
USTC/NSRL, Hefei, Anhui, People’s Republic of China
Y. Dong
Institute of Applied Physics and Computational Mathematics, People’s Republic of China
Y. Du
Institute of Fluid Physics,, China Academy of Engineering Physics, Mianyang, People’s Republic of China

Funding: NSFC
A pulsed RF cavity would be heavily detuned caused by beam loading of multipactor current in the RF filling process. Multipactor zone would be expended by several times than that in static states with assumptions of fixed voltage and no beam loading. The dynamic of multipactor in the RF filling process was simulated by coupling with parameters of external circuit with the developed simulation code, and test in experiments with a parallel-plate resonator. Threshold of RF voltage, which means the lower boundary of peak voltage of multipactor zone, had been quantified with different cavity parameters. When we increased the gap length, the measured threshold became larger due to the ionization in background gas. Then the secondary emission factor would be increased in simulation for consistence with the experiment results. Additionally, some multipactor phenomenon could not be predicted precisely because the simulation code did not take account of ionization. The hysteresis of phase and energy of ionization electrons would be a new driving factor for the growth of multipactor in certain conditions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB361

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paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 15 August 2021

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MOPAB365

Construction and First Test Results of the Barrier and Harmonic RF Systems for the NICA Collider

cavity, collider, vacuum, injection

1136

A.G. Tribendis, Y.A. Biryuchevsky, K.N. Chernov, A.N. Dranitchnikov, E. Kenzhebulatov, A.A. Kondakov, A.A. Krasnov, Ya.G. Kruchkov, S.A. Krutikhin, G.Y. Kurkin, A.M. Malyshev, A.Yu. Martynovsky, N.V. Mityanina, S.V. Motygin, A.A. Murasev, V.N. Osipov, V.M. Petrov, E. Pyata, E. Rotov, V.V. Tarnetsky, I.A. Zapryagaev, A.A. Zhukov
BINP SB RAS, Novosibirsk, Russia
O.I. Brovko, A.M. Malyshev, I.N. Meshkov, E. Syresin
JINR, Dubna, Moscow Region, Russia
I.N. Meshkov
Saint Petersburg State University, Saint Petersburg, Russia
E. Rotov
NSU, Novosibirsk, Russia
A.G. Tribendis
NSTU, Novosibirsk, Russia
A.V. Zinkevich
Triada-TV, Novosibirsk, Russia

This paper reports on the design features and construction progress of the three RF systems for the NICA collider being built at JINR, Dubna. Each of the two collider rings has three RF systems named RF1 to 3. RF1 is a barrier bucket system used for particles capturing and accumulation during injection, RF2 and 3 are resonant systems operating at 22nd and 66th harmonics of the revolution frequency and used for the 22 bunches formation. The RF systems are designed and produced by Budker INP. Solid state RF power amplifiers developed by the Triada-TV company, Novosibirsk, are used for driving the RF2 and three cavities. Two RF1 stations were already delivered to JINR, the prototypes of the RF2 and 3 stations were built and successfully tested at BINP. Series production of all eight RF2 and sixteen RF3 stations is in progress. The design modifications and test results are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB365

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paper received ※ 18 May 2021 paper accepted ※ 24 May 2021 issue date ※ 19 August 2021

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MOPAB385

An Overview of RF Systems for the EIC

cavity, SRF, HOM, luminosity

1179

R.A. Rimmer, J.P. Preble
JLab, Newport News, Virginia, USA
K.S. Smith, A. Zaltsman
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under DOE Contract No. DE-SC0012704, by Jefferson Science Associates under contract DE-SC0002769, and by SLAC under Contract No. DE-AC02-76SF00515.
The Electron Ion Collider (EIC) to be constructed at Brookhaven National Laboratory in the USA will be a complex system of accelerators providing high luminosity, high polarization, variable center of mass energy collisions between electrons and protons or ions. To achieve this a variety of RF systems are required. They must provide for capture, formation and storage of Ampere-class beams in the electron and hadron storage rings (ESR and HSR), fast acceleration of high-charge polarized electron bunches in the rapid cycling synchrotron (RCS), provision of cold high current electron bunches in the high-energy cooler ERL and precise high-gradient crabbing of electrons and hadrons either side of the interaction point. The challenges include strong HOM damping in the storage ring cavities and cooler ERL, very high fundamental mode power in the ESR and cooler injector, extremely stable low-noise operation of the crab cavities, mitigation of transient beam loading from gaps, and operating over a wide range of energies and beam currents. We describe the high-level system parameters and principal design choices made and progress on the R&D plan to develop these state of the art systems.

Poster MOPAB385 [1.268 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB385

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paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 22 August 2021

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MOPAB393

Design of an RF-Dipole Crabbing Cavity System for the Electron-Ion Collider

cavity, HOM, cryomodule, impedance

1200

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
J. Henry, F. Marhauser, H. Park, R.A. Rimmer
JLab, Newport News, Virginia, USA

The Electron-Ion Collider requires several crabbing systems to facilitate head-on collisions between electron and proton beams in increasing the luminosity at the interaction point. One of the critical rf systems is the 197 MHz crabbing system that will be used in crabbing the proton beam. Many factors such as the low operating frequency, large transverse voltage requirement, tight longitudinal and transverse impedance thresholds, and limited beam line space makes the crabbing cavity design challenging. The rf-dipole cavity design is considered as one of the crabbing cavity options for the 197 MHz crabbing system. The cavity is designed including the HOM couplers, FPC and other ancillaries. This paper presents the detailed electromagnetic design, mechanical analysis, and conceptual cryomodule design of the crabbing system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB393

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paper received ※ 26 May 2021 paper accepted ※ 02 June 2021 issue date ※ 11 August 2021

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MOPAB405

Study of Targets to Produce Molybdenum-99 Using 30 MeV Electron Linear Accelerator

target, photon, radiation, linac

1222

T.S. Dixit, A.P. Deshpande, R. Krishnan, A. Shaikh
SAMEER, Mumbai, India

Funding: Ministry of Electronics and Information Technology, Government of India (MeitY)
Two approaches to produce 99Mo are studied using GEANT4 are reported in this paper. First, in converter target approach, bremsstrahlung photons are generated in a high Z target. The emitted photons then hit 100Mo secondary target, producing 99Mo through (gamma, n) reaction. Second, in direct target approach, high energy electron beam hits 100Mo target, where both (e, gamma) and (gamma, n) reactions take place simultaneously. A 30 MeV, 5-10 kW beam power electron linac is under development at SAMEER. The acceleration gradient required to achieve 30 MeV energy will be provided by two linacs operated in series configuration and the high average beam power will be achieved by running the system at high duty operation. Main aim of this study is to optimize experimental parameters to maximize specific activity of 99Mo. Since, 100Mo is very expensive material therefore judicious use of the material is very important. Hence, optimization of electron beam energy and target dimensions are studied in detail in both the approaches. It is found that the direct target approach gives higher specific activity compared to the converter target approach.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB405

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paper received ※ 19 May 2021 paper accepted ※ 06 June 2021 issue date ※ 26 August 2021

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MOPAB409

FLUKA Simulations of ²²⁵Ac Production Using Electron Accelerators: Validation Through Comparison with Published Experiments

experiment, target, radiation, photon

1226

T.V. Szabo, I.C. Moraes
CNPEM, Campinas, SP, Brazil
F.A. Bacchim Neto
LNLS, Campinas, Brazil
P.V. Guillaumon
USP/LAL, Sao Paulo, Brazil
H.B. de Oliveira
IPEN, São Paulo, Brazil

Targeted Alpha Therapy (TAT) is an active area of study worldwide. This technique has shown a potential in nuclear medicine to treat metastatic disease by alpha particles that deposit energy in small regions nearby cancer cells. Ac-225 is an important alpha-emitting that can be used for cancer TAT. This radioisotope shows good potential for medical applications, therefore is important to study ways of increase its production and availability. One possible path for the Ac-225 product is to radiate a radium target (Ra-226) on a linear electron accelerator (LINAC). Isotope production studies could be implemented using computational tools. In this work, Monte Carlo simulations with FLUKA code were performed and compared to experimental results *. We studied Ac-225 production by photonuclear reactions using a 24 MeV electron beam LINAC hitting a tungsten electron-photon converter. Different energies and geometries were also simulated to obtain optimal production conditions. The specific activity values obtained with simulations had a good agreement with published experimental results.
* MASLOV, O., et. al. Preparation of 225Ac by 226Ra(g, n) photonuclear reaction on an mt25 microtron. Radiochemistry

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB409

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 19 August 2021

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MOPAB410

Preliminary Studies of a Compact VHEE Linear Accelerator System for FLASH Radiotherapy

linac, radiation, operation, impedance

1229

L. Giuliano, F. Bosco, M. Carillo, D. De Arcangelis, L. Faillace, L. Ficcadenti, M. Migliorati, A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy
D. Alesini, M. Behtouei, B. Spataro
INFN/LNF, Frascati, Italy
G. Cuttone, G. Torrisi
INFN/LNS, Catania, Italy
V. Favaudon, S. Heinrich, A. Patriarca
Institut Curie - Centre de Protonthérapie d’Orsay, Orsay, France

Funding: The work is supported by La Sapienza University, research grant "grandi progetti di ricerca 2020".
The Flash Radio Therapy is a revolutionary new technique in the cancer cure: it spares healthy tissue from the damage of the ionizing radiation maintaining the tumor control as efficient as in conventional radiotherapy. To allow the implementation of the FLASH Therapy concept into actual clinical use, it is necessary to have a linear accelerator able to deliver the very high dose and very high dose rate (>10⁶ Gy/s) in a very short irradiation time (beam on time < 100ms). Low energy S-band Linacs (up to 7 MeV) are being used in Radiobiology and pre-clinic applications but in order to treat deep tumors, the energy of the electrons should achieve the range of 60-100 MeV. In this paper, we address the main issues in the design of a compact C band (5.712 GHz) electron linac-VHEE for FLASH Radio Therapy. We present preliminary studies on C-band structures at La Sapienza and at INFN-LNS, aiming to reach a high accelerating gradient and high current necessary to deliver a dose >1 Gy/pulse, with very short electron pulse.

Poster MOPAB410 [0.650 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB410

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 26 August 2021

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MOPAB412

Accelerator Production of Mo-99 Using Mo-100

target, radiation, operation, diagnostics

1237

J.L. McCarter, M.J. Brennan, S.M. Burns, J.T. Harvey, S.W. Kelley, T.A. Montenegro, Q. Schiller
NorthStar Medical Technologies, LLC, Beloit, USA

Funding: DE-NA0001878
Tc-99m is an essential radionuclide for nearly 40,000 diagnostic nuclear medicine tests in the U.S. each day. Its daily production depends on Mo-99, which must be replenished weekly due to Mo-99’s 2.75 day half-life. Mo-99, in the past, was supplied from uranium fission production, depending on overseas nuclear reactors that average 50 years old. Their age in combination with shipment uncertainties make the availability of Mo-99 fragile and subject to severe shortages. The U.S. now has one domestic, FDA-approved supplier that produces Mo-99, NorthStar Medical Radioisotopes. Currently, NorthStar produces Mo-99 via the irradiation of Mo-98 in a nuclear reactor. In the future, NorthStar will also irradiate Mo-100 with accelerator created x-rays to produce Mo-99. This process will use 2 distinct, 40 MeV, 125 kW average electron accelerators, Rhodotrons produced by IBA. Accelerator produced Mo-99 has several advantages over that produced by reactors, including a dual supply and an ability to adjust irradiation timing to meet radiopharmacy demands, such as Sunday delivery. NorthStar is currently installing and commissioning this accelerator based system, entering production in late-2022.

Poster MOPAB412 [2.150 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB412

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paper received ※ 24 May 2021 paper accepted ※ 07 June 2021 issue date ※ 14 August 2021

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TUXA03

Progress in Mastering Electron Clouds at the Large Hadron Collider

simulation, operation, luminosity, experiment

1273

G. Iadarola, B. Bradu, L. Mether, K. Paraschou, V. Petit, G. Rumolo, L. Sabato, G. Skripka, M. Taborelli, L.J. Tavian
CERN, Geneva, Switzerland
K. Paraschou
AUTH, Thessaloniki, Greece

During the second operational run of the Large Hadron Collider (LHC) a bunch spacing of 25 ns was used for the first time for luminosity production. With such a spacing, electron cloud effects are much more severe than with the 50-ns spacing, which had been used in the previous run. Beam-induced conditioning of the beam chambers mitigated the e-cloud formation to an extent that allowed an effective exploitation of 25 ns beams. Nevertheless, even after years of conditioning, e-cloud effects remained very visible, affecting beam stability and beam quality, and generating strong heat loads on the beam screens of the superconducting magnets with puzzling features. In preparation for the High Luminosity LHC upgrade, remarkable progress has been made in the modeling of the e-cloud formation and of its influence on beam stability, slow losses and emittance blow up, as well as in the understanding of the underlying behavior of the beam-chamber surface. In this contribution, we describe the main experimental observations from beam operation, the outcome of laboratory analysis conducted on beam screens extracted after the run, and the main advancements in the modeling of these phenomena.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXA03

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paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 21 August 2021

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TUXA04

Coherent Excitations and Circular Attractors in Cooled Ion Bunches

collider, operation, experiment, proton

1279

S. Seletskiy, A.V. Fedotov, D. Kayran
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy
In electron coolers, under certain conditions, a mismatch in either gamma-factors or trajectory angles between an electron and an ion beam can cause the formation of a circular attractor in the ion beam phase space. This leads to coherent excitations of the ions with a small synchrotron or betatron amplitude and results in unusual beam dynamics, including bifurcations. In this paper, we consider the effect of coherent excitations and discuss its implications both for Low Energy RHIC Electron Cooler (LEReC) and for high energy electron coolers proposed for the Electron-Ion Collider (EIC).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXA04

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paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 11 August 2021

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TUXA07

Beam Dynamics Study in a Dual Energy Storage Ring for Ion Beam Cooling*

storage-ring, cavity, focusing, emittance

1290

B. Dhital, G.A. Krafft
ODU, Norfolk, Virginia, USA
Y.S. Derbenev, D. Douglas, A. Hutton, G.A. Krafft, F. Lin, V.S. Morozov, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: * Work supported by the U.S. Department of Energy, Office of Science, and Office of Nuclear Physics under Contracts DE-AC05-06OR23177 and DE-AC02-06CH11357. / Jefferson Lab EIC Fellowship2020.
A dual energy storage ring designed for beam cooling consists of two closed rings with significantly different energies: the cooling and damping rings. These two rings are connected by an energy recovering superconducting RF structure that provides the necessary energy difference. In our design, the RF acceleration has a main linac and harmonic cavities both running at crest that at first accelerates the beam from low energy E_L to high energy E_H and then decelerates the beam from E_H to E_L in the next pass. The purpose of the harmonic cavities is to extend the bunch length in a dual energy storage ring as such a longer bunch length may be very useful in a cooling application. Besides these cavities, a bunching cavity running on zero-crossing phase is used outside of the common beamline to provide the necessary longitudinal focusing for the system. In this paper, we present a preliminary lattice design along with the fundamental beam dynamics study in such a dual energy storage ring.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXA07

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 25 August 2021

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TUXB01

A 3 MeV All Optical Terahertz-Driven Electron Source at Tsinghua University

acceleration, laser, gun, GUI

1294

H. Xu, Y.-C. Du, W.-H. Huang, R.K. Li, C.-X. Tang, L.X. Yan
TUB, Beijing, People’s Republic of China

Funding: Science Challenge Project No.TZ2018005
Efficient acceleration and manipulation of high-brightness electron beams using terahertz waves in a compact setup has been recently a hot research topic in acceleration community. Previous works have achieved multi-MV/m acceleration gradient and dozens of keV energy gain while leaving room for further improvements in the high-energy regime. Here, we experimentally demonstrate whole-bunch acceleration and cascaded terahertz-driven acceleration of a relativistic beam with a record energy gain of 204 keV. A terahertz-driven all-optical electron source is now under development, which hold great potential for terahertz-driven ultrafast electron diffraction and related scientific discoveries.
* Xu, H., Yan, L., Du, Y. et al. Cascaded high-gradient terahertz-driven acceleration of relativistic electron beams. Nat. Photonics (2021). https://doi.org/10.1038/s41566-021-00779-x

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXB01

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paper received ※ 19 May 2021 paper accepted ※ 01 June 2021 issue date ※ 28 August 2021

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TUXB04

Fabrication and Tuning of a THz-Driven Electron Gun

gun, cavity, GUI, resonance

1297

S.M. Lewis, A.A. Haase, J.W. Merrick, E.A. Nanni, M.A.K. Othman, S.G. Tantawi
SLAC, Menlo Park, California, USA
S.M. Lewis
Fermilab, Batavia, Illinois, USA

Funding: This work was supported by the Department of Energy Contract No. DE-AC02-76SF00515 (SLAC) and by NSF Grant No. PHY-1734015.
We have developed a THz-driven field emission electron gun and beam characterization assembly. The two cell standing-wave gun operates in the pi mode at 110.08 GHz. It is designed to produce 360 keV electrons with 500 kW of input power supplied by a 110 GHz gyrotron. Multiple gun structures were electroformed in copper using a high precision diamond-turned mandrel. The field emission cathode is a rounded copper tip located in the first cell. The cavity resonances were mechanically tuned using azimuthal compression. This work will discuss details of the fabrication and tuning and present the results of low power measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXB04

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paper received ※ 18 May 2021 paper accepted ※ 22 June 2021 issue date ※ 28 August 2021

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TUXC06

Visualizing Lattice Dynamic Behavior by Acquiring a Single Time-Resolved MeV

lattice, laser, detector, experiment

1311

X. Yang, T.V. Shaftan, V.V. Smaluk, J. Tao, L. Wu, Y. Zhu
BNL, Upton, New York, USA
W. Wan
ShanghaiTech University, Shanghai, People’s Republic of China

We explore the possibility of visualizing the lattice dynamic behavior by acquiring a single time-resolved MeV UED image. Conventionally, multiple UED shots with varying time delays are needed to map out the entire dynamic process. The measurement precision is limited by the timing jitter between the pulses of laser pump and UED probe. We show that, by converting the longitudinal time of an electron bunch to the transverse position of a Bragg peak on the detector, one can obtain the full lattice dynamic process in a single electron pulse. We propose a novel design of a time-resolved UED with the capability of capturing a wide range of dynamic features in a single diffraction image. The work presented here is not only an extension of the ultrashort-pulse pump/long-pulse probe scheme being used in transient spectroscopy studies for decades but also advances the capabilities of MeV UED for future applications with tunable electron probe profile and detecting time range with femtosecond resolution. Furthermore, we present numerical simulations illustrating the capability of acquiring a single time-resolved diffraction image based on the case-by-case studies of lattice dynamic behavior.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXC06

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paper received ※ 14 May 2021 paper accepted ※ 28 July 2021 issue date ※ 30 August 2021

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TUXC07

Modified Halbach Magnets for Emerging Accelerator Applications

permanent-magnet, quadrupole, dipole, collider

1315

S.J. Brooks
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The original circular Halbach magnet design creates a strong pure multipole field from permanent magnet pieces without intervening iron. This design has been extended recently at the CBETA 4-turn ERL, whose return loop includes combined-function (dipole+quadrupole) Halbach-derived magnets, plus a modular system of tuning shims to improve all 216 magnets’ relative field accuracy to better than 10^-3. This paper describes further modifications of the Halbach design enable a larger range of accelerator applications in the future: (1) open-midplane designs to allow synchrotron radiation in light sources and other high-energy electron rings, ERLs or RLAs to escape. (2) Quadrupole magnets with an oval aperture allow larger gradients than a circular aperture, provided the beam is more extended in one axis than the other, as usual for a quadrupole in a focussing system. These can be used in compact hadron therapy gantries. (3) New collider complexes often require multiple rings for acceleration or top-up, accumulation, collision and cooling. Multi-aperture permanent magnets are possible to cheaply and compactly build ring systems with several stable orbits separated by a few cm.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXC07

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paper received ※ 14 May 2021 paper accepted ※ 08 July 2021 issue date ※ 29 August 2021

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TUPAB015

Beam Loading Compensation of APS Cavity with Off-Crest Acceleration in ILC e-Driven Positron Source

positron, beam-loading, linac, target

1368

M. Kuriki, S. Konno, H. Nagoshi
HU/AdSM, Higashi-Hiroshima, Japan
T. Omori, J. Urakawa, K. Yokoya
KEK, Ibaraki, Japan
T. Takahashi
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan

In E-Driven positron source of ILC, the generated positron is captured by RF accelerator by APS cavity. The positron is initially placed at the deceleration phase and gradually slipped down to acceleration phase. Because the beam-loading is expected to be more than 1A with a multi-bunch format, the compensation is essential to obtain uniform intensity over the pulse. A conventional method for the compensation is controlling the timing, but it doesn’t work in off-crest case. In this manuscript, we discuss the compensation with the phase and amplitude modulation on the input RF.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB015

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paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 02 September 2021

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TUPAB020

A Sub-Micron Resolution, Bunch-by-Bunch Beam Trajectory Feedback System and Its Application to Reducing Wakefield Effects in Single-Pass Beamlines

feedback, wakefield, cavity, kicker

1382

D.R. Bett, P. Burrows, C. Perry, R.L. Ramjiawan
JAI, Oxford, United Kingdom
D.R. Bett
CERN, Geneva, Switzerland
K. Kubo, T. Okugi, N. Terunuma
KEK, Ibaraki, Japan

A high-precision intra-bunch-train beam orbit feedback correction system has been developed and tested at the KEK Accelerator Test Facility, ATF2. The system uses the vertical position of the bunch measured at two beam position monitors to calculate a pair of kicks which are applied to the next bunch using two upstream kickers, thereby correcting both the vertical position and trajectory angle. Using trains of two electron bunches separated in time by 187.6ns, the system was optimised so as to stabilize the beam offset at the feedback BPMs to better than 350nm, yielding a local trajectory angle correction to within 250nrad. The quality of the correction was verified using three downstream witness BPMs and the results were found to be in agreement with the predictions of a linear lattice model used to propagate the beam trajectory from the feedback region. This same model predicts a corrected be am jitter of c.1nm at the focal point of the accelerator. Measurements with a beam size monitor at this location demonstrate that reducing the trajectory jitter of the beam by a factor of 4 also reduces the increase in the measured beam size as a function of beam charge by a factor of ~1.6.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB020

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paper received ※ 13 May 2021 paper accepted ※ 01 July 2021 issue date ※ 22 August 2021

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TUPAB027

Review of Accelerator Limitations and Routes to Ultimate Beams

collider, acceleration, luminosity, photon

1397

F. Zimmermann
CERN, Geneva, Switzerland
R.W. Aßmann
DESY, Hamburg, Germany
M. Bai, G. Franchetti
GSI, Darmstadt, Germany

Funding: This work was supported in part by the European Commission under the HORIZON 2020 project I.FAST, no. 101004730.
Various physical and technology-dependent limits are encountered for key performance parameters of accelerators such as high-gradient acceleration, high-field bending, beam size, beam brightness, beam intensity and luminosity. This paper will review these limits and the associated challenges. Possible figures-of-merit and pathways to ultimate colliders will also be explored.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB027

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paper received ※ 16 May 2021 paper accepted ※ 02 August 2021 issue date ※ 29 August 2021

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TUPAB028

Permanent Magnets Future Electron Ion Colliders at RHIC and LHeC

linac, permanent-magnet, focusing, collider

1401

D. Trbojevic, S.J. Brooks, V. Litvinenko, T. Roser
BNL, Upton, New York, USA
G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
We present a new ’green energy’ approach to the Energy Recovery Linac (ERL) and Recirculating Linac Accelerators (RLA) for the future Electron Ion Colliders (EIC) using single beam line made of very strong focusing combined function permanent magnets and the Fixed Field Alternating Linear Gradient (FFA-LG) principle. We are basing our design on recent very successful commissioning results of the Cornell University and Brookhaven National Laboratory ERL Test Accelerator.

Poster TUPAB028 [2.720 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB028

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paper received ※ 17 May 2021 paper accepted ※ 27 May 2021 issue date ※ 16 August 2021

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TUPAB033

Photocathode Stress Test Bench at INFN LASA

cathode, laser, gun, high-voltage

1413

D. Sertore, D. Giove, G. Guerini Rocco, L. Monaco
INFN/LASA, Segrate (MI), Italy
A. Bacci, F. Canella, S. Cialdi, I. Drebot, D. Giannotti, L. Serafini
INFN-Milano, Milano, Italy
D. Cipriani, E. Suerra
Università degli Studi di Milano, Milano, Italy
G. Galzerano
POLIMI, Milano, Italy

In the framework of the preparatory activities to the BriXSino project, a test bench for testing Cs₂Te photocathode at 100 MHz laser repetition rate has been installed at INFN LASA. This high repetition operation mode is foreseen to be the base operation mode of BriXSino and a qualification of the Cs₂Te photocathodes is a key component. While we are not at full specification due to the limited HV of the present DC gun, we discuss the status of the test bench and the initial results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB033

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paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 16 August 2021

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TUPAB034

Development of Multi-Alkali Antimonides Photocathodes for High-Brightness RF Photoinjectors

cathode, emittance, site, laser

1416

S.K. Mohanty, M. Krasilnikov, A. Oppelt, H.J. Qian, F. Stephan
DESY Zeuthen, Zeuthen, Germany
G. Guerini Rocco, C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
P. Michelato, L. Monaco, D. Sertore
INFN/LASA, Segrate (MI), Italy

Multi-alkali antimonide-based photocathodes are suitable candidate for the electron sources of next-generation high brightness RF photoinjectors due to their excellent photoemissive properties especially, like low thermal emittances and high sensitivity to visible light. The former stands out, paving the way towards CW operations. Based on the previous successful development of Cesium Telluride photocathodes, we are now channelling our efforts toward an R&D activity focused on KCsSb and NaKSb(Cs) photocathodes. Parallel to that R&D activity, we have installed a new dedicated photocathode production system at the INFN-LASA to start the preparation of these photocathodes for their test in the PITZ photoinjector at DESY in Zeuthen. In this paper, detailed experimental results obtained from the KCsSb, along with a preliminary result from the NaKSb(Cs) photocathode material as well as the status of the overall project are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB034

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 02 September 2021

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TUPAB036

The Accelerator Design Progress for EIC Strong Hadron Cooling

hadron, proton, linac, emittance

1424

E. Wang, S. Peggs, V. Ptitsyn, F.J. Willeke, W. Xu
BNL, Upton, New York, USA
S.V. Benson
JLab, Newport News, Virginia, USA
D. Douglas
Douglas Consulting, York, Virginia, USA
C.M. Gulliford, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
C.E. Mayes
Xelera Research LLC, Ithaca, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy,
The Electron-Ion Collider will achieve a luminosity of 10³⁴ cm^-2 s⁻¹ by incorporating strong hadron cooling to counteract hadron Intra-Beam Scattering, using a coherent electron cooling scheme. An accelerator will deliver the beams with key parameters, such as 1 nC bunch charge, and 1e-4 energy spread. The paper presents the design and beam dynamics simulation results. Methods to minimize beam noise, the challenges of the accelerator design, and the R&D topics being pursued are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB036

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paper received ※ 16 May 2021 paper accepted ※ 11 June 2021 issue date ※ 26 August 2021

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TUPAB037

The Design of a High Charge Polarized Preinjector for the Electron-Ion Collider

cathode, gun, cavity, linac

1428

E. Wang, W. Liu, V.H. Ranjbar, J. Skaritka, N. Tsoupas
BNL, Upton, New York, USA
J.M. Grames, J. Guo
JLab, Newport News, Virginia, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy
The design of the electron pre-injector of the Electron-Ion Collider (EIC) project to generate 4 x 7 nC bunch has been advancing to meet the requirements for injection into the Rapid Cycling Synchrotron (RCS). The major challenges are high charge transport and achieving small energy spread from 3 GHz traveling-wave plate(TWP). The designed preinjector includes the polarized electron source, bunching section, TWP Linac, zigzag phase space manipulation and spin rotator. In this report, we will discuss the RF frequency selection and the way to reduce energy spread down to 0.2% by longitudinal phase space manipulate. We will also report the results of beamline simulation using space charge code and the conceptual design of spin rotator.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB037

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paper received ※ 16 May 2021 paper accepted ※ 15 June 2021 issue date ※ 31 August 2021

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TUPAB038

Simulation of the Filling Pattern Dependent Regenerative Beam Breakup Instabilities in Energy Recover Linacs

HOM, cavity, linac, simulation

1431

S. Setiniyaz, P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom
R. Apsimon
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The interaction of a transversely displaced beam with the higher modes (HOM) of the accelerating cavities causes building up HOM voltages in the cavity, which in turn kicks the beam and increases the offset further. This is known as regenerative beam breakup (BBU) instability and it sets the beam threshold current for the stable beam operation. A study by Setiniyaz et al.~[Setiniyaz2020] showed the filling pattern and recombination schemes of multi-turn energy recovery linacs (ERLs) can create many different beam loading transients, which can have a big impact on the cavity fundamental mode voltage and RF stabilizes. In this work, we extend the study of the filling pattern and recombination schemes to the BBU instabilities and threshold current. In the ERLs, the accelerated and decelerated bunches can be ordered differently while they pass through the cavity and form different filling patterns. Each pattern has a unique bunch energy sequence and bunch arrival times and hence interacts with cavity uniquely and thus drives BBU differently. In this paper, we introduce a simulation tool to investigate the filling pattern dependence of the ERL BBU instability.
* S. Setiniyaz, R. Apsimon, and P. H. Williams, Phys. Rev. Accel. Beams 23, 072002, 2020.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB038

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paper received ※ 20 May 2021 paper accepted ※ 09 June 2021 issue date ※ 13 August 2021

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TUPAB040

Design Concept for the Second Interaction Region for Electron-Ion Collider

detector, proton, dipole, optics

1435

B.R. Gamage, V. Burkert, R. Ent, Y. Furletova, D.W. Higinbotham, A. Hutton, F. Lin, T.J. Michalski, V.S. Morozov, R. Rajput-Ghoshal, D. Romanov, T. Satogata, A. Seryi, A.V. Sy, C. Weiss, M. Wiseman, W. Wittmer, Y. Zhang
JLab, Newport News, Virginia, USA
E.C. Aschenauer, J.S. Berg, A. Jentsch, A. Kiselev, C. Montag, R.B. Palmer, B. Parker, V. Ptitsyn, F.J. Willeke, H. Witte
BNL, Upton, New York, USA
C. Hyde
ODU, Norfolk, Virginia, USA
P. Nadel-Turonski
SBU, Stony Brook, New York, USA

Funding: Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 and Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The possibility of two interaction regions (IRs) is a design requirement for Electron-Ion Collider (EIC). There is also a significant interest from the nuclear physics community to have a 2nd IR with measurement capabilities complementary to those of the 1st IR. While the 2nd IR will be in operation over the entire energy range of ~20GeV to ~140GeV center of mass (CM). The 2nd IR can also provide an acceptance coverage complementary to that of the 1st. In this paper, we present a brief overview and the current progress of the 2nd IR design in terms of the parameters, magnet layout, and beam dynamics.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB040

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paper received ※ 24 May 2021 paper accepted ※ 25 August 2021 issue date ※ 31 August 2021

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TUPAB041

Detector Solenoid Compensation for the Electron-Ion Collider

solenoid, coupling, detector, cavity

1439

B.R. Gamage, T.J. Michalski, V.S. Morozov, R. Rajput-Ghoshal, A. Seryi, W. Wittmer, Y. Zhang
JLab, Newport News, Virginia, USA
E. Gianfelice-Wendt
Fermilab, Batavia, Illinois, USA
A. Kiselev, H. Lovelace III, B. Parker, S. Peggs, S. Tepikian, F.J. Willeke, H. Witte, Q. Wu
BNL, Upton, New York, USA

Funding: Jefferson Science Associates, LLC Contract No. DE-AC05-06OR23177, Fermi Research Alliance, LLC Contract No. DE-AC02-07CH11359, and Brookhaven Science Associates, LLC Contract No. DE-SC0012704
The central detector in the present EIC design includes a 4 m long solenoid with an integrated strength of up to 12 Tm. The electron beam passes on-axis through the solenoid, but the hadron beam has an angle of 25 mrad. Thus the solenoid couples horizontal and vertical betatron motion in both electron and hadron storage rings, and causes a vertical closed orbit excursion in the hadron ring. The solenoid also couples the transverse and longitudinal motions of both beams, when crab cavities are also considered. In this paper, we present schemes for closed orbit correction and coupling compensation at the IP, including crabbing.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB041

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paper received ※ 28 May 2021 paper accepted ※ 22 August 2021 issue date ※ 31 August 2021

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TUPAB042

Large Radial Shifts in the EIC Hadron Storage Ring

dipole, hadron, closed-orbit, insertion

1443

S. Peggs, J.S. Berg, K.A. Drees, X. Gu, C. Liu, H. Lovelace III, Y. Luo, G.J. Marr, A. Marusic, F. Méot, R.J. Michnoff, V. Ptitsyn, G. Robert-Demolaize, M. Valette, S. Verdú-Andrés
BNL, Upton, New York, USA
K.E. Deitrick
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
B.R. Gamage
JLab, Newport News, Virginia, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The Electron Ion Collider will collide hadrons in the Hadron Storage Ring (HSR) with ultra-relativistic electrons in the Electron Storage Ring. The HSR design trajectory includes a large radial shift over a large fraction of its circumference, in order to adjust the hadron path length to synchronize collisions over a broad range of hadron energies. The design trajectory goes on-axis through the magnets, crab cavities and other components in the six HSR Insertion Regions. This paper discusses the issues involved and reports on past and future beam experiments in the Relativistic Heavy Ion Collider, which will be upgraded to become the HSR.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB042

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paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 30 August 2021

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TUPAB044

Preliminary Study of the on-Axis Swap-Out Injection Scheme for the Southern Advanced Photon Source

injection, storage-ring, kicker, septum

1447

Y. Han, X.H. Lu, Y. Zhao
IHEP CSNS, Guangdong Province, People’s Republic of China
L. Huang, Y. Jiao, X. Liu, S. Wang
IHEP, Beijing, People’s Republic of China

The Southern Advanced Photon Source (SAPS) is a project under design, which aims at constructing a 4th generation storage ring with emittance below 100 pm.rad at the electron beam energy of around 3.5 GeV. The extremely low emittance will result in a very small dynamic aperture for the storage ring which makes it difficult to use the conventional off-axis accumulation injection. In this case, it is probably necessary to consider the transverse on-axis injection or the longitudinal injection. In this paper, the transverse on-axis swap-out injection scheme for the SAPS storage ring is presented. The preliminary parameters of the septum magnets and fast kickers are carefully evaluated.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB044

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paper received ※ 17 May 2021 paper accepted ※ 10 June 2021 issue date ※ 10 August 2021

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TUPAB045

The Low Energy Injector Design for the Southern Advanced Photon Source

linac, cavity, gun, bunching

1450

Y. Han
IHEP CSNS, Guangdong Province, People’s Republic of China
Y. Jiao, B. Li, X. Liu, S. Wang
IHEP, Beijing, People’s Republic of China

The Southern Advanced Photon Source (SAPS) is a project under design, which aims at constructing a 4th generation storage ring with emittance below 100 pm.rad at the electron beam energy of around 3.5 GeV. At present, two injector options are under consideration. One is a full energy booster plus a low energy injector, and another is a full energy linac injector. In this paper, a preliminary design of the low energy injector is presented, which consists of an DC thermionic electron gun, a bunching section and an accelerating section. The beam energy at the end of the injector is about 150 MeV.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB045

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paper received ※ 17 May 2021 paper accepted ※ 09 June 2021 issue date ※ 21 August 2021

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TUPAB047

Bunch Compressor Design in the Full Energy Linac Injector for the Southern Advanced Photon Source

linac, simulation, bunching, laser

1458

B. Li
IHEP CSNS, Guangdong Province, People’s Republic of China
Y. Jiao, X. Liu, S. Wang
IHEP, Beijing, People’s Republic of China

A mid-energy fourth-generation storage ring light source named the Southern Advanced Photon Source (SAPS), has been considered to be built neighboring the China Spallation Neutron Source (CSNS). A full energy linac has been proposed as an injector to the storage ring, with the capability to generate high brightness electron beams to feed a Free Electron Laser (FEL) at a later stage. To achieve the high peak current in FELs, space charge, RF structure wakefield, coherent synchrotron radiation (CSR), RF curvature, and the second-order momentum compaction factor should be carefully considered and optimized during the bunch compression processes. In this paper, physic design and simulation results of the bunch compressors are described.

Poster TUPAB047 [1.918 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB047

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paper received ※ 15 May 2021 paper accepted ※ 09 June 2021 issue date ※ 29 August 2021

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TUPAB052

Current Study of Applying Machine Learning to Accelerator Physics at IHEP

network, lattice, target, photon

1477

J. Wan, Y. Jiao
IHEP, Beijing, People’s Republic of China

Funding: National Natural Science Foundation of China(No.11922512), Youth Innovation Promotion Association of Chinese Academy of Sciences(No.Y201904) and National Key R&D Program of China(No.2016YFA0401900).
In recent years, machine learning (ML) has attracted increasing interest among the accelerator field. As a complex collection of multiple physical subsystems, the design and operation of an accelerator can be very nonlinear and complicated, while ML is taken as a powerful tool to solve such nonlinear and complicated problems. In this study, we report on several successful applications of ML to accelerator physics at IHEP. The nonlinear dynamics optimization of the High Energy Photon Source (HEPS) that is a 4th-generation light source is a challenging topic. In this optimization, we use a ML surrogate model to fast select the potentially competitive solutions for a multiobjective genetic algorithm that can significantly improve the convergence rate and the diversity among obtained solutions. Besides, we also tried to apply a generative adversarial net to solve one-to-many problems of longitudinal beam current profile shaping. Unlike most supervised machine learning methods than cannot learn one-to-many maps, the generative adversarial net-based method is able to predict multiple solutions instead of one for a 4-dipole chicane to realize several desired custom current profiles.

Poster TUPAB052 [0.913 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB052

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paper received ※ 11 May 2021 paper accepted ※ 21 June 2021 issue date ※ 12 August 2021

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TUPAB066

Status of the Short-Pulse Source at DELTA

laser, undulator, bunching, simulation

1518

A. Held, B. Büsing, H. Kaiser, S. Khan, D. Krieg, A.R. Krishnan, C. Mai
DELTA, Dortmund, Germany

Funding: Work supported by BMBF (05K19PEB).
At the synchrotron light source DELTA operated by the TU Dortmund University, the short-pulse source employs the seeding scheme coherent harmonic generation (CHG) and provides ultrashort pulses in the vacuum ultraviolet and terahertz regime. Here, the interaction of laser pulses with the stored electron bunches result in a modulation of the longitudinal electron density which gives rise to coherent emission at harmonics of the laser wavelength. Recently, investigations of the influence of the Gouy phase shift at the focal point of the laser pulses on the laser-electron interaction have been performed. For the planned upgrade towards the more sophisticated seeding scheme echo-enabled harmonic generation (EEHG) featuring a twofold laser-electron interaction, simulations of the ideal parameters of the laser beams have been carried out.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB066

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paper received ※ 19 May 2021 paper accepted ※ 22 July 2021 issue date ※ 30 August 2021

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TUPAB069

The Sabina Terahertz/Infrared Beamline at SPARC-Lab Facility

radiation, experiment, photon, laser

1525

S. Macis
La Sapienza University of Rome, Rome, Italy
M. Bellaveglia, M. Cestelli Guidi, E. Chiadroni, F. Dipace, A. Ghigo, L. Giannessi, A. Giribono, L. Sabbatini, C. Vaccarezza
INFN/LNF, Frascati, Italy
A. Doria, A. Petralia
ENEA C.R. Frascati, Frascati (Roma), Italy
S. Lupi
Sapienza University of Rome, Roma, Italy
V. Petrillo
INFN-Milano, Milano, Italy

Funding: SABINA is a project co-funded by Regione Lazio within POR-FESR 2014-2020 program.
Following the EU Terahertz (THz) Road Map*, high-intensity, ps-long, THz)/Infrared (IR) radiation is going to become a fundamental spectroscopy tool for probing and control low-energy quantum systems ranging from graphene, and Topological Insulators, to novel superconductors** ***. In the framework of the SABINA project, a novel THz/IR beamline based on an APPLE-X undulator emission will be developed at the SPARC-Lab facility at LNF-INFN. Light will be propagated from the SPARC-Lab to a new user lab facility nearly 20 m far away. This beamline will cover a broad spectral region from 3 THz to 30 THz, showing ps- pulses and energy of tens of µJ with variable polarization from linear to circular. The corresponding electric fields up to 10 MV/cm, are able to induce non-linear phenomena in many quantum systems. The beamline, open to user experiments, will be equipped with a 5 T magnetic cryostat and will be synchronized with a fs laser for THz/IR pump, VIS/UV probe experiments.
[*] S.S. Dhillon et al., J. Phys. D: Appl. Phys. 50, 043001 (2017);
[**] F. Giorgianni et al., Nature Commun. 7, 11421 (2016);
[***] P. Di Pietro et al., Phys. Rev. Lett. 124, 226403 (2020);

Poster TUPAB069 [0.884 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB069

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paper received ※ 16 May 2021 paper accepted ※ 21 June 2021 issue date ※ 27 August 2021

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TUPAB071

Beam Line Design and Instrumentation for THz@PITZ - the Proof-of-Principle Experiment on a THz SASE FEL at the PITZ Facility

undulator, FEL, radiation, experiment

1528

T. Weilbach, P. Boonpornprasert, G.Z. Georgiev, G. Koss, M. Krasilnikov, X. Li, A. Lueangaramwong, F. Mueller, A. Oppelt, S. Philipp, F. Stephan, L.V. Vu
DESY Zeuthen, Zeuthen, Germany
H. Shaker
CLS, Saskatoon, Saskatchewan, Canada

In order to allow THz pump-X-ray probe experiments at full bunch repetition rate for users at the European XFEL, the Photo Injector Test Facility at DESY in Zeuthen (PITZ) is building a prototype of an accelerator-based THz source. The goal is to generate THz SASE FEL radiation with a mJ energy level per bunch using an LCLS-I undulator driven by the electron beam from PITZ. Therefore, the existing PITZ beam line is extended into a tunnel annex downstream of the existing accelerator tunnel. The beam line extension in the PITZ tunnel consists of three quadrupole magnets, a bunch compressor, a collimation system and a beam dump. In the second tunnel a dipole magnet allows to serve two beam lines, one of them the THz@PITZ beam line. It consists of one LCLS-I undulator for the production of the THz radiation, a quadrupole triplet in front of it and a quadrupole doublet behind it. For the electron beam diagnostic six new screen stations are built, three of them also allow for the observation of the THz radiation for measurements. In addition six BPMs and a new BLM system for machine protection and FEL gain curve measurement will be installed. The progress of this work will be presented.

Poster TUPAB071 [1.978 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB071

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paper received ※ 18 May 2021 paper accepted ※ 14 June 2021 issue date ※ 17 August 2021

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TUPAB072

The Status of a Grating Monochromator for Soft X-Ray Self-Seeding Experiment at SHINE

laser, FEL, free-electron-laser, cavity

1532

K.Q. Zhang
SSRF, Shanghai, People’s Republic of China
H.X. Deng, C. Feng, B. Liu, T. Liu
SARI-CAS, Pudong, Shanghai, People’s Republic of China

The research status of a grating monochromator for soft X-ray self-seeding experiment at SHINE has been presented in this paper. The monochromator system includes the vacuum cavity, optical elements, and mechanical movement devices. Until now, the vacuum cavity has finished the manufactured process completely, the optical mirrors have finished machining and measured by the longitudinal trace profiler (LTP) and atomic force microscope (AFM). To make sure the monochromator system can achieve an optical resolution of 1/10000 at the photon energy of 700-1300eV, the system has been integrated and tested recently. In this year, the previous online experiment will be performed in the shanghai soft X-ray free-electron laser (FEL) user facility.

Poster TUPAB072 [0.717 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB072

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paper received ※ 11 May 2021 paper accepted ※ 09 June 2021 issue date ※ 01 September 2021

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TUPAB073

The Design of EEHG Cascaded Harmonic Lasing for SXFEL User Facility

FEL, undulator, laser, radiation

1536

K.Q. Zhang, C. Feng
SSRF, Shanghai, People’s Republic of China
H.X. Deng, B. Liu, T. Liu
SARI-CAS, Pudong, Shanghai, People’s Republic of China

The preliminary design and simulation results of EEHG cascaded harmonic lasing for the SXFEL user facility have been presented in this paper. Using the basic seeded beamline of the SXFEL user facility, the designed parameters are optimized to obtain full coherent FEL output at the 90th harmonic of a 265 nm seed laser. According to the designed parameters and the layout of the SXFEL user facility, the detailed simulations are carried out, the results show that the seeded beamline of the SXFEL user facility can generate 2.93 nm full coherent radiation by the proposed method, which indicates that the method can extend the photon energy range of a seeded FEL and the method can be achieved at the SXFEL user facility.

Poster TUPAB073 [0.955 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB073

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paper received ※ 11 May 2021 paper accepted ※ 10 June 2021 issue date ※ 17 August 2021

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TUPAB078

Relative Timing Jitter Effects on Two-stage Seeded FEL at SHINE

FEL, laser, timing, radiation

1551

H.X. Yang
SINAP, Shanghai, People’s Republic of China
H.X. Deng, B. Liu, D. Wang, K.S. Zhou
SARI-CAS, Pudong, Shanghai, People’s Republic of China

Funding: The National Key Research and Development Program of China (Grants No. 2016YFA0401901, No. 2018YFE0103100) and the National Natural Science Foundation of China (Grants No. 11935020, No. 11775293).
The synchronization between the ultrashort electron beam and external seed laser is essential for seeded FELs, especially for a multi-stage one. In this paper, we demonstrate a simple method to obtain the correlations between the pulse energy and relative timing jitter for evaluating the corresponding effects. In this method, the sensitivity of the output FEL performance against electron beam properties is demonstrated by scanning the electron beam and seed lasers, and the fitted curve is used to predict the pulse energy in different timing jitter by random sampling. The results indicate that the pulse energy of the first-stage EEHG is more stable than the second-stage HGHG. Meanwhile, the rise of bunch charge from 100 pC to 300 pC can reduce the timing control requirement by a factor of least 3 for the RMS timing jitter in our numerical simulations based on the parameters of Shanghai High-Repetition-Rate XFEL and Extreme Light Facility. The timing jitter study can demonstrate the feasibility of the EEHG-HGHG cascading scheme in different current profiles for generating Fourier-transform-limited soft X-ray FEL.

Poster TUPAB078 [0.866 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB078

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paper received ※ 11 May 2021 paper accepted ※ 11 June 2021 issue date ※ 18 August 2021

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TUPAB079

Using ER@CEBAF to Show that a Multipass ERL Can Drive an XFEL

FEL, operation, controls, acceleration

1555

G. Perez-Segurana
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
I.R. Bailey, P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom
I.R. Bailey
Lancaster University, Lancaster, United Kingdom
R.M. Bodenstein, S.A. Bogacz, D. Douglas, Y. Roblin, T. Satogata
JLab, Newport News, Virginia, USA
T. Satogata
ODU, Norfolk, Virginia, USA
P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

A multi-pass recirculating superconducting CW linac offers a cost effective path to a multi-user facility with unprecedented scientific and industrial reach over a wide range of disciplines. We propose such a facility as an option for a potential UK-XFEL. Energy Recovery enables multi-MHz FEL sources, for example, an X-ray FEL oscillator or regenerative amplifier FEL. Additionally, combining with external lasers and/or self-interaction would provide access to MeV and GeV gamma-rays via inverse Compton scattering at high average power for nuclear and particle physics applications. An opportunity exists to demonstrate the necessary point-to-parallel longitudinal matches to drive an XFEL and successfully energy recover at the upcoming 5-pass up, 5-pass down Energy Recovery experiment on CEBAF at JLab termed ER@CEBAF. We show candidate matches and simulations supporting the minimal necessary modifications to CEBAF this will require. This includes linearisation of the longitudinal phase space in the injector and a reduction in the dispersion of the arcs, both of which increase the energy acceptance of CEBAF. We expect to commence initial tests of these adaptations on CEBAF during 2021.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB079

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paper received ※ 17 May 2021 paper accepted ※ 27 July 2021 issue date ※ 10 August 2021

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TUPAB080

Design and Status of the Beam Switchyard of the Shanghai Soft X-Ray FEL User Facility

FEL, kicker, undulator, linac

1559

S. Chen, R. Wang
SSRF, Shanghai, People’s Republic of China
H.X. Deng, C. Feng, X. Fu, B. Liu
SARI-CAS, Pudong, Shanghai, People’s Republic of China

SXFEL-UF, a soft X-ray FEL user facility located in Shanghai, has been upgraded from the existing test facility. Electron energy increases from 840 MeV to 1.5 GeV and a SASE FEL line will be added besides the existing seeding FEL line. It has started commissioning since early this year. In order for simultaneous operation of the two FEL lines, a beam switchyard is built between the linac and the two FEL lines. In this paper, the physics design of the beam switchyard is described.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB080

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paper received ※ 19 May 2021 paper accepted ※ 11 June 2021 issue date ※ 30 August 2021

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TUPAB081

Design of the Beam Distribution System of SHINE

undulator, linac, septum, kicker

1562

S. Chen, M. Gu, R. Wang
SSRF, Shanghai, People’s Republic of China
H.X. Deng, X. Fu
SARI-CAS, Pudong, Shanghai, People’s Republic of China

In shanghai, a hard X-ray free electron laser project named SHINE is under design. It will be based on a superconducting linac running in CW mode. On the first stage, there will be three parallel undulator lines downstream the linac. For simultaneous operation of the three undulator lines, a beam distribution system based on fast kickers will be installed between linac and undulator lines. The physics design of this beam distribution system is described in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB081

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paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 20 August 2021

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TUPAB082

Analysis of the Effect of Energy Chirp in Implementing EEHG at SXL

bunching, simulation, FEL, linac

1566

M.A. Pop, F. Curbis, B.S. Kyle, S.P. Pirani, W. Qin, S. Werin
MAX IV Laboratory, Lund University, Lund, Sweden
F. Curbis, S. Werin
Lund University, Lund, Sweden
W. Qin
DESY, Hamburg, Germany

As a part of the efforts to improve the longitudinal coherence in the design of the Soft X-ray FEL (the SXL) at MAX IV, we present a possible implementation of the EEHG harmonic seeding scheme partly integrated into the second bunch compressor of the existing LINAC. A special focus is given to the effect of CSR on the resulting EEHG bunching and on how this unwanted effect might be controlled.

Poster TUPAB082 [1.825 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB082

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paper received ※ 15 May 2021 paper accepted ※ 28 July 2021 issue date ※ 19 August 2021

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TUPAB084

An Empirically-Derived ABCD Matrix for Transverse Dynamics Studies in Seeded Free-Electron Lasers

FEL, radiation, laser, free-electron-laser

1573

R. Robles
Stanford University, Stanford, California, USA
Z. Huang, G. Marcus
SLAC, Menlo Park, California, USA

Funding: DOE Contract DE-AC02-76SF00515.
We present a simple empirical method for deriving an ABCD matrix for studying the transverse dynamics of the radiation field in seeded, high-gain free-electron lasers before saturation. In spite of the inherently nonlinear nature of FEL optical guiding, the ABCD matrix we find is able to predict the evolution of the FEL mode size and centroid to a high degree of accuracy across a large range of input mode characteristics. This scheme enables extremely fast simulation of transverse dynamics, which in turn greatly simplifies numerical studies of seeded FEL systems. Of particular interest in that regard is the x-ray regenerative amplifier free-electron laser, in which the x-ray beam propagates through an optical cavity many hundreds of times, thereby making traditional simulation methods cumbersome and time consuming.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB084

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 15 August 2021

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TUPAB085

Three-Dimensional Radiative Effects in the Compression of Ultra-Short Electron Micro-Bunches

emittance, FEL, laser, simulation

1577

R. Robles, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
S.B. van der Geer
Pulsar Physics, Eindhoven, The Netherlands

Funding: DOE Contract DE-SC0009914 DOE Contract DE-SC0020409 National Science Foundation Grant No. PHY-1549132
Micro-bunched current profiles have recently gained traction as an alternative to bulk compression in certain free-electron laser applications. The attraction of the micro-bunched structure is owed in part to its promise to minimize deleterious effects associated with coherent synchrotron radiation during compression. Simultaneously, these profiles push the boundaries of traditional one-dimensional CSR simulation models which assume the bunch length to far exceed the transverse beam size in the bunch rest frame - an assumption which may be violated by the sub-micron length micro-bunches. Here we present simulation studies of the impact of three-dimensional CSR effects on micro-bunching based compression schemes using the General Particle Tracer code.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB085

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 19 August 2021

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TUPAB086

FLASH²⁰²⁰⁺ Plans for a New Coherent Source at DESY

FEL, laser, experiment, undulator

1581

E. Allaria, N. Baboi, K. Baev, M. Beye, G. Brenner, F. Christie, C. Gerth, I. Hartl, K. Honkavaara, B. Manschwetus, J. Mueller-Dieckmann, R. Pan, E. Plönjes-Palm, O. Rasmussen, J. Rönsch-Schulenburg, L. Schaper, E. Schneidmiller, S. Schreiber, K.I. Tiedtke, M. Tischer, S. Toleikis, R. Treusch, M. Vogt, L. Winkelmann, M.V. Yurkov, J. Zemella
DESY, Hamburg, Germany

With FLASH²⁰²⁰⁺, a major upgrade of the FLASH facility has started to meet the new requirements of the growing soft-x ray user community. The design of the FEL beamlines aims at photon properties suitable to the needs of future user experiments with high repetition rate XUV and soft X-ray radiation. By the end of the project, both existing FEL lines at FLASH will be equipped with fully tunable undulators capable of delivering photon pulses with variable polarization. The use of the external seeding at 1 MHz in burst mode is part of the design of the new FLASH1 beamline, while FLASH2 will exploit novel lasing concepts based on different undulator configurations. The new FLASH²⁰²⁰⁺ will rely on an electron beam energy of 1.35 GeV that will extend the accessible wavelength range to the oxygen K-edge with variable polarization. The facility will be completed with new laser sources for pump and probe experiment and new experimental stations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB086

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paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 27 August 2021

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TUPAB087

Full Characterization of the Bunch-Compressor Dipoles for FLUTE

dipole, linac, HOM, controls

1585

Y. Nie, A. Bernhard, E. Bründermann, A.-S. Müller, M.J. Nasse, R. Ruprecht, J. Schäfer, M. Schuh, Y. Tong
KIT, Karlsruhe, Germany

Funding: This work is supported by the BMBF project 05H18VKRB1 HIRING (Federal Ministry of Education and Research).
The Ferninfrarot Linac- Und Test-Experiment (FLUTE) is a KIT-operated linac-based test facility for accelerator research and development as well as a compact, ultra-broadband and short-pulse terahertz (THz) source. As a key component of FLUTE, the bunch compressor (chicane) consisting of four specially designed dipoles will be used to compress the 40-50 MeV electron bunches after the linac down to single fs bunch length. The maximum vertical magnetic field of the dipoles reach 0.22 T, with an effective length of 200 mm. The good field region is ±40 mm and ±10.5 mm in the horizontal and vertical direction, respectively. The latest measurement results of the dipoles in terms of field homogeneity, excitation and field reproducibility within the good field regions will be reported, which meet the predefined specifications. The measured 3D magnetic field distributions have been used to perform beam dynamics simulations of the bunch compressor. Effects of the real field properties on the beam dynamics, which are different from that of the ASTRA built-in dipole field, will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB087

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paper received ※ 10 May 2021 paper accepted ※ 27 May 2021 issue date ※ 14 August 2021

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TUPAB089

Proof-of-Principle Experiment Design for PEHG-FEL in SXFEL User Facility

FEL, laser, radiation, experiment

1589

Z. Qi, H.X. Deng, C. Feng, B. Liu
SARI-CAS, Pudong, Shanghai, People’s Republic of China
S. Chen, Z.T. Zhao
SSRF, Shanghai, People’s Republic of China

In this paper, we demonstrate a proof-of-principle experimental design for phase-merging enhanced harmonic generation (PEHG) free electron laser (FEL) in Shanghai Soft X-ray Free Electron Laser (SXFEL) user facility. The simulation results indicate that, taking advantage of the beam switchyard, the normal modulator and the seeded FEL line in SXFEL user facility, together with an oblique incident seed laser, we can perform the phase-merging effect in PEHG and finally get an 8.86nm FEL radiation through the undulator, which is the 30th harmonic of the seed laser.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB089

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 24 August 2021

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TUPAB092

Demonstration FELs Using UC-XFEL Technologies at the SAMURAI Laboratory

FEL, undulator, cryogenics, laser

1592

N. Majernik, G. Andonian, O. Camacho, A. Fukasawa, G.E. Lawler, W.J. Lynn, B. Naranjo, J.B. Rosenzweig, Y. Sakai, O. Williams
UCLA, Los Angeles, California, USA
R. Robles
SLAC, Menlo Park, California, USA

Funding: DOE HEP Grant DE-SC0020409, National Science Foundation Grant No. PHY-1549132
The ultra-compact x-ray free-electron laser (UC-XFEL), described in [J. B. Rosenzweig, et al. 2020 New J. Phys. 22 093067], combines several cutting edge beam physics techniques and technologies to realize an x-ray free electron laser at a fraction of the cost and footprint of existing XFEL installations. These elements include cryogenic, normally conducting RF structures for both the gun and linac, IFEL bunch compression, and short-period undulators. In this work, several stepping-stone, demonstrator scenarios under discussion for the UCLA SAMURAI Laboratory are detailed and simulated, employing different subsets of these elements. The cost, footprint, and technology risk for these scenarios are considered in addition to the anticipated engineering and physics experience gained.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB092

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paper received ※ 19 May 2021 paper accepted ※ 11 August 2021 issue date ※ 19 August 2021

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TUPAB098

Recent Progress Toward a Conduction-Cooled Superconducting Radiofrequency Electron Gun

cavity, simulation, SRF, accelerating-gradient

1604

O. Mohsen, N. Adams, V. Korampally, A. McKeown, D. Mihalcea, P. Piot, I. Salehinia, N. Tom
Northern Illinois University, DeKalb, Illinois, USA
R. Dhuley, M.G. Geelhoed, D. Mihalcea, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA
P. Piot
ANL, Lemont, Illinois, USA

Funding: This work was supported by the US Department of Energy (DOE) under contract DE-SC0018367
High-repetition-rate electron sources have widespread applications. This contribution discusses the progress toward a proof-of-principle demonstration for a conduction-cooled electron source. The source consists of a simple modification of an elliptical cavity that enhances the field electric field at the photocathode surface. The source was cooled to cryogenic temperatures and preliminary measurements for the quality factor and accelerating field were performed. Additionally, we present future plans to improve the source along with simulated beam-dynamics performances.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB098

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paper received ※ 29 May 2021 paper accepted ※ 17 June 2021 issue date ※ 14 August 2021

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TUPAB099

Construction of an Infrared FEL at the Compact ERL

FEL, undulator, laser, operation

1608

R. Kato, M. Adachi, S. Eguchi, K. Harada, N. Higashi, Y. Honda, T. Miyajima, S. Nagahashi, N. Nakamura, K.N. Nigorikawa, T. Nogami, T. Obina, H. Sagehashi, H. Sakai, M. Shimada, T. Shioya, M. Tadano, R. Takai, O.A. Tanaka, Y. Tanimoto, K. Tsuchiya, T. Uchiyama, A. Ueda, M. Yamamoto
KEK, Ibaraki, Japan
R. Hajima
QST, Tokai, Japan
N.P. Norvell
SLAC, Menlo Park, California, USA
F. Sakamoto
Akita National College of Technology, Akita, Japan
M. Shimada
HSRC, Higashi-Hiroshima, Japan

Funding: Work supported by NEDO project "Development of advanced laser processing with intelligence based high-brightness and high-efficiency laser technologies (TACMI project)".
The compact Energy Recovery Linac (cERL) has been in operation at KEK since 2013 to demonstrate ERL performance and develop ERL technology. Recently KEK has launched an infrared FEL project with a competitive funding. The purpose of this project is to build a mid-infrared FEL at the cERL, and to use that FEL as a light source for construction of the processing database required for industrial lasers. The FEL system is composed of two 3-m undulators and a matching section between them, and generates light with a maximum pulse energy of 0.1 micro-J at the wavelength of 20 microns with an 81.25 MHz repetition rate. The FEL is also expected to become a proof-of-concept machine for ERL base FELs for future EUV lithography.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB099

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paper received ※ 20 May 2021 paper accepted ※ 14 June 2021 issue date ※ 17 August 2021

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TUPAB100

FEL Design Elements of SABINA: A Free Electron Laser For THz-MIR Polarized Radiation Emission

undulator, radiation, FEL, simulation

1612

F. Dipace, E. Chiadroni, M. Ferrario, A. Ghigo, L. Giannessi, A. Giribono, L. Sabbatini, C. Vaccarezza
INFN/LNF, Frascati, Italy
A. Doria, A. Petralia
ENEA C.R. Frascati, Frascati (Roma), Italy
S. Lupi
Sapienza University of Rome, Roma, Italy
S. Macis
La Sapienza University of Rome, Rome, Italy
V. Petrillo
Universita’ degli Studi di Milano, Milano, Italy
V. Petrillo
INFN-Milano, Milano, Italy

Funding: SABINA is a project co-funded by Regione Lazio within POR-FESR 2014-2020 program.
SABINA, acronym of "Source of Advanced Beam Imaging for Novel Applications", will be a Self-Amplified Spontaneous Emission Free Electron Laser (SASE FEL) providing a wide spectral range (from THz to MIR) of intense, short and variable polarization pulses for investigation in physics, chemistry, biology, cultural heritage, and material science. In order to reach these goals high brightness electron beams within a 30-100 MeV energy range, produced at SPARC photo-injector, will be transported up to an APPLE-X undulator through a dogleg. Space charge effects and Coherent Synchrotron Radiation (CSR) effects must be held under control to preserve beam quality. Studies on beam transport along the undulator and of the properties of the radiation field have been performed with "Genesis 1.3" simulation code. A downstream THz optics photon delivery system has also been designed to transport radiation on the long path from the undulator exit up to user experimental area.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB100

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paper received ※ 19 May 2021 paper accepted ※ 11 June 2021 issue date ※ 18 August 2021

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TUPAB101

Monte Carlo Simulations and Neutron and Gamma Fluence Measurements to Investigate Stray Radiation in the European XFEL Undulator System

undulator, radiation, simulation, neutron

1615

O.E. Falowska-Pietrzak, A. Hedqvist, F. Hellberg
Stockholm University, Stockholm, Sweden
N. Bassler
DCPT, Aarhus N, Denmark
A. Leuschner, D. Nölle
DESY, Hamburg, Germany
F. Wolff-Fabris
EuXFEL, Schenefeld, Germany

The European X-ray Free Electron Laser (XFEL) is an user facility research centre generating extremely bright and ultra-short SASE x-ray pulses. The laser flashes are generated when electrons of GeV energies pass the undulator systems. Even if the dominating contribution of the radiation field in the undulator is from spontaneous undulator radiation, also electron losses can be observed, e.g. during beam steering or due to beam halo, not captured by the upstream collimation system. The interactions of those particles with the vacuum vessel wall result in the emission of stray radiation. The LB 6419 detector allows to measure both the neutron and the gamma component in the pulsed radiation fields nearby the undulators*. Usually, the real-time measurements show the dominance of the gamma signals. However, in case of particle loss occurs, a neutron signal is observed. In addition, Monte Carlo (MC) simulations conducted using the Geant4 code indicate that neutrons are also present within the undulator’s magnets volume. In this work, we present the LB 6419 measurement data and compare these to our MC simulations, to characterize the radiation field nearby the undulator segment.
* KLETT, A., LEUSCHNER, A., TESCH, N., A dose meter for pulsed neutron fields, Radiat Meas 45 (2010) 1242-1244

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB101

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 25 August 2021

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TUPAB103

Discussion on CSR instability in EEHG Simulation

bunching, laser, FEL, simulation

1622

D. Samoilenko, W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
F. Curbis, M.A. Pop, S. Werin
MAX IV Laboratory, Lund University, Lund, Sweden
P. Niknejadi, G. Paraskaki
DESY, Hamburg, Germany
F. Pannek
University of Hamburg, Hamburg, Germany

Echo-Enabled Harmonic Generation (EEHG) is an external seeding technique for XUV and soft X-ray Free Electron Lasers (FEL). It has recently been experimentally demonstrated and currently many facilities worldwide intend to incorporate it in user operation. The EEHG process relies on very accurate and complex transformations of electron beam phase space by means of a series of undulators coupled to lasers and dispersive chicanes. As a result of the phase space manipulation, electrons are bunched at a high harmonic of the seed laser wavelength allowing coherent emission at few nm wavelength. Dispersion occurring in strong chicanes is imperative for implementation of this scheme and effective electron bunching generation. However, strong chicanes at the same time can be source of beam instability effects, such as Coherent Synchrotron Radiation (CSR), that can significantly grow in these conditions and suppress the bunching process. Therefore, there is a common need to investigate such effects in detail. Here, we discuss their treatment with simulation codes applied to a typical EEHG setup.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB103

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 25 August 2021

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TUPAB104

Redesign of the FLASH2 Post-SASE Undulator Beamline

undulator, quadrupole, photon, MMI

1626

F. Christie, J. Rönsch-Schulenburg, S. Schreiber, M. Vogt, J. Zemella
DESY, Hamburg, Germany

FLASH2 is one of the two SASE (Self-Amplified Spontaneous Emission) undulator beamlines lines comprising variable gap undulators to produce radiation in the XUV and soft X-ray regime at FLASH. Downstream of the SASE undulators the beamline is currently undergoing a major redesign. During shutdowns in summer 2020 and winter 2021 two PolariX TDSs (Polarizable X-band Transverse Deflecting Structure) were installed, as well as additional diagnostics, to monitor the longitudinal phase space density of the electron bunches. Additionally, an afterburner undulator will be integrated in the next shutdown to produce circularly polarized light with wavelengths down to 1.39 nm. In this paper, we will present the modifications that were and will be made to the electron beamline in the course of this redesign.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB104

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paper received ※ 19 May 2021 paper accepted ※ 21 July 2021 issue date ※ 24 August 2021

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TUPAB105

Simulation Studies for Dark Current Signature From DLS RF Gun

simulation, cavity, solenoid, cathode

1630

J. Karmakar, M. Aggarwal, S. Ghosh, B. Karmakar, P. Patra, B.K. Sahu, A. Sharma
IUAC, New Delhi, India

The Delhi Light source (DLS) is an upcoming compact THz facility at IUAC, New Delhi, based on pre-bunched FEL. RF conditioning of the 2.6 cell S-band RF gun is presently carried out with a Cu photo-cathode (PC) plug and dark current is produced when substantial accelerating field is reached inside the cavity. To identify the possible field emission sites contributing to dark current, single electron ASTRA simulations are done with a phase scan of the RF field. The simulation is extended to include multi-particle emission from the PC edge as a ring. The energies present in the dark current is analysed from the the Fowler Nordheim current plot and energy phase scan plot. The distribution of few dark current energies and their respective trajectories upto the YAG screen at a given solenoid setting is traced and shown in the simulations. We also present the dark current images captured during the initial RF conditioning and try to compare it with the simulations.

Poster TUPAB105 [0.742 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB105

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paper received ※ 19 May 2021 paper accepted ※ 17 August 2021 issue date ※ 28 August 2021

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TUPAB106

Simulation Calculations of Compact THz Facility at IUAC, New Delhi

undulator, radiation, simulation, optics

1633

J. Karmakar, S. Ghosh
IUAC, New Delhi, India

A compact THz radiation source based on the principle of pre-bunched Free Electron Laser is at the commissioning stage at Inter University Accelerator Centre (IUAC), New Delhi. The facility will generate low emittance train of electron micro-bunches (2, 4, 8 or 16 numbers) from a RF photo-cathode gun in the energy range of 4 to 8 MeV and inject into a compact undulator to generate coherent THz radiation in the frequency range of ~0.18 to 3.0 THz. To optimize the intensity at a given frequency, the beam bunching factor and the betatron oscillation amplitude in the non-wiggling plane of the electronμbunches inside the undulator has been maximized and minimized respectively. The paper presents the optimized beam optics simulation results for two frequencies viz 0.5 and 2 THz. The on-axis radiation spectral intensity computed by in-house developed code using the trajectory data of the beam optics simulation is also presented for the two frequencies.

Poster TUPAB106 [1.208 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB106

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paper received ※ 18 May 2021 paper accepted ※ 15 August 2021 issue date ※ 31 August 2021

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TUPAB107

Accelerator and Light Source Research Program at Duke University

FEL, polarization, storage-ring, undulator

1636

Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
The accelerator and light source research program at Duke Free-Electron Laser Laboratory (DFELL), TUNL, is focused on the development of the storage ring based free-electron lasers (FELs) and a state-of-the-art Compton gamma-ray source, the High Intensity Gamma-ray Source (HIGS) driven by the storage ring FEL. With a maximum total flux of about 3·10¹⁰ gamma/s and a spectral flux of more than 1,000 gamma/s/eV around 10 MeV, the HIGS is the world’s highest-flux Compton gamma-ray source. Operated in the energy range from 1 to 100 MeV, the HIGS is a premier Compton gamma-ray facility in the world for a variety of nuclear physics research programs, both fundamental and applied. In this work, we will describe our recent light source development to enable the production of gamma rays in the higher energy range from 100 and 120 MeV. We will also provide a summary of our recent accelerator physics and FEL physics research activities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB107

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paper received ※ 26 May 2021 paper accepted ※ 14 July 2021 issue date ※ 16 August 2021

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TUPAB109

Characterization of the X-Ray Angular Pointing Jitter in the LCLS Hard X-ray Undulator Line

undulator, FEL, cavity, detector

1640

R.A. Margraf, Z. Huang, J.P. MacArthur, G. Marcus, T. Sato, D. Zhu
SLAC, Menlo Park, California, USA
Z. Huang
Stanford University, Stanford, California, USA

Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
The angular pointing jitter of X-ray pulses produced by an X-ray Free-Electron Laser (XFEL) depends on both intrinsic properties of the SASE (Self-amplified spontaneous emission) process and jitters in beamline variables such as electron orbit. This jitter is of interest to the Cavity-Based XFEL (CBXFEL)* project at SLAC, which will lase seven undulators inside an X-ray cavity of four diamond Bragg mirrors. The CBXFEL cavity has a narrow angular bandwidth, thus large angular jitters cause X-rays to leak out of the cavity and degrade cavity efficiency. To understand contributors to angular pointing jitter, we studied the pointing jitter of the Linac Coherent Light Source (LCLS) Hard X-ray Undulator line (HXU). Monochromatic and pink X-rays were characterized at the X-ray Pump Probe (XPP) instrument. We found pulses with high monochromatized pulse energy and small electron beam orbit in the undulator have the lowest angular pointing jitter. We present here our measurement results, discuss why these factors correlate with pointing stability, and propose a strategy for CBXFEL to reduce angular pointing jitter and account for angular pointing jitter in cavity efficiency measurements.
*Gabriel Marcus et al. "CBXFEL Physics Requirements Document for the Optical cavity Based X-Ray Free Electron Lasers Research and Development Project." SLAC-I-120-103-121-00. Apr 2020.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB109

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paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 18 August 2021

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TUPAB110

Measurement and Correction of RF Kicks in the LCLS Accelerator to Improve Two-Bunch Operation

FEL, klystron, cavity, experiment

1644

R.A. Margraf, F.-J. Decker, Z. Huang, G. Marcus
SLAC, Menlo Park, California, USA
Z. Huang
Stanford University, Stanford, California, USA

Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
RF kicks, caused by a misalignment of an electron beam and acceleration structure, produce an electron orbit in the accelerator which decreases the final energy of the accelerated electron beam and is detrimental to lasing electron bunches in an X-ray Free Electron Laser (XFEL). RF kicks can depend on the RF waveform of the accelerating structure, so controlling this effect is particularly important when two or more electron bunches are accelerated within an RF fill time. Multibunch modes have been successfully developed for the Linac Coherent Light Source (LCLS) accelerator at SLAC,* and are being continually improved to accommodate new experiments. One such experiment, the Cavity-Based XFEL (CBXFEL)** project will require two electron bunches separated by 218.5 ns which must be identical in energy and orbit. To reduce variation in energy and orbit between the two bunches, we studied the RF kicks produced by each of 75 accelerator segments in the LCLS linac at several RF timings. Here, we discuss these measurements and propose a method to correct RF kicks in the LCLS accelerator using corrector dipoles and quadrupoles.
* F.-J. Decker, et al. Recent Developments and Plans for Two Bunch Operation, Proc. of FEL2017, TUP023.
** Gabriel Marcus et al. CBXFEL Physics Requirements Document. SLAC-I-120-103-121-00. 2020.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB110

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paper received ※ 19 May 2021 paper accepted ※ 15 June 2021 issue date ※ 25 August 2021

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TUPAB111

Layout of the Laser Heater for FLASH²⁰²⁰⁺

laser, undulator, FEL, free-electron-laser

1647

C. Gerth, E. Allaria, A. Choudhuri, L. Schaper, E. Schneidmiller, S. Schreiber, M. Tischer, P. Vagin, M. Vogt, L. Winkelmann, M.V. Yurkov, J. Zemella
DESY, Hamburg, Germany

The major upgrade FLASH²⁰²⁰⁺ of the FEL user facility FLASH includes an improved injector layout for the generation of the high-brightness electron beam as well as an externally seeded FEL beamline. Microbunching gain of initial modulations or shot-noise fluctuations degrade the electron beam quality, which is in particular harmful to the external seed process. To minimize the microbunching gain by a controlled increase of the uncorrelated energy spread, the installation of a laser heater is foreseen directly upstream of the first bunch compression chicane. In this paper, we present the layout of the laser heater section, which follows the original proposal published almost 20 years ago and differs in several aspects from the common layout implemented at many other FEL facilities. The considerations that have been made for the optimisation of the laser heater parameters are described in detail.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB111

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paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 11 August 2021

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TUPAB113

Highlights From the Conceptual Design Report of the Soft X-Ray Laser at MAX IV

FEL, undulator, laser, linac

1651

F. Curbis, J. Andersson, L. Isaksson, B.S. Kyle, F. Lindau, E. Mansten, H. Tarawneh, P.F. Tavares, S. Thorin, A.S. Vorozhtsov
MAX IV Laboratory, Lund University, Lund, Sweden
S. Bonetti
Stockholm University, Stockholm, Sweden
V.A. Goryashko, P.M. Salén
Uppsala University, Uppsala, Sweden
P. Johnsson, S.P. Pirani, M.A. Pop, W. Qin, S. Werin
Lund University, Lund, Sweden
M. Larsson
Stockholm University, Department of Physics, Stockholm, Sweden
A. Nilsson
FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden
J.A. Sellberg
KTH Physics, Stockholm, Sweden

Funding: Knut and Alice Wallenberg Foundation
The SXL (Soft X-ray Laser) project developed a conceptual design for a soft X-ray Free Electron Laser in the 1–5 nm wavelength range, driven by the existing MAX IV 3 GeV linac. In this contribution we will focus on the FEL operation modes developed for the first phase of the project based on two different linac modes. The design work was supported by the Knut and Alice Wallenberg foundation and by several Swedish universities and organizations (Stockholm, Uppsala, KTH Royal Institute of Technology, Stockholm-Uppsala FEL center, MAX IV laboratory and Lund University).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB113

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 18 August 2021

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TUPAB114

FEL Performance and Beam Quality Assessment of Undulator Line for the CompactLight Facility.

undulator, FEL, brilliance, photon

1655

H.M. Castañeda Cortés, D.J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: H2020 CompactLight has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 777431
The H2020 CompactLight Project aims for the design of innovative, cost-effective, compact FEL facilities to generate higher peak brilliance radiation in the soft and hard X-ray. In this paper we assess via simulation studies the performance of a variably polarising APPLE-X afterburner positioned downstream of a helical Super Conducting Undulator (SCU). We discuss the optimum balance between the active SCU length and the afterburner length, considering the peak brilliance and pulse energy of the output. Our studies are complemented with analysis of the optical beam quality of the afterburner output to determine the design constraints of the photon beamline that delivers the FEL output to the experimental areas.
* Mak, A., Salen, P., Goryashko, V., Clarke, J., http://uu.diva-portal.org/smash/record.jsf?pid=diva2\%3A1280300&dswid=3236
** Lutman, A. et al. Nature Photonics 10, 468

Poster TUPAB114 [1.210 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB114

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paper received ※ 11 May 2021 paper accepted ※ 10 June 2021 issue date ※ 23 August 2021

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TUPAB115

Status Report of the Superconducting Free-Electron Laser FLASH at DESY

experiment, FEL, undulator, operation

1659

J. Rönsch-Schulenburg, F. Christie, K. Honkavaara, M. Kuhlmann, S. Schreiber, R. Treusch, M. Vogt, J. Zemella
DESY, Hamburg, Germany

The free-electron laser in Hamburg (FLASH) is a high brilliance XUV and soft X-ray SASE FEL user-facility at DESY. FLASH’s superconducting linac can accelerate several thousand electron bunches per second in 10 Hz bursts of up to 800 µs length. The long bunch trains can be split in two parts and shared between two undulator beamlines. During 2020, FLASH supplied, in standard operation, up to 500 bunches at 10 Hz in two bunch trains with independent fill patterns and compression schemes. The FLASH2 undulator beamline comprises variable gap undulators that allow different novel lasing schemes. A third beamline accommodates the FLASHForward plasma wakefield acceleration experiment. We report on the FLASH operation in 2019 - 2021 and present a few highlights.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB115

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 22 August 2021

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TUPAB116

Toward THz Coherent Undulator Radiation Experiment with a Combination of Velocity Bunchings

radiation, undulator, bunching, acceleration

1663

Y. Sumitomo, K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, T. Tanaka
LEBRA, Funabashi, Japan

Funding: Japan Society for the Promotion of Science (JSPS), Grant-in-Aid for Scientific Research (KAKENHI), Grant Number JP19K12631.
We have launched a research program to generate the THz coherent undulator radiations, following the proposal of the combination of velocity bunchings * at Nihon University. The combination of velocity bunchings is an efficient way of bunch compression allowing a range of energy choices, in other words, a range of quasi-monochromatic radiation wavelengths generated at the undulator. In addition to the existing wideband THz light sources (0.1 - 2 THz) by the coherent edge and transition radiations currently available at Nihon Univ., the development of a high peak-power and quasi-monochromatic coherent radiation should accelerate the activities including the material science related to the THz bandwidths. In this presentation, we illustrate the program and report the current status of the experiment.
* Y. Sumitomo et al., J. Phys. Conf. Ser., vol. 1067, p. 032017, 2018.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB116

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paper received ※ 19 May 2021 paper accepted ※ 15 June 2021 issue date ※ 17 August 2021

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TUPAB119

Beam Loss Study for the Implementation of Dechirper at the European XFEL

FEL, undulator, radiation, simulation

1670

J.J. Guo
University of Chinese Academy of Sciences, Beijing, People’s Republic of China
W. Decking, M.W. Guetg, J.J. Guo, S. Liu, W. Qin, I. Zagorodnov
DESY, Hamburg, Germany
Q. Gu, J.J. Guo
SINAP, Shanghai, People’s Republic of China
Q. Gu
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China

The European XFEL is a free-electron laser facility based on superconducting linac with high repetition rate up to 4.5 MHz. Wakefield structure (also called dechirper module) is planned to be installed in front of the SASE beam line at the European FEL, which can be used as a kicker for two-color scheme or a dechirper to control the bandwidth of SASE radiation. When the beam pass through the dechirper module, strong longitudinal and transverse wakefields can be excited to introduce a correlated energy chirp and a kick along the bunch. However, due to the relatively small gap of dechirper, beam halo particles hitting the dechirper module can lead to energy deposition and generate additional radiation, which can cause serious damage to the downstream undulators. For this reason, simulations have been performed using BDSIM to define the maximum acceptable beam halo, and the results are presented in this paper.

Poster TUPAB119 [1.489 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB119

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paper received ※ 16 May 2021 paper accepted ※ 15 June 2021 issue date ※ 19 August 2021

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TUPAB121

Photoinjector Drive Laser Temporal Shaping for Shanghai Soft X-Ray Free Electron Laser

laser, cathode, FEL, flattop

1674

C.L. Li, X.T. Wang, W.Y. Zhang
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
X.L. Dai
SSRF, Shanghai, People’s Republic of China
H.X. Deng, L. Feng, B. Liu, J.G. Wang
SARI-CAS, Pudong, Shanghai, People’s Republic of China

Shanghai soft X ray free electron laser (SXFEL) initial designed shape of the photocathode driver laser is flattop produced by α-BBO stacking. The advantage of this design is attractive in producing electron bunch with low initial emittance and high uniformity along the electron bunch. However, some unavoidable modulations are generated along the laser pulse which trigger the electron bunch modulation generated at the source, which is due to the fast response time (tens of femtosecond) of copper cathode. In order to eliminate the modulation of electron bunch, temporal Gaussian driver laser was designed and tested, measurement results show the electron bunch longitudinal modulation was removed. In this paper, we present two kinds of driver laser pulse temporal shaping methods based on α-BBO stacking and UV grating pair shaping. Moreover, corresponding electron bunch temporal profile are also presented.

Poster TUPAB121 [2.469 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB121

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 10 August 2021

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TUPAB122

SASE3 Variable Polarization Project at the European XFEL

undulator, polarization, vacuum, FEL

1678

S.K. Karabekyan, S. Abeghyan, M. Bagha-Shanjani, S. Casalbuoni, U. Englisch, G. Geloni, J. Grünert, S. Hauf, C. Holz, D. La Civita, J. Laksman, D. Mamchyk, M.P. Planas, F. Preisskorn, S. Serkez, H. Sinn, A. Violante, G. Wellenreuther, M. Wuenschel, M. Yakopov, C. Youngman
EuXFEL, Schenefeld, Germany
A. Block, W. Decking, N. Golubeva, K. Knebel, T. Ladwig, D.L. Lenz, D. Lipka, R. Mattusch, N. Mildner, E. Negodin, D. Nölle, J. Prenting, F. Saretzki, M. Schlösser, F. Schmidt-Föhre, E. Schneidmiller, D. Thoden, T. Wamsat, S. Wendt, T. Wilksen, T. Wohlenberg, M.V. Yurkov
DESY, Hamburg, Germany
M. Brügger, M. Calvi, S. Danner, R. Ganter, L. Huber, A. Keller, M.S. Schmidt, T. Schmidt
PSI, Villigen PSI, Switzerland
D.E. Kim
PAL, Pohang, Republic of Korea
Y. Li
IHEP, People’s Republic of China

At the European XFEL, two undulator systems for hard and one for soft X-rays have been successfully put into operation. The SASE3 soft X-ray undulator system generates linearly polarized radiation in the horizontal plane. One of the requirements for extending the radiation characteristics is the ability to obtain different polarization modes. These include both right and left circular, elliptical polarization, or linear polarization at an arbitrary angle. For this purpose, a system consisting of four APPLE X helical undulators developed at the Paul Scherrer Institute (PSI) is used. This paper presents the design parameters of the SASE3 undulator system after modifying it with the helical afterburner. It also describes the methods and the design solutions different from those used at PSI. The status and schedule of the project are introduced.

Poster TUPAB122 [0.553 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB122

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paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 02 September 2021

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TUPAB126

Spectral Gap in the Middle Infrared FEL Oscillator of FELiCHEM

FEL, GUI, laser, free-electron-laser

1685

Y.P. Zhu, H.T. Li, Z. Zhao
USTC/NSRL, Hefei, Anhui, People’s Republic of China

A phenomenon of spectral gap is observed in the Middle Infrared FEL Oscillator of FELiCHEM: the laser power falls down at the particular wavelength. Starting with the experimental data, this paper focuses on the simulation calculation and analysis of the effect from using the partial waveguide. The relationship between waveguide and spectral gap is revealed.

Poster TUPAB126 [1.063 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB126

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paper received ※ 17 May 2021 paper accepted ※ 14 June 2021 issue date ※ 14 August 2021

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TUPAB127

Spare Gun Multi-Physics Analysis for LCLS-II

gun, cavity, cathode, simulation

1688

L. Xiao, C. Adolphsen, A. Cedillo, E.N. Jongewaard, X. Liu, C.-K. Ng, F. Zhou
SLAC, Menlo Park, California, USA

LBNL APEX VHF normal conducting gun was adopted for LCLS-II CW operation to provide ultra-bright high repetition rate X-ray pulses. The initial LCLS-II gun and injector commissioning showed excessive dark current dominated by field emission around the cathode plug outer diameter and the gun cavity nose. There is a concern that the dark current may get worse with time of operation. It is planning to build a spare rf gun largely based on the current LCLS-II gun to replace current LCLS-II gun. The proposed spare gun has a reduced the peak electrical fields around the cathode plug corner and cavity nose by 10% through further optimizing APEX gun cavity shape. In addition, there are some moderate modifications on the engineering design to increase mechanical robustness and vacuum performance. SLAC developed parallel finite-element electromagnetic code suite ACE3P is used to apply for the spare gun modeling including RF, thermal and structural analysis at static and transient states to ensure its successful operation in LCLS-II. In this paper, the spare gun multi-physics analysis is described.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB127

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paper received ※ 19 May 2021 paper accepted ※ 20 August 2021 issue date ※ 25 August 2021

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TUPAB131

Measurement of Coherent Smith-Purcell Radiation Using Ultra-Short Electron Bunch at T-Acts

radiation, experiment, bunching, background

1696

H. Yamada, H. Hama, F. Hinode, K. Kanomata, S. Kashiwagi, S. Miura, T. Muto, I. Nagasawa, K. Nanbu, H. Saito, K. Shibata, K. Takahashi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan

The coherent Smith-Purcell radiation (SPR) emitted as a short electron bunch passes over a periodic metal surface is expected to be applied as a non-destructive beam diagnostic tool. The longitudinal profile of the electron bunch can be deduced by the measured spectrum of the coherent SPR, which is compared with the theoretical one for single electron. There are several theoretical models that explain the SPR mechanism, such as the surface current (SC) model and the van den Berg model. But the difference of estimation in radiation intensity between different models is not trivial, and also the experimental data to evaluate those validity is not enough. At test accelerator, t-ACTS, in Tohoku University we are conducting experimental research on coherent SPR in the terahertz frequency region using an ultra-short electron bunch of about 100 fs. The status and results of the experiment will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB131

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paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 23 August 2021

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TUPAB136

On Nonlinear Electron Beam Dynamics in a Plasma Environment

plasma, emittance, linear-dynamics, wakefield

1707

H.Y. Barminova
MEPhI, Moscow, Russia
B. Kak
RUDN University, Moscow, Russia

The nonlinear dynamics of an electron beam propagating in a low-density plasma is investigated. The beam envelope equation is obtained analytically for the case of an axisymmetric beam using a model approximation close to the Kapchinsky-Vladimirsky model. Solutions of the envelope equation are presented for various initial conditions (beam current, initial beam radius, transverse beam emittance).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB136

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paper received ※ 19 May 2021 paper accepted ※ 26 May 2021 issue date ※ 30 August 2021

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TUPAB138

Determination of the Phase of Wakefield Driven by a Self-Modulated Proton Bunch in Plasma

plasma, wakefield, proton, emittance

1710

K. Moon, M. Chung
UNIST, Ulsan, Republic of Korea
P. Muggli
MPI-P, München, Germany

Funding: This work was partly supported by the National Research Foundation of Korea (Nos. NRF-2016R1A5A1013277 and NRF-2020R1A2C1010835)
The phase of wakefield driven by a self-modulated proton bunch depends on the type of seeding method and by the beam-plasma parameters.* Particularly when a preceding electron bunch generates seed wakefield, the proton bunch modulation is strongly affected by the seed bunch dynamics along with the plasma. Intrinsic wakefield dephasing from self-modulation of proton bunch can lead to complex evolution of the bunch and wakefield, making it difficult to design an experimental setup for witness beam injection. Using the particle-in-cell code FBPIC,** we investigate in detail the trends of seed electron and driver proton bunch parameter sensitivity to the phase of wakefield in time in the proton bunch frame. We focus on the parameters affecting the phase of the wakefield through the beam’s radial dynamics, such as beam emittance, radial size, energy, and beam to plasma density ratio. Parameter variations are compared to those in the case of the phase of wakefield driven by a non-evolving seed bunch.
*F. Batsch, arXiv:2012.09676 [physics.plasm-ph]
**R. Lehe, M. Kirchen, I.A. Andriyash, B.B. Godfrey, and J.-L. Vay, Comput. Phys. Comm. 203, 66-82 (2016)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB138

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 25 August 2021

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TUPAB141

On the Development of a Low Peak-Power, High Repetition-Rate Laser Plasma Accelerator at IPEN

laser, plasma, experiment, photon

1713

A. Bonatto
Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
E.P. Maldonado
ITA, São José dos Campos, Brazil
R.P. Nunes
UFRGS, Porto Alegre, Brazil
R.E. Samad, F.B.D. Tabacow, N.D. Vieira, A.V.F. Zuffi
IPEN-CNEN/SP, São Paulo, Brazil

Funding: FAPESP (Grant #2018/25961), CNPq and CAPES.
In this work, the current status on the development of a laser plasma accelerator at the Nuclear and Energy Research Institute (Instituto de Pesquisas Nucleares e Energéticas, IPEN/CNEN), in São Paulo, Brazil, is presented. Short pulses to be produced by an under-development near-TW, kHz laser system will be used to ionize a gas jet, with a density profile designed to optimize the self-injection of plasma electrons. The same laser pulse will also drive a plasma wakefield, which will allow for electron acceleration in the self-modulated regime. The current milestone is to develop the experimental setup, including electron beam and plasma diagnostics, required to produce electron bunches with energies of a few MeV. Once this has been achieved, the next milestone is to produce beams with energies higher than 50 MeV. Besides kickstarting the laser wakefield accelerator (LWFA) technology in Brazil, this project aims to pave the way for conducting research on the production of radioisotopes by photonuclear reactions, triggered by LWFA-accelerated beams.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB141

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paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 25 August 2021

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TUPAB142

Simulation Study of Laser Wakefield Acceleration Varying the Down-Ramp Length of a Gas Jet

plasma, laser, simulation, injection

1717

R.P. Nunes
UFRGS, Porto Alegre, Brazil
A. Bonatto
Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
E.P. Maldonado
ITA, São José dos Campos, Brazil
R.E. Samad, N.D. Vieira
IPEN-CNEN/SP, São Paulo, Brazil

In this work, particle-in-cell simulations were carried out to investigate the role of the down-ramp length of a H\textsubscript{2} gas jet in accelerating electrons ionized by the laser pulse. The laser and plasma density were chosen so that the system is operating in the self-modulated regime. Preliminary results show how the down-ramp length can control the injection of electrons in the first bubble induced in the plasma by the laser pulse.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB142

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paper received ※ 20 May 2021 paper accepted ※ 15 June 2021 issue date ※ 22 August 2021

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TUPAB143

Laser Pulse Dynamics in the Self-Modulated Regime

laser, plasma, wakefield, simulation

1721

R.P. Nunes
UFRGS, Porto Alegre, Brazil
A. Bonatto
Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
E.P. Maldonado
ITA, São José dos Campos, Brazil
R.E. Samad, N.D. Vieira
IPEN-CNEN/SP, São Paulo, Brazil

In this work, particle-in-cell simulations were carried out to investigate the dynamics of a laser pulse propagating along a H₂ gas jet. The laser-driven wakefield and the density of ionized electrons are analyzed during the pulse propagation through the gas jet. The laser and plasma quantities were chosen in order to have the system operating in the self-modulated regime. Results show how the self-modulation fragments the laser pulse, originating higher-amplitude pulses that can induce bubble formation with wave-breaking and particle injection.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB143

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paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 28 August 2021

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TUPAB145

Methods for Numerical Noise Mitigation in Quasistatic Three-Dimensional Particle-in-Cell Code LCODE3D

plasma, simulation, wakefield, acceleration

1725

I.Yu. Kargapolov, K.V. Lotov, A. Sosedkin
Budker INP & NSU, Novosibirsk, Russia
I.A. Shalimova
ICM&MG SB RAS, Novosibirsk, Russia
I.A. Shalimova, P.V. Tuev
NSU, Novosibirsk, Russia
P.V. Tuev
BINP SB RAS, Novosibirsk, Russia

We discuss a new quasistatic 3D particle-in-cell code LCODE3D for simulating plasma wakefield acceleration, which is a modified version of the quasistatic 2D3V code LCODE, focus on the numerical noise of the plasma solver and propose methods for reducing it. We compare different particle shape functions, as these functions affect the code stability. We also introduce the so-called dual plasma approach, which improves stability and dampens small-scale noise. After applying the proposed methods, the results of the new code closely agree with LCODE simulation results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB145

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 01 September 2021

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TUPAB146

High Brightness Electron Beams from Dragon Tail Injection and the E-312 Experiment at FACET-II

plasma, laser, injection, experiment

1728

P. Manwani, N. Majernik, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
D.L. Bruhwiler
RadiaSoft LLC, Boulder, Colorado, USA
B. Hidding
USTRAT/SUPA, Glasgow, United Kingdom
M.D. Litos
Colorado University at Boulder, Boulder, Colorado, USA

Funding: This work was performed with support of the US Department of Energy under Contract No. DE-SC0009914
The advent of optically triggered injection in multi component plasma wakefield accelerators has been shown to enable a substantial increase in witness electron beam quality. Here we present a novel way of using the overlap of laser and beam radial fields to locally liberate electrons from the tunneling ionization of the non-ionized gas species. These liberated ultracold electrons gain sufficient energy to be trapped in the accelerating phase at the back of the plasma blowout. This method of controlled injection has advantages in precision timing since injection is locked to peak beam current and has the potential of generating beams with very low emittance and energy spread. This method has been investigated using particle-in-cell (PIC) simulations. This scenario corresponds to a planned experiment, E-312, at SLAC’s FACET-II facility.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB146

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paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 22 August 2021

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TUPAB147

Asymmetric Beam Driven Plasma Wakefields at the AWA

plasma, wakefield, simulation, emittance

1732

P. Manwani, H.S. Ancelin, G. Andonian, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, California, USA
G. Andonian
RadiaBeam, Santa Monica, California, USA
G. Ha, J.G. Power
ANL, Lemont, Illinois, USA
M. Yadav
The University of Liverpool, Liverpool, United Kingdom
M. Yadav
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was performed with the support of the US Department of Energy, Division of High Energy Physics under Contract No. DE-SC0017648 and DE-SC0009914
In future plasma wakefield acceleration-based scenarios for linear colliders, beams with highly asymmetric emittance are expected. In this case, the blowout region is no longer axisymmetric, but elliptical in cross-section, which implies that the focusing is not equal in the two transverse planes. In this paper, we analyze simulations for studying the asymmetries in flat-beam driven plasma acceleration using the round-to-flat-beam transformer at the Argonne Wakefield Accelerator. Beams with high charge and emittance ratios, in excess of 100:1, are routinely available at the AWA. We use particle-in-cell codes to compare various scenarios including a weak blowout, where the plasma focusing effect exhibits higher order mode asymmetry. Further, practical considerations for tunable plasma density using capillary discharge and laser ionization are compared for implementation into experimental designs.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB147

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paper received ※ 20 May 2021 paper accepted ※ 13 July 2021 issue date ※ 02 September 2021

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TUPAB148

Optical-Period Bunch Trains to Resonantly Excite High Gradient Wakefields in the Quasi-Nonlinear Regime and the E-317 Experiment at FACET-II

plasma, wakefield, experiment, focusing

1736

P. Manwani, C.E. Hansel, N. Majernik, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, California, USA
M. Yadav
The University of Liverpool, Liverpool, United Kingdom
M. Yadav
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was performed with the support of the US Department of Energy under Contract No. DE-SC0009914 and National Science Foundation under Grant No. PHY-1549132
Periodic electron bunch trains spaced at the laser wavelength created via inverse free electron laser (IFEL) bunching can be used to resonantly excite plasmas in the quasi-nonlinear (QNL) regime. The excitation can produce plasma blowout conditions using very low emittance beams despite having a small charge per bunch. The resulting plasma density perturbation is extremely nonlinear locally, but preserves the resonant response of the plasma electrons at the plasma frequency. This excitation can produce plasma blowout conditions using very low emittance beams despite having a small charge per bunch. To match the resonance condition, the plasma wavelength has to be equal to the laser period of a few microns. This corresponds to a high density plasma resulting in extremely large wakefield amplitudes. Matching the beam into such a dense plasma requires an extremely short focusing beta function. We present the beam-plasma interaction using quasi-static particle-in-cell (PIC) simulations and discuss the micro-bunching and focusing mechanism required for this scheme which would be a precursor to the planned experiment, E-317, at SLAC’s FACET-II facility.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB148

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paper received ※ 20 May 2021 paper accepted ※ 08 July 2021 issue date ※ 24 August 2021

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TUPAB153

Modeling of Capillary Discharge Plasmas for Wakefield Accelerators and Beam Transport

plasma, simulation, laser, GUI

1740

N.M. Cook, J.A. Carlsson, S.J. Coleman, A. Diaw, J.P. Edelen
RadiaSoft LLC, Boulder, Colorado, USA
E.C. Hansen, P. Tzeferacos
Flash Center for Computational Science, Chicago, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0018719.
Next generation accelerators demand sophisticated beam sources to reach ultra-low emittances at large accelerating gradients, along with improved optics to transport these beams without degradation. Capillary discharge plasmas can address each of these challenges. As sources, capillaries have been shown to increase the energy and quality of wakefield accelerators, and as active plasma lenses they provide orders-of-magnitude increases in peak magnetic field. Capillaries are sensitive to energy deposition, heat transfer, ionization dynamics, and magnetic field penetration; therefore, capillary design requires careful modeling. We present simulations of capillary discharge plasmas using FLASH, a publicly-available multi-physics code developed at the University of Chicago. We report on the implementation of 2D and 3D models of capillary plasma density and temperature evolution with realistic boundary and discharge conditions. We then demonstrate laser energy deposition to model channel formation for guiding intense laser pulses. Lastly, we examine active capillary plasmas with varying fill species and compare our simulations against experimental studies.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB153

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paper received ※ 24 May 2021 paper accepted ※ 29 July 2021 issue date ※ 30 August 2021

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TUPAB155

Obtaining Accelerated Electron Bunch of High Quality in Plasma Wakefield Accelerator

plasma, wakefield, acceleration, accelerating-gradient

1744

R.T. Ovsiannikov
KhNU, Kharkov, Ukraine
I.P. Levchuk (Yarovaya), V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

Funding: "This work is supported by National Research Fundation of Ukraine "Leading and Young Scientists Research Support", grant agreement # 2020.02/0299."
Earlier, high-gradient accelerating electrons of a relativistic beam was demonstrated. However, due to dynamic processes in the plasma, there are problems in maintaining the small size and small energy spread of the accelerated electron bunch while maintaining sufficient values of the accelerating wakefields. Also, the question arises about the values of the limiting bunch dimensions at which the accelerating process is stable. To form a stable accelerated electron bunch, a method is usually used that involves the formation of the same accelerating fields at the location of the bunch. The same fields (plateau due to beam loading (see *, **)) in the region of the accelerated bunch allow all its parts to move as a whole, and ensure the preservation of the spatial distribution of electrons over time, which, in fact, means an accelerated beam of good quality. In this report, the problem of electron bunch accelerating by a short or long electron driver-bunch is considered.
* Romeo S., Ferrario M., Rossi A.R. Phys. Rev. Accel. Beams. 23 (2020) 071301.
** Maslov V.I. et al. Problems of Atomic Science and Technology. 6 (2020) 47.

Poster TUPAB155 [1.723 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB155

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paper received ※ 18 May 2021 paper accepted ※ 16 June 2021 issue date ※ 23 August 2021

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TUPAB156

Optimal Field Shape, Accelerating Positron Bunch in Plasma Wakefield

plasma, wakefield, positron, acceleration

1747

R.T. Ovsiannikov
KhNU, Kharkov, Ukraine
I.P. Levchuk (Yarovaya), V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

Funding: This work is supported by National Research Fundation of Ukraine "Leading and Young Scientists Research Support", grant agreement # 2020.02/0299.
The quality of the electron or positron beam, accelerated in plasma accelerators, is still insufficient for applications. Accurate control over the properties of the electron or positron beam is a key issue for wakefield plasma accelerators. The effect of the presence of a witness-beam (the effect of the spatial charge distribution of the witness beam) (see [*, **]) to compensate the energy spread of the positron beam in plasma wakefield accelerators has been studied. This paper presents the results of a numerical simulation on the optimization of the parameters of the driver-bunch and witness-bunch for the formation of a self-consistent longitudinal distribution of the accelerating plateau-type field, which leads to the same values of the wakefield for the whole bunch of accelerated particles and minimizing bunch degradation during acceleration by means of an ion-driver-bunch with external injection into the plasma wake accelerator. The dependence of the longitudinal distribution of the accelerating wakefield on the density and shape of the accelerated bunch in the blowout regime was investigated. Plateau formation and energy spread compensation were observed.
* Romeo S., Ferrario M., Rossi A.R. Phys. Rev. Accel. Beams. 23 (2020) 071301.
** Katsouleas T. et al. Particle Accelerators. 22 (1987) 81.

Poster TUPAB156 [1.200 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB156

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paper received ※ 18 May 2021 paper accepted ※ 16 June 2021 issue date ※ 15 August 2021

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TUPAB157

Obtaining Long Accelerated Electron Bunch of Good Quality in Plasma Wakefield Accelerator at High Transformer Ratio

wakefield, plasma, acceleration, simulation

1750

R.T. Ovsiannikov
KhNU, Kharkov, Ukraine
I.P. Levchuk (Yarovaya), V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

Funding: "This work is supported by National Research Fundation of Ukraine "Leading and Young Scientists Research Support", grant agreement # 2020.02/0299."
The efficiency of electron acceleration by a wakefield, excited in a plasma by an electron bunch, is determined by the transformer ratio (see *, **). The transformer ratio is the ratio of energy acquired by the witness to energy lost by the driver. The transformer ratio can be increased by shaping driver-bunch. In this work, using a non-linear version of the 2d3v code lcode (see ***), numerical simulation of excitation of a wakefield in a plasma in blowout regime by a shaped relativistic electron bunch was performed. There is also the problem of maintaining the small dimension and small energy spread of the accelerated electron bunch while maintaining sufficient values of the accelerating gradient and the transformer ratio. Also, the question arises about the values of the limiting dimension of the witness-bunch at which the acceleration process is stable. Numerical simulation solves the problem of electron bunch acceleration of the best quality with simultaneous maximization of the transformer ratio and maximization of the witness bunch length, at which the accelerating gradient and the focusing force are constant.
*Maslov V.I. et al. Problems of Atomic Science and Technology. 4 (2012) 128.
**Baturin S.S., Zholents A. Phys. Rev. ST Accel. Beams. 20 (2017) 061302.
***Lotov K.V. Phys. Plasmas. 5 (1998) 785.

Poster TUPAB157 [1.920 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB157

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paper received ※ 18 May 2021 paper accepted ※ 23 June 2021 issue date ※ 28 August 2021

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TUPAB158

Electron Witness Constraints for AWAKE

emittance, plasma, acceleration, wakefield

1753

J.P. Farmer, P. Muggli
MPI-P, München, Germany
E. Gschwendtner
CERN, Meyrin, Switzerland
L. Liang
The University of Manchester, Manchester, United Kingdom
M.S. Weidl
MPI/IPP, Garching, Germany

The AWAKE project at CERN successfully demonstrated the use of a proton driver to accelerate an electron witness in plasma*. One of the key goals for AWAKE Run2 is to better control this acceleration, separating the proton-beam-modulation and electron-acceleration stages in order to achieve high energy electrons with high beam quality. Controlled acceleration additionally requires careful tuning of the witness bunch parameters at the injection point. In this work, we use particle-in-cell simulations to study the tolerances for this matching, and discuss techniques to loosen these constraints.
*Adli et al. (AWAKE Collaboration), Nature (2018)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB158

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paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 23 August 2021

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TUPAB159

Awake Run 2 at CERN

plasma, experiment, proton, acceleration

1757

E. Gschwendtner
CERN, Meyrin, Switzerland

The AWAKE Run 2 experiment, starting in 2021 at CERN, aims to achieve high-charge bunches of electrons accelerated to high energy (~10 GeV) while maintaining beam quality. AWAKE Run 2 also aims to show that the process is scalable so that, by the end of the run, the AWAKE-scheme technology could be used for first particle physics applications. The first two phases of Run 2 include the investigation of the seeding of the proton bunch self-modulation with the current electron beam in the existing AWAKE facility and the test of a second new plasma source with a density step allowing to maintain strong accelerating fields. In the third phase of Run 2, electrons with an energy of 150 MeV, produced in a newly installed electron source, will be injected into a second plasma source and accelerated to high energies (several GeVs) while keeping good emittance. In the fourth phase, it is planned to replace the second plasma source with a scalable one, which eventually could be used for long-distance acceleration and first applications. In this paper, we present the program of the four phases of AWAKE Run 2, the technical challenges and the proposed schedule.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB159

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paper received ※ 17 May 2021 paper accepted ※ 11 June 2021 issue date ※ 14 August 2021

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TUPAB160

Preparation for Electron-Seeding of Proton Bunch Self-Modulation in AWAKE

plasma, proton, experiment, simulation

1761

G. Zevi Della Porta, E. Gschwendtner, L. Verra
CERN, Meyrin, Switzerland
K. Moon
UNIST, Ulsan, Republic of Korea
P. Muggli, L. Verra
MPI, Muenchen, Germany

The next milestone of the Advanced Wakefield Experiment (AWAKE) at CERN will be to demonstrate that the self-modulation of a long proton bunch can be seeded by a short electron bunch preceding it. This seeding method will lead to phase-reproducible self-modulation of the entire proton bunch, as required for the future AWAKE program. In the Spring of 2021, before receiving proton beams from the CERN SPS, AWAKE plans to hold a dry run of the electron seeding experiments, to commission the system and to determine the parameter scans that will be used in experiments with protons. Electron bunches of 10-20 MeV with varying charge, radius, emittance and energy will be sent in 10 m of low-density plasma. The effects of beam-plasma interactions on the amplitude of the wakefields driven by the different bunches will be studied by observing the energy spectra at the end of the plasma. This paper presents preliminary experimental results from the first two days of measurements as well as the beginning of a simulation-based study of electron propagation in plasma.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB160

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paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 11 August 2021

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TUPAB163

Developing a 50 MeV LPA-Based Injector at ATHENA for a Compact Storage Ring

plasma, laser, storage-ring, target

1765

E. Panofski, J. Dirkwinkel, T. Hülsenbusch, A.R. Maier, J. Osterhoff, G. Palmer, T. Parikh, P.A. Walker, P. Winkler
DESY, Hamburg, Germany
C. Braun, T.F.J. Eichner, L. Hübner, S. Jalas, L. Jeppe, M. Kirchen, P. Messner, M. Schnepp, M. Trunk, C.M. Werle
University of Hamburg, Hamburg, Germany
E. Bründermann, B. Härer, A.-S. Müller, C. Widmann
KIT, Karlsruhe, Germany
M. Kaluza, A. Sävert
HIJ, Jena, Germany

The laser-driven generation of relativistic electron beams in plasma and their acceleration to high energies with GV/m-gradients has been successfully demonstrated. Now, it is time to focus on the application of laser-plasma accelerated (LPA) beams. The "Accelerator Technology HElmholtz iNfrAstructure" (ATHENA) of the Helmholtz Association fosters innovative particle accelerators and high-power laser technology. As part of the ATHENAe pillar several different applications driven by LPAs are to be developed, such as a compact FEL, medical imaging and the first realization of LPA-beam injection into a storage ring. The latter endeavor is conducted in close collaboration between Deutsche Elektronen-Synchrotron (DESY), Karlsruhe Institute of Technology (KIT) and Helmholtz Institute Jena. In the cSTART project at KIT, a compact storage ring optimized for short bunches and suitable to accept LPA-based electron bunches is in preparation. In this conference contribution we will introduce the 50 MeV LPA-based injector and give an overview about the project goals. The key parameters of the plasma injector will be presented. Finally, the current status of the project will be summarized.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB163

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paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 30 August 2021

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TUPAB177

Simulating Magnetized Electron Cooling for EIC with JSPEC

scattering, simulation, target, HOM

1813

S.J. Coleman, D.L. Bruhwiler, B. Nash, I.V. Pogorelov
RadiaSoft LLC, Boulder, Colorado, USA
H. Zhang
JLab, Newport News, Virginia, USA

We present a possible electron cooling configuration for the proposed Electron Ion Collider (EIC) facility, developed using a Nelder-Mead Simplex optimization procedure built into JSPEC, an electron cooling code developed at Jefferson Lab. We show the time evolution of the emittance of the ion beam in the presence of this cooler evaluated assuming the ion distribution remains Gaussian. We also show that bi-gaussian distributions emerge in simulations of ion macro-particles. We show how intra-beam scattering can be treated with a core-tail model in simulations of ion macro-particles. The Sirepo/JSPEC* and Sirepo/Jupyter** apps will be presented, with instructions enabling the community to reproduce our simulations.
* https://www.sirepo.com/jspec
** https://www.sirepo.com/jupyter

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB177

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paper received ※ 19 May 2021 paper accepted ※ 15 June 2021 issue date ※ 19 August 2021

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TUPAB178

Recommissioning of the CRYRING@ESR Electron Cooler

experiment, target, acceleration, operation

1816

C. Krantz, Z. Andelkovic, C. Dimopoulou, W. Geithner, T. Hackler, F. Herfurth, R. Hess, M. Lestinsky, E. Menz, A. Reiter, J. Roßbach, C. Schroeder, A. Täschner, G. Vorobjev
GSI, Darmstadt, Germany
C. Brandau, S. Schippers
Justus-Liebig-University Giessen, I. Physics Institute, Atomic and Molecular Physics, Giessen, Germany
V. Hannen, D. Winzen
Westfälische Wilhelms-Universität Münster, Institut für Kernphysik, Münster, Germany
C. Weinheimer
Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, Münster, Germany

Funding: Parts of this work have been supported by the German Federal Ministry of Education and Research (BMBF) under contract numbers 05P19PMFA1 and 05P19RGFA1.
The heavy-ion storage ring CRYRING has been recommissioned downstream of GSI’s ESR, which it complements as dedicated low-energy machine. A key element of CRYRING@ESR is its electron cooler, which features one of the coldest electron beams available. This enables efficient phase-space cooling and, in addition, provides very high energy resolution when used as internal electron target. We report on technical upgrades that have been made as part of the re-installation of the cooler at GSI/FAIR and share first results obtained after recommissioning.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB178

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paper received ※ 18 May 2021 paper accepted ※ 16 June 2021 issue date ※ 19 August 2021

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TUPAB179

Design of an MBEC Cooler for the EIC

proton, kicker, hadron, simulation

1819

W.F. Bergan, P. Baxevanis, M. Blaskiewicz, E. Wang
BNL, Upton, New York, USA
G. Stupakov
SLAC, Menlo Park, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
Reaching maximal luminosity for the planned electron-ion collider (EIC) calls for some form of strong hadron cooling to counteract beam emittance increase from IBS. We discuss plans to use microbunched electron cooling (MBEC) to achieve this. The principle of this method is that the hadron beam will copropogate with a beam of electrons, imprinting its own density modulation on the electron beam. These electron phase space perturbations are amplified before copropogating with the hadrons again in a kicker section. By making the hadron transit time between modulator and kicker dependent on hadron energy and transverse offset, the energy kicks which they receive from the electrons will tend to reduce their longitudinal and transverse emittances. We discuss details of the analytic theory and searches for optimal realistic parameter settings to achieve a maximal cooling rate while limiting the effects of diffusion and electron beam saturation. We also place limits on the necessary electron beam quality. These results are corroborated by simulations.

Poster TUPAB179 [4.006 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB179

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paper received ※ 19 May 2021 paper accepted ※ 18 June 2021 issue date ※ 19 August 2021

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TUPAB180

Plasma Simulations for an MBEC Cooler for the EIC

hadron, simulation, kicker, proton

1823

W.F. Bergan
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
In order to reach its maximum luminosity, the electron-ion collider (EIC) is being designed to use microbunched electron cooling (MBEC) to cool the hadron beam. This involves having the hadron beam imprint on a beam of electrons, enhancing the perturbations in the electron beam using the microbunching instability, and feeding back on the original hadron beam to correct deviations in hadron energy, and, through the use of dispersion, the transverse emittances. This process has been modelled analytically in the linear regime*. However, in order to maximize the cooling rate, we wish to know how much saturation in the electron beam is acceptable before the effects of nonlinearity cause significant deviations from the analytic results. To understand this, we have developed a code to do fast one-dimensional plasma simulations of hadrons and electrons as they move through the MBEC section of the EIC. In addition to permitting us to understand the effects of saturation, other effects are included which do not fit easily in the analytic formalism.
* G. Stupakov and P. Baxevanis, PRAB 22, 034401 (2019).

Poster TUPAB180 [1.955 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB180

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 29 August 2021

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TUPAB181

Demonstration of Electron Cooling using a Pulsed Beam from an Electrostatic Electron Cooler

experiment, space-charge, timing, emittance

1827

M.W. Bruker, S.V. Benson, A. Hutton, K. Jordan, T. Powers, R.A. Rimmer, T. Satogata, A.V. Sy, H. Wang, S. Wang, H. Zhang, Y. Zhang
JLab, Newport News, Virginia, USA
J. Li, F. Ma, X.M. Ma, L.J. Mao, X.P. Sha, M.T. Tang, J.C. Yang, X.D. Yang, H.W. Zhao
IMP/CAS, Lanzhou, People’s Republic of China
H. Zhao
BNL, Upton, New York, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Electron cooling continues to be an invaluable technique to reduce and maintain the emittance in hadron storage rings in cases where stochastic cooling is inefficient and radiative cooling is negligible. Extending the energy range of electron coolers beyond what is feasible with the conventional, electrostatic approach necessitates the use of RF fields for acceleration and, thus, a bunched electron beam. To experimentally investigate how the relative time structure of the two beams affects the cooling properties, we have set up a pulsed-beam cooling device by adding a synchronized pulsing circuit to the conventional electron source of the CSRm cooler at Institute of Modern Physics *. We show the effect of the electron bunch length and longitudinal ion focusing strength on the temporal evolution of the longitudinal and transverse ion beam profile and demonstrate the detrimental effect of timing jitter as predicted by theory and simulations. Compared to actual RF-based coolers, the simplicity and flexibility of our setup will facilitate further investigations of specific aspects of bunched cooling such as synchro-betatron coupling and phase dithering.
* M. W. Bruker et al., Phys. Rev. Accel. Beams 24, 012801 (2021)

Poster TUPAB181 [3.699 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB181

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paper received ※ 19 May 2021 paper accepted ※ 15 June 2021 issue date ※ 19 August 2021

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TUPAB182

The Electron Cooling for High Energy

high-voltage, gun, collider, experiment

1831

V.B. Reva, E.A. Bekhtenev, O.V. Belikov, M.I. Bryzgunov, A.V. Bubley, V.A. Chekavinskiy, A.P. Denisov, M.G. Fedotov, A.D. Goncharov, K. Gorchakov, V.C. Gosteyev, I.A. Gusev, G.V. Karpov, M.N. Kondaurov, V.R. Kozak, N.S. Kremnev, V.M. Panasyuk, V.V. Parkhomchuk, A.V. Petrozhitskii, D.N. Pureskin, A.A. Putmakov, D.V. Senkov, K.S. Shtro, D.N. Skorobogatov, R.V. Vakhrushev, A.A. Zharikov
BINP SB RAS, Novosibirsk, Russia

The project of new accelerator complex NICA relating to nuclear and hadron physics require a more powerful longitudinal and transverse cooling that stimulates searching new technical solutions. The new accelerator complex NICA is designed at the Joint Institute for Nuclear Research (JINR, Dubna, Russia) to do experiment with ion-ion and ion-proton collision in the energy range 1-4.5 GeV/u for studying the properties of dense baryonic matter at extreme values of temperature and density with planned luminosity 10²⁷ cm^-2s^-1. This value can be obtained with help of very short bunches with small transverse size. This beam quality can be realized with help of stochastic and electron cooling at energy of the physics experiment. The electron cooling system on 2.5 MeV consists of two coolers, which cool both ion beams simultaneously. The Budker Institute of Nuclear Physics (BINP SB RAS) has already built and commissioned the electron cooling system for the NICA booster, and now it develops the high voltage electron cooling system for the collider. The article describes the construction and status of the cooler development.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB182

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paper received ※ 18 May 2021 paper accepted ※ 22 June 2021 issue date ※ 23 August 2021

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TUPAB200

Status of the Electron Lens for Space Charge Compensation in SIS18

gun, solenoid, cathode, space-charge

1880

K. Schulte-Urlichs, S. Artikova, D. Ondreka, P.J. Spiller
GSI, Darmstadt, Germany
P. Apse-Apsitis, I. Steiks
Riga Technical University, Riga, Latvia
M. Droba, O. Meusel, H. Podlech, K.I. Thoma
IAP, Frankfurt am Main, Germany

At GSI a project has been initiated to investigate the option of space charge compensation (SCC) by use of an electron lens in order to overcome space charge (SC) limits in the synchrotrons SIS18 and SIS100 for the Facility for Antiproton and Ion Research (FAIR). The repeated crossing of resonance lines due to the synchrotron motion in bunched beams is considered one of the main drivers of SC induced beam loss in the synchrotrons. Electron lenses provide a compensation of ion beam SC by virtue of their negative charge interacting with the ions in the overlap region while a time-varying compensation can be achieved by the modulation of the electron beam. In order to demonstrate space charge compensation of bunched ion beams, an electron lens is under development for the application in SIS18. In this contribution, the status of the electron lens design will be reported putting special emphasis on its main components: the RF modulated electron gun, that is being developed within an ARIES collaboration, and the magnet system.

Poster TUPAB200 [1.869 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB200

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 17 August 2021

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TUPAB201

Vacuum Tube Operation Tuning for a High Intensity Beam Acceleration in J-PARC RCS

acceleration, vacuum, operation, controls

1884

M. Yamamoto, M. Nomura, H. Okita, T. Shimada, F. Tamura
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
M. Furusawa, K. Hara, K. Hasegawa, C. Ohmori, Y. Sugiyama, M. Yoshii
KEK, Tokai, Ibaraki, Japan

Tetrode vacuum tubes in the J-PARC RCS are used under a reduced filament voltage condition compared with the rating value to prolong the tube life time. One tube reached the end of life in 2020; it was the first case in the RCS after 60,000 hours operation time. This means the reduced filament voltage works well because the tube has been running beyond an expected life time suggested by the tube manufacturer. However, an electron emission from the filament is decreased by the reduced filament voltage. Although the large amplitude of the anode current is necessary for the high intensity beam acceleration to compensate an wake voltage, a solid-state amplifier to drive a control grid circuit almost reaches the output power limit because of the poor electron emission. We changed the filament voltage reduction rate from 15 % to 5 %; the required power of the solid-state amplifier was fairly reduced, whereas the accelerated beam power was same. We will describe the measurement results of the vacuum tube parameters in terms of the filament voltage tuning.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB201

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paper received ※ 17 May 2021 paper accepted ※ 17 June 2021 issue date ※ 20 August 2021

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TUPAB218

Fully Covariant Two-Particle Space-Charge Dynamics Using the Liénard-Wiechert Potentials

electromagnetic-fields, space-charge, FEL, dipole

1931

B.T. Folsom, E. Laface
ESS, Lund, Sweden

Space charge models typically assume instantaneous propagation of the electromagnetic fields between particles in a bunch, describing forces in the frame of the reference particle. In this paper, we construct a space-charge tracking code from the retarded Liénard-Wiechert potentials, which are covariant by design, in a Lagrangian formulation. Such potentials are manipulated with covariant derivatives to produce the necessary equations of motion that will be solved in a test system of two particles at various relative energies. Magnetic dipole moment dynamics are also evaluated where applicable.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB218

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paper received ※ 19 May 2021 paper accepted ※ 19 July 2021 issue date ※ 26 August 2021

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TUPAB222

Application and Development of the Streak Camera Measurement System at HLS-II

experiment, operation, storage-ring, synchrotron

1942

Y.K. Zhao, S.S. Jin, P. Lu, B.G. Sun, J.G. Wang, F.F. Wu, T.Y. Zhou
USTC/NSRL, Hefei, Anhui, People’s Republic of China

The dual-axial scan streak camera plays an important role in the super-fast optical measurement and the beam diagnosis of the accelerators. Indeed, the development of the synchrotron light measurement system by virtue of the streak camera provides an effective tool and research platform for accelerator physics and super-fast optical phenomenon. In this paper, the configuration of the streak camera measurement system is roughly described. And the experimental researches are simultaneously performed, including the bunch lengthening, the potential-well distortion, the longitudinal bunch oscillations, and the beam evolution during the single bunch operation mode in the HLS-II storage ring. Moreover, the effects of the RF modulation on the beam lifetime and longitudinal bunch beam dynamics are carried out.

Poster TUPAB222 [1.713 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB222

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paper received ※ 10 May 2021 paper accepted ※ 16 June 2021 issue date ※ 16 August 2021

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TUPAB226

Study of the Third-Order Parametric Resonance Induced by RF Modulation

simulation, storage-ring, synchrotron, injection

1956

P.F. Liang, H.S. Xu
IHEP, Beijing, People’s Republic of China

There were both analytic and experimental studies on the effects of RF modulation on bunch lengthening in electron storage rings. Nevertheless, the increase of bunch energy spread will happen in the meantime. Therefore, the degradation of bunch quality may limit the potential applications of the RF modulation technique. As a consequence, we believe that the comprehensive studies of the parametric resonance induced by RF modulation are necessary for understanding the physics picture better and seeking new possibilities of applications of this technique. The studies on the beam dynamics closed to the 3v_s RF phase modulation would be presented here. Based on the basic longitudinal synchrotron equations of motion, we obtained analytically the longitudinal modulated Hamiltonian and various parameters in longitudinal phase space, such as the fixed points, island tune, island width. The validity of the analytic results was checked by simulations. Furthermore, the dependence of the bunch parameters, such as energy spread and bunch length, on the modulation settings is also discussed in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB226

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 14 August 2021

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TUPAB235

Dynamic Aperture Optimization in the EIC Electron Storage Ring with Two Interaction Points

lattice, sextupole, collider, dynamic-aperture

1984

D. Marx, Y. Li, C. Montag, S. Tepikian, F.J. Willeke
BNL, Upton, New York, USA
Y. Cai, Y.M. Nosochkov
SLAC, Menlo Park, California, USA
G.H. Hoffstaetter, J.E. Unger
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 and by SLAC under Contract No. DE-AC02-76SF00515 with the U.S. Department of Energy.
In the Electron-Ion Collider (EIC), which is currently being designed for construction at Brookhaven National Laboratory, electrons from the electron storage ring will collide with hadrons, producing luminosities up to 10³⁴ cm^-2 s^-1. The baseline design includes only one interaction point (IP), and optics have been found with a suitable dynamic aperture in each dimension. However, the EIC project asks for the option of a second IP. The strong focusing required at the IPs creates a very large natural chromaticity (about -125 in the vertical plane for the ring). Compensating this linear chromaticity while simultaneously controlling the nonlinear chromaticity to high order to achieve a sufficient momentum acceptance of 1% (10 σ) at 18 GeV is a considerable challenge. A scheme to compensate higher-order chromatic effects from 2 IPs by setting the phase advance between them does not, by itself, provide the required momentum acceptance for the EIC Electron Storage Ring. A thorough design of the nonlinear optics is underway to increase the momentum acceptance using multiple sextupole families, and the latest results are presented here.

Poster TUPAB235 [3.426 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB235

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paper received ※ 19 May 2021 paper accepted ※ 19 July 2021 issue date ※ 11 August 2021

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TUPAB236

Progress on the Electron Gun Design for a McMillan Electron Lens in the Fermilab Integrable Optics Test Accelerator (IOTA)

gun, cathode, simulation, optics

1988

B.L. Cathey, G. Stancari
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
This paper covers the progress made so far in designing the first McMillan electron lens for the Fermilab IOTA ring. The novel design allows for an increase in tune spread without limiting the dynamic aperture due to its integrability. Shown are simulations for an electron gun design to generate the specific required current density distribution for the nonlinear integrable system in IOTA.

Poster TUPAB236 [5.391 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB236

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paper received ※ 19 May 2021 paper accepted ※ 19 July 2021 issue date ※ 25 August 2021

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TUPAB241

Characterization of the RF-Cavities geometry in Order to Optimize the Beam Parameters in S-Band On-Axis LINACs

cavity, target, emittance, impedance

2005

A. Khosravi, B. Shokri
LAPRI, Tehran, Iran
N. Khosravi
ILSF, Tehran, Iran

The RF characteristics of an accelerating tube are primarily assigned to geometrical features of a cavity. As a consequence of this geometry, the final electric field will make the shape of our Gaussian bunch and the final dose. The accelerating field can be studied considering the nose cone, gap, and bore radius. In dual electron linacs, the role of input power and bunch current is inevitable. Therefore, the geometrical issues of RF-cavities are studied in a 6MeV electron on-axis SW tube. To make an accurate comparison, each RF-cavity is designed and optimized by POISSON SU-PERFISH. The optimized cavities are imported to the PIC solver of CST. Then the beam characteristics are studied on a predefined target.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB241

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paper received ※ 18 May 2021 paper accepted ※ 14 June 2021 issue date ※ 13 August 2021

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TUPAB243

Investigation of the Buncher Effect on Beam Properties in SW 3-6 MeV LINACs

cavity, emittance, target, impedance

2012

A. Khosravi, B. Shokri
LAPRI, Tehran, Iran
N. Khosravi
ILSF, Tehran, Iran

The best quality of an electron beam is the primary goal of a linear accelerator design. Beam-study on a buncher section can lead us to a better perspective of the modulation and acceleration of a beam to optimize the final Gaussian beam. Five setups of different bunchers are designed, optimized, and presented in this article. A more brilliant and converged beam with a higher current, transverse emittance and smaller beam size is the study’s goal.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB243

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paper received ※ 18 May 2021 paper accepted ※ 14 June 2021 issue date ※ 12 August 2021

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TUPAB246

Numerical Simulation and Beam-Dynamics Study of a Hollow-Core Woodpile Coupler for Dielectric Laser Accelerators

GUI, photon, laser, acceleration

2022

G.S. Mauro, D. Mascali, G. Sorbello, G. Torrisi
INFN/LNS, Catania, Italy
A. Bacci
INFN/LASA, Segrate (MI), Italy
C. De Angelis, A. Locatelli
University of Brescia, Brescia, Italy
A.R. Rossi
INFN-Milano, Milano, Italy
G. Sorbello
University of Catania, Catania, Italy

Hollow core dielectric microstructures powered by lasers represent a new and promising area of accelerator research thanks to the higher damage threshold and accelerating gradients with respect to metals at optical wavelengths. In this paper we present the design of a dielectric Electromagnetic Band Gap (EBG) mode converter for high-power coupling of the accelerating mode in Dielectric Laser Accelerators (DLAs). The design is wavelength-independent, and here we propose an implementation operating at 90.505 GHz (wavelength 3.3 mm) based on a silicon woodpile structure. The coupler is composed by two perpendicularly coupled hollow-core waveguides: a TE-like mode waveguide (excited from RF/laser power) and a TM-like mode accelerating waveguide. The structure has been numerically designed and optimized, presenting Insertion Losses (IL) < 0.3 dB and an efficient mode conversion in the operating bandwidth. The properties and effectiveness of the confined accelerating mode have been optimized in order to derive the needed accelerating gradient. The simulated electric field has been used as input for Astra beam-dynamics simulations in order to compute the beam properties.

Poster TUPAB246 [2.209 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB246

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paper received ※ 18 May 2021 paper accepted ※ 27 July 2021 issue date ※ 13 August 2021

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TUPAB247

Influence of the Profile of the Dielectric Structure on the Electric Fields Excited by a Laser in Dielectric Accelerators Based on Chip

acceleration, laser, experiment, simulation

2026

A. Vasyliev, O.O. Bolshov, K. Galaydych, A.I. Povrozin, G.V. Sotnikov
NSC/KIPT, Kharkov, Ukraine

Funding: The National Research Foundation of Ukraine, program "Leading and Young Scientists Research Support" (project # 2020.02/0299).
To provide experimental researches at the NSC KIPT theoretical studies and computations of the electron acceleration in a dielectric laser accelerator have been carried out. Laser accelerator consists of two periodic quartz structures on diffraction gratings or Chips, symmetrically located along both sides of the vacuum accelerating channel. Using PIC numerical simulations, electromagnetic fields excited by laser radiation with a wavelength of 800 nm in dielectric laser accelerators were investigated. The influence of the shape and depth of the profile of diffraction gratings or Chip structures on the distribution of the electric field in the interaction space has been studied. For modeling, different types of profiles were taken, both in serial and a unique structure. In consequence of the analysis of the obtained results, estimated efficiency of acceleration was defined for each type of profile. The rectangular profile of the diffraction grating with the maximum accelerating gradient was selected as optimal for the next experiments.

Poster TUPAB247 [1.195 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB247

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paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 18 August 2021

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TUPAB249

Diffraction at the Open-Ended Dielectric-Loaded Circular Waveguide

GUI, radiation, wakefield, acceleration

2033

S.N. Galyamin, A.V. Tyukhtin, V.V. Vorobev
Saint Petersburg State University, Saint Petersburg, Russia

Funding: Work supported by Russian Science Foundation (Grant No. 18-72-10137).
Contemporary beam and THz technologies are tightly interlaced during last years. Strong THz fields allow realization of THz driven electron guns, THz bunch compression, streaking* and THz driven wakefield acceleration**. Inversely, dielectric capillaries similar to those used for THz bunch manipulation can be in turn utilized for development of high-power narrow-band THz sources***. Mentioned cases involve interaction of THz waves and particle bunches with an open end of certain dielectric loaded waveguide structure, most frequently a circular capillary. For further development of the discussed prospective topics a rigorous approach allowing analytical investigation of both radiation from open-ended capillaries and their excitation by external source would be extremely useful. We present an elegant and efficient rigorous method for solving circular open-ended dielectric-loaded waveguide diffraction problems based on Wiener-Hopf technique. We deal with the case of uniform dielectric loading and internal excitation by a waveguide mode. S-parameters, near-field and far-field distributions are presented. The obtained results can be also applied to the narrow band wakefield.
* L. Zhao et al., Phys. Rev. Lett., 124, 054802 (2020).
** M.T. Hibberd et al., Nat. Photonics, 14, 755-759 (2020).
*** D. Wang et al., Rev. Sci. Instr., 89(9), 093301 (2018).

Poster TUPAB249 [2.160 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB249

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 19 August 2021

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TUPAB251

Impedance Studies of a Corrugated Pipe for KARA

impedance, resonance, simulation, radiation

2039

S. Maier, M. Brosi, A. Mochihashi, A.-S. Müller, M.J. Nasse, M. Schwarz
KIT, Karlsruhe, Germany

Funding: DFG project 431704792 in the ANR-DFG collaboration project ULTRASYNC and the DFG-funded Doctoral School "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology".
At the KIT storage ring KARA (KArlsruhe Research Accelerator) it is planned to install an impedance manipulation structure in a versatile chamber to study and eventually control the influence of an additional impedance on the beam dynamics and the emitted coherent synchrotron radiation. For this purpose the impedance of a corrugated pipe is under investigation. In this contribution, we present first results of simulations showing the impact of different structure parameters on its impedance and wake potential.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB251

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 22 August 2021

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TUPAB254

Limiting Coherent Longitudinal Beam Oscillations in the EIC Electron Storage Ring

feedback, cavity, emittance, hadron

2046

B. Podobedov
Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA
M. Blaskiewicz
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
We study coherent longitudinal beam oscillations in the EIC electron storage ring (ESR). We show that to avoid unacceptable hadron emittance growth due to finite crossing angle, the amplitude of these oscillations needs to be limited to a fraction of a millimeter. Using an analytical model we estimate the amplitude of these oscillations under the two scenarios: 1) the beam is passively stable and the oscillations are driven by RF phase noise only; 2) a coupled-bunch instability, presently expected in the ESR, is damped by a longitudinal feedback system. We show that, for the 2nd scenario, comfortable specifications for RF phase noise and feedback sensor noise will be sufficient to maintain the oscillation amplitude within the required limits.

Poster TUPAB254 [1.347 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB254

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paper received ※ 12 May 2021 paper accepted ※ 18 June 2021 issue date ※ 26 August 2021

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TUPAB255

Longitudinal Beam Dynamics and Coherent Synchrotron Radiation at cSTART

synchrotron, radiation, storage-ring, synchrotron-radiation

2050

M. Schwarz, E. Bründermann, D. El Khechen, B. Härer, A. Malygin, A.-S. Müller, M.J. Nasse, A.I. Papash, R. Ruprecht, J. Schäfer, M. Schuh, P. Wesolowski
KIT, Karlsruhe, Germany

The compact STorage ring for Accelerator Research and Technology (cSTART) project aims to store electron bunches of LWFA-like beams in a very large momentum acceptance storage ring. The project will be realized at the Karlsruhe Institute of Technology (KIT, Germany). Initially, the Ferninfrarot Linac- Und Test-Experiment (FLUTE), a source of ultra-short bunches, will serve as an injector for cSTART to benchmark and emulate laser-wakefield accelerator-like beams. In a second stage a laser-plasma accelerator will be used as an injector, which is being developed as part of the ATHENA project in collaboration with DESY and Helmholtz Institute Jena (HIJ). With an energy of 50 MeV and damping times of several seconds, the electron beam does not reach equilibrium emittance. Furthermore, the critical frequency of synchrotron radiation is 53 THz and in the same order as the bunch spectrum, which implies that the entire bunch radiates coherently. We perform longitudinal particle tracking simulations to investigate the evolution of the bunch length and spectrum as well as the emitted coherent synchrotron radiation. Finally, different options for the RF system are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB255

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paper received ※ 17 May 2021 paper accepted ※ 21 June 2021 issue date ※ 11 August 2021

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TUPAB257

Analysis of Multibunch Spectrum for an Uneven Bunch Distribution in a Storage Ring

impedance, collider, storage-ring, distributed

2058

R. Li, F. Marhauser
JLab, Newport News, Virginia, USA

Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Modern storage-ring designs often require an uneven bunch distribution pattern. An uneven bunch fill pattern can result in complex structures for the beam current spectra. Particularly at high average beam currents, these complex current spectra need to be taken into account in concern of beam-dynamical effects. In this study, we analyze a beam current spectrum for various filling patterns with bunch trains and gaps. The characteristics of the resulting beam current spectra are illustrated and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB257

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paper received ※ 21 June 2021 paper accepted ※ 28 June 2021 issue date ※ 13 August 2021

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TUPAB258

Impact of Coherent Beam-Beam Interaction on the Landau Damping of the Transverse Coupled-Bunch Instability

dipole, damping, coupling, proton

2062

R. Li
JLab, Newport News, Virginia, USA
M. Blaskiewicz
BNL, Upton, New York, USA

Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
In the EIC design, at high average-current operation, the transverse coupled-bunch instability (TCBI) induced by the long-range transverse resistive-wall wakefield in the electron storage ring (eSR) has a fast growth rate and requires efficient mitigation. A natural mitigation mechanism is provided by the beam-beam interaction at the interaction point (IP), which gives a strong Landau damping for the TCBI in the eSR. In this study, using a simplified simulation model, we investigate how this Landau damping from the beam-beam interaction behaves when the coherent beam-beam interaction at IP is considered. Our method and results will be presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB258

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paper received ※ 21 June 2021 paper accepted ※ 01 July 2021 issue date ※ 31 August 2021

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TUPAB260

A Beam Screen to Prepare the RHIC Vacuum Chamber for EIC Hadron Beams: Conceptual Design and Requirements

vacuum, hadron, dipole, collider

2066

S. Verdú-Andrés, M. Blaskiewicz, J.M. Brennan, X. Gu, R.C. Gupta, A. Hershcovitch, M. Mapes, G.T. McIntyre, J.F. Muratore, S.K. Nayak, S. Peggs, V. Ptitsyn, R. Than, J.E. Tuozzolo, D. Weiss
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The Electon Ion Collider (EIC) hadron ring will use the existing Relativistic Heavy Ion Collider storage rings, including the superconducting magnet arcs. The vacuum chambers in the superconducting magnets and the cold mass interconnects were not designed for EIC beams and so must be updated to reduce its resistive-wall heating and to suppress electron clouds. To do so without compromising the EIC luminosity goal, a stainless steel beam screen with co-laminated copper and a thin layer of amorphous carbon will be installed. This paper describes the main requirements that our solution for the hadron ring vacuum chamber needs to satisfy, including impedance, aperture limitations, vacuum, thermal and structural stability, mechanical design, installation and operation. The conceptual design of the beam screen currently under development is introduced.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB260

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paper received ※ 19 May 2021 paper accepted ※ 22 August 2021 issue date ※ 25 August 2021

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TUPAB272

Observation of Long-Range Wakefield Effects Generated in an Off-Resonance Tesla-Type Cavity

cavity, HOM, resonance, wakefield

2101

A.H. Lumpkin, D.R. Edstrom, A. Lunin, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA
J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz, B.T. Jacobson, J.P. Sikora
SLAC, Menlo Park, California, USA

Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics
The interest in controlling emittance dilution effects due to off-axis beam transport in accelerator cavities and the resulting dipolar modes is especially important for the facilities with lower emittance beams. The Fermilab Accelerator Science and Technology (FAST) facility has a unique configuration of two single cavities after the photocathode rf gun followed by a cryomodule. The second capture cavity (CC2) was run 15 kHz off resonance and without rf power while a 25-MeV beam was injected into it. The beam centroid effects were tracked by 10 rf button BPMs with bunch-by-bunch position readout capability downstream in a 12-m drift. Possible LRW effects seemed to dominate our previously observed near-resonant HOM effects at mode 14 in this cavity. This mode also shifted in frequency compared to that of the tuned case based on direct measurements. Submacropulse vertical position slewing of 1400 microns at 11 m downstream was observed with a 125 pC/bunch, 50 bunches per macropulse, and 25-MeV beam. The y-position slew amplitudes as a function of z were also measured. Horizontal positions also showed a slew effect. Both are emittance-dilution effects which one wants to mitigate.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB272

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 16 August 2021

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TUPAB273

Observations on Submicropulse Electron-Beam Effects From Short-Range Wakefields in Tesla-Type Superconducting Rf Cavities

cavity, wakefield, laser, HOM

2105

A.H. Lumpkin, D.R. Edstrom, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA
J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz, A.L. Edelen, B.T. Jacobson, F. Zhou
SLAC, Menlo Park, California, USA

Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
In previous experiments at the Fermilab Accelerator Science and Technology (FAST) facility, the effects of higher-order modes (HOMs) in TESLA-type cavities on submacropulse centroid motion were elucidated*. We now have extended our investigations to short-range wakefields (SRWs) in these cavities. The latter result in submicropulse effects where the transverse wakefields cause head-tail centroid shifts. We used a Hamamatsu C5680 UV-visible synchroscan streak camera to synchronously sum the OTR from each of the 50 micropulses in the macropulse. We generated the y-t effect in the 41-MeV beam by purposely steering the beam off axis in y at the entrance of the first capture cavity. The head-tail transverse kicks within the 11-ps-long micropulses of 500 pC each were observed at the 100-micron level for steering off-axis in one cavity and several 100 microns for two cavities. These SRW results will be compared to simulations from the ASTRA model of a single micropulse in FAST. Since the SRW kicks go inversely with energy, these emittance-dilution effects are particularly relevant to the LCLS-II injector commissioning plans where <1 MeV beam will be injected into a TESLA-type cryomodule.
* A.H. Lumpkin et al, Phys. Rev. Accel. and Beams 23, 054401 (2020).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB273

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 02 September 2021

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TUPAB274

Investigations of Long-Range Wakefield Effects in a TESLA-type Cryomodule at FAST

HOM, cavity, cryomodule, wakefield

2109

A.H. Lumpkin, D.R. Edstrom, P.S. Prieto, J. Ruan, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA
J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz, B.T. Jacobson, J.P. Sikora, F. Zhou
SLAC, Menlo Park, California, USA

Funding: *Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The preservation of low emittance of electron beams during transport in the accelerating structures of large facilities is an ongoing challenge. In the cases of the TESLA-type superconducting rf cavities currently used in the European X-ray Free-electron Laser (XFEL) and the under-construction Linac Coherent Light Source upgrade (LCLS-II), off-axis beam transport may result in emittance dilution due to transverse long-range wakefields (LRWs) and short-range wakefields (SRW)***. To investigate such effects, experiments were performed at the Fermilab Accelerator Science and Technology (FAST) facility with its unique configuration of two TESLA-type cavities after the photocathode rf gun followed by an 8-cavity cryomodule CM). We generated beam trajectory changes with the H/V125 corrector set located 4 m upstream of the cryomodule. At 125 pC/bunch, 50 bunches, 25-MeV input, and 100-MeV exit energy, we observed for the first time submacropulse position slews of up to 500 microns at locations ~3 m after the CM and a centroid oscillation at a difference frequency of 240 kHz further downstream. Both are emittance-dilution effects which we mitigated with selective upstream beam steering.
***W.K.H. Panofsky and M. Bander, Rev. Sci. Instr. 39, 206 (1968).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB274

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 18 August 2021

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TUPAB277

Bunch Length Characterizations for the Solaris Injector LINAC

radiation, linac, diagnostics, experiment

2117

A. Curcio, M.A. Knafel, G.W. Kowalski, R. Panaś, M. Waniczek, A.I. Wawrzyniak
NSRC SOLARIS, Kraków, Poland

During 2020 the first characterization of bunch length and bunch profile in the Solaris injector LINAC has been performed since the start of its operation. In absence of more sophisticated bunch length diagnostics, we have adopted an inversion algorithm applied to beam energy spectra. In practice, the method applies a transformation matrix which maps the particle energy into the particle longitudinal coordinate along the bunch. The construction of this matrix is made analytically, based on the solution of the Liouville equation for the study of the longitudinal beam dynamics. The analytic approach has been benchmarked with experimental measurements of the beam properties along the machine and cross-checked with other tools, as particle tracking and/or beam optics codes. The final results are presented. Moreover, a new diagnostic station at the end of the LINAC has been installed which will host experiments of coherent radiation emission that will be used to confirm the validity of our observations. Preliminary simulations of the coherent spectra are finally reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB277

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paper received ※ 18 May 2021 paper accepted ※ 17 June 2021 issue date ※ 29 August 2021

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TUPAB279

First Tests of Beam Position Monitor Electronics with Bunch Resolving Capabilities

storage-ring, FPGA, electronics, pick-up

2124

G. Rehm, F. Falkenstern, J. Kuszynski, A. Schälicke
HZB, Berlin, Germany

We are reporting on first tests of a beam position monitor using 1 GS/s data streams of signals from a four button pickup. The system digitizes signals of ~2 GHz bandwidth using a choice of sampling frequency that realizes equivalent time sampling. The data is subsequently processed in the Fourier domain to unfold the aliased spectral lines and apply an impulse response correction per channel. After transforming back into time domain, individual bunch signals can be clearly identified and selected for further processing and decimation. The paper will provide detail on the hardware implementation and demonstrate the bunch resolving capabilities, long term stability and beam intensity dependence using beam tests in BESSY-II and synthetic signals.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB279

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paper received ※ 18 May 2021 paper accepted ※ 06 July 2021 issue date ※ 26 August 2021

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TUPAB280

Quantum Gas Jet Scanner Based Beam Profile Monitors

injection, focusing, beam-diagnostic, diagnostics

2128

N. Kumar, A. Salehilashkajani, C.P. Welsch, H.D. Zhang
Cockcroft Institute, Warrington, Cheshire, United Kingdom
N. Kumar, A. Salehilashkajani, C.P. Welsch, H.D. Zhang
The University of Liverpool, Liverpool, United Kingdom

Funding: This work is supported by the HL-LHC-UK project funded by STFC and CERN and the STFC Cockcroft core grant No. ST/G008248/1.
A quantum gas jet scanner-based beam profile monitor is under development at the Cockcroft Institute (CI), the UK for beam diagnostics based on the principle of ionization detection induced in a quantum gas jet interacting with an ionizing primary beam that shall be characterized. It promises superior position resolution and high signal intensity resulting from a strongly focused quantum gas jet. In order to achieve the gas jet with a diameter of less than 100 µm, a novel focusing method exploiting the quantum wave function of the neutral gas atoms, generate an interference pattern with a single maximum acting as an ultra-thin gas jet. An ‘atom sieve’ has been designed for generating the interference pattern, applying the principle of a photon sieve. It will be analogous to a mechanical wire scanner though with a minimal interception. The idea of moving a quantum gas jet through the beam is proposed for transverse profiling. This contribution provides a general overview of the design, working principle, the results obtained from initial measurements carried out at CI and University of Bergen (Norway), for designing the same and possible methods for optimizing the scanner’s design.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB280

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paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 13 August 2021

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TUPAB281

Gas-Mixing to Improve the Resolution of Non-Invasive Gas Jet-Based Ionization Profile Monitors

injection, simulation, background, vacuum

2132

N. Kumar, A. Salehilashkajani, C.P. Welsch, H.D. Zhang
Cockcroft Institute, Warrington, Cheshire, United Kingdom
N. Kumar, A. Salehilashkajani, C.P. Welsch, H.D. Zhang
The University of Liverpool, Liverpool, United Kingdom

Funding: This work is supported by the HL-LHC-UK project funded by STFC and CERN and the STFC Cockcroft core grant No. ST/G008248/1.
Ionization beam profile monitor using a supersonic gas jet is an attractive option for the characterization of low and medium energy beams. In this scheme, a primary beam crosses a 45-degree tilted thin gas curtain which causes ionization of gas molecules in the jet. The generated ions are then collected using an electrostatic extraction system to determine the 2D transverse profile of the primary beam. The most commonly used gases for the jet are neon and nitrogen. The signal from the gas jet is always super-imposed with the signal resulting from residual gases in the interaction chamber. CST simulations indicate that the gas jet speed is a key factor for the separation of the jet and the residual gas signals. To obtain a good signal separation, one can increase the velocity of the gas jet. This can be accomplished by generating a gas jet that mixes heavier and lighter gases. This contribution gives a general overview of the monitor design, discusses the effects of gas mixing and CST simulation results. It also presents experimental results obtained with Helium, and Nitrogen, as well as a mixture of them using different percentages and the impact on measurement resolution.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB281

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 12 August 2021

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TUPAB283

Feasibility Study of ChDR Diagnostic Device in the LHC

radiation, diagnostics, proton, flattop

2139

K. Łasocha
Jagiellonian University, Kraków, Poland
M. Bergamaschi, M. Krupa, K. Łasocha, T. Lefèvre, S. Mazzoni, N. Mounet, E. Senes
CERN, Geneva, Switzerland
D.M. Harryman
JAI, Egham, Surrey, United Kingdom
P. Karataev
Royal Holloway, University of London, Surrey, United Kingdom
A. Potylitsyn
TPU, Tomsk, Russia
A. Schloegelhofer
TU Vienna, Wien, Austria

In recent years Cherenkov Diffraction Radiation (ChDR) has been reported as a phenomenon suitable for various types of particle accelerator diagnostics. As it would typically work best for highly relativistic beam, past studies and experiments have been mostly focusing on the lepton machines. This contribution investigates the prospects on the utilization of ChDR as a diagnostic tool for the Large Hadron Collider (LHC). Based on theoretical considerations and simulation results we estimate the properties of the expected radiation, both in the incoherent and coherent domain, and we compare them with the requirements of the existing diagnostic systems. We also address the potential problem of the use of dielectric radiators in circular machines, where secondary electrons could potentially lead to the creation of electron clouds inside the beam pipe that may affect the radiator.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB283

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paper received ※ 14 May 2021 paper accepted ※ 18 June 2021 issue date ※ 12 August 2021

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TUPAB284

BPM for the High Energy Beam Transport Line of MINERVA Project at SCK•CEN

linac, instrumentation, experiment, proton

2143

H. Kraft, L. Perrot
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

This paper presents the status of developments concerning button type BPM. Results of our analytical model BPMOK will compare the measurements done at IPHI facility at CEA-Saclay and GANIL/SPIRAL2 in Caen. The measurements aims to compare the response of the analytical model depending on beam positions, sizes, intensities and energies. BPMOK is validated to predict BPM responses in order to make parametric studies. Starting from already existing BPM built for the MINERVA LINAC, the analytical model is used to design the BPM for the HEBT.

Poster TUPAB284 [1.475 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB284

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paper received ※ 10 May 2021 paper accepted ※ 02 June 2021 issue date ※ 11 August 2021

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TUPAB285

Broadband Imaging of Coherent Radiation as a Single-Shot Bunch Length Monitor with Femtosecond Resolution

radiation, simulation, detector, network

2147

J. Wolfenden, R.B. Fiorito, E. Kukstas, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
M. Brandin, B.S. Kyle, E. Mansten, S. Thorin
MAX IV Laboratory, Lund University, Lund, Sweden
R.B. Fiorito, C.P. Welsch, J. Wolfenden
Cockcroft Institute, Warrington, Cheshire, United Kingdom
E. Mansten
Lund University, Division of Atomic Physics, Lund, Sweden
T.H. Pacey
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: This work is supported by the AWAKE-UK project funded by STFC and the STFC Cockcroft core grant No. ST/G008248/1
Bunch length measurements with femtosecond resolution are a key component in the optimisation of beam quality in FELs, storage rings, and plasma-based accelerators. This contribution presents the development of a novel single-shot bunch length monitor with femtosecond resolution, based on broadband imaging of the spatial distribution of emitted coherent radiation. The technique can be applied to many radiation sources; in this study the focus is coherent transition radiation (CTR) at the MAX IV Short Pulse Facility. Bunch lengths of interest at this facility are <100 fs FWHM; therefore the CTR is in the THz to Far-IR range. To this end, a THz imaging system has been developed, utilising high resistivity float zone silicon lenses and a pyroelectric camera; building upon previous results where single-shot compression monitoring was achieved. This contribution presents simulations of this new CTR imaging system to demonstrate the synchrotron radiation mitigation and imaging capability provided, alongside initial measurements and a bunch length fitting algorithm, capable of shot-to-shot operation. A new machine learning analysis method is also discussed.

Poster TUPAB285 [2.008 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB285

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paper received ※ 17 May 2021 paper accepted ※ 24 June 2021 issue date ※ 25 August 2021

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TUPAB290

Demonstration of Machine Learning Front-End Optimization of the Advanced Photon Source Linac

linac, controls, gun, photon

2163

A. Hanuka, J.P. Duris
SLAC, Menlo Park, California, USA
H. Shang, Y. Sun
ANL, Lemont, Illinois, USA

The electron beam for the Advanced Photon Source (APS) at Argonne National Laboratory is generated from a thermionic RF gun and accelerated by an S-band linear accelerator – the APS linac. While the APS linac lattice is set up using a model developed with ELEGANT, the thermionic RF gun front-end beam dynamics have been difficult to model. One of the issues is that beam properties from thermionic guns can vary. As a result, linac front-end beam tuning is required to establish good matching and maximize the charge transported through the linac. A traditional Nelder-Mead simplex optimizer has been used to find the best settings for the sixteen quadrupoles and steering magnets. However, it takes a long time and requires some fair initial conditions. The Gaussian Process (GP) optimizer does not have the initial condition limitation and runs several times faster. In this paper, we report our data collection and analysis for the training of the GP hyperparameters and discuss the application of GP optimizer on the APS linac front-end optimization for maximum bunch charge transportation efficiency through the linac.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB290

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paper received ※ 09 May 2021 paper accepted ※ 28 July 2021 issue date ※ 19 August 2021

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TUPAB298

First Steps Toward an Autonomous Accelerator, a Common Project Between DESY and KIT

laser, controls, operation, simulation

2182

A. Eichler, F. Burkart, J. Kaiser, W. Kuropka, O. Stein
DESY, Hamburg, Germany
E. Bründermann, A. Santamaria Garcia, C. Xu
KIT, Karlsruhe, Germany

Funding: Helmholtz Artificial Cooperation Unit
Reinforcement Learning algorithms have risen in popularity in recent years in the accelerator physics community, showing potential in beam control and in the optimization and automation of tasks in accelerator operation. The Helmholtz AI project "Machine Learning toward Autonomous Accelerators" is a collaboration between DESY and KIT that works on investigating and developing RL applications for the automatic start-up of electron linear accelerators. The work is carried out in parallel at two similar research accelerators: ARES at DESY and FLUTE at KIT, giving the unique opportunity of transfer learning between facilities. One of the first steps of this project is the establishment of a common interface between the simulations and the machine, in order to test and apply various optimization approaches interchangeably between the two accelerators. In this paper we present the first results on the common interface and its application to beam focusing in ARES, and the idea of laser shaping with spatial light modulators at FLUTE.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB298

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paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 11 August 2021

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TUPAB302

Arrival Time Stabilization at Flash Using the Bunch Arrival Corrector Cavity (BACCA)

cavity, feedback, laser, SRF

2194

B. Lautenschlager, L. Butkowski, M.K. Czwalinna, B. Dursun, M. Hierholzer, S. Pfeiffer, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany

For pump-probe and seeding experiments at free electron lasers, a femtosecond precise bunch arrival time stability is mandatory. To stabilize the arrival times a fast longitudinal intra bunch-train feedback (L-IBFB) using bunch arrival time monitors is applied. The electron bunch energy prior to a bunch compression chicane is modulated by superconducting radio frequency (SRF) cavities to compensate fast arrival time fluctuations of the subsequent bunches. A broadband normal conducting RF cavity was installed in front of the first bunch compression chicane at FLASH. The L-IBFB uses the normal conducting cavity for small but fast energy corrections together with the SRF cavities for larger and slower corrections. Current measurements show arrival time stabilities of the electron bunches towards 5 fs (rms) at the end of the linac, if the normal conducting cavity acts together with the SRF cavities in the L-IBFB system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB302

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 12 August 2021

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TUPAB306

Status of Beam-Based Feedback Research and Development for Continuous Wave SRF Linac ELBE

controls, feedback, cavity, LLRF

2200

A. Maalberg, M. Kuntzsch
HZDR, Dresden, Germany
E. Petlenkov
TalTech, Tallinn, Estonia

The superconducting electron linear accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf is a versatile light source operated in continuous wave mode. As the demand on the beam stability increases, the improvement of the beam control schemes currently installed at ELBE becomes highly relevant. This improvement can be achieved by an upgrade of the existing digital MicroTCA.4-based LLRF control scheme by beam-based feedback. By presenting both the design and implementation details of the new control scheme this contribution reports the status of the work in progress.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB306

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 19 August 2021

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TUPAB313

Arrangement Optimization of Quadrupoles and Correctors for Beam Alignment

quadrupole, alignment, focusing, FEL

2221

L. Xu, Q.M. Zhang
Xi’an Jiaotong University, People’s Republic of China
H.X. Deng
SARI-CAS, Pudong, Shanghai, People’s Republic of China
N. Huang
UCAS, Beijing, People’s Republic of China
N. Huang
SINAP, Shanghai, People’s Republic of China

In the X-ray free-electron laser (XFEL), the alignment and stability of beam orbit have a great impact on power and qualities of the generated X-ray pulses. Currently, the beam-based alignment (BBA) is the most widely used technique in beam alignment. In order to find the best arrangement of quadrupoles and correctors, a mathematical model is established based on the transmission matrix method. With this model, several simple arrangements of quadrupoles and correctors are selected to simulate the beam alignment process. It is found that when two correctors adjust two quadrupoles, the beam can pass through the center of quadrupoles approximately collimated.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB313

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paper received ※ 16 May 2021 paper accepted ※ 17 August 2021 issue date ※ 31 August 2021

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TUPAB324

Real-Time Radiation Monitoring System with Interlock Protection Mechanism in Taiwan Photon Source

radiation, monitoring, neutron, synchrotron

2256

Y.C. Lin, A.Y. Chen, C.-R. Chen, S.J. Huang, S.P. Kao, S.Y. Lin, J.C. Liu, P.J. Wen
NSRRC, Hsinchu, Taiwan

To ensure radiation safety for personnel working in the facility, the Radiation and Operation Safety Division has installed a real-time radiation monitoring system in the working area to monitor gamma rays and neutrons, for which the annual dosage limit is designed to be less than 1 mSv/year. Considering 2000 working hours for users and staff members, we have derived a control dose rate limit 2 µSv/4h for interlock protection. If the accumulated radiation dose monitored with the system exceeds 2µSv within a 4-h counting interval, the radiation monitoring station sends a signal to the interlock system to stop injection until the next counting period interval. This paper introduces the radiation monitoring system and its related design information in Taiwan Photon Source.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB324

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paper received ※ 14 May 2021 paper accepted ※ 21 June 2021 issue date ※ 13 August 2021

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TUPAB339

High Power Test of the Antenna Adjustable Power Coupler for 325 MHz Superconducting Cavities

cavity, vacuum, multipactoring, pick-up

2286

J.Y. Yoon, E.-S. Kim, C.S. Park, S.H. Park
KUS, Sejong, Republic of Korea
J. Bahng
Korea University Sejong Campus, Sejong, Republic of Korea
E. Kako
KEK, Ibaraki, Japan
K.R. Kim
PAL, Pohang, Republic of Korea

Funding: The Ministry of Education (South Korea)
The power coupler is development at Korea University for a Single Spoke Resonator (SSR) of heavy ion accelerator. Our power coupler is a coaxial capacitive type based on a conventional 3-1/8 inch electronic industries alliance (EIA) 50 Ω coaxial transmission line with a titanium nitride (TiN) coated single ceramic window. A high power test is rectangular test cavity with high vacuum and various measuring equipment, such as an arc detector, a power meter, and an electron pick-up probe. The interlock system under vacuum and arc instrumentations prevent the RF window from breaking the power coupler window during the high power test. We conduct high power tests for more than 12 hrs at 12 kW in a 325 MHz continous wave (CW) mode to verify the performance of the designed power coupler.
*Superconducting, *Power Coupler

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB339

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paper received ※ 12 May 2021 paper accepted ※ 21 June 2021 issue date ※ 22 August 2021

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TUPAB343

Final Design Studies for the VSR DEMO 1.5 GHz Coupler

multipactoring, SRF, operation, cavity

2300

E. Sharples-Milne, V. Dürr, P. Echevarria, J. Knobloch, A. Neumann, A.V. Vélez
HZB, Berlin, Germany

With the 1.5 GHz couplers for the Variable pulse length Storage Ring (VSR) DEMO now in the manufacturing stages, the studies that led to the final coupler design will be presented. The system specific constraints and design modifications that combat the challenges of thermomechanical stresses, higher order mode (HOM) propagation and dimensional constraints are explored. This includes S-Parameter analysis, an in-depth study of the coupling factor, and multipacting studies for the average (1.5 kW) and peak (16 kW) power.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB343

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 01 September 2021

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TUPAB349

High Efficiency, Low Cost RF Sources for Accelerators and Colliders

cavity, klystron, controls, simulation

2322

R.L. Ives, T. Bui, G. Collins, H. Freund, T.W. Habermann, D. Marsden, M.E. Read
CCR, San Mateo, California, USA
B.E. Chase, J. Reid
Fermilab, Batavia, Illinois, USA
N. Chaudhary, J.R. Conant, T. Cox, R. Ho, C. McVey, C.M. Walker
CPI, Palo Alto, California, USA
J.C. Frisch, L. Ma
SLAC, Menlo Park, California, USA
A. Jensen
Leidos Corp, Billerica, MA, USA
J.M. Potter
JP Accelerator Works, Los Alamos, New Mexico, USA
W. Sessions
Georgia Tech Research Institute, Smyrna, Georgia, USA

Funding: U.S. Department of Energy
Calabazas Creek Research, Inc. (CCR) and its collaborators are developing high efficiency, low cost RF sources. Phase and Amplitude Controlled Magnetrons: CCR, Fermilab, and Communications & Power Industries, LLC (CPI) recently developed a 100 kW, 1.3 GHz magnetron system with amplitude and phase control. The system operated at more than 80% efficiency and demonstrated rapid control of amplitude and phase. Multiple Beam Triodes: CCR, in collaboration with CPI and JP Accelerator Works, Inc., is developing 200 kW, pulsed and CW RF sources from 350 to 700 MHz with projected efficiencies exceeding 80% and cost of $0.50/Watt. Prototype tubes are scheduled for tests in spring 2021. High Efficiency Klystrons:CCR, CPI, and Leidos, Inc. are building a 1.3 GHz, 100 kW klystron operating at 80% efficiency. High power testing is scheduled for summer 2021. Multiple Beam IOTs: CCR and Georgia Tech Research Institute are developing MBIOTs with simplified input coupling and high efficiency. Simulations indicate that 3rd harmonic drive power can increase the efficiency 8-10 %. The program is developing a prototype tube to produce 200 kW peak, 100 kW average power at 704 MHz.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB349

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paper received ※ 18 May 2021 paper accepted ※ 01 June 2021 issue date ※ 24 August 2021

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TUPAB356

Electron Beam Driven Cavities

cavity, simulation, linac, klystron

2342

M. Schuett, U. Ratzinger
IAP, Frankfurt am Main, Germany

State of the art high power feeder for RF cavities used as accelerators generally require RF amplifiers consisting of a vacuum tube, such as a klystron or Grid Tubes. In addition, a number of cost intensive RF auxiliary devices are needed: Modulator, waveguides, circulator, power dump and couplers. The equipment requires significant floor space within the linac building. Alternatively, we propose a direct driven system. Aμbunched electron beam is injected directly into the cavity. A high perveance bunched electron beam can be generated by a standard electron gun combined with a deflecting beam chopper*, an off-the-shelf IOT or klystron, respectively. The pulse rate is determined by the resonance frequency of the cavity. The resonator hereby acts like the output cavity of a klystron: Within its propagation through the cavity the beam is decelerated increasing the stored energy of the accelerator. We present 3D particle PIC simulations evaluating the geometry and beam properties in order to optimize the coupling efficiency and cavity excitation of state-of-art CH particle accelerator structures.
* S. Setzer, T. Weiland and U. Ratzinger, A Chopped Electron Beam Driver for H-Type Cavities, 20th ‘International Linac Conference, Monterey, California, August 21-25, 2000, pp. 1001-1003

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB356

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 21 August 2021

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TUPAB357

Development of the X-Band Megawatt-Class Coaxial Magnetrons

linac, radiation, high-voltage, experiment

2346

J.Y. Liu, H.B. Chen, Y.S. Han, J. Shi, C.-X. Tang, C.J. Wang, J. Wang, H. Zha
TUB, Beijing, People’s Republic of China

X-band coaxial magnetrons are preferred for industrial and medical accelerators owing to the compact size, low cost and high efficiency. A conditioning and high power test stand for X-band magnetrons has been built in Tsinghua University. Two X-band magnetrons named "MGT-1#" and "MGT-2#" were tested at this stand. The maximum anode currents of both magnetrons reached 100 A after the conditioning process. Maximum peak output power of 1.71 MW and 1.89 MW was achieved for "MGT-1#" and "MGT-2#", respectively. The efficiencies of the two magnetrons are both about 50%.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB357

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 17 August 2021

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TUPAB366

Design and Realization of New Solenoids for High Brightness Electron Beam Injectors

solenoid, gun, cathode, simulation

2374

A. Vannozzi, D. Alesini, A. Giribono, C. Vaccarezza
INFN/LNF, Frascati (Roma), Italy

High-brightness, high-current electron beams are the main requirement for fourth generation light sources such as free-electron lasers (FELs), energy recovery Linacs (ERLs) and high-energy linear colliders. The most successful device for producing such beams is the Radio-Frequency photoinjector where a key element is the gun solenoid. Its main task is to limit the beam emittance growth in the first acceleration stages by imposing a spiraling motion to the beam. This paper is focused on two magnets: the first one is the solenoid gun for the new photoinjector at INFN-LNF SPARC_LAB test facility. The design, the realization, and all the measurements performed at the factory and at LNF are shown. Moreover, the design of a solenoid for a novel C-band gun for CompactLight project is presented. Both magnets have been designed with the goal to reach the same integrated field of the gun solenoid currently installed at SPARC_LAB, with an integrated field quality of 5·10^-4 in a good field radius of 30mm and 10mm radius respectively for SPARC_LAB and CompactLight solenoid. This one is equipped with a bucking coil to limit the field on cathode that could led to an undesired emittance growth.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB366

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paper received ※ 19 May 2021 paper accepted ※ 18 June 2021 issue date ※ 12 August 2021

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TUPAB374

Development of a Quench Detection System for the FAIR Superconducting Devices

controls, quadrupole, superconducting-magnet, interface

2394

V. Raginel, M. Dziewiecki, W. Freisleben, P.B. Szwangruber, L. Theiner
GSI, Darmstadt, Germany

The Facility for Antiproton and Ion Research (FAIR), which is presently under construction in Darmstadt (Germany), will incorporate a large variety of superconducting devices like magnets, currents leads and bus bars. These components depend on an active protection in case of a transition from superconducting to the resistive state, so-called quench. In this framework, a FAIR Quench Detection System (F-QDS) is being developed based on analog and digital electronics and will be implemented in several machines of the FAIR complex. This paper describes the development of the F-QDS. An overview of the F-QDS electronics is given followed by a description of the system integration to the infrastructure of various machines. Initial test results of the F-QDS prototype system are presented and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB374

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paper received ※ 25 May 2021 paper accepted ※ 05 July 2021 issue date ※ 14 August 2021

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TUPAB375

Commissioning and Operation of Superconducting Multipole Wiggler at Siam Photon Source

photon, MMI, operation, wiggler

2398

P. Sunwong, S. Boonsuya, S. Chaichuay, T. Chanwattana, Ch. Dhammatong, A. Kwankasem, C.P. Preecha, T. Pulampong, K. Sittisard, V. Sooksrimuang, S. Srichan, P. Sudmuang, N. Suradet, S. Tancharakorn
SLRI, Nakhon Ratchasima, Thailand

A new insertion device, Superconducting Multipole Wiggler (SMPW) with the peak field strength of 3.5 T, was installed in the storage ring of Siam Photon Source as a radiation source for a new hard X-ray beamline. Cool-down process, as well as magnet training, was performed with careful tuning of liquid helium filling procedure for efficient management of liquid helium supply. The filling procedure was also optimized for safe operation of the magnet. The SMPW commission-ing was successfully carried out with electron beam and the effect of SMPW on electron beam dynamics was observed. It can be minimized using quadrupole magnets and horizontal/vertical correctors.

Poster TUPAB375 [1.160 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB375

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paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 10 August 2021

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TUPAB381

Thermal Analysis of the RHIC Arc Dipole Magnet Cold Mass with the EIC Beam Screen

dipole, vacuum, hadron, cryogenics

2413

S.K. Nayak, M. Anerella, M. Blaskiewicz, J.M. Brennan, R.C. Gupta, M. Mapes, G.T. McIntyre, S. Peggs, R. Than, J.E. Tuozzolo, S. Verdú-Andrés, D. Weiss
BNL, Upton, New York, USA

Funding: Funding agency Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The EIC will make use of the existing RHIC storage rings with their superconducting (SC) magnet arcs. A stainless-steel beam screen with co-laminated copper and a thin amorphous carbon (aC) film on the inner surface will be installed in the beam pipe of the SC magnets. The copper will reduce the beam-induced resistive-wall (RW) heating from operation with the higher intensity EIC beams, that if not addressed would make the magnets quench. Limiting the RW heating is also important to achieve an adequately low vacuum level. The aC coating will reduce secondary electron yield which could also cause heating and limit intensity. Among all the RHIC SC magnets, the arc dipoles present the biggest challenge to the design and installation of beam screens. The arc dipoles, which make up for 78% (2.5 km) length of all SC magnets in RHIC, expect the largest RW heating due to their smallest aperture. These magnets are also the longest (9.45 m each), thus experiencing the largest temperature rise over their length, and have a large sagitta (48.5 mm) that increases the difficulty to install the beam screen in place. This paper presents a detailed thermal analysis of the magnet-screen system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB381

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paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 19 August 2021

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TUPAB399

RF Characterisation of New Coatings for Future Circular Collider Beam Screens

impedance, laser, collider, cavity

2453

P. Krkotić, F. Pérez, M. Pont, N.D. Tagdulang
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
S. Calatroni
CERN, Meyrin, Switzerland
X. Granados, J. Gutierrez, T. Puig, A. Romanov, G.T. Telles
ICMAB, Bellatera, Spain
A.N. Hannah, O.B. Malyshev, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J.M. O’Callaghan Castella
Universitat Politécnica de Catalunya, Barcelona, Spain
D. Whitehead
The University of Manchester, Laser Processing Research Center, Manchester, United Kingdom

For the future high energy colliders being under the design at this moment, the choice of a low surface impedance beam screen coating material has become of fundamental importance to ensure sufficiently low beam impedance and consequently guaranteed stable operation at high currents. We have studied the use of high-temperature superconducting coated conductors as possible coating materials for the beam screen of the FCC-hh. In addition, amorphous carbon coating and laser-based surface treatment techniques are effective surface treatments to lower the secondary electron yield and minimise the electron cloud build-up. We have developed and adapted different experimental setups based on resonating structures at frequencies below 10 GHz to study the response of these coatings and their modified surfaces under the influence of RF fields and DC magnetic fields up to 9 T. Taking the FCC-hh as a reference, we will show that the surface resistance for REBCO-CCs is much lower than that of Cu. Further we show that the additional surface modifications can be optimised to minimise their impact on the surface impedance. Results from selected coatings will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB399

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paper received ※ 19 May 2021 paper accepted ※ 25 June 2021 issue date ※ 16 August 2021

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TUPAB405

Design of High Energy Linac for Generation of Isotopes for Medical Applications

linac, target, gun, controls

2472

A.P. Deshpande, S.R. Bhat, T.S. Dixit, P.S. Jadhav, A.S. Kottawar, R. Krishnan, M.S. Kumbhare, J. Mishra, C.S. Nainwad, S.R. Name, R. Sandeep Kumar, A. Shaikh, K.A. Thakur, M.M. Vidwans, A. Waingankar
SAMEER, Mumbai, India
A.K. Mishra
INMAS, New Delhi, India
N. Upadhyay
University of Mumbai, Mumbai, India

Funding: Ministry of Electronics and Information Technology (MeitY), Govt. of India.
After successful implementation of 6 and 15 MeV electron linear accelerator (linac) technology for Cancer Therapy in India, we initiated the development of high energy high current accelerator for the production of radioisotopes for diagnostic applications. The accelerator will be of 30 MeV energy with 350 µA average current provided by a gridded gun. The linac is a side coupled standing wave accelerator operating at 2998 MHz frequency operating at p/2 mode. The choice of p/2 operating mode is particularly suitable for this case where the repetition rate will be around 400 Hz. Klystron with 7 MW peak power and 36 kW average power will be used as the RF source. The modulator will be a solid-state modulator. The control system is FPGA based setup developed in-house at SAMEER. A retractable target with tungsten will be used as a converter to generate X-rays via bremsstrahlung. The x-rays will then interact with enriched 100Mo target to produce 99Mo via (g, n) reaction. Eluted 99mTc will be used for diagnostic applications. The paper lists the challenges and novel schemes developed at SAMEER to make a compact, rugged, and easy to use system keeping in mind local conditions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB405

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 21 August 2021

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TUPAB409

FLUKA and Geant4 Monte Carlo Simulations of a Desktop, Flat Panel Source Array for 3D Medical Imaging

photon, simulation, experiment, detector

2483

T. Primidis, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
T. Primidis, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
V. Soloviev
Adaptix Imaging, Didcot, United Kingdom

Funding: Funded by the Accelerators for Security, Healthcare and Environment CDT from the United Kingdom Research and Innovation Science and Technology Facilities Council, reference ID ST/R002142/1
Digital tomosynthesis (DT) is a 3D imaging modality with a lower cost and lower dose than computed tomography. A DT system made of a flat panel array with 45 X-ray sources, but compact enough to fit on the desktop is near market realisation by the company Adaptix Ltd. This work presents a framework of FLUKA and Geant4 Monte Carlo (MC) simulations of the Adaptix system including the X-ray beam generation and the final image quality. The results show that MC methods offer an insight into the performance details of such an innovative device at different levels between the X-ray emitter array and the detector. As such, a large portion of the design and optimisation of such novel X-ray imaging systems can be done with a single toolkit. Finally, the modularity of the approach allows other tools to be imported at various steps within the framework and thus provide answers to questions that cannot be addressed by general-purpose MC codes.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB409

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paper received ※ 17 May 2021 paper accepted ※ 31 May 2021 issue date ※ 14 August 2021

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TUPAB412

New 3 MeV and 7 MeV Accelerators for Cargo Screening and NDT

target, gun, linac, software

2491

S. Proskin, D. Fischer, A.V. Mishin
Varex Imaging, Salt Lake City, USA

For decades evaluating of cargo and non-destructive testing of objects have been utilizing high energy systems based on particle accelerators. End users wish for lower prices, better image quality, and convenience of utilization. In recent years Varex Imaging, world leader in innovation, development, and manufacture of X-ray imaging component solutions, has been developing a series of new accelerator products with improved parameters and a goal of replacing existing dated systems and growing of emerging markets. New S-band energy regulated 3 MeV and 7 MeV linear accelerators have been designed, tested at Varex Imaging and their customer sites. Novel linacs benefit is in dramatically increased output, reduced beam spot, longer operation, and improved versatility. Authors will outline recent progress and future endeavors in linear accelerator development with regards to improvement of accelerating structures, X-ray targets, and corresponding RF components*.
This work would have not been successful without outstanding contribution of the whole Linac Group of Varex Imaging and established partnerships with our customers

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB412

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paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 30 August 2021

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TUPAB416

Depth-Dose Distribution Dependence on the Energy Profile of Linear and Laser Wakefield Accelerator Electron Beams

radiation, linac, simulation, HOM

2502

T.A. Nguyen
VNUHCM, Ho Chi Minh, Viet Nam
C. Rangacharyulu
University of Saskatchewan, Saskatoon, Canada
C.V. Tao
HCMUS, Ho Chi Minh City, Viet Nam

The depth-dose distributions of 10 MeV electron beams used for food irradiation and sterilization purposes at Research and Development Center for Radiation Technology, HCMC, Vietnam are measured and the results are well reproduced by the MCNP simulations. We extend the simulations to predict the dose depth distribution for 10 MeV electron beams with the energy profiles of a model Laser Wake Field accelerator (LWFA). The dosimetry and simulation results show that the maximum dose of the depth-dose curve inside the product is 1.4 times surface dose with an area density limit of 8.6 g/cm² for two-sided irradiation with nearly mono-energetic beams from the linear accelerator and the corresponding parameters for LWFA are 1.2 times surface dose and 13.0 g/cm², respectively.

Poster TUPAB416 [1.506 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB416

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paper received ※ 17 May 2021 paper accepted ※ 11 June 2021 issue date ※ 22 August 2021

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TUPAB417

Pushing Spatial Resolution Limits In Single-Shot Time-Resolved Transmission Electron Microscopy at the UCLA Pegasus Laboratory

space-charge, gun, simulation, cavity

2506

P.E. Denham, P. Musumeci
UCLA, Los Angeles, USA

Funding: This work was supported by DOESTTR grant No. DE-SC0013115 and by by the National Science Foundation under STROBE Science and Technology Center Grant No. DMR-1548924
We present the design of a high-speed single shot relativistic electron microscope planned for implementation at the UCLA PEGASUS Laboratory capable of imaging with less than 30~nm spatial resolution and image acquisition time on the order of 10~ps. This work is based on a multi-cavity acceleration scheme for producing relativistic beams (3.75 MeV) with suppressed rms energy spread (σ_δ ≈5e-5), and a means to reduce smooth space charge aberrations by generating a quasi-optimal 4D particle distribution at the sample plane. start-to-end simulation results are used to validate the entire setup. Ultimately, a feasible working point is demonstrated.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB417

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paper received ※ 19 May 2021 paper accepted ※ 28 July 2021 issue date ※ 12 August 2021

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WEXA02

Operational Electron Cooling in the Relativistic Heavy Ion Collider

operation, collider, cathode, cavity

2516

A.V. Fedotov, K.A. Drees, W. Fischer, X. Gu, D. Kayran, J. Kewisch, C. Liu, K. Mernick, M.G. Minty, V. Schoefer, H. Zhao
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
Since the invention of the electron cooling technique its application to cool hadron beams in colliders was considered for numerous accelerator physics projects worldwide. However, achieving the required high-brightness electron beams of required quality and cooling of ion beams in collisions was deemed to be challenging. An electron cooling of ion beams employing a high-energy approach with RF-accelerated electron bunches was recently successfully implemented at BNL. It was used to cool ion beams in both collider rings with ion beams in collision. Electron cooling in RHIC became fully operational during the 2020 physics run and led to substantial improvements in luminosity. This presentation will discuss implementation, optimization and challenges of electron cooling for colliding ion beams in RHIC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA02

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paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 13 August 2021

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WEXA04

The RCS Design Status for the Electron Ion Collider

resonance, injection, lattice, emittance

2521

V.H. Ranjbar, M. Blaskiewicz, Z.A. Conway, D.M. Gassner, C. Hetzel, B. Lepore, H. Lovelace III, I. Marneris, F. Méot, C. Montag, J. Skaritka, N. Tsoupas, E. Wang, F.J. Willeke
BNL, Upton, New York, USA
J.M. Grames, J. Guo, F. Lin, V.S. Morozov, T. Satogata
JLab, Newport News, Virginia, USA
D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The design of the Electron-Ion Collider Rapid Cycling Synchrotron (RCS) to be constructed at Brookhaven National Laboratory is advancing to meet the injection requirements for the Electron Storage Ring (ESR). Over the past year activities are focused on developing the approach to inject two 28 nC bunches every second, up from the original design of one 10nC bunch every second. The solution requires several key changes concerning the injection and extraction kickers, charge accumulation via bunch merging and a carefully calibrated RF acceleration profile to match the longitudinal emittance required by the ESR.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA04

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paper received ※ 19 May 2021 paper accepted ※ 26 August 2021 issue date ※ 31 August 2021

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WEXC04

Simulations of Beam Strikes on Advanced Photon Source Upgrade Collimators using FLASH, MARS, and elegant

simulation, photon, storage-ring, radiation

2562

J.C. Dooling, M. Borland, A.M. Grannan, C.J. Graziani, R.R. Lindberg, G. Navrotski
ANL, Lemont, Illinois, USA
N.M. Cook
RadiaSoft LLC, Boulder, Colorado, USA
D.W. Lee, Y. Lee
UCSC, Santa Cruz, California, USA

Funding: Work supported by the U.S. D.O.E.,Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02- 06CH11357.
Modeling of high-energy-density electron beams on collimators proposed for the Advanced Photon Source Upgrade (APS-U) storage ring (SR) is carried out with codes FLASH, MARS, and elegant. Code results are compared with experimental data from two separate beam dump studies conducted in the present APS SR. Whole beam dumps of the 6-GeV, 200 mA, ultra-low emittance beam will deposit acute doses of 30 MGy within 10 to 20 microseconds, leading to hydrodynamic behavior in the collimator material. Goals for coupling the codes include accurate modeling of the hydrodynamic behavior, methods to mitigate damage, and understanding the effects of the resulting shower downstream of the collimator. Relevant experiments, though valuable, are difficult and expensive to conduct. The coupled codes will provide a method to model differing geometries, materials, and loss scenarios. Efforts thus far have been directed toward using FLASH to reproduce observed damage seen in aluminum test pieces subjected to varying beam strike currents. Stabilizing the Eulerian mesh against large energy density gradients as well as establishing release criteria from solid to fluid forms are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXC04

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paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 30 August 2021

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WEPAB001

Accelerator Challenges of the LHeC Project

emittance, optics, linac, proton

2570

B.J. Holzer, K.D.J. André, O.S. Brüning
CERN, Geneva, Switzerland
S.A. Bogacz
JLab, Newport News, Virginia, USA
M. Klein
The University of Liverpool, Liverpool, United Kingdom

The LHeC project studies the design of a future electron-proton collider at CERN that will run in parallel to the standard LHC operation. For this purpose, the existing LHC storage ring will be combined with an Energy Recovery Linac (ERL), to accelerate electrons up to kinetic energy of 50 GeV. This concept - also applicable to the FCC-eh collider and studied at the PERLE project as prototype version - allows a peak luminosity of 10³⁴ cm^-2 s^-1. A sophisticated design of the RF structures, linacs, arcs, and interaction region is required. The electrons are accelerated and, after the interaction point, their energy is recovered through the same RF structures. While this energy recovery concept is a very promising approach, severe challenges are set by the layout of the interaction region, the beam separation concept and the design of the linac and arc lattice for the highest possible momentum acceptance. Emittance control and beam-beam effect of both, electron and proton beams, have been studied in front-to-end simulations and will be presented. We summarise the design principles of the ERL, the optimization of the arc lattice, and the main parameters of the project.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB001

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paper received ※ 17 May 2021 paper accepted ※ 21 June 2021 issue date ※ 31 August 2021

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WEPAB002

The Interaction Region of the Electron-Ion Collider EIC

radiation, synchrotron-radiation, synchrotron, detector

2574

H. Witte, J. Adam, M. Anerella, E.C. Aschenauer, J.S. Berg, M. Blaskiewicz, A. Blednykh, W. Christie, J.P. Cozzolino, K.A. Drees, D.M. Gassner, K. Hamdi, C. Hetzel, H.M. Hocker, D. Holmes, A. Jentsch, A. Kiselev, P. Kovach, H. Lovelace III, Y. Luo, G.J. Mahler, A. Marone, G.T. McIntyre, C. Montag, R.B. Palmer, B. Parker, S. Peggs, S.R. Plate, V. Ptitsyn, G. Robert-Demolaize, C.E. Runyan, J. Schmalzle, K.S. Smith, S. Tepikian, P. Thieberger, J.E. Tuozzolo, F.J. Willeke, Q. Wu, Z. Zhang
BNL, Upton, New York, USA
B.R. Gamage, T.J. Michalski, V.S. Morozov, M.L. Stutzman, W. Wittmer
JLab, Newport News, Virginia, USA
M.K. Sullivan
SLAC, Menlo Park, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
This paper presents an overview of the Interaction Region (IR) design for the planned Electron-Ion Collider (EIC) at Brookhaven National Laboratory. The IR is designed to meet the requirements of the nuclear physics community *. The IR design features a ±4.5 m free space for the detector; a forward spectrometer magnet is used for the detection of hadrons scattered under small angles. The hadrons are separated from the neutrons allowing detection of neutrons up to ±4 mrad. On the rear side, the electrons are separated from photons using a weak dipole magnet for the luminosity monitor and to detect scattered electrons (e-tagger). To avoid synchrotron radiation backgrounds in the detector no strong electron bending magnet is placed within 40 m upstream of the IP. The magnet apertures on the rear side are large enough to allow synchrotron radiation to pass through the magnets. The beam pipe has been optimized to reduce the impedance; the total power loss in the central vacuum chamber is expected to be less than 90 W. To reduce risk and cost the IR is designed to employ standard NbTi superconducting magnets, which are described in a separate paper.
* An Assessment of U.S.-Based Electron-Ion Collider Science. (2018). Washington, D.C.: National Academies Press. https://doi.org/10.17226/25171

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB002

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paper received ※ 18 May 2021 paper accepted ※ 25 June 2021 issue date ※ 27 August 2021

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WEPAB003

Overview of the Magnets Required for the Interaction Region of the Electron-Ion Collider (EIC)

dipole, hadron, quadrupole, collider

2578

H. Witte, K. Amm, M. Anerella, J. Avronsart, A. Ben Yahia, J.P. Cozzolino, R.C. Gupta, H.M. Hocker, P. Kovach, G.J. Mahler, A. Marone, R.B. Palmer, B. Parker, S.R. Plate, C.E. Runyan, J. Schmalzle
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The planned electron-ion collider (EIC) at Brookhaven National Laboratory (BNL) is designed to deliver a peak luminosity of 1x10³⁴ cm^-2 s^-1. This paper presents an overview of the magnets required for the interaction region of the BNL EIC. To reduce risk and cost the IR is designed to employ conventional NbTi superconducting magnets. In the forward direction the magnets for the hadrons are required to pass a large neutron cone and particles with a transverse momentum of up to 1.3 GeV/c, which leads to large aperture requirements. In the rear direction the synchrotron radiation fan produced by the electron beam must not hit the magnet apertures, which determines their aperture. For the forward direction a mostly interleaved scheme is used for the optics, whereas for the rear side 2-in-1 magnets are employed. We present an overview of the EIC IR magnet design including the forward spectrometer magnet B0.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB003

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paper received ※ 18 May 2021 paper accepted ※ 01 July 2021 issue date ※ 15 August 2021

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WEPAB004

Electron-Ion Luminosity Maximization in the EIC

luminosity, collider, emittance, hadron

2582

W. Fischer, E.C. Aschenauer, M. Blaskiewicz, K.A. Drees, A.V. Fedotov, H. Huang, C. Montag, V. Ptitsyn, D. Raparia, V. Schoefer, K.S. Smith, P. Thieberger, F.J. Willeke
BNL, Upton, New York, USA
Y. Zhang
JLab, Newport News, Virginia, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The electron-ion luminosity in EIC has a number of limits, including the ion intensity available from the injectors, the total ion beam current, the electron bunch intensity, the total electron current, the synchrotron radiation power, the beam-beam effect, the achievable beta functions at the interaction points (IPs), the maximum angular spreads at the IP, the ion emittances reachable with stochastic or strong cooling, the ratio of horizontal to vertical emittance, and space charge effects. We map the e-A luminosity over the center-of-mass energy range for some ions ranging from deuterons to uranium ions. For e-Au collisions the present design provides for electron-nucleon (e-Au) peak luminosities of 1.7x1033 cm^-2s⁻¹ with stochastic cooling, and 4.7x1033 cm^-2s⁻¹ with strong hadron cooling.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB004

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paper received ※ 18 May 2021 paper accepted ※ 21 June 2021 issue date ※ 02 September 2021

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WEPAB005

Design Status Update of the Electron-Ion Collider

hadron, collider, storage-ring, interaction-region

2585

C. Montag, E.C. Aschenauer, G. Bassi, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, A. Blednykh, J.M. Brennan, S.J. Brooks, K.A. Brown, Z.A. Conway, K.A. Drees, A.V. Fedotov, W. Fischer, C. Folz, D.M. Gassner, X. Gu, R.C. Gupta, Y. Hao, A. Hershcovitch, C. Hetzel, D. Holmes, H. Huang, W.A. Jackson, J. Kewisch, Y. Li, C. Liu, H. Lovelace III, Y. Luo, M. Mapes, D. Marx, G.T. McIntyre, F. Méot, M.G. Minty, S.K. Nayak, R.B. Palmer, B. Parker, S. Peggs, B. Podobedov, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, S. Seletskiy, V.V. Smaluk, K.S. Smith, S. Tepikian, R. Than, P. Thieberger, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, S. Verdú-Andrés, E. Wang, D. Weiss, F.J. Willeke, H. Witte, Q. Wu, W. Xu, A. Zaltsman, W. Zhang
BNL, Upton, New York, USA
S.V. Benson, J.M. Grames, F. Lin, T.J. Michalski, V.S. Morozov, E.A. Nissen, J.P. Preble, R.A. Rimmer, T. Satogata, A. Seryi, M. Wiseman, W. Wittmer, Y. Zhang
JLab, Newport News, Virginia, USA
Y. Cai, Y.M. Nosochkov, G. Stupakov, M.K. Sullivan
SLAC, Menlo Park, California, USA
K.E. Deitrick, C.M. Gulliford, G.H. Hoffstaetter, J.E. Unger
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
E. Gianfelice-Wendt
Fermilab, Batavia, Illinois, USA
T. Satogata
ODU, Norfolk, Virginia, USA
D. Xu
FRIB, East Lansing, Michigan, USA

Funding: Work supported by BSA, LLC under Contract No. DE-SC0012704, by JSA, LLC under Contract No. DE-AC05-06OR23177, and by SLAC under Contract No. DE-AC02-76SF00515 with the U.S. Department of Energy.
The design of the electron-ion collider EIC to be constructed at Brookhaven National Laboratory has been continuously evolving towards a realistic and robust design that meets all the requirements set forth by the nuclear physics community in the White Paper. Over the past year activities have been focused on maturing the design, and on developing alternatives to mitigate risk. These include improvements of the interaction region design as well as modifications of the hadron ring vacuum system to accommodate the high average and peak beam currents. Beam dynamics studies have been performed to determine and optimize the dynamic aperture in the two collider rings and the beam-beam performance. We will present the EIC design with a focus on recent developments.

Poster WEPAB005 [2.095 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB005

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paper received ※ 14 May 2021 paper accepted ※ 22 June 2021 issue date ※ 17 August 2021

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WEPAB008

Numerical Noise Study in EIC Beam-Beam Simulations

simulation, proton, emittance, resonance

2592

D. Xu, Y. Hao
FRIB, East Lansing, Michigan, USA
Y. Luo, C. Montag
BNL, Upton, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

In the Electron-Ion Collider (EIC) design, a flat beam collision scheme is adopted to achieve 1e34 luminosity. We found that the vertical growth of the proton beam is much larger than of the round beam. In this article we present the numerical noise study about the number of macroparticles, the electron slice number, and the electron bunch length. Both weak-strong and strong-strong simulation methods are used. It turns out the proton emittance growth in the strong-strong simulation mainly comes from the numberical noise. This study helps us to perform beam-beam simulation correctly for EIC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB008

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paper received ※ 17 May 2021 paper accepted ※ 16 August 2021 issue date ※ 31 August 2021

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WEPAB009

Study of Harmonic Crab Cavity in EIC Beam-Beam Simulations

cavity, simulation, resonance, betatron

2595

D. Xu, Y. Hao
FRIB, East Lansing, Michigan, USA
Y. Luo, C. Montag
BNL, Upton, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

In the Electron-Ion Collider (EIC) design, crab cavities are adopted to compensate the geometric luminosity loss from the crossing angle. From previous studies, higher-order synchro-betatron resonances are excited since the hadron beam is long and the crossing angle is large. To reduce the luminosity degradation rate, different combinations of harmonic crab cavities are studied with both weak-strong and strong-strong simulation methods. The frequency map analysis (FMA) is also used for comparison. This study helps determine the crab cavity parameters for the future EIC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB009

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paper received ※ 17 May 2021 paper accepted ※ 23 June 2021 issue date ※ 30 August 2021

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WEPAB013

A New Algorithm for Positron Source Parameter Optimisation

positron, target, simulation, linac

2609

Y. Zhao, L. Ma
SDU, Shandong, People’s Republic of China
S. Döbert, A. Latina
CERN, Geneva, Switzerland

In this report, we proposed a new simple and efficient algorithm for positron source parameter optimisation, which is based on iterations of scan of free parameters in the simulation. The new algorithm is fast, simple and convincing since the results can be visually drawn and flexibly tuned and it has an advantage that it can easily handle realistic parametric problems with more than one objective quantities to optimise. The optimisation of the main parameters of the CLIC positron source at the 380 GeV stage is presented as an example to demonstrate how the algorithm works.

Poster WEPAB013 [1.352 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB013

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paper received ※ 15 May 2021 paper accepted ※ 24 June 2021 issue date ※ 19 August 2021

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WEPAB014

Optimisation of the CLIC Positron Source

positron, target, simulation, linac

2613

Y. Zhao, L. Ma
SDU, Shandong, People’s Republic of China
H.M.A. Bajas, S. Döbert, A. Latina
CERN, Geneva, Switzerland

In this report, we reoptimised the CLIC positron source at all collision energy stages. Simulation, optimisation algorithm and results were all improved compared with previous studies. Two different target schemes were studied and compared in terms of the advantages and disadvantages. The spot size of the injected electron beam was also optimised to achieve a compromise between large positron yields and safe energy deposition. The matching device for the capture of positrons was simulated and optimised with both improved analytic and realistic field maps. Conical aperture and front and rear gaps of the matching device were also considered for the first time. The optimised positron source is expected to have the lowest cost.

Poster WEPAB014 [1.825 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB014

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paper received ※ 15 May 2021 paper accepted ※ 21 June 2021 issue date ※ 23 August 2021

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WEPAB015

Comparison of Different Matching Device Field Profiles for the FCC-ee Positron Source

positron, target, linac, simulation

2617

Y. Zhao, L. Ma
SDU, Shandong, People’s Republic of China
B. Auchmann, P. Craievich, J. Kosse, R. Zennaro
PSI, Villigen PSI, Switzerland
I. Chaikovska, R. Chehab
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
S. Döbert, A. Latina
CERN, Meyrin, Switzerland
P.V. Martyshkin
BINP SB RAS, Novosibirsk, Russia

In this report, we compared different matching device field profiles for the FCC-ee positron source. The matching device is used to capture positrons with magnetic field. A flux concentrator was designed with a conical inner chamber. A smaller aperture and a larger aperture were studied. An analytic field profile was also studied using an adiabatic formula. The peak field of the analytic profile as well as beam and target parameters was optimised to achieve a maximum positron yield. A safe energy deposition in the target was guaranteed by requiring a constraint on the deposited power and peak energy deposition density.

Poster WEPAB015 [3.066 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB015

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paper received ※ 15 May 2021 paper accepted ※ 23 June 2021 issue date ※ 12 August 2021

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WEPAB016

Snowmass’21 Accelerator Frontier

collider, hadron, target, luminosity

2621

V.D. Shiltsev
Fermilab, Batavia, Illinois, USA
S.A. Gourlay
LBNL, Berkeley, California, USA
T.O. Raubenheimer
SLAC, Menlo Park, California, USA

Snowmass’21 is decadal particle physics community planning study. It provides an opportunity for the entire particle physics community to come together to identify and document a scientific vision for the future of particle physics in the U.S. and its international partners. Snowmass will define the most important questions for the field of particle physics and identify promising opportunities to address them. The P5, Particle Physics Project Prioritization Panel, will take the scientific input from Snowmass and develop a strategic plan for U.S. particle physics that can be executed over a 10 year timescale, in the context of a 20-year global vision for the field. Here we present the goals, progress and plans of the Snowmass’21 Accelerator Frontier.

Poster WEPAB016 [1.108 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB016

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paper received ※ 17 May 2021 paper accepted ※ 23 June 2021 issue date ※ 18 August 2021

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WEPAB018

Space-Charge Effects in Ionization Beam Profile Monitors

proton, booster, space-charge, synchrotron

2628

V.D. Shiltsev
Fermilab, Batavia, Illinois, USA

Ionization profile monitors (IPMs) are widely used in accelerators for non-destructive and fast diagnostics of high energy particle beams. At high beam intensities, the space-charge forces make the measured IPM profiles significantly different from those of the beams. We analyze dynamics of the secondaries in IPMs and develop an effective algorithm to reconstruct the beam sizes from the measured IPM profiles. Efficiency of the developed theory is illustrated in application to the Fermilab 8 GeV proton Booster IPMs.

Poster WEPAB018 [0.731 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB018

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 19 August 2021

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WEPAB019

RF Harmonic Kicker R&D Demonstration and Its Application to the RCS Injection of the EIC

kicker, injection, cavity, operation

2632

G.-T. Park, M.W. Bruker, J.M. Grames, J. Guo, R.A. Rimmer, S.O. Solomon, H. Wang
JLab, Newport News, Virginia, USA

The Rapid Cycling Synchrotron (RCS) of the Electron-Ion Collider (EIC) at Brookhaven National Laboratory (BNL) * is an accelerating component of the electron injection complex, which provides polarized electrons in electron-ion collisions in the main Electron Storage Ring (ESR). We present the injection scheme into the RCS based on an ultra-fast harmonic kicker, whose "five odd-harmonic modes" prototype was developed in the context of the Jefferson Lab EIC (JLEIC) conceptual design **. In its early stage of R&D, the sharp (~3 ns width) waveform construction, beam dynamics, and pulsed power operation with short ramping time (~10 us) will be discussed together with the fabrication work of the JLEIC prototype ***.
* BNL, "Electron Ion Collider Conceptual Design Report", 2020
** G. Park et. al, JLAB-TN-044
*** G. Park et. al., JLAB-TN-046

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB019

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paper received ※ 17 May 2021 paper accepted ※ 22 June 2021 issue date ※ 27 August 2021

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WEPAB021

Development and Testing of a Cherenkov Beam Loss Monitor in CLEAR Facility

experiment, detector, photon, beam-losses

2640

S. Benitez Berrocal, E. Effinger, W. Farabolini, A. Gilardi, P. Korysko, E. Lima, B. Salvachua, W. Viganò
CERN, Geneva 23, Switzerland
P. Lane
University of Huddersfield, Huddersfield, United Kingdom

Beam Loss Monitors are fundamental diagnostic systems in particle accelerators. Beam losses are measured by a wide range of detectors with excellent results; most of these devices are used to measure local beam losses. However, in some accelerators there is the need to measure beam losses continuously localized over longer distances i.e., several tens of meters. For this reason, a beam loss detector based on long optical fibres is now under study. As part of the design, several simulations, comparing different possible detection scenarios, have been performed in FLUKA and bench-marked with experimental data. An experimental campaign was performed with an electron beam in the CERN Linear Electron Accelerator for Research (CLEAR) in November 2020. The light emitted from the optical fibre was captured using Silicon Photo-Multipliers (SiPM) coupled at each fibre’s end. In this poster, the first results of a beam loss detector based on the capture of Cherenkov photons generated by charged particles inside multimode silica fibres are presented.

Poster WEPAB021 [0.724 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB021

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paper received ※ 18 May 2021 paper accepted ※ 21 June 2021 issue date ※ 28 August 2021

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WEPAB031

Frequency Dependence of Plasma Cascade Amplification

plasma, distributed, simulation, hadron

2672

G. Wang, V. Litvinenko, J. Ma
BNL, Upton, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A new type of amplifier, plasma cascade amplifier (PCA) has been proposed for a coherent electron cooling (CeC) system. Previously, the 1D model for PCA assumes that the transverse distribution of the density perturbation in the electrons is uniform and consequently, the plasma frequency does not depend on the wavelength of the perturbation. This assumption is valid if the longitudinal wavelength of the beam frame is much shorter than the transverse width of perturbation. In this work, we explore the PCI gain at a long wavelength by assuming the perturbation in the electron density has a non-uniform transverse profile. Specifically, we solve the 3D Poisson equation for given charge distribution (longitudinal sinusoidal, transversely Gaussian, or Beer-can), average the electric field over the transverse plane, and then apply it to 1D Vlasov equation. Similar to the previous calculation, the Vlasov equation can be reduced to a Hill’s equation but the plasma frequency now depends on the longitudinal wavelength of the density perturbation in the electrons. By numerically solving Hill’s equation, we obtain the gain of a PCA and compare it with the results from 3D SPACE simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB031

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paper received ※ 20 May 2021 paper accepted ※ 23 June 2021 issue date ※ 17 August 2021

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WEPAB032

Studies of the Short-Range Wakefields for the Electron Storage Ring in the Electron Ion Collider

simulation, vacuum, wakefield, dipole

2675

G. Wang, M. Blaskiewicz, A. Blednykh, M.P. Sangroula
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
During the estimates of impedance budget for the Electron Storage Ring (ESR) of Electron-Ion Collider (EIC), various codes, including GdfidL, CST and ECHO3D, have been used to calculate the short-range wake-fields due to the vacuum components. The ECHO 3D code demonstrates more reliable results for the tapered type of structures rather than the GdfidL code, where the stepsize needs to be dramatically decreased to achieve a high-performance calculation. Impedance of the following components are discussed and compared in details: Interaction Region (IR) chamber, bellows, and synchrotron radiation mask (flange absorber).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB032

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paper received ※ 19 May 2021 paper accepted ※ 10 June 2021 issue date ※ 16 August 2021

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WEPAB039

Construction of a Compact Electron Injector Using a Gridded RF Thermionic Gun and a C-Band Accelerator

linac, injection, operation, emittance

2687

T. Inagaki, T. Asaka, T. Hara, T. Hiraiwa, N. Hosoda, E. Iwai, C. Kondo, H. Maesaka, T. Ohshima, H. Tanaka
RIKEN SPring-8 Center, Hyogo, Japan
H. Dewa, T. Magome, Y. Minagawa, T. Sakurai
JASRI/SPring-8, Hyogo-ken, Japan
T. Fukui
RIKEN SPring-8 Center, Innovative Light Sources Division, Hyogo, Japan
S. Hashimoto
LASTI, Hyogo, Japan
S.I. Inoue, K. Kajimoto, S. Nakata, T. Seno, H. Sumitomo, R. Takesako, S. Tanaka, R. Yamamoto, M. Yoshioka
SES, Hyogo-pref., Japan
K. Yanagida
JASRI, Hyogo, Japan

A compact and low-cost 1 GeV injector linac was designed and constructed to provide injection beams to the soft X-ray synchrotron radiation facility NewSUBARU instead of the SPring-8 injector system, which will be shutdown. The total length of the injector linac needs to be less than 70 m to fit into the existing tunnel. To this end, an RF electron gun with a gridded thermionic cathode directly attached to a 238 MHz RF cavity was developed and adopted. The 500 keV, 0.6 ns, 1 nC beam emitted from the cavity is compressed to 3 ps by velocity bunching driven by a 476 MHz RF cavity and a S-band RF structure. The short-pulsed beams are accelerated up to 1 GeV with 16 C-band RF structures. In the C-band accelerator section, the klystron output of 50 MW is multiplied 4 times by a pulse compressor and fed to the 4 RF structures to generate a high accelerating field of 31 MV/m. A low-level RF system consisting of a MTCA.4 based high-speed digitizers and RF frontend boards has been constructed. This injector system is used at the 3 GeV SR facility currently under construction in Sendai. In this paper, we report the design outline and the operational performance of the injector system.

Poster WEPAB039 [2.419 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB039

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paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 29 August 2021

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WEPAB040

Characterization of Low Emittance Electron Beams Generated by Transverse Laser Beam Shaping

laser, emittance, flattop, cathode

2690

M. Groß, N. Aftab, P. Boonpornprasert, G.Z. Georgiev, J. Good, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, D. Melkumyan, S.K. Mohanty, R. Niemczyk, A. Oppelt, H.J. Qian, G. Shu, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany
Y. Chen, G. Loisch
DESY, Hamburg, Germany
I. Will
MBI, Berlin, Germany

Linac based X-ray free electron laser demand a high beam quality from the electron source, therefore RF photoinjectors are used to generate the electron bunches for state of the art beam brightness. One important figure of merit for these injectors is the transverse emittance of the generated electron beam, which can be minimized by shaping the photocathode laser pulses. Best performance can be achieved with ellipsoidal laser pulses, but 3D shaping is technically challenging. Typically, a quasi-uniform transverse laser profile is truncated from the Gaussian profile generated by the laser with an aperture to reduce the transverse nonlinear space charge forces. This is investigated in detail by optimizing the laser transverse profile at the Photoinjector Test facility at DESY in Zeuthen (PITZ), where photoinjector R&D is conducted for the E-XFEL and FLASH free electron lasers at DESY in Hamburg. In this contribution we present experimental results at high acceleration gradients (up to 60 MV/m) for both 250 pC and 500 pC. For a bunch charge of 500 pC an emittance reduction of about 30% compared to the commonly used transverse flat-top laser distribution was achieved.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB040

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paper received ※ 17 May 2021 paper accepted ※ 02 June 2021 issue date ※ 31 August 2021

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WEPAB042

Linac-200: A New Electron Test Beam Facility at JINR

controls, linac, gun, klystron

2697

M.A. Nozdrin, M. Gostkin, V. Kobets, Y.A. Samofalova, G. Shirkov, A. Trifonov, K. Yunenko, A. Zhemchugov
JINR, Dubna, Moscow Region, Russia

Commissioning of a new electron test beam facility Linac-200 comes to the end at JINR (Dubna, Russia). The core of the facility is a refurbished MEA accelerator from NIKHEF. The key accelerator subsystems including controls, vacuum, precise temperature regulation were redesigned or deeply upgraded. The facility provides electron beams with energy up to 200 MeV while the beam current varying smoothly from 40 mA down to almost zero (single electrons in a bunch). The main goal of the facility is providing test beams for particle detector R&D, studies of novel approaches to the beam diagnostics, and education and training of graduate and postgraduate students. The current status and operation parameters of the facility will be reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB042

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paper received ※ 18 May 2021 paper accepted ※ 23 June 2021 issue date ※ 25 August 2021

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WEPAB043

Consolidation and Future Upgrades to the CLEAR User Facility at CERN

experiment, laser, gun, radiation

2700

L.A. Dyks, P. Korysko
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
P. Burrows
JAI, Oxford, United Kingdom
R. Corsini, S. Curt, W. Farabolini, D. Gamba, L. Garolfi, A. Gilardi, E. Granados, G. McMonagle, H. Panuganti
CERN, Geneva, Switzerland
W. Farabolini
CEA-DRF-IRFU, France
A. Gilardi
University of Napoli Federico II, Napoli, Italy
K.N. Sjobak
University of Oslo, Oslo, Norway

The CERN Linear Electron Accelerator for Research (CLEAR) at CERN has been operating since 2017 as a dedicated user facility providing beams for a varied range of experiments. CLEAR consists of a 20 m long linear accelerator (linac), able to produce beams from a Cs₂Te photocathode and accelerate them to energies of between 60 MeV and 220 MeV. Following the linac, an experimental beamline is located, in which irradiation tests, wakefield and impedances tudies, plasma lens experiments, beam diagnostics development, and terahertz (THz) emission studies, are performed. In this paper, we present recent upgrades to the entire beamline, as well as the design of future upgrades, such as a dogleg section connecting to an additional proposed experimental beamline. The gain in performance due to these upgrades is presented with a full range of available beam properties documented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB043

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paper received ※ 18 May 2021 paper accepted ※ 24 June 2021 issue date ※ 29 August 2021

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WEPAB044

Status of VHEE Radiotherapy Related Studies at the CLEAR User Facility at CERN

experiment, radiation, linac, focusing

2704

R. Corsini, W. Farabolini, A. Gilardi
CERN, Geneva, Switzerland
L.A. Dyks, P. Korysko
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
W. Farabolini
CEA-DRF-IRFU, France
A. Gilardi
University of Napoli Federico II, Napoli, Italy
K.N. Sjobak
University of Oslo, Oslo, Norway

Despite the increase in interest in using Very High Energy Electron (VHEE) beams for cancer radiotherapy many unanswered questions in its development remain. The use of test facilities will be an essential tool used to solve these issues. The 200 MeV electron beam from the CERN Linear Accelerator for Research (CLEAR) has been used extensively, in collaboration with several research institutes, to perform dosimetry studies and explore potential applications of VHEE beams to radiotherapy, including the exploitation of the so called FLASH effect. In this paper, we present an overview of past studies with emphasis on the more recent results. We describe methods, techniques and equipment developed at CERN in this framework, and give an outlook on future activities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB044

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paper received ※ 18 May 2021 paper accepted ※ 23 June 2021 issue date ※ 13 August 2021

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WEPAB045

European XFEL High-Power RF System - the First 4 Years of Operation

klystron, operation, FEL, GUI

2708

M. Bousonville, S. Choroba, T. Grevsmühl, S. Göller, A. Hauberg, V.V. Katalev, K. Machau, V. Vogel, B. Yildirim
DESY, Hamburg, Germany

In 2016, the installation of the European XFEL was completed and its 26 RF stations started operation in 2017. Each RF station consists of a 10 MW-1.3 GHz-multibeam klystron, a HV pulse modulator and a waveguide system to supply the superconducting cavities and the normal-conducting electron gun with RF power. During commissioning and subsequent operation, the RF stations were closely monitored and causes of failures were investigated. For the optimisation of the RF systems, the various RF station failures were evaluated according to their impact on accelerator operation and the measures to eliminate them were prioritised accordingly. This report describes the operation experience and improvements of the high-power RF stations during the first 4 years of operation.

Poster WEPAB045 [6.887 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB045

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 13 August 2021

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WEPAB048

Design of an Optical Cavity for Generating Intense THz Pulse Based on Coherent Cherenkov Radiation

radiation, cavity, gun, experiment

2711

P. Wang, Y. Koshiba, T. Murakami, K. Murakoshi, K. Sakaue, Y. Tadenuma, M. Washio
Waseda University, Tokyo, Japan
R. Kuroda
AIST, Tsukuba, Japan
K. Sakaue
The University of Tokyo, Graduate School of Engineering, Bunkyo, Japan

We have been studying terahertz (THz) generation via Cherenkov radiation with high-quality electron beams from a photocathode rf (radio frequency) gun. In our early studies, we have succeeded in the generation of coherent Cherenkov radiation by controlling the tilt of the electron beam using an rf-deflector. For further enhancement, we are planning to stack the THz pulses in an optical cavity. Multi-bunch operation of the rf-gun will generate electron beams with a repetition rate of 119 MHz, and THz pulses as well. These pulses will be accumulated in the cavity for up to 150 pulses. In this conference, we report the design study of the enhancement cavity and discuss the performance of the THz source.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB048

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 22 August 2021

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WEPAB051

Beam Dynamics for a High Field C-Band Hybrid Photoinjector

emittance, cathode, linac, gun

2714

L. Faillace, F. Bosco, M. Carillo, L. Giuliano, M. Migliorati, A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy
R.B. Agustsson, I.I. Gadjev, S.V. Kutsaev, A.Y. Murokh
RadiaBeam, Marina del Rey, California, USA
M. Behtouei, A. Giribono, B. Spataro, C. Vaccarezza
INFN/LNF, Frascati, Italy
A. Fukasawa, N. Majernik, J.B. Rosenzweig, O. Williams
UCLA, Los Angeles, California, USA
S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This work supported by DARPA GRIT under contract no. 20204571 and partially by INFN National Committee V through the ARYA project.
In this paper, we present a new class of a hybrid photoinjector in C-Band. This project is the effort result of a UCLA/Sapienza/INFN-LNF/SLAC/RadiaBeam collaboration. This device is an integrated structure consisting of an initial standing-wave 2.5-cell gun connected to a traveling-wave section at the input coupler. Such a scheme nearly avoids power reflection back to the klystron, removing the need for a high-power circulator. It also introduces strong velocity bunching due to a 90° phase shift in the accelerating field. A relatively high cathode electric field of 120 MV/m produces a ~4 MeV beam with ~20 MW input RF power in a small foot-print. The beam transverse dynamics are controlled with a ~0.27 T focusing solenoid. We show the simulation results of the RF/magnetic design and the optimized beam dynamics that shows 6D phase space compensation at 250 pC. Proper beam shaping at the cathode yields a ~0.5 mm-mrad transverse emittance. A beam waist occurs simultaneously with a longitudinal focus of <400 fs rms and peak current >600 A. We discuss application of this injector to an Inverse-Compton Scattering system and present corresponding start-to-end beam dynamics simulations.

Poster WEPAB051 [0.827 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB051

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paper received ※ 18 May 2021 paper accepted ※ 01 July 2021 issue date ※ 22 August 2021

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WEPAB052

Development of an EO Sampling System for the Analysis of THz Waves Generated by Coherent Cherenkov Radiation

radiation, laser, experiment, timing

2718

K. Murakoshi, Y. Koshiba, T. Murakami, K. Sakaue, Y. Tadenuma, P. Wang, M. Washio
Waseda University, Tokyo, Japan
R. Kuroda
AIST, Tsukuba, Japan
K. Sakaue
The University of Tokyo, Graduate School of Engineering, Bunkyo, Japan

THz waves, located between microwaves and light waves, have transparency, directionality and fingerprint spectrum of specific materials. Therefore, they are expected to be useful for various applications. We have been studying THz waves generation via Cherenkov radiation with electron beams from a photocathode rf-gun. In our early studies, we have succeeded in the generation of coherent Cherenkov radiation by tilted electron beams using an rf-deflector. Furthermore, we have generated quasi-monochromatic THz waves by spatially modulated electron beams and have succeeded in its measurement by bandpass filters. This study aims to obtain the THz wave form in time domain by electro-optic (EO) sampling, which is an useful detection system for obtaining the information of the electric field and the phase simultaneously with high S/N. In this conference, we report about our probe laser system, results of the time-domain spectroscopy measurement of THz waves by EO sampling, and future prospects.

Poster WEPAB052 [0.861 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB052

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 26 August 2021

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WEPAB054

Electromagnetic and Beam Dynamics Studies of the ThomX LINAC

HOM, linac, gun, solenoid

2721

M. Alkadi, C. Bruni, M. El Khaldi, M. Jacquet
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
H. Monard
IJCLab, ORSAY, France

ThomX is a new generation compact Compton source. The machine is composed of a 50/70 MeV injector linac and a storage ring where an electron bunch collides with a laser pulse accumulated in a Fabry-Perot resonator. The compact source, built at Irene Joliot-Curie Laboratory (IJCLAB) in the Orsay campus of Paris-Saclay University, is designed to produce a total flux of 10¹³ ph/s and a brightness of 1011 ph / (s.mm2.mrad2) in 0.1% of bandwidth with a tunable energy ranging from 45 keV to 90 keV on the X-ray beam axis. The photo-injector is composed of a homemade 2.5 cell photocathode RF-gun, placed between two solenoids. An energy of 5 MeV is reached with a 80 MV/m electric field gradient. During the commissioning phase, a 4.8 m S-band LIL section will be used to achieve a 50 MeV corresponding to a 45 keV X-ray energy. The LIL accelerating section is a quasi-constant gradient traveling wave structure. The energy gain in the section is 45 MeV, corresponding to an average effective accelerating gradient of 10 MV/m for an input RF power of 9 MW. Here we present the electromagnetic and beam dynamics studies of the ThomX LINAC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB054

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 31 August 2021

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WEPAB055

Development of a Linac for Injection of Ultrashort Electron Bunches Into Laser Plasma Electron Accelerators

laser, plasma, acceleration, linac

2725

S. Masuda, N. Kumagai, T. Masuda, Y. Otake
JASRI, Hyogo, Japan
Y. Koshiba, S. Otsuka
Waseda University, Tokyo, Japan
T. Sakai, T. Tanaka
LEBRA, Funabashi, Japan
K. Sakaue
The University of Tokyo, The School of Engineering, Tokyo, Japan

Funding: This work is supported by JST-Mirai Program Grant Number JPMJMI17A1, Japan.
We are developing a C-band linac that produces ultrashort electron bunches as an injector for laser plasma accelerators. A plasma wave excited by a high intense ultrashort laser pulse has a wavelength of the order of 10 to 100 fs and transverse dimensions of the order of 10 to 100 um. To inject the bunch into a proper phase of the plasma wave, a length and transverse sizes of the bunch must be much smaller than the plasma wave structure. A laser triggered photo cathode electron RF-gun and a 2pi/3 mode traveling wave buncher with 24 cells for ultrashort electron bunch production have been developed based on electron beam tracking simulations that show the bunch length is less than 10 fs with a charge of 100 fC at a focus on the plasma wave. The simulations also show that sufficiently small transverse sizes of the bunch at the focus can be obtained by a Q triplet. A highly accurate timing lower than the plasma wavelength (~10fs) is required for the synchronization between the electron bunch injection and the plasma wave excitation. An RF master oscillator with low SSB phase noise (-150dBc/Hz@10MHz) has been developed for the synchronization. We will report present development status.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB055

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paper received ※ 19 May 2021 paper accepted ※ 15 July 2021 issue date ※ 26 August 2021

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WEPAB062

Investigation of the Thomson Scattering Influence on Electron Beam Parameters in an Energy-Recovering Linear Accelerator on the Example of MESA

photon, scattering, HOM, laser

2732

C.L. Lorey, K. Aulenbacher, A. Meseck
KPH, Mainz, Germany

Funding: funded by DFG through GRK2128 ACCELENCE
At the Johannes Gutenberg University (JGU) in Mainz, the Mainz Energy-recovering Superconducting Accelerator (MESA) is currently under construction. It is designed to deliver electron beams of up to 155 MeV. As it can be operated in an energy-recovery (ER) mode thus allowing for high repetition rate, it is a promising candidate for a high flux Thomson scattering based gamma source. This paper will provide a status update on the study of the impact of Thomson scattering on electron beam parameters and the underlying mechanics. Further, the implementation into a simulation code will be discussed.

Poster WEPAB062 [1.307 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB062

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paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 11 August 2021

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WEPAB063

Status of the Polarized Source and Beam Preparation System at MESA

laser, experiment, emittance, simulation

2736

S. Friederich, K. Aulenbacher, C. Matejcek
IKP, Mainz, Germany
K. Aulenbacher
HIM, Mainz, Germany
K. Aulenbacher
GSI, Darmstadt, Germany

Funding: This work is supported by the DFG excellence initiative PRISMA+.
The MESA Low-energy Beam Apparatus (MELBA) connects the DC photoemission source STEAM with the injector accelerator MAMBO. MELBA is capable of adjusting the longitudinal phase space for the requirements of the pre-acceleration by using a chopper and buncher while providing small transverse emittances. Measurements of the transverse phase space and longitudinal beam dimension taken at a test setup are presented. These results serve now for further improvements, e.g design changes in our corrector magnets. In addition, the revised MELBA will include two Wien filters and a solenoid for spin manipulation. A double scattering Mott polarimeter for spin diagnostics and a second source for the extraction of high bunch charges is foreseen using a branched off beam line. RF-synchronized laser diodes will be used with infrared wavelength as a driver for the spin-polarized photoemission. In this report we present the latest layout of MELBA and simulation results.

Poster WEPAB063 [1.752 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB063

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paper received ※ 19 May 2021 paper accepted ※ 16 July 2021 issue date ※ 25 August 2021

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WEPAB064

Front-to-End Simulations of the Energy Recovery Linac for the LHeC Project

emittance, proton, radiation, linac

2740

K.D.J. André, B.J. Holzer
CERN, Geneva, Switzerland

The LHeC project aims to study the electron-proton deep inelastic scattering at the TeV energy scale with an innovative accelerator program. It exploits the promising energy recovery technology in order to collide an intense 50 GeV lepton beam with one hadron beam from the High Luminosity Large Hadron Collider (HL-LHC) in parallel to the hadron-hadron operation. The paper presents the studies that have been performed to assess the performance of the machine and the efficiency of the energy recovery process for different scalings of the ERL. The studies include emittance blow-up due to synchrotron radiation emission and beam-disruption created by the strong beam-beam force at the interaction point. The design principles of the ERL structure are discussed, including the particle detector bypass and the interaction region, and the results of the tracking simulations are presented, considering the complete multi-turn ERL process. Special attention is turned to the lepton beam emittance budget and the resulting energy recovery performance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB064

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paper received ※ 18 May 2021 paper accepted ※ 24 June 2021 issue date ※ 12 August 2021

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WEPAB065

Studies of the Energy Recovery Performance of the PERLE Project

linac, cavity, HOM, radiation

2744

K.D.J. André, B.J. Holzer
CERN, Geneva, Switzerland
S.A. Bogacz
JLab, Newport News, Virginia, USA

The Powerful Energy Recovery Linac for Experiments (PERLE) is an accelerator facility for the development and application of the energy recovery technique for an intense 500 MeV electron beam. The paper presents the studies that have been performed to assess the quality of the ERL lattice design and beam optics. The studies include the Coherent Synchrotron Radiation (CSR) emission and wakefields in the superconducting radio-frequency structures of the linacs. The lattice design and optics principles of the ERL structure are discussed, involving the vertical deflection system and the 180° arcs. Finally, the results of the front-to-end tracking simulations that consider the complete multi-turn energy recovery process are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB065

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paper received ※ 18 May 2021 paper accepted ※ 24 June 2021 issue date ※ 14 August 2021

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WEPAB067

High Duty Cycle EUV Radiation Source Based on Inverse Compton Scattering

laser, gun, photon, emittance

2748

R. Huang, Q.K. Jia, C. Li
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by the National Natural Science Foundation of China Grant Number 11805200, and National Key Research and Development Program of China No. 2016YFA0401901.
ICS can obtain quasi-monochromatic and directional EUV radiation via a MeV-scale energy electron beam and a micron-scale wavelength laser beam, which enables a dramatic reduction in dimension and expense of the system, and makes it an attractive technology in research, industry, medicine and homeland security. Here we describe an EUV source based on high repetition ICS system. The scheme exploits the output from the laser-electron interaction between a MW-ps laser at MHz repetition-rate and a high quality electron beam with an energy of a few MeV at MHz repetition-rate.

Poster WEPAB067 [1.551 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB067

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paper received ※ 23 May 2021 paper accepted ※ 24 June 2021 issue date ※ 11 August 2021

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WEPAB071

Design and Construction of an Intense Terahertz-Wave Source Based on Coherent Cherenkov Radiation Matched to Circle Plane Wave

radiation, FEL, experiment, controls

2751

N. Sei, H. Ogawa
AIST, Tsukuba, Ibaraki, Japan
K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, Y. Sumitomo, Y. Takahashi, T. Tanaka
LEBRA, Funabashi, Japan
T. Takahashi
Kyoto University, Research Reactor Institute, Osaka, Japan

Funding: This work was supported by Japan Society for the Promotion of Science KAKENHI JP19H04406 and the Visiting Researchers Program of Kyoto University Research Reactor Institute (R2013).
National Institute of Advanced Industrial Science and Technology has been studied terahertz (THz) coherent radiation in collaboration with Nihon University and Kyoto University. We have been developed a coherent transition radiation (CTR) source with macropulse power of 1 mJ using a screen monitor in the parametric X-ray line at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. However, to obtain a THz-wave source with higher intensity, we have undertaken a development of a new THz-wave source based on coherent Cherenkov radiation (CCR) matched to circle plane wave. Bypassing an electron beam through a hollow conical dielectric having an apex angle equal to the Cherenkov angle, the wavefront of the CCR generated on the inner surface of the hollow conical dielectric matches on the basal plane. Therefore, it is possible to obtain a high-power beam that is easy to transport. We have already produced a hollow conical dielectric made of high-resistivity silicon and considered a position controller for the hollow conical dielectric. In this presentation, the status of the new THz-wave source will be reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB071

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paper received ※ 18 May 2021 paper accepted ※ 22 June 2021 issue date ※ 15 August 2021

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WEPAB072

PAX: A Plasma-Driven Attosecond X-Ray Source

plasma, experiment, FEL, simulation

2755

C. Emma, J. Cryan, M.J. Hogan, K. Larsen, J.P. MacArthur, A. Marinelli, G.R. White, X.L. Xu
SLAC, Menlo Park, California, USA
A.C. Fisher, R.M. Hessami, P. Musumeci
UCLA, Los Angeles, California, USA
R. Robles
Stanford University, Stanford, California, USA

Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515. This work was also partially supported by DOE grant DESC0009914
Plasma accelerators can generate ultra high brightness electron beams which open the door to light sources with smaller physical footprint and properties unachievable with conventional accelerator technology. In this work * we show that electron beams from Plasma WakeField Accelerators (PWFAs) can generate coherent tunable soft X-ray pulses with TW peak power and duration of tens of attoseconds in a meter-length undulator. These X-ray pulses are an order of magnitude more powerful, shorter and can be produced with better stability than state-of-the-art X-ray Free Electron Lasers (XFELs). The X-ray emission in this approach is driven by coherent radiation from a pre-bunched, near Mega Ampere (MA) current electron beam of attosecond duration rather than the SASE FEL process starting from noise. This approach significantly relaxes the restrictive requirements on emittance, energy spread, and pointing stability which has thus far hindered the realization of a high-gain FEL driven by a plasma accelerator. We discuss the approach and progress towards the experimental realization of this concept at the FACET-II accelerator facility.
* C. Emma, X. Xu, A. Fisher, J. P. MacArthur, J. Cryan, M. J. Hogan, P. Musumeci, G. White, A. Marinelli, "Terawatt attosecond X-ray source driven by a plasma accelerator", arXiv:2011.07163 (2020)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB072

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paper received ※ 20 May 2021 paper accepted ※ 24 June 2021 issue date ※ 23 August 2021

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WEPAB075

Xenos: X-Ray Monte Carlo Code Suite

simulation, positron, photon, operation

2766

S. Humphries
Field Precision, Albuquerque, New Mexico, USA

Xenos is an integrated 3D code suite for the design of X-ray sources and electron beam devices. The component programs run under all versions of Windows. This paper describes unique features of Xenos compared to other Monte Carlo packages: 1) representation of geometry and deposited dose on a finite-element mesh supported by an interactive mesh generator, 2) inclusion of full 3D electric and magnetic fields in Monte Carlo simulations, 3) an integrated user environment for input and output calculations (e.g., electron gun design, target heating, …) and 4) extended parallel-computing support for high-accuracy solutions. Xenos employs the full capabilities of multi-core computers and allows parallel computations on an unlimited number of independent computers.
* Sempau J., et.al. (2003), "Experimental benchmarks of the Monte Carlo code PENELOPE", Nucl. Instrum. Meth. B 207, 107-123.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB075

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paper received ※ 10 May 2021 paper accepted ※ 23 June 2021 issue date ※ 13 August 2021

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WEPAB077

High Power Terahertz Cherenkov Free Electron Laser from a Waveguide with a Thin Dielectric Layer by a Near-Relativistic Electron Beam

GUI, radiation, wakefield, bunching

2769

W.W. Li, T.L. He, Z.G. He, R. Huang, Q.K. Jia, S.M. Jiang, L. Wang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: National Natural Science Foundation of China (11705198, 11775216, 11805200) Fundamental Research Funds for the Central Universities (No. WK2310000082 and No. WK2310000090)
Corrugated and dielectric structures have been widely used for producing accelerator based terahertz radiation source. Recently, the novel schemes of the sub-terahertz free electron laser (FEL) from a metallic waveguide with corrugated walls and a normal dielectric loaded waveguide driven by a near-relativistic (beam energy of a few MeV) picosecond electron beam were studied respectively. Such a beam is used for driving resonant modes in the waveguide, and if the pipe is long enough, the interaction of these modes with the co-propagating electron beam will result in micro-bunching and the coherent enhancement of the wakefield radiation. It offers a promising candidate for compact accelerator-based high power terahertz source which can be realized with relatively low energy and low peak-current electron beams. However the choices of the waveguide above is less effective in order to obtain high power with frequency around 1THz. In this paper, we propose to use the waveguide with a thin dielectric layer instead, and high power radiation (>~10 MW) around 1 THz is expected to obtain in the proposed structure according to the simulation results.

Poster WEPAB077 [1.332 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB077

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paper received ※ 12 May 2021 paper accepted ※ 23 June 2021 issue date ※ 19 August 2021

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WEPAB087

Observation of Undulator Radiation Generated by a Single Electron Circulating in a Storage Ring and Possible Applications

synchrotron, radiation, photon, undulator

2790

I. Lobach
University of Chicago, Chicago, Illinois, USA
A. Halavanau, Z. Huang
SLAC, Menlo Park, California, USA
K. Kim
ANL, Lemont, Illinois, USA
S. Nagaitsev, A.L. Romanov, G. Stancari, A. Valishev
Fermilab, Batavia, Illinois, USA

An experimental study into the undulator radiation, generated by a single electron was carried out at the Integrable Optics Test Accelerator (IOTA) storage ring at Fermilab. The individual photons were detected by a Single Photon Avalanche Diode (SPAD) at an average rate of 1 detection per 300 revolutions in the ring. The detection events were continuously recorded by a picosecond event timer for as long as 1 minute at a time. The collected data were used to test if there is any deviation from the classically predicted Poissonian photostatistics. It was motivated by the observation * of sub-Poissonian statistics in a similar experiment. The observation * could be an instrumentation effect related to low detection efficiency and long detector dead time. In our experiment, the detector (SPAD) has a much higher efficiency (65%) and a much lower dead time. In addition, we show that the collected data (recorded detection times) can be used to study the synchrotron motion of a single electron and infer some parameters of the ring. For example, by comparing the results of simulation and measurement for the synchrotron motion we were able to estimate the magnitude of the RF phase jitter.
* Teng Chen and John M. J. Madey, Phys. Rev. Lett. 86, 5906, June 2001

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB087

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paper received ※ 17 May 2021 paper accepted ※ 24 June 2021 issue date ※ 27 August 2021

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WEPAB092

Redesign of the Jefferson Lab -300 kV DC Photo-Gun for High Bunch Charge Operations

cathode, gun, high-voltage, simulation

2802

S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft, G.G. Palacios Serrano
ODU, Norfolk, Virginia, USA
J.F. Benesch, J.R. Delayen, C. Hernandez-Garcia, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman
JLab, Newport News, Virginia, USA

Funding: The U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177, JSA initiatives fund program and Laboratory Directed Research and Development program.
Production of high bunch charge beams for the Electron-Ion Collider (EIC) is a challenging task. High bunch charge (a few nC) electron beam studies at Jefferson Lab using an inverted insulator DC high voltage photo-gun showed evidence of space charge limitations starting at 0.3 nC, limiting the maximum delivered bunch charge to 0.7 nC for beam at -225 kV, 75 ps (FWHM) pulse width, and 1.64 mm (rms) laser spot size. The low extracted charge is due to the modest longitudinal electric field (Ez) at the photocathode leading to beam loss at the anode and downstream beam pipe. To reach the few nC high bunch charge goal, and to correct the beam deflection exerted by the non-symmetric nature of the inverted insulator photo-gun the existing photo-gun was modified. This contribution discusses the electrostatic design of the modified photo-gun obtained using CST Studio Suite’s electromagnetic field solver. Beam dynamics simulations performed using General Particle Tracer (GPT) with the resulting electrostatic field map obtained from the modified electrodes confirmed the validity of the new design.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB092

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paper received ※ 20 May 2021 paper accepted ※ 02 June 2021 issue date ※ 19 August 2021

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WEPAB093

Space Charge Effects in Low Energy Magnetized Electron Beam

cathode, laser, solenoid, space-charge

2806

S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft
ODU, Norfolk, Virginia, USA
J.F. Benesch, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman, S. Zhang
JLab, Newport News, Virginia, USA

Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 and Laboratory Directed Research and Development program.
Magnetized electron cooling is one of the major approaches towards obtaining the required high luminosity in the proposed Electron-Ion Collider (EIC). In order to increase the cooling efficiency, a bunched electron beam with a high bunch charge and high repetition rate is required. At Jefferson Lab, we generated magnetized electron beams with high bunch charge using a new compact DC high voltage photogun biased at -300 kV with bialkali-antimonide photocathode and a commercial ultra-fast laser. This contribution discusses how magnetization affects space charge dominated beams as a function of magnetic field strength, gun high voltage, and laser pulse width, and spot size in comparison with simulations performed using General Particle Tracer.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB093

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paper received ※ 19 May 2021 paper accepted ※ 08 June 2021 issue date ※ 23 August 2021

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WEPAB096

RF Testbed for Cryogenic Photoemission Studies

cathode, cryogenics, gun, brightness

2810

G.E. Lawler, A. Fukasawa, N. Majernik, J.B. Rosenzweig, A. Suraj, M. Yadav
UCLA, Los Angeles, California, USA
Z. Li
SLAC, Menlo Park, California, USA
M. Yadav
The University of Liverpool, Liverpool, United Kingdom
M. Yadav
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE Contract DE-SC0020409
Producing higher brightness beams at the cathode is one of the main focuses for future electron beam applications. For photocathodes operating close to their emission threshold, the cathode lattice temperature begins to dominate the minimum achievable intrinsic emittance. At UCLA, we are designing a radiofrequency (RF) test bed for measuring the temperature dependence of the mean transverse energy (MTE) and quantum efficiency for a number of candidate cathode materials. We intend to quantify the attainable brightness improvements at the cathode from cryogenic operation and establish a proof-of-principle cryogenic RF gun for future studies of a 1.6 cell cryogenic photoinjector for the UCLA ultra compact XFEL concept (UC-XFEL). The test bed will use a C-band 0.5-cell RF gun designed to operate down to 40K, producing an on-axis accelerating field of 120 MV/m. The cryogenic system uses conduction cooling and a load-lock system is being designed for transport and storage of air-sensitive high brightness cathodes.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB096

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 21 August 2021

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WEPAB097

Initial Nanoblade-Enhanced Laser-Induced Cathode Emission Measurements

laser, cathode, simulation, experiment

2814

G.E. Lawler, J.I. Mann, J.B. Rosenzweig, V.S. Yu
UCLA, Los Angeles, California, USA
R.J. Roussel
University of Chicago, Chicago, Illinois, USA

Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE HEP Grant DE-SC0009914
Nanostructured photocathodes offer a unique functionality not possible in traditional photocathodes, increasing beam brightness by reducing the effective emission area. Inspired by field emitter tips, we examine a possible extension for higher current operation, an extended nanoblade capable of producing asymmetric emittance electron beams. A full understanding of emission is necessary to establish the effectiveness of nanoblades as usable cathode for electron accelerators. Utilizing wet etching of silicon wafers, we arrive at a robust sample capable of dissipating incident laser fields in excess of 20 GV/m without permanent damage. Initial predictions and experiments from the nanotip case predict energies up to the keV scale from electron rescattering and fine features on the order of the photon quantum. We will present initial electron data from 800 nm Ti:S laser illumination and measurements of a focused 1 keV beam.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB097

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 26 August 2021

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WEPAB098

Cryogenic Component and Material Testing for Compact Electron Beamlines

cryogenics, cavity, cathode, gun

2818

G.E. Lawler, N. Majernik, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE Contract DE-SC0020409
Cryogenic regimes of operation are, for various reasons, highly advantageous for normal conducting accelerator structures. Liquid cryogen-based systems are costly to implement and maintain. As a result, developing cryogenic test facilities at a smaller more cost effective scale using cryo-coolers is attractive. Before real implementations of a cryo-cooler based beamline, a significant amount of information is necessary regarding the behavior and properties of various components and materials at cryogenic temperatures. Finding this information lacking for our particular beamline case and by extension similar electron beamlines, we endeavor to generate a thorough beamline-relevant material and component properties down to the range of a liquid nitrogen temperatures (77 K) and the nominal operating temperature of a modest Gifford-McMahon cryocooler (45 K).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB098

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 18 August 2021

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WEPAB099

Near-Threshold Nonlinear Photoemission From Cu(100)

laser, cathode, experiment, photon

2822

C.J. Knill, S.S. Karkare
Arizona State University, Tempe, USA
H.A. Padmore
LBNL, Berkeley, California, USA

Funding: National Science Foundation Grant No. PHY-1549132
Photocathodes that have a low mean transverse energy (MTE) are crucial to the development of compact X-ray Free Electron Lasers (XFEL) and ultrafast electron diffraction (UED) experiments. For FELs, low MTE cathodes result in a lower requirement for electron energy when lasing at a defined energy, and for a defined electron energy result in lasing at higher energy. For UED experiments, low MTE cathodes give a longer coherence length, allowing measurements on larger unit cell materials. A record low MTE of 5 meV has been recently demonstrated from a Cu (100) surface when measured near the photoemission threshold and cooled down to 30 K with liquid Helium [*]. For UED and XFEL applications that require a high charge density, the low quantum efficiency of Cu (100) near threshold necessitates the use of a high laser fluence to achieve the desired charge density [**]. At high laser fluences the MTE is limited by nonlinear effects, and therefore it is necessary to investigate near photoemission threshold at these high laser fluences. In this paper we report on nonlinear, near-threshold photoemission from a Cu (100) cathode, and its effect on the MTE.
* S. Karkare et al, Phys. Rev. Lett. 125, 054801 (2020)
** J. Bae et al, J. Appl. Phys., 124, 244903 (2018)

Poster WEPAB099 [0.829 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB099

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paper received ※ 19 May 2021 paper accepted ※ 21 July 2021 issue date ※ 20 August 2021

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WEPAB100

Heat Dissipation of Photocathodes at High Laser Intensities for a New DC Electron Source

cathode, experiment, laser, operation

2826

M.A. Dehn, K. Aulenbacher
IKP, Mainz, Germany
K. Aulenbacher
HIM, Mainz, Germany
K. Aulenbacher
GSI, Darmstadt, Germany

Funding: This project was supported by the German science ministry BMBF through the Verbundforschung
Laser intensities of 1W or more are required to extract average beam currents of more than 10mA from photocathodes. Most of this laser power is converted into thermal load within the cathode and has to be dissipated to avoid excessive heating of the cathode and thus a significant reduction in lifetime. At Johannes Gutenberg-University Mainz, we are developing a new high current DC electron source operating at an energy of 100keV, where an efficient heat dissipation of the photocathode is achieved by a mechanical design of the supporting structure.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB100

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 26 August 2021

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WEPAB101

An Improved Model for Photoemission of Space Charge Dominated Picosecond Electron Bunches: Theory and Experiment

cathode, experiment, laser, space-charge

2829

S.M. Polozov, V.I. Rashchikov
MEPhI, Moscow, Russia
M. Krasilnikov
DESY Zeuthen, Zeuthen, Germany

The emission of a short highly charged electron bunch in a radiofrequency photogun is discussed. The traditional space charge limited emission numerical model is extended by an introduction of positively charged ions arising in the cathode region and dynamically changing during the emission. Estimates on the time characteristics of the charge migrating process in the semiconductor region are given. The numerical results are compared with the results of other numerical models and with experimental observations at the Photo Injector Test facility at DESY in Zeuthen (PITZ).

Poster WEPAB101 [1.601 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB101

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paper received ※ 08 May 2021 paper accepted ※ 07 June 2021 issue date ※ 29 August 2021

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WEPAB102

Half-Metal Spin Filter for Highly Polarized Emission from GaAs Photocathodes

polarization, cathode, lattice, hardware

2833

S. Poddar, C.-J. Jing, E.J. Montgomery
Euclid Beamlabs, Bolingbrook, USA
P. Lukashev
University of Northern Iowa, Cedar Falls, Iowa, USA
C. Palmstrøm
UCSB, Santa Barbara, California, USA
M.L. Stutzman, S. Zhang
JLab, Newport News, Virginia, USA

Funding: Work supported by Department of Energy grant number DE-SC0020564.
GaAs-based photocathodes are one of the major sources of spin-polarized electrons and are crucial for the upcoming Electron-Ion collider experiments which includes study of proton spin and spin parity violation in the standard model. The theoretical polarization limit in unstrained GaAs photocathodes is 50 % but only 35 % is routinely achieved in experiments. Spin selective filtering allows to boost the spin polarization beyond the 50 % theoretical limit. In this work, first-principle electronic calculations using standard Density Functional Theory are performed to predict possible Heusler alloy half-metal candidates to be used as spin-filter. Simulations are also performed to investigate the half-metallicity as function of the magnetic spin direction. Several devices are experimentally fabricated using dedicated Molecular Beam Epitaxy growth system. We implemented Quantum Efficiency and Polarization testing of these half-metal/GaAs heterostructures using a dedicated Mott polarimeter system. Photoemission can also be seen on magnetically switching the spin-filter direction accompanied by a change in sign of the asymmetry which is a qualitative proof of the spin-filtering effect.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB102

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paper received ※ 20 May 2021 paper accepted ※ 28 July 2021 issue date ※ 18 August 2021

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WEPAB103

Systematic Beam Parameter Studies at the Injector Section of FLUTE

laser, emittance, cathode, quadrupole

2837

T. Schmelzer, E. Bründermann, D. Hoffmann, I. Križnar, S. Marsching, A.-S. Müller, M.J. Nasse, R. Ruprecht, J. Schäfer, M. Schuh, N.J. Smale, P. Wesolowski, T. Windbichler
KIT, Karlsruhe, Germany

Funding: This work is supported by the DFG-funded Doctoral School "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology (KSETA)"
FLUTE (Ferninfrarot Linac- und Test-Experiment) is a compact linac-based test facility for accelerator R&D and source of intense THz radiation for photon science. In preparation for the next experiments, the electron beam of the injector section of FLUTE has been characterized. In systematic studies the electron beam parameters, e.g., beam energy and emittance, are measured with several diagnostic systems. This knowledge allows the establishment of different operation settings and the optimization of electron beam parameters for future experiments.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB103

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paper received ※ 19 May 2021 paper accepted ※ 26 August 2021 issue date ※ 01 September 2021

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WEPAB104

Improving the Operational Lifetime of the CEBAF Photo-Gun by Anode Biasing

cathode, laser, simulation, gun

2840

J.T. Yoskowitz, G.A. Krafft, G.G. Palacios Serrano, S.A.K. Wijethunga
ODU, Norfolk, Virginia, USA
J.M. Grames, J. Hansknecht, C. Hernandez-Garcia, M. Poelker, M.L. Stutzman, R. Suleiman
JLab, Newport News, Virginia, USA
S.B. van der Geer
Pulsar Physics, Eindhoven, The Netherlands

Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
The operating lifetime of GaAs-based photocathodes in DC high voltage electron photo-guns is dominated by the ionization rate of residual beamline gas molecules. In this work, experiments were performed to quantify the improvement in photocathode charge lifetime by biasing the photo-gun anode with a positive voltage, which repels ions generated downstream of the anode. The photo-cathode charge lifetime improved by almost a factor of two when the anode was biased compared to the usual grounded configuration. Simulations were performed using the particle tracking code General Particle Tracer (GPT) with a new custom element. The simulation results showed that both the number and energy of ions play a role in the pattern of QE degradation. The experiment results and conclusions supported by GPT simulations will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB104

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paper received ※ 20 May 2021 paper accepted ※ 02 June 2021 issue date ※ 24 August 2021

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WEPAB105

Simulating Electron Impact Ionization Using a General Particle Tracer (GPT) Custom Element

simulation, gun, cathode, high-voltage

2843

J.T. Yoskowitz, G.A. Krafft
ODU, Norfolk, Virginia, USA
J.M. Grames
JLab, Newport News, Virginia, USA
G.R. Montoya Soto
Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
C.A. Valerio
ECFM-UAS, Culiacan, Sinaloa, Mexico
S.B. van der Geer
Pulsar Physics, Eindhoven, The Netherlands

Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177, Consejo Nacional de Ciencia y Tecnología (CONACYT).
A new C++ custom element has been developed with the framework of General Particle Tracer (GPT) to simulate electron impact ionization of residual gas molecules. The custom element uses Monte-Carlo routines to determine both the ion production rate and the secondary electron kinetic energy based on user-defined gas densities and theoretical values for the ionization cross section and the secondary electron differential cross section. It then uses relativistic kinematics to track the secondary electron, the scattered electron, and the newly formed ion after ionization. The ion production rate and the secondary electron energy distribution determined by the custom element have been benchmarked against theoretical calculations and against simulations made using the simulation package IBSimu. While the custom element was originally built for particle accelerator simulations, it is readily extensible to other applications. The custom element will be described in detail and examples of applications at the Thomas Jefferson National Accelerator Facility will be presented for ion production in a DC high voltage photo-gun.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB105

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paper received ※ 20 May 2021 paper accepted ※ 25 June 2021 issue date ※ 02 September 2021

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WEPAB106

Study on Durability Improvement of Cs-Te Photocathode by Means of Alkali Halide Protective Films

cathode, experiment, ECR, laser

2847

K. Ezawa, R. Fukuoka, Y. Koshiba, T. Tamba, M. Washio
Waseda University, Tokyo, Japan
K. Sakaue
The University of Tokyo, Graduate School of Engineering, Bunkyo, Japan

We have been conducting basic and applied research for generating high quality electron beams, using 1.6 cell laser photocathode RF-gun. In our laboratory, Cesium Telluride (Cs-Te), one of the semiconductor photocathodes, is used as an electron source for accelerator experiments. This semiconductor photocathode is known for high quantum efficiency (Q.E.) about 5~10% and 3-month 1/e lifetime. High Q.E. photocathodes can reduce the power requirement of the laser system, and long lifetime photocathodes can decrease the maintenance frequency, contributing to an efficient experimental environment. For these reasons, high Q.E. and long lifetime photocathodes are necessary in accelerator experiments. In order to produce robust photocathodes and extend the lifetime, we have conducted covering Cs-Te photocathodes with CsBr and CsI protective films. In this conference, we report the thickness dependency on the lifetime of Cs-Te photocathodes when we intentionally exposed oxygen gas to coated and non-coated Cs-Te photocathodes.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB106

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 01 September 2021

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WEPAB109

Initial Study of GaN Thin Films for Photocathodes Prepared by Magnetron Sputtering on Copper Substrates

cathode, plasma, gun, experiment

2850

M. Vogel, X. Jiang, C. Wang
University Siegen, Siegen, Germany
P. Murcek, J. Schaber, R. Xiang
HZDR, Dresden, Germany

Funding: This research is funded by the Federal Ministry of Education and Research of Germany in the framework of BETH (project number 05K19PSB).
On the path for high brightness electron beams, Gallium Nitride (GaN) is one promising candidate for a photo-cathode material. In this contribution, we report on the continuation of the study to optimize the crystallization quality and crystallography of Mg-doped GaN samples on copper substrates that are synthesized by RF magnetron sputtering. SEM and XRD results show that the pretreatment methods and the sputtering conditions (temperature, sputtering power, and partial pressure of the reactive gas) can both affect the morphology and crystal quality of GaN films. The initial QE measurements of these samples are done in our newly build in-situ QE measurement system and the first results of QE analyses done at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) are presented in a dedicated contribution.
Part of this work was performed at the Micro- and Nanoanalytics Facility (MNaF) of the University of Siegen.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB109

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 29 August 2021

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WEPAB110

Solid-State Driven X-Band Linac for Electron Microscopy

cavity, linac, simulation, gun

2853

A. Dhar, E.A. Nanni, M.A.K. Othman, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This work was supported by the Department of Energy Contract No. DE-AC02-76SF00515.
Microcrystal electron diffraction (MicroED) is a technique used by scientists to image molecular crystals with cryo-electron microscopy (cryo-EM)*. However, cryo-EMs remain expensive, limiting MicroED’s accessibility. Current cryo-EMs accelerate electrons to 200-300 keV using DC electron guns with a nA of current and low emittance. However at higher voltages these DC guns rapidly grow in size. Replacing these electron guns with a compact linac powered by solid-state sources could lower cost while maintaining beam quality, thereby increasing accessibility. Utilizing compact high shunt impedance X-band structures ensures that each RF cycle contains at most a few electrons, preserving beam coherence. CW operation of the RF linac is possible with distributed solid-state architectures** that use 100W solid-state amplifiers at X-band frequencies. We present an initial design for a prototype low-cost CW RF linac for high-throughput MicroED producing 200 keV electrons with a standing-wave architecture where each cell is individually powered by a solid-state amplifier. This design also provides an upgrade path for future compact MeV-scale sources on the order of 1 meter in size.
* Jones, C. G. et al. ACS central science 4, 1587-1592 (2018).
** D. C. Nguyen et al, Proc. 9th International Particle Accelerator Conference (IPAC’18), no. 9, pp. 520-523

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB110

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 19 August 2021

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WEPAB111

Controlled Degradation by Oxygen Exposure in the Performance of a Ag (100) Single-Crystal Photocathode

cathode, experiment, cryogenics, emittance

2856

L.A.J. Soomary, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
L.B. Jones, T.C.Q. Noakes
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The search for high-performance photocathode electron sources is a priority in the accelerator science community. The surface characteristics of a photocathode define many important factors of the photoemission including the work function, intrinsic emittance, and quantum efficiency of the photocathode. These factors in turn define the electron beam performance which is measurable as normalized emittance, brightness, and energy spread*. Strategies for improving these parameters vary, but understanding and influencing the relevant cathode surface physics which underpin these attributes is a primary focus for the electron source community**. As such, pure metal photocathodes and their performance at UV wavelengths are of interest as seen at the LCLS at SLAC and CLARA at Daresbury. We present performance data for an Ag (100) single-crystal photocathode under illumination at 266 nm wavelength, with known levels of surface roughness, using our Transverse Energy Spread Spectrometer (TESS)*** both at room and cryogenic temperatures. Crucially our data shows the effect of progressive degradation in the photo-cathode performance as a consequence of exposure to controlled levels of oxygen.
* D.H. Dowell, et al., Nucl. Instr. and Meth. A (2010), doi:10.1016/j.nima.2010.03.104
** Appl. Phys. Lett. 89, 224103 (2006); doi:10.1063/1.2387968
*** Proc. FEL’13, TUPPS033, 290-293

Poster WEPAB111 [0.866 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB111

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paper received ※ 20 May 2021 paper accepted ※ 22 June 2021 issue date ※ 21 August 2021

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WEPAB112

Performance Characterisation of a Cu (100) Single-Crystal Photocathode

cathode, emittance, experiment, photon

2860

L.A.J. Soomary, D.P. Juarez-Lopez, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
L.B. Jones, T.C.Q. Noakes
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The search for high performance photocathode electron sources is a priority in the accelerator science community. The surface characteristics of a photocathode define important factors of the photoemission including the intrinsic emittance, the quantum efficiency and the work function of the photocathode. These factors in turn define the electron beam performance which are measurable as emittance, brightness and energy spread. We have used ASTeC’s Multiprobe (SAPI)* to characterise and analyse photocathode performance using multiple techniques including XPS, STM, and LEED imaging, and their Transverse Energy Spread Spectrometer (TESS)** to measure mean transverse energy (MTE). We present characterisation measurements for a Cu (100) single-crystal photocathode sample with data from SAPI confirming the crystallographic face and showing surface composition and roughness, supported by data from TESS showing the photocathode electron beam energy spread.
* B.L. Militsyn, 4-th EuCARD2 WP12.5 meeting, Warsaw, 14-15 March 2017
**Proc. FEL’13, TUPPS033, 290-293

Poster WEPAB112 [0.814 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB112

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paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 25 August 2021

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WEPAB113

Stripline Kickers for Injection Into PETRA IV

kicker, impedance, injection, electronics

2863

G. Loisch, I.V. Agapov, S.A. Antipov, J. Keil, F. Obier
DESY, Hamburg, Germany
M.A. Jebramcik
CERN, Meyrin, Switzerland

PETRA IV is the planned ultralow-emittance upgrade of the PETRA III synchrotron light source at DESY, Hamburg. The current design includes an on-axis beam injection scheme using fast stripline kickers. These kickers have to fulfill the requirements on kick-strength, field quality, pulse rise-rate and a matched beam impedance. 3D finite element simulations in conjunction with Bayesian optimisation are used to meet these requirements simultaneously. Here, we will discuss the requirements on the PETRA IV injection kickers and the current design status.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB113

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 23 August 2021

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WEPAB115

Beam Preparation with Temporally Modulated Photocathode Laser Pulses for a Seeded THz FEL

FEL, laser, cathode, simulation

2866

G.Z. Georgiev, N. Aftab, P. Boonpornprasert, J. Good, M. Groß, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, A. Lueangaramwong, D. Melkumyan, S.K. Mohanty, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach
DESY Zeuthen, Zeuthen, Germany
N. Chaisueb
Chiang Mai University, Chiang Mai, Thailand
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

The need for carrier-envelope-phase (CEP) stable THz pump pulses is recognized at many pump-probe experiments at the European XFEL. At the Photo Injector Test Facility at DESY in Zeuthen (PITZ), a proof-of-principle experiment of an accelerator-based THz FEL source is in preparation. Since the CEP stability of FEL pulses is not guaranteed in the SASE regime, a seeding scheme is needed. A common scheme for seeding is to drive the microbunching process with external laser pulses, which are power-limited in the THz range. Alternatively, a pre-bunched beam, generated for example by applying a temporally modulated photocathode laser pulse, can be used to drive the FEL. The beam dynamics with such a seeding method are studied with ASTRA tracking code simulations with space-charge forces as well as experimentally. The results of these studies are shown and discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB115

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paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 21 August 2021

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WEPAB118

Loss Maps Along the ThomX Transfer Line and the Ring First Turn

HOM, beam-losses, injection, diagnostics

2874

A. Moutardier, C. Bruni, I. Chaikovska, S. Chancé, N. Delerue, E.E. Ergenlik, V. Kubytskyi, H. Monard
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

Funding: Research Agency under the Equipex convention ANR-10-EQPX-0051.
We report on studies of the loss maps for particles travelling from the end of the ThomX’s linac along the transfer line to the end of the ring first turn in preparation of the machine commissioning. ThomX is a 50-MeV-electron accelerator prototype which will use Compton backscattering to generate a high flux of hard X-rays. The accelerator tracking code MadX is used to simulate electrons’ propagation and compute losses. These maps may be projected at any localisation along the bunch path or plotted along the bunch path. This information is particularly relevant at the locations of the monitoring devices (screens, position monitors,…) where loss predictions will be compared with measurements.

Poster WEPAB118 [3.173 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB118

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paper received ※ 28 May 2021 paper accepted ※ 28 July 2021 issue date ※ 25 August 2021

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WEPAB122

Development of Fast and Super-Fast Kicker System for SLS 2.0 Injection

kicker, injection, impedance, damping

2889

M. Paraliev, M. Aiba, S. Dordevic, C.H. Gough, A. Streun
PSI, Villigen PSI, Switzerland

Swiss Light Source plans a major upgrade to turn the existing Storage Ring (SR) into a modern diffraction-limited light source called SLS 2.0. As part of this project, the injection system has to be upgraded as well in order to ensure reliable and efficient injection in the reduced beam aperture. A 4 kicker bump and a new thin septum will ensure the conventional injection in the SR. To further minimize the perturbation of the stored beam during injection two new schemes are in development: "Fast" and "Super-fast" one. The "Fast" injection scheme should be able to ensure single-bunch off-axis top-up injection affecting only 10 to 20 SR bunches that are 2 ns apart. The "Super-fast" one should bring the perturbed bunches down to only one. In on-axis mode it should be able to inject a top-up bunch between two SR bunches with minimum disturbance of the adjacent ones. To do this a combination of special beam injection schemes and an extremely fast (ns) kicker system is required. We will discuss the status of the development, the problems, and the solutions for reaching such a challenging goal.

Poster WEPAB122 [1.371 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB122

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 02 September 2021

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WEPAB126

Pulsed Wire Magnetic Field Measurement System for Short-Period Long Undulators

undulator, FEL, laser, detector

2903

J.E. Baader, S. Casalbuoni
EuXFEL, Schenefeld, Germany

The pulsed wire method is an attractive option to measure the magnetic field in insertion devices, mainly for those with restricted access (e.g., small gaps, in-vacuum/cryogenic environments, etc.). Besides first and second field integrals, experiments have proved the feasibility of reconstructing the magnetic field profile. Undulators with a small gap and short period are - and are planned to be - used at diffraction-limited storage rings and free-electron lasers. This contribution outlines the pulsed wire system’s requirements to perform magnetic field reconstruction in such undulators. We examine the main expected limitations, particularly the dispersive, finite pulse-width, discretization error, and sag effects. Furthermore, we present the current status of developing the pulsed wire system at the European XFEL.

Poster WEPAB126 [1.184 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB126

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paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 11 August 2021

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WEPAB130

Experience with Algorithm-Guided Tuning of APS-U Undulators

undulator, radiation, MMI, permanent-magnet

2915

M.F. Qian, R.J. Dejus, Y. Piao, I. Vasserman, J.Z. Xu
ANL, Lemont, Illinois, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, under contract number DE AC02-06CH11357.
The Advanced Photon Source (APS) is undergoing a major upgrade to its storage ring. The APS Upgrade (APS-U) project plans to build over 40 new hybrid permanent magnet undulators (HPMUs) and rebuild over 20 existing HPMUs. To meet the APS-U undulator requirements, the quality of the undulator magnetic field needs to be fine-tuned to the specifications. The traditional methods that depend on the tuning specialist experience are not desirable for tuning large quantities of undulators. We developed algorithms that automate the tuning of permanent magnet undulators. For tuning of the undulator trajectory and phase, the algorithms optimize the tuning parameters with differential evolution-based global optimization. The algorithms have been successfully applied to over 18 APS HPMUs. The results and experiences of the tuning are reported in detail.

Poster WEPAB130 [0.543 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB130

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 31 August 2021

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WEPAB131

Magnetic Tuning and Installation Modifications of U48 Undulator for the Delhi Light Source (DLS)

undulator, controls, vacuum, focusing

2918

M. Tischer, P. Neumann, A. Schöps, P. Vagin, T. Vielitz, T. Wohlenberg
DESY, Hamburg, Germany
M. Aggarwal, R.N. Dutt, S. Ghosh, J. Karmakar, S. Sahu
IUAC, New Delhi, India
J. Bahrdt, E.C.M. Rial
HZB, Berlin, Germany

A compact THz radiation facility based on the principle of a pre-bunched Free Electron Laser, called Delhi Light Source (DLS) is at the final stage of commissioning at IUAC, New Delhi, India. For generation of THz radiation in DLS, an undulator with period length of 48 mm (U48), built by HZB and refurbished at DESY will be used. The magnetic tuning and the field measurements have been done on the U48 along with the design and installation of correction coils at the entrance/exit of the U48. In addition, horizontal and vertical ambient field correction coils were integrated into the magnet girders. A quadrupole correction coil along the vacuum chamber in order to mitigate the defocusing effect of the U48 on the electron beam has been designed. The current through all coils has been adjusted as a function of the gap by the new control system designed for the U48. In addition, an extruded aluminium vacuum chamber was designed and fabricated and will be aligned with the the undulator soon.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB131

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paper received ※ 19 May 2021 paper accepted ※ 05 July 2021 issue date ※ 16 August 2021

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WEPAB132

Towards a Superconducting Undulator Afterburner for the European XFEL

FEL, photon, undulator, vacuum

2921

S. Casalbuoni, J.E. Baader, G. Geloni, V. Grattoni, D. La Civita, C. Lechner, B. Marchetti, S. Serkez, H. Sinn
EuXFEL, Schenefeld, Germany
W. Decking, L. Lilje, S. Liu, T. Wohlenberg, I. Zagorodnov
DESY, Hamburg, Germany

We propose to develop, characterize and operate a superconducting undulator (SCU) afterburner consisting of 5 undulator modules (1 module = 2 times SCU coil of 2 m length and 1 phase shifter) at the SASE2 hard X-ray beamline of European XFEL. This afterburner has the potential to produce an output of more than 10¹⁰ ph/pulse at photon energies above 30 keV. The project is divided into the production of a pre-series prototype module and a small-series production of 5 modules. Central goals of this R&D activity are: the demonstration of the functionality of SCUs at an X-ray FEL, the set up of the needed infrastructure to characterize and operate SCUs, the industrialization of such undulators, and the reduction of the price per module. In this contribution, the main parameters and specifications of the pre-series prototype module (S-PRESSO) are described.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB132

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paper received ※ 15 May 2021 paper accepted ※ 05 July 2021 issue date ※ 28 August 2021

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WEPAB135

Progress of the Development of a Superconducting Undulator as a THz Source for FELs

undulator, radiation, FEL, experiment

2933

J. Gethmann, S. Casalbuoni, N. Glamann, A.W. Grau, A.-S. Müller, D. Saez de Jauregui
KIT, Karlsruhe, Germany
D. Astapovych, H. De Gersem, E. Gjonaj
TEMF, TU Darmstadt, Darmstadt, Germany
S. Casalbuoni
EuXFEL, Schenefeld, Germany

Funding: This work is supported by the BMBF project 05K19VK2 SCUXFEL (Federal Ministry of Education and Research) and by the DFG-funded Doctoral School KSETA: Science and Technology.
To produce radiation in the THz frequency range at X-ray Free Electron Lasers, undulators with large period length, high fields, and large gaps are required. These demands can be fulfilled by superconducting undulators. In this contribution, the actual requirements on the main parameters of such a superconducting undulator will be discussed and the progress of the design will be discussed. In addition, beam impedance and heat load results obtained analytically as well as by large-scale wakefield simulations will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB135

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paper received ※ 19 May 2021 paper accepted ※ 02 July 2021 issue date ※ 24 August 2021

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WEPAB138

Superconducting RF Gun with High Current and the Capability to Generate Polarized Electron Beams

gun, SRF, cathode, cavity

2936

I. Petrushina
SUNY SB, Stony Brook, New York, USA
S.A. Belomestnykh, S. Kazakov, T.N. Khabiboulline, M. Martinello, Y.M. Pischalnikov, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
J.C. Brutus, P. Inacker, Y.C. Jing, V. Litvinenko, J. Skaritka, E. Wang
BNL, Upton, New York, USA
J.M. Grames, M. Poelker, R. Suleiman, E.J-M. Voutier
JLab, Newport News, Virginia, USA

High-current low-emittance CW electron beams are indispensable for nuclear and high-energy physics fixed target and collider experiments, cooling high energy hadron beams, generating CW beams of monoenergetic X-rays (in FELs) and gamma-rays (in Compton sources). Polarization of electrons in these beams provides extra value by opening a new set of observables and frequently improving the data quality. We report on the upgrade of the unique and fully functional CW SRF 1.25 MeV SRF gun, built as part of the Coherent electron Cooling (CeC) project, which has demonstrated sustained CW operation with CsK2Sb photocathodes generating electron bunches with record-low transverse emittances and record-high bunch charge exceeding 10 nC. We propose to extend the capabilities of this system to high average current of 100 milliampere in two steps: increasing the current 30-fold at each step with the goal to demonstrate reliable long-term operation of the high-current low-emittance CW SRF guns. We also propose to test polarized GaAs photocathodes in the ultra-high vacuum (UHV) environment of the SRF gun, which has never been successfully demonstrated in RF accelerators.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB138

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paper received ※ 25 May 2021 paper accepted ※ 29 July 2021 issue date ※ 23 August 2021

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WEPAB140

Second Beam Test and Numerical Investigation of the Imperial College Plasma (Gabor) Lens Prototype

plasma, focusing, proton, laser

2943

T.S. Dascalu
Imperial College London, London, United Kingdom
R. Bingham, C.G. Whyte
USTRAT/SUPA, Glasgow, United Kingdom
C.L. Cheung, H.T. Lau, K.R. Long, T. Nonnenmacher, J.K. Pozimski
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

Funding: STFC through the Imperial Impact Acceleration Account
The design of the Laser-hybrid Accelerator for Radiobiological Applications (LhARA) is based on a series of plasma lenses to capture, focus, and select the energy of the ions produced in the laser-target interaction. A second beam test of the first plasma lens prototype, built at the Imperial College London, took place in October 2017 at the Ion Beam Centre of the University of Surrey. 1.4 MeV proton pencil beams were imaged 0.67m downstream of the lens on a scintillator screen over a wide range of settings. On top of the focusing effect, the electron plasma converted pencil beams into rings. The intensity of each ring shows a different degree of modulation along its circumference. Analysis of the results indicates non-uniformity and an off-axis rotation of the electron plasma. The effect on the beam is presented and compared to the results of a simulation of the plasma dynamics and proton beam transport through the lens. A particle-tracking code was used to study the impact of plasma instabilities on the focusing forces produced by the lens. The m = 1 diocotron instability was associated with the formation of rings from the pencil beams.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB140

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paper received ※ 19 May 2021 paper accepted ※ 21 August 2021 issue date ※ 29 August 2021

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WEPAB141

Preliminary Simulation of CERN’s Linac4 H⁻ Source Beam Formation

plasma, simulation, extraction, linac

2947

A. Vnuchenko, J. Lettry
CERN, Geneva, Switzerland
U. Fantz, S. Mochalskyy, D. Wünderlich
MPI/IPP, Garching, Germany
T. Minea, A. Revel
CNRS LPGP Univ Paris Sud, Orsay, France

Linac4 is the new (H⁻) linear injector of CERN’s accelerator complex. This contribution describes the modelling activities required to get insight into H⁻ beam formation processes and their impact on beam properties. The simulation region starts from a homogeneous hydrogen plasma, the plasma then expands through the magnetic filter field. H⁻ ions and electrons are electrostatically extracted through the meniscus (line of separation between the plasma and the extracted beam) and eventually accelerated. The physics is simulated via the 3D PIC code ONIX. This code, originally dedicated to ITER’s neutral injector sources, has been modified to match single aperture sources. A new type of boundary condition is described, as well as the field distribution and geometry of the standard IS03 and a dedicated proto-type of CERN’s Linac4 H⁻ source. A plasma electrode prototype designed to provide metallic boundary conditions was produced and tested. This plasma electrode geometry enables Optical Emission Spectroscopy in the region closest to meniscus. A set of plasma parameters was chosen as input characterizing the plasma. Preliminary simulation results of beam formation region are presented.

Poster WEPAB141 [0.710 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB141

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paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 24 August 2021

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WEPAB143

Sub-MeV Ion Generation by Standing Wave Excitation of Ionized Gases

acceleration, plasma, laser, simulation

2951

Sz. Turnár, G. Almási, J. Hebling, Cs. Korpa, M.I. Mechler, L. Pálfalvi, Z. Tibai
University of Pecs, Pécs, Hungary

Funding: Hungarian Scientific Research Fund (OTKA) (125808, 129134) ÚNKP-20-3 New National Excellence Program of the Ministry for Innovation and Technology from the source of the National Research
Many ion acceleration techniques have been suggested and thoroughly studied in the last two decades*. One of the promising techniques is the Coulomb explosion acceleration (CEA)**. Using CEA in clusters could result in symmetric acceleration if there are not any other significant mechanisms. We proposed a THz-driven accelerator scheme that is based on CEA in proton, deuterium and heavy water gas plasmas. Two counter-propagating THz pulses are focused to the ionized region of the gas jet. Following the ripping of the electrons from the gas plasmas by ultrafast standing waves, the Coulomb explosion accelerates the positive ions. According to our calculation, using 2 x 34 mJ THz pulses electrons and protons with 1.1 nC charge are accelerated up to 0.4 MeV and 0.1 MeV, respectively. The total energy of the particles is 0.7 % of the energy of the THz pulses. We examined the effect of the initial bunch charge, bunch size and shape on the final energy spectra and the directional distribution of the particles. Our presented technique is scalable from a few µm to a few thousand µm driving wavelengths and can be used for electron and heavy-ion acceleration.
*J. Badziak, IOP Conf. Series: J Phys: Conf. Series 959, 012001 (2018).
** M. Murakami and K. Mima, Phys. of Plasmas 16, 103108 (2009).

Poster WEPAB143 [3.467 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB143

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 21 August 2021

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WEPAB147

Simulations of Nanoblade-Enhanced Laser-Induced Cathode Emissions and Analyses of Yield, MTE, and Brightness

simulation, laser, space-charge, brightness

2957

J.I. Mann, G.E. Lawler, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
T. Arias, J.K. Nangoi
Cornell University, Ithaca, New York, USA

Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE HEP Grant DE-SC0009914.
Laser-induced field emission of electrons from metallic nanotips has been well studied. Unfortunately, nanotips suffer low damage thresholds with enhanced fields around 10 GV/m. The nanoblade, akin to a nanotip extruded in one lateral dimension, may reach upwards of 40 GV/m due to its robust thermomechanical properties. This increased surface field promises brighter electron emissions. We perform simulations of strong-field emissions from metallic nanoblades via the 1-D time-dependent Schr\"odinger equation with effective Jellium and nonlinear collective image charge potentials, including the strong field gradients induced by the nanostructure. We measure spectra and yields and compare to recent experiments. Potential analytical forms of image potential limited yield for a spectrally rich emission are presented. Calculations of mean transverse energy are provided as well as a prospective method of mitigation with the goal of increasing brightness.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB147

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paper received ※ 19 May 2021 paper accepted ※ 06 July 2021 issue date ※ 31 August 2021

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WEPAB148

RF Design of an X-Band TM02 Mode Cavity for Field Emitter Testing

cavity, coupling, insertion, multipactoring

2961

Z. Li, S.G. Tantawi
SLAC, Menlo Park, California, USA
S.V. Baryshev, T. Posos, M.E. Schneider
Michigan State University, East Lansing, Michigan, USA

Funding: Work at SLAC was supported by DOE under contract No. DE-AC02-76SF00515. Work at MSU was supported by DOE under Award No. DE-SC0020429 and under Cooperative Agreement Award No. DE-SC0018362.
Planar polycrystalline synthetic diamond with nitrogen-doping/incorporation was found to be a remarkable field emitter. It is capable of generating a high charge beam and handling moderate vacuum conditions. Integrating it with an efficient RF cavity could therefore provide a compact electron source for RF injectors. Understanding the performance metrics of the emitter in RF fields is essential toward developing such a device. We investigated a test setup of the field emitter at the X-band frequency. The setup included an X-band cavity operating at the TM02 mode. The field emitter material will be plated on the tip of a insertion rod on the cavity back plate. Part of the back plate and the emitter rod are demountable, allowing for exchange of the field emitters. The TM02 mode was chosen such that the design of the demountable back plate does not induce field enhancement at the installation gap. The cavity were optimized to achieve a high surface field at the emitter tip and a maximum energy gain of the emitted electrons at a given input power. We will present the RF and mechanical design of such a TM02 X-band cavity for field emitter testing.

Poster WEPAB148 [1.642 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB148

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paper received ※ 14 May 2021 paper accepted ※ 12 July 2021 issue date ※ 25 August 2021

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WEPAB149

The RF Gun for the Siberian Circular Light Source "SKIF"

cavity, gun, cathode, linac

2965

V. Volkov, A.M. Batrakov, S.M. Gurov, S.E. Karnaev, A.A. Kondakov, S.A. Krutikhin, G.Y. Kurkin, A.E. Levichev, O.I. Meshkov, V.K. Ovchar, A.V. Pavlenko, O.A. Pavlov, A.G. Tribendis, N.G. Vasileva
BINP SB RAS, Novosibirsk, Russia
A.E. Levichev, A.V. Pavlenko
NSU, Novosibirsk, Russia
A.G. Tribendis
NSTU, Novosibirsk, Russia

The Siberian Circular Light Source is a new medium-energy high brightness synchrotron light facility that is under construction on the Budker Institute of Nuclear Physics (BINP) in Russia, Novosibirsk. The accelerator facility is divided for convenience into three components; a 3 GeV storage ring, a full-energy booster synchrotron, and a 200 MeV injector linac with a thermionic gridded RF gun electron source. This paper describes the RF gun design and plans for operations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB149

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 10 August 2021

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WEPAB152

Carbon Nanotubes as Cold Electron Field Emitters for Electron Cooling in the CERN Extra Low Energy Antiproton (ELENA) Ring

vacuum, proton, experiment, antiproton

2975

B. Galante, G. Tranquille
CERN, Meyrin, Switzerland
O. Apsimon, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
J. Resta-López
IFIC, Valencia, Spain

In ELENA electron cooling reduces the emittance of the antiproton beam allowing to deliver a high-quality beam to the experiments at the unprecedented low energy of 100 keV. To cool the antiproton beam at this low energy, the electron gun must emit electrons with as monoenergetic a distribution as possible. The currently used thermionic gun limits the cooling performance due to the relatively high transverse energy spread of the emitted electrons. Optimization is therefore being studied, aiming at developing a cold-cathode electron gun. This has led to the investigation of carbon nanotubes (CNTs) as cold electron field emitters. CNTs are considered the most promising field emitter material due to their high aspect ratio, chemical stability, and capability to deliver high current densities. To assess the feasibility of using such material operationally a full characterization is required, focussing on key parameters such as emitted current, emission stability, and lifetime. This contribution will present the status of ongoing experiments reporting on the conditioning process necessary to reach good stability over time and the emitting performance of different CNT arrays.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB152

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paper received ※ 18 May 2021 paper accepted ※ 25 June 2021 issue date ※ 17 August 2021

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WEPAB157

Understanding the Growth Dynamics Cs-Sb Thin Films via In-Situ Characterization Techniques: Towards Epitaxial Alkali Antimonide Photocathodes

cathode, brightness, lattice, scattering

2979

A. Galdi, I.V. Bazarov, L. Cultrera, J.M. Maxson
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J. Balajka, W.J.I. DeBenedetti, M. Hines, C. Hu, L. Moreschini, H. Paik, C.T. Parzyck, K.M. Shen
Cornell University, Ithaca, New York, USA

Funding: National Science Foundation award PHY-1549132, the Center for Bright Beams and PARADIM, Cooperative Agreement No.DMR-1539918.
Alkali antimonide photocathodes, such as Cs3Sb, have attractive properties, such as low emittance and high quantum efficiency, which makes them excellent candidates for next-generation high-brightness electron sources. A large number of studies in literature focus on quantum efficiency and lifetime, and fewer report chemical and structural analysis, despite the latter ultimately determine the brightness at the photocathode. Epitaxial, single-crystalline films would allow to study the intrinsic properties of alkali antimonide photocathodes and to optimize them for maximum brightness, but this goal remains elusive. A strong limiting factor is the extreme air sensitivity, preventing ex-situ structural and chemical analysis. We report a study on the growth of Cs-Sb films via molecular beam epitaxy with reflection high-energy electron diffraction to monitor the growth in real time. The samples were characterized via in-situ ultraviolet photoelectron spectroscopy, x-ray photoelectron spectroscopy and scanning tunneling microscopy. Cs3Sb and CsSb phases can be stabilized on appropriate single crystal substrates, with the latter reproducibly resulting in atomically smooth surfaces.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB157

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paper received ※ 19 May 2021 paper accepted ※ 30 June 2021 issue date ※ 01 September 2021

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WEPAB158

Compact Terahertz-Powered Electron Photo-Gun

gun, cathode, injection, acceleration

2983

T. Kroh, H. Çankaya, U. Demirbas, M. Fakhari, N.H. Matlis, M. Pergament, T. Rohwer
CFEL, Hamburg, Germany
R.W. Aßmann, H. Dinter, M.J. Kellermeier
DESY, Hamburg, Germany
M. Hemmer, F.X. Kärtner
Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany
F.X. Kärtner
The Hamburg Center for Ultrafast Imaging, University of Hamburg, Hamburg, Germany

Funding: This work is supported by the Cluster of Excellence "CUI: Advanced Imaging of Matter" of the Deutsche Forschungsgemeinschaft (DFG) - EXC 2056 - project ID 390715994.
Novel accelerator concepts such as all-optical THz based compact accelerators promise to enable new science due to unique features such as reduced timing-jitter and improved space-charge broadening of the generated electron bunches. However, multi-keV electron photo-guns based on short single-cycle THz pulses for acceleration have not been demonstrated experimentally so far. Here, we present a modular THz-driven electron gun with both tunable interaction length and output orifice allowing optimization of the sub-mm interaction volume. First extraction of multi-keV electrons is demonstrated and the parameter space as well as resulting performance of the THz-driven gun by varying the timing of the two single-cycle THz pulses and the UV photo-excitation pulse are explored. Such compact gun prototypes are not only promising as injectors for compact THz-based LINACs but also as source for ultrafast electron diffraction experiments.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB158

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 10 August 2021

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WEPAB164

Electrodeless Diamond Beam Halo Monitor

experiment, coupling, radiation, vacuum

2990

S.V. Kuzikov, S.P. Antipov, P.V. Avrakhov, E. Dosov, E.W. Knight, Y. Zhao
Euclid TechLabs, Solon, Ohio, USA
J.G. Power, J. Shao
ANL, Lemont, Illinois, USA

Funding: This work was supported by DoE SBIR grant # DE-SC0019642.
Beam halo measurement is important for novel x-ray free-electron lasers which have remarkably high repetition rate and average power. We propose diamond as a radiation hard material that can be used to measure the flux of passing particles based on a particle-induced conductivity effect. Our diamond electrodeless monitor is based on a microwave measurement of the change in the resonator coupling and eigenfrequency. For measurements, we put a sensitive diamond sample in a resonator that intercepts the halo. By measuring the change in RF properties of the resonator, one can infer the beam halo parameters scanning across the beam to map its transverse distribution. In recent experiments we used a Vertical Beam Test Stand (VBS), delivered DC electron beam of the 20-200 keV energy with the current up to 50 µA, to characterize several diamond samples. We have designed and fabricated a scanning diamond monitor, based on an X-band resonator, which was tested at Argonne Wakefield Accelerator (AWA) with a multi-MeV electron beam.

Poster WEPAB164 [5.138 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB164

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paper received ※ 14 May 2021 paper accepted ※ 07 June 2021 issue date ※ 11 August 2021

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WEPAB169

Towards Ultra-Smooth Alkali Antimonide Photocathode Epitaxy

lattice, cathode, interface, emittance

3001

E.J. Montgomery
Private Address, Bolingbrook, USA
O. Chubenko, G.S. Gevorkyan, S.S. Karkare, P. Saha
Arizona State University, Tempe, USA
R.G. Hennig, J.T. Paul
University of Florida, Gainesville, Florida, USA
C. Jing, S. Poddar
Euclid Beamlabs, Bolingbrook, USA
H.A. Padmore
LBNL, Berkeley, California, USA

Funding: Work supported by Department of Energy, Office of Science, Office of Basic Energy Sciences, under grant number DE-SC0020575.
Photocathodes lead in brightness among electron emitters, but transverse momenta are unavoidably nonzero. Ultra-low transverse emittance would enable brighter, higher energy x-ray free-electron lasers (FEL), improved colliders, and more coherent, detailed ultrafast electron diffraction/microscopy (UED/UEM). Although high quantum efficiency (QE) is desired to avoid laser-induced nonlinearities, the state-of-the-art is 100 pC bunches from copper, 0.4 mm-mrad emittance. Advances towards 0.1 mm-mrad require ultra-low emittance, high QE, cryo-compatible materials. We report efforts towards epitaxial growth of cesium antimonide on lattice matched substrates. DFT calculations were performed to downselect from a list of candidate lattice matches. Co-evaporations achieving >3% QE at 532 nm followed by atomic force and Kelvin probe microscopy (AFM and KPFM) show ultra-low 313 pm rms (root mean square) physical and 2.65 mV rms chemical roughness. We simulate roughness-induced mean transverse energy (MTE) to predict <1 meV from roughness effects at 10 MV/m in as-grown optically thick cathodes, promising low emittance via epitaxial growth.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB169

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 13 August 2021

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WEPAB172

Recent Developments of the IDEAS-Halo Detector

experiment, detector, vacuum, FEL

3005

A. Liu, J.R. Callahan, B.T. Freemire
Euclid TechLabs, Solon, Ohio, USA
J.F. Power, J.H. Shao
ANL, Lemont, Illinois, USA

Funding: This work was performed at Euclid and Argonne National Laboratory, and was supported by the US DOE Office of Science under contract number DE-SC0019538.
Euclid Techlabs has been designing and testing a cost-effective iris diaphragm beam halo/profile detector, which can be easily configured to work with various primary beam energies and sites. Besides working as a measurement device, it can also work as a controllable beam scraper/collimator. This novel iris diaphragm detector utilizes the current signal produced by the beam charge deposition on the moveable conductive iris blades, to accurately measure the beam distribution from the outlier to the beam core. In this paper, we discuss the recent developments of our iris diaphragm e-beam apparatus series (IDEAS)-halo detector, including its geometry upgrades and newest beam experiments done at the AWA cathode testbed (ACT) of Argonne National Laboratory.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB172

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paper received ※ 03 June 2021 paper accepted ※ 22 July 2021 issue date ※ 27 August 2021

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WEPAB174

Study of the Electron Seeded Proton Self-Modulation Using FBPIC

plasma, proton, wakefield, simulation

3008

L. Liang, G.X. Xia
The University of Manchester, Manchester, United Kingdom
A. Bonatto
Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
L. Liang, G.X. Xia
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work is supported by the Cockcroft Institute Core Grant and the STFC AWAKE Run 2 grant ST/T001917/1
In order to make a full use of the whole proton bunch to drive large amplitude plasma wakefields and suppress the uncontrolled growth of any possible instabilities at the head of the proton bunch, the AWAKE Run 2 experiment plans to use an electron bunch to seed the formation of the proton bunch self-modulation. Additionally, a density step in the plasma channel will be used to freeze the selfmodulation process to keep the wakefield amplitude. In this work, numerical simulations performed with FBPIC are used to investigate the electron seeded proton self-modulation and the effect of the plasma density step as well.

Poster WEPAB174 [1.751 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB174

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paper received ※ 10 May 2021 paper accepted ※ 28 June 2021 issue date ※ 27 August 2021

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WEPAB175

Simulation Study of Electron Beam Acceleration with Non-Gaussian Transverse Profiles for AWAKE Run 2

emittance, plasma, acceleration, wakefield

3012

L. Liang, G.X. Xia
The University of Manchester, Manchester, United Kingdom
J.P. Farmer
MPI-P, München, Germany
L. Liang, G.X. Xia
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: The authors would like to acknowledge the support from the Cockcroft Institute Core Grant and the STFC AWAKE Run 2 grant ST/T001917/1
In the physics plan for AWAKE Run 2, two known effects, beam loading the longitudinal wakefield and beam matching to the pure plasma ion channel, will be implemented for the better control of electron acceleration. It is founded in our study of beam matching that the transverse profile of the initial witness beam have a significant impact on its acceleration quality. In this paper, particle-in-cell (PIC) simulations are used to study factors that affect the acceleration quality of electron beams with different transverse profiles.

Poster WEPAB175 [1.860 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB175

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paper received ※ 10 May 2021 paper accepted ※ 25 June 2021 issue date ※ 14 August 2021

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WEPAB181

New Opportunities in Low Energy Antiproton Research

proton, antiproton, experiment, FEL

3035

C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 721559.
Experiments with low-energy antiprotons are at the cutting edge of science and offer unique opportunities to test some of the fundamental laws of physics. The experiments are, however, very difficult to realize. They critically depend on high-performance numerical tools that can model realistic beam transport and storage and also require advanced beam monitors and detectors that can fully characterize the beam. Finally, novel experiments need to be designed that exploit the enhanced beam quality that the new ELENA ring at CERN provides. This paper presents some selected findings from the pan-European AVA network’s three scientific work packages. It shows results from studies into electron cooling at the new ELENA storage ring, research into carbon nanotubes as cold electron field emitters for electron cooling, and how antiproton-atom collision experiments can be optimized using GEANT4. Finally, the paper gives an overview of the network’s interdisciplinary training program.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB181

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paper received ※ 16 May 2021 paper accepted ※ 11 June 2021 issue date ※ 02 September 2021

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WEPAB187

The ENUBET Multi Momentum Secondary Beamline Design

target, kaon, proton, experiment

3053

E.G. Parozzi, N. Charitonidis
CERN, Geneva, Switzerland
G. Brunetti, E.G. Parozzi, F. Terranova
Universita Milano Bicocca, MILANO, Italy
A. Longhin, M. Pari, F. Pupilli
INFN- Sez. di Padova, Padova, Italy
A. Longhin, M. Pari
Univ. degli Studi di Padova, Padova, Italy
E.G. Parozzi, F. Terranova
INFN MIB, MILANO, Italy

The aim of neutrino physics for the next decades is to detect effects due to CP violation, mass hierarchy, and search for effects beyond the Standard Model predictions. Future experiments need precise measurements of the neutrino interaction cross-sections at the ~GeV/c regime, currently limited by the exact knowledge of the initial neutrino flux on a ~10-20% uncertainty level. The ENUBET project is proposing a novel facility, capable of constraining the neutrino flux normalization through the precise monitoring of the Ke3 (K±>e+pi0nu) decay products in an instrumented decay tunnel. ENUBET can also monitor muons from the two body kaon and pion decays (nu flux) and measure the neutrino energy with a 10% precision without relying on the event reconstruction at the neutrino detector. We present here a novel design based on a broad (4-8.5 GeV/c) momentum range secondary beamline, that widen the cross-section energy range that can be explored by ENUBET. In this poster, we discuss the target optimization studies and we show the early results on the new line’s optics and the layout design. We discuss the expected performance of this line and the forthcoming activities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB187

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paper received ※ 13 May 2021 paper accepted ※ 29 July 2021 issue date ※ 11 August 2021

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WEPAB189

EIC Hadron Beamline Vacuum Studies

vacuum, hadron, emittance, cryogenics

3060

D. Weiss, M. Mapes, J.E. Tuozzolo, S. Verdú-Andrés
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Ninety percent of the EIC hadron ring beamline is cold-bore comprising strings of interconnected 4.55 K RHIC superconducting (SC) magnets. The EIC operating specification requires shorter bunches and 3x higher intensity beams which are not appropriate for the present RHIC stainless steel cold-bore beam tube. The intensity and emittance of the hadron beams will degrade due to interactions with residual gas or vacuum instabilities arising from the expected resistive-wall (RW) heating, electron clouds, and beam-induced desorption mechanisms. Without strategies to limit RW heating, major cryogenic system modifications are needed to prevent SC magnet quenches. The SC magnet cold-bore beam tubes will be equipped with a high RRR copper clad stainless steel sleeve to significantly reduce RW heating and so the effect on the SC magnet cryogenic heat load and temperature. A thin amorphous carbon film applied to the beam facing copper surface will suppress electron cloud formation. This paper discusses the vacuum requirements imposed by the EIC hadron beams and the plans to achieve the necessary vacuum and thermal stability that ensure acceptable beam quality and lifetime.

Poster WEPAB189 [3.321 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB189

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paper received ※ 17 May 2021 paper accepted ※ 21 August 2021 issue date ※ 25 August 2021

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WEPAB191

Magnet System for a Proton/helium ECR Ion Source

ECR, plasma, solenoid, ion-source

3066

M.S. Dmitriyev, K.G. Artamonov, M.V. Dyakonov, M.I. Zhigailova
MEPhI, Moscow, Russia

The study of the magnetic system of ECRIS with operating frequency of 2.45 GHz for producing protons and double-charged helium ions has been carried out. The results of the numerical simulation of the ECRIS magnetic system based on permanent magnets have been performed. The possibility of shifting the ring magnets in both injection and extraction regions is considered to adjust maximum and minimum values of the axial distribution of a magnetic field in a plasma chamber. The possibility of shifting the bar magnets of the hexapole is shown to provide the adjustment of the radial magnetic field Brad at the chamber wall. Additional solenoids are introduced to the system for providing the required Binj and Bext adjustment and tuning the axial magnetic field distribution including the minimum on the axis Bmin. Furthermore, the magnetic system allows to switch the operation mode of the ECR source to the microwave mode.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB191

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paper received ※ 20 May 2021 paper accepted ※ 08 June 2021 issue date ※ 30 August 2021

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WEPAB199

Study on the Important Technologies of 300MeV Upgrade for the CSNS Injection System

injection, power-supply, vacuum, neutron

3089

M.Y. Huang, C.D. Deng, L. Kang, L. Liu, Y. Liu, X. Qi, S. Wang, Q.B. Wu, Y.W. Wu, S.Y. Xu, W.Q. Zhang, Y.L. Zhang
IHEP, Beijing, People’s Republic of China
J.X. Chen, T. Huang, H.C. Liu
IHEP CSNS, Guangdong Province, People’s Republic of China

Funding: This work was supported by National Natural Science Foundation of China (Project Nos. U1832210 and 12075134).
The China Spallation Neutron Source (CSNS-I) have achieved the design goal of 100kW beam power on the target in Feb., 2020. As the second phase of the CSNS, CSNS-II will achieve a beam power on the target of 500 kW. The injection energy of CSNS-II will be increased from 80 MeV to 300 MeV and the average beam current of the Linac will increase 5 times. Therefore, the injection system will require a complete upgrade. In this paper, the design scheme of the injection system for CSNS-II will be introduced. The key technologies of the upgrade injection system will be carefully analyzed and pre-developed, such as the pulse power supplies and their magnets, the special-shaped ceramic vacuum chambers, the main stripping foil, the stripped electron collection, and so on.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB199

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paper received ※ 17 May 2021 paper accepted ※ 09 June 2021 issue date ※ 26 August 2021

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WEPAB209

Review of Medical Accelerator Development at Sameer, India

linac, photon, cavity, acceleration

3113

T.S. Dixit, N. Bansode, A.P. Bhagwat, S.T. Chavan, A.P. Deshpande, G. Gaikwad, S. Ghosh, R. Krishnan, C.S. Nainwad, G.D. Panchal, S.N. Pethe, K.A. Thakur, V.B. Ukey, M.M. Vidwans
SAMEER, Mumbai, India

Funding: Ministry of Electronics and Information Technology (MeitY), Government of India
At the Medical Electronics Division of SAMEER, R&D for the development of a 4 MeV energy electron linac for Cancer therapy was taken up in the late ’80s. An S-band standing wave side coupled structure operating at pi/2 mode was developed for electron acceleration. The linac was integrated with other subsystems in collaboration with CSIO and PGIMER and the first machine was commissioned at PGI, Chandigarh in 1990. Thereafter, a lot of modifications like energy, dose rate, iso-center height etc. were made in the system, and later 4 more machines were commissioned in hospitals for treatment. More than 1,50,000 patients have been treated using SAMEER’s 6 MeV oncology system. Subsequently, development of dual-mode and variable energy electron and photon output machines was undertaken. Two-photon energies of 6 and 15 MV and multiple electron energies starting from 6 to 18 MeV for treatment was offered from the linac. The electron energy variation was done using plunger mechanism in the side coupling cavity. This linac was successfully baked and RF tested for various parameters. This paper describes the experimental parameters achieved for both low and high energy dual-mode linac.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB209

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paper received ※ 14 May 2021 paper accepted ※ 07 July 2021 issue date ※ 01 September 2021

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WEPAB228

Modelling and Counteracting Microbunching Instability in Spreader Lines of Radiofrequency and Plasma-Based Accelerators for Free-Electron Lasers

bunching, laser, free-electron-laser, scattering

3165

G. Perosa
Università degli Studi di Trieste, Trieste, Italy
S. Di Mitri
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

High energy radiofrequency and plasma-driven accelerators target electron beam brightness suitable for x-ray free-electron lasers. Microbunching instability can be enhanced during beam transport through the spreader line from the accelerator to the undulator, degrading the brightness of the accelerated beam and therefore reducing the lasing efficiency. We present a semi-analytical model of the instability, benchmarked with experimental data at the FERMI free-electron laser, in the presence of intrabeam scattering and beam heating. Strategies for minimization of the instability both in conventional and plasma-based accelerators are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB228

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paper received ※ 19 May 2021 paper accepted ※ 08 July 2021 issue date ※ 10 August 2021

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WEPAB229

Transverse Density Pileup and Pattern Formation in Dense Ultracold Electron Beamlets under Coulomb Expansion

simulation, ECR, FEL, damping

3169

A.J. Tencate, K. Bhuyan, B. Erdélyi
Northern Illinois University, DeKalb, Illinois, USA

Funding: This work was sponsored by the US Department of Energy Office of Science under Grant DE-SC0020241.
Dynamic Coulomb expansion of dense particle bunches can lead to transverse density shock-like propagation for nonuniform bunch distributions. Furthermore, under favorable circumstances, multiple bunches in close proximity can collide without crossing to form wheel-and-spoke patterns. This process has been observed experimentally for Rubidium ions, but not yet for electrons, where the dynamics occur over far shorter length scales. We simulate the interaction of electron bunches while varying the initial transverse temperature and density profiles to determine the thresholds that characterize this pattern formation. Additionally, we consider the effects of asymmetries and the impact of a low-density halo on the overall process. The simulations are conducted using a novel high-fidelity algorithm for collisional particle dynamics.

Poster WEPAB229 [7.411 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB229

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paper received ※ 19 May 2021 paper accepted ※ 02 July 2021 issue date ※ 22 August 2021

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WEPAB233

Excitation of Micro-Bunching in Short Electron Bunches Using RF Amplitude Modulation

bunching, synchrotron, radiation, experiment

3173

T. Boltz, E. Blomley, M. Brosi, E. Bründermann, B. Härer, A. Mochihashi, A.-S. Müller, P. Schreiber, M. Schuh, M. Yan
KIT, Karlsruhe, Germany

In its short-bunch operation mode, the KIT storage ring KARA provides picosecond-long electron bunches, which emit coherent synchrotron radiation (CSR) up to the terahertz frequency range. Due to the high spatial compression under these conditions, the self-interaction of the bunch with its own emitted CSR induces a wake-field, which significantly influences the longitudinal charge distribution. Above a given threshold current, this leads to the formation of dynamically evolving micro-structures within the bunch and is thus called micro-bunching instability. As CSR is emitted at wavelengths corresponding to the spatial dimension of the emitter, these small structures lead to an increased emission of CSR at higher frequencies. The instability is therefore deliberately induced at KARA to provide intense THz radiation to dedicated experiments. To further increase the emitted power in the desired frequency range, we consider the potential of RF amplitude modulations to intentionally excite this form of micro-bunching in short electron bunches. This work is supported by the BMBF project 05K19VKC TiMo (Federal Ministry of Education and Research).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB233

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 23 August 2021

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WEPAB234

Simulating Two Dimensional Coherent Synchrotron Radiation in Python

emittance, simulation, radiation, synchrotron-radiation

3177

W. Lou, Y. Cai, C.E. Mayes, G.R. White
SLAC, Menlo Park, California, USA

Coherent Synchrotron Radiation (CSR) in bending magnets poses an important limit for electron beams to reach high brightness in novel accelerators. While the longitudinal wakefield has been well studied in one-dimensional CSR theory and implemented in various simulation codes, transverse wakefields have received less attention. Following the recently developed two-dimensional CSR theory, we developed a Python code simulating the steady-state two-dimensional CSR effects. The computed CSR wakes have been benchmarked with theory and other simulation codes. To speed up computation speed, the code applies vectorization, parallel processing, and Numba in Python.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB234

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paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 14 August 2021

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WEPAB240

Increasing the Single-Bunch Instability Threshold by Bunch Splitting Due to RF Phase Modulation

synchrotron, radiation, detector, synchrotron-radiation

3193

J.L. Steinmann, E. Blomley, M. Brosi, E. Bründermann, A. Mochihashi, A.-S. Müller, M. Schuh, P. Schönfeldt
KIT, Karlsruhe, Germany

Funding: This work is funded by the BMBF contract number: 05K16VKA.
RF phase modulation at twice the synchrotron frequency can be used to split a stored electron bunch into two or more bunchlets orbiting each other. We report on time-resolved measurements at the Karlsruhe Research Accelerator (KARA), where this bunch splitting was used to increase the threshold current of the microbunching instability, happening in the short-bunch operation mode. Turning the modulation on and off reproducibly affects the sawtooth behavior of the emitted coherent synchrotron radiation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB240

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paper received ※ 19 May 2021 paper accepted ※ 08 July 2021 issue date ※ 02 September 2021

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WEPAB251

Beam Dynamics Optimization of LCLS-II HE Linear Accelerator Design

emittance, undulator, radiation, FEL

3224

J. Qiang
LBNL, Berkeley, California, USA
T.O. Raubenheimer, M.D. Woodley
SLAC, Menlo Park, California, USA

The LCLS-II-HE as a high energy upgrade of the high repetition rate X-ray FEL under construction at SLAC will provide great opportunities for scientific discovery by generating coherent, high brightness hard X-ray radiation. In this paper, we report on beam dynamics optimization of the LCLS-II HE linear accelerator design with a 100pC and a 20pC charge beam to attain high quality electron beam for X-ray FEL radiation. We also present preliminary results of beam dynamics optimization of a 100pC beam from a low emittance superconducting injector.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB251

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paper received ※ 18 May 2021 paper accepted ※ 21 June 2021 issue date ※ 18 August 2021

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WEPAB252

Transient Beam-Beam Effect During Electron Bunch Replacement in the EIC

emittance, proton, injection, simulation

3228

J. Qiang
LBNL, Berkeley, California, USA
M. Blaskiewicz, Y. Luo, C. Montag, F.J. Willeke, D. Xu
BNL, Upton, New York, USA
Y. Hao
FRIB, East Lansing, Michigan, USA

The high luminosity, high polarization electron-ion collider (EIC) will provide great opportunities in nuclear physics study. In order to maintain high polarization, the electron beam will be replaced every few minutes during the collider operation. This frequent replacement of electron beams can affect proton beam quality during the collision. In this paper, we report on the study of the transient effect of electron beam replacement on proton beam emittance growth through strong-strong beam-beam simulation. The effect of electron beam injection imperfection will be included in the study.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB252

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paper received ※ 17 May 2021 paper accepted ※ 21 June 2021 issue date ※ 26 August 2021

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WEPAB254

Design of a 10 MeV Beamline at the Upgraded Injector Test Facility for e-Beam Irradiation

radiation, solenoid, focusing, cavity

3232

X. Li, H. Baumgart, G. Ciovati
ODU, Norfolk, Virginia, USA
G. Ciovati, F.E. Hannon, S. Wang
JLab, Newport News, Virginia, USA

Funding: Jefferson lab LDRD.
Electron beam irradiation near 10 MeV is suitable for wastewater treatment. The Upgraded Injector Test Facility (UITF) at Jefferson Lab is a CW superconducting linear accelerator capable of providing an electron beam of energy up to 10 MeV and up to 100 µA current. This contribution presents the beam transport simulations for a beamline to be used for the irradiation of wastewater samples at the UITF. The simulations were done using the code General Particle Tracer with the goal of obtaining an 8 MeV electron beam of radius (3-σ) of ~2.4 cm. The achieved energy spread is ~74.5 keV. The space charge effects were investigated when the bunch charge is varied to be up to 1000 times and the results showed that they do not affect the beam quality significantly.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB254

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paper received ※ 20 May 2021 paper accepted ※ 25 June 2021 issue date ※ 18 August 2021

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WEPAB255

Simulation Studies on the Interactions of Electron Beam with Wastewater

radiation, simulation, photon, target

3236

X. Li, H. Baumgart, G. Ciovati
ODU, Norfolk, Virginia, USA
G. Ciovati, F.E. Hannon, S. Wang
JLab, Newport News, Virginia, USA

Funding: Jefferson Lab LDRD
The manufactured chemical pollutants, like 1,4 dioxane and PFAS (per- and polyfluroralkyl substances), found in the underground water and/or drinking water are challenging to be removed or biodegraded. Energetic electrons are capable of mediating and removing them. This paper utilizes FLUKA code to evaluate the beam-wastewater interaction effects with different energy, space and divergence distributions of the electron beam. With 8 MeV average energy, the electron beam exits from a 0.0127 cm thick titanium window, travels through a 4.3 cm distance air and a second 0.0127 cm thick stainless water container window with 2.43 cm radius, and finally is injected into the water area, where the volume of water is around 75 cubic cm. The distribution parameters of the electron beam are from the GPT (General Particle Tracer) simulations for UITF (Upgraded Injector Test Facility) in Jefferson lab. By varying the distributions, several measurements including the dose (or energy deposition) distribution, electron fluence, photon fluence are scored and compared. Taking the comparisons into consideration, this paper is aiming to find better electron beams for the wastewater irradiation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB255

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paper received ※ 20 May 2021 paper accepted ※ 25 June 2021 issue date ※ 12 August 2021

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WEPAB256

Three-Dimensional Space Charge Oscillations in a Hybrid Photoinjector

emittance, plasma, simulation, cathode

3240

M. Carillo, M. Behtouei, F. Bosco, L. Faillace, A. Giribono, L. Giuliano, M. Migliorati, A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy
L. Ficcadenti
INFN-Roma, Roma, Italy
J.B. Rosenzweig
UCLA, Los Angeles, California, USA
B. Spataro, C. Vaccarezza
INFN/LNF, Frascati, Italy

Funding: This work supported by DARPA GRIT under contract no. 20204571 and partially by INFN National committee V through the ARYA project.
A new hybrid C-band photo-injector, consisting of a standing wave RF gun connected to a traveling wave structure, operating in a velocity bunching regime, has shown to produce an extremely high brightness beam with very low emittance and a very high peak current through a simultaneous compression of the beam in the longitudinal and transverse dimensions. A beam slice analysis has been performed in order to understand the evolution of the relevant physical parameters of the beam in the longitudinal and transverse phase spaces along the structure. A simple model for the envelope equation has been developed to describe the beam behavior in this particular dynamics regime that we term "triple waist", since all three dimensions reach a minimum condition almost simultaneously. The model analyzes the transverse envelope dynamics at the exit of the hybrid photo-injector, in the downstream drift where the triple waist occurs. The analytical solutions obtained from the envelope equation are compared with the simulations, showing a good agreement. Finally, these results have been analyzed also in terms of plasma oscillation to obtain a further physical interpretation of the beam dynamics.

Poster WEPAB256 [1.162 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB256

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paper received ※ 19 May 2021 paper accepted ※ 21 July 2021 issue date ※ 12 August 2021

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WEPAB257

Matching of a Space-Charge Dominated Beam into the Undulator of the THz SASE FEL at PITZ

undulator, experiment, quadrupole, FEL

3244

X. Li, Z. Aboulbanine, G.D. Adhikari, N. Aftab, Z.G. Amirkhanyan, P. Boonpornprasert, M.E. Castro Carballo, N. Chaisueb, G.Z. Georgiev, J. Good, M. Groß, C. Koschitzki, M. Krasilnikov, O. Lishilin, A. Lueangaramwong, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach
DESY Zeuthen, Zeuthen, Germany

The Photo Injector Test facility at DESY in Zeuthen (PITZ) is developing a THz SASE FEL as a prototype high repetition rate accelerator-based source for the THz-pumped, X-ray-probed experiments at the European XFEL. For the generation of THz pulses of mJ-level energy from SASE, an electron beam with a high charge (up to 4 nC) and high peak current (~200 A) will be injected into an LCLS-I undulator, which is currently being installed at the end of the photo-injector. The narrow vacuum chamber (11x5 mm) between the magnetic poles and the strong vertical focusing from the undulator, as well as the lack of beam diagnostics, have made it a challenge to match the space-charge dominated beam into the undulator without beam loss during the following transport. In this paper, boundary conditions of a matched electron beam will be discussed and the simulation and experimental study on our matching strategy will be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB257

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paper received ※ 08 May 2021 paper accepted ※ 02 July 2021 issue date ※ 24 August 2021

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WEPAB265

Simulations of Cooling Rate for Coherent Electron Cooling with Plasma Cascade Amplifier

simulation, kicker, plasma, hadron

3261

J. Ma, V. Litvinenko, G. Wang
BNL, Upton, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
Coherent electron cooling (CeC) is a novel technique for rapidly cooling high-energy, high-intensity hadron beams. A plasma cascade amplifier (PCA) has been proposed for the CeC experiment in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). The cooling rate of CeC experiment with PCA has been predicted in 3D start-to-end CeC simulations using code SPACE.

Poster WEPAB265 [1.507 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB265

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paper received ※ 13 May 2021 paper accepted ※ 10 June 2021 issue date ※ 15 August 2021

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WEPAB266

Simulation Studies of Plasma Cascade Amplifier

simulation, plasma, emittance, experiment

3265

J. Ma, V. Litvinenko, G. Wang
BNL, Upton, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
Plasma cascade amplifier (PCA) is an advanced design of amplifier for the coherent electron cooling (CeC) experiment in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). Working principle of PCA is the new plasma cascadeμbunching instability occurring in electron beams propagating along a straight trajectory. PCA is cost-effective as it does not require separating electron and hadron beams. SPACE, a parallel, relativistic 3D electromagnetic Particle-in-Cell (PIC) code, has been used for simulation studies of PCA.

Poster WEPAB266 [2.317 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB266

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paper received ※ 13 May 2021 paper accepted ※ 10 June 2021 issue date ※ 16 August 2021

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WEPAB273

Cooling and Diffusion Rates in Coherent Electron Cooling Concepts

proton, kicker, plasma, hadron

3281

S. Nagaitsev, V.A. Lebedev
Fermilab, Batavia, Illinois, USA
W.F. Bergan, E. Wang
BNL, Upton, New York, USA
G. Stupakov
SLAC, Menlo Park, California, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
We present analytic cooling and diffusion rates for a simplified model of coherent electron cooling (CEC), based on a proton energy kick at each turn. This model also allows to estimate analytically the rms value of electron beam density fluctuations in the "kicker" section. Having such analytic expressions should allow for better understanding of the CEC mechanism, and for a quicker analysis and optimization of main system parameters. Our analysis is applicable to any CEC amplification mechanism, as long as the wake (kick) function is available.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB273

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paper received ※ 10 May 2021 paper accepted ※ 28 July 2021 issue date ※ 15 August 2021

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WEPAB285

High Resolution Arrival Time Measurement of the Seed Laser

laser, FEL, timing, experiment

3320

J.G. Wang, H.X. Deng, L. Feng, C.L. Li, B. Liu
SARI-CAS, Pudong, Shanghai, People’s Republic of China
X.T. Wang, W.Y. Zhang
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China

The Shanghai soft X-ray Free-Electron Laser facility (SXFEL) is a fourth-generation linac-based light source, capable of producing X-ray pulses with a duration of tens of femtosecond. The seed laser for external seeding FEL, therefore, has tight requirements for relative arrival time to the electron bunch. To reach the required energy and wavelength for external seeding FEL, further optical amplification and frequency conversion is needed. These include reflection and propagation in different material and in air, in addition, also include the long laser transport beamline to the undulator, make the laser pulses arrival time influenced by environmental variation. To reach the required specification, high-resolution measurement of the laser arrival time is necessary. In this paper, we present a general concept for the measurement of the laser arrival time.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB285

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paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 19 August 2021

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WEPAB286

Design of the Laser-to-RF Synchronization at 1.3 GHz for SHINE

laser, electronics, timing, FEM

3323

J.G. Wang, H.X. Deng, L. Feng, C.L. Li, B. Liu
SARI-CAS, Pudong, Shanghai, People’s Republic of China
X.T. Wang, W.Y. Zhang
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China

A next-generation photo-science facility like Shanghai HIgh repetition rate XFEL aNd Extreme light facility (SHINE) is aiming to generate femtosecond X-ray pulses with unprecedented brightness to film chemical and physical reactions with sub-atomic level spatio-temporal resolution. To fulfill this scientific goal, high-precision timing synchronization is essential. The pulsed optical synchronization has become an indispensable scheme for femtosecond precision synchronization of X-ray free-electron lasers. One of the critical tasks of pulsed optical synchronization is to synchronize various microwave sources. For the future SHINE, ultralow-noise pulses generated by a mode-locked laser are distributed over large distances via stabilized fiber links to all critical facility end-stations. In order to achieve low timing jitter and long-term stability of 1.3 GHz RF reference signal for the accuracy Low-Level RF(RF) field control, an Electro-optical intensity Modulator (EOM) based scheme is being developed at SHINE. In this paper, we present the progress on the design of the optical part and the integrated electronics of the laser-to-RF synchronization.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB286

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paper received ※ 20 May 2021 paper accepted ※ 12 July 2021 issue date ※ 23 August 2021

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WEPAB289

Machine Learning Based Spatial Light Modulator Control for the Photoinjector Laser at FLUTE

laser, network, target, experiment

3332

C. Xu, E. Bründermann, A.-S. Müller, M.J. Nasse, A. Santamaria Garcia, C. Sax, C. Widmann
KIT, Karlsruhe, Germany
A. Eichler
DESY, Hamburg, Germany

Funding: C. Xu acknowledges the support by the DFG-funded Doctoral School "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology".
FLUTE (Ferninfrarot Linac- und Test-Experiment) at KIT is a compact linac-based test facility for novel accelerator technology and a source of intense THz radiation. FLUTE is designed to provide a wide range of electron bunch charges from the pC- to nC-range, high electric fields up to 1.2 GV/m, and ultra-short THz pulses down to the fs-timescale. The electrons are generated at the RF photoinjector, where the electron gun is driven by a commercial titanium sapphire laser. In this kind of setup the electron beam properties are determined by the photoinjector, but more importantly by the characteristics of the laser pulses. Spatial light modulators can be used to transversely and longitudinally shape the laser pulse, offering a flexible way to shape the laser beam and subsequently the electron beam, influencing the produced THz pulses. However, nonlinear effects inherent to the laser manipulation (transportation, compression, third harmonic generation) can distort the original pulse. In this paper we propose to use machine learning methods to manipulate the laser and electron bunch, aiming to generate tailor-made THz pulses. The method is demonstrated experimentally in a test setup.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB289

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paper received ※ 19 May 2021 paper accepted ※ 06 July 2021 issue date ※ 23 August 2021

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WEPAB290

Pointing Stabilization Algorithms Explored and Implemented with the Low Energy RHIC Electron Cooling Laser

laser, operation, feedback, cathode

3336

L.K. Nguyen
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The electron beam for the Low Energy RHIC electron Cooler (LEReC) at Brookhaven National Laboratory (BNL) is generated by a high-power fiber laser illuminating a photocathode, with a total propagation distance of 34 m separating the laser output and the photocathode. This propagation is facilitated by three independent laser tables that have varying responses to changes in time of day, weather, and season. Alignment drifts induced by these environmental changes are mitigated by an active "slow" pointing stabilization system found along the length of the transport, and this in-house system was commissioned as part of the full laser transport in 2019, as previously reported*. In 2020, the system became fully operational alongside LEReC, the world’s first electron cooler in a collider, and helped establish the transverse stability of the electron beam required for cooling. A summary of the different slow stabilization algorithms, which were continually refined during the run in order to achieve long-term center-of-mass stability of the laser spot on the photocathode to within 10 microns RMS, is provided.
* L. K. Nguyen et al., "Active Pointing Stabilization Techniques Applied to the Low Energy RHIC Electron Cooling Laser Transport at BNL", presented at NAPAC’19, paper THYBA6.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB290

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paper received ※ 19 May 2021 paper accepted ※ 02 July 2021 issue date ※ 30 August 2021

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WEPAB306

Applying Machine Learning to Optimization of Cooling Rate at Low Energy RHIC Electron Cooler

simulation, network, experiment, emittance

3391

Y. Gao, K.A. Brown, P.S. Dyer, S. Seletskiy, H. Zhao
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The Low Energy RHIC electron Cooler (LEReC) is a novel, state-of-the-art, electron accelerator for cooling RHIC ion beams, which was recently built and commissioned. Optimization of cooling with LEReC requires fine-tuning of numerous LEReC parameters. In this work, initial optimization results of using Machine Learning (ML) methods - Bayesian Optimization (BO) and Q-learning are presented. Specially, we focus on exploring the influence of the electron trajectory on the cooling rate. In the first part, simulations are conducted by utilizing a LEReC simulator. The results show that both methods have the capability of deriving electron positions that can optimize the cooling rate. Moreover, BO takes fewer samples to converge than the Q-learning method. In the second part, Bayesian optimization is further trained on the historical cooling data. In the new samples generated by the BO, the percentage of larger cooling rates data is greatly enhanced compared with the original historical data.

Poster WEPAB306 [1.083 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB306

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paper received ※ 12 May 2021 paper accepted ※ 01 July 2021 issue date ※ 23 August 2021

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WEPAB318

Prediction and Clustering of Longitudinal Phase Space Images and Machine Parameters Using Neural Networks and K-Means Algorithm

FEL, network, simulation, ECR

3417

M. Maheshwari
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
D.J. Dunning, J.K. Jones, M.P. King, H.R. Kockelbergh, A.E. Pollard
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Machine learning algorithms were used for image and parameter recognition and generation with the aim to optimise the CLARA facility at Daresbury, using start-to-end simulation data. Convolutional and fully connected neural networks were trained using TensorFlow-Keras for different instances, with examples including predicting Longitudinal Phase Space (LPS) images with machine parameters as input and FEL parameter prediction (e.g. pulse energy) from LPS images. The K-means clustering algorithm was used to cluster the LPS images to highlight patterns within the data. Machine learning techniques can enhance the way large amounts of data are processed and analysed and so have great potential for application in accelerator science R&D.

Poster WEPAB318 [1.062 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB318

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paper received ※ 17 May 2021 paper accepted ※ 05 July 2021 issue date ※ 14 August 2021

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WEPAB321

ALS-U Instrumentation Overview

timing, instrumentation, controls, hardware

3427

J.M. Weber, J.C. Bell, M.J. Chin, S. De Santis, R.F. Gunion, S. Murthy, W.E. Norum, G.J. Portmann, C. Serrano
LBNL, Berkeley, California, USA
W.K. Lewis
Osprey DCS LLC, Ocean City, USA

Funding: Work supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The Advanced Light Source Upgrade (ALS-U) to a diffraction-limited storage ring with a small vacuum chamber diameter requires excellent orbit stability and a fast response orbit interlock for machine protection. The on-axis swap-out injection scheme and dual RF frequencies demand fast monitoring of pulsed injection magnets and a novel approach to timing. Recent development efforts at ALS and advances in PLLs, FPGAs, and RFSoCs that provide higher performance and mixed-signal integration can be leveraged for instrumentation solutions to these accelerator challenges. An overview of preliminary ALS-U instrumentation system designs and status will be presented.

Poster WEPAB321 [23.306 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB321

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paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 18 August 2021

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WEPAB322

Status of Digital BPM Signal Processor for SHINE

cavity, FPGA, FEL, electronics

3430

L.W. Lai, F.Z. Chen, Y.B. Leng, T. Wu, Y.M. Zhou
SSRF, Shanghai, People’s Republic of China
J. Wan
SINAP, Shanghai, People’s Republic of China

Funding: Youth Innovation Promotion Association, CAS (Grant No. 2019290); The National Key Research and Development Program of China (Grant No. 2016YFA0401903).
Digital signal processors that can handle 1MHz bunch rate BPM signal processing are under development for SHINE. Two different processors have been developed at the same time, including an intermediate frequency signal processor with a sampling rate higher than 500MHz, which can be used in general BPM applications; and a direct RF sampling processor, which can directly sample the C band cavity BPM signal without analog down-conversion modules and greatly simplifies the cavity BPM system. This paper will introduce the design, development status, and performance evaluations of the processors.

Poster WEPAB322 [1.919 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB322

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paper received ※ 20 May 2021 paper accepted ※ 10 June 2021 issue date ※ 24 August 2021

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WEPAB327

Sheet Electron Probe for Beam Tomography

proton, diagnostics, cathode, simulation

3437

V.G. Dudnikov, M.A. Cummings, G. Dudnikova
Muons, Inc, Illinois, USA

Funding: Work is funded by DOE SBIR grant DE-SC0021581
An electron beam probe has been successfully used for the determination of accelerated particle density distributions. However, the apparatus used for this diagnostic had a large size and complex design which limit the broad use of this diagnostic for tomography of accelerated bunches. We propose a new approach to electron beam tomography: we will generate a continuous sheet of electrons. As the ion beam bunches pass through the sheet, they cause distortions in the distribution of sheet electrons arriving at CCD device on the other side of the beam that is interpreted to give a continuous measurement of the beam profile. The apparatus to generate the sheet beam is a strip cathode, which, compared to the scanning electron beam probe, is smaller, has a simpler design and less expensive manufacturing, has better magnetic shielding, has higher sensitivity, higher resolution, has better accuracy of measurement and better time resolution. With this device, it is possible to develop almost ideal tomography diagnostics of bunches in linear accelerators and in circular accelerators and storage rings.

Poster WEPAB327 [0.640 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB327

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paper received ※ 19 May 2021 paper accepted ※ 15 July 2021 issue date ※ 25 August 2021

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WEPAB328

Rapid Surface Microanalysis Using a Low Temperature Plasma

plasma, cathode, radiation, target

3440

V.G. Dudnikov, M.A. Cummings, R.P. Johnson
Muons, Inc, Illinois, USA

There is a need for rapid, high-resolution (micron or sub-micron) scanning of surfaces of special nuclear materials (SNM) and surrogate materials to locate and identify regions of abnormalities. One technique that is commonly used to analyze the composition of solid surfaces and thin films is secondary-ion mass spectrometry (SIMS). SIMS devices are very complex and expensive. We propose to develop simpler, less expensive surface analysis devices, based on glow-discharge optical emission spectroscopy (GOES) that can provide excellent spatial resolution. Ions from a plasma discharge sputtered atoms from the surface and the discharge electrons effectively excite and ionize the sputtered atoms. GOES uses the light emitted by the excited particles for quantitative analysis. In the GOES device, the ion flux is extracted from the gas-discharge plasma and focused to a micron size on the sample, providing very local sputtering and local elemental analysis. The radiation from the sputtered atoms is passed through an optical fiber to an optical spectrometer and recorded. To register the distribution of elements over the sample, the sample is scanned electro-mechanically.

Poster WEPAB328 [0.385 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB328

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paper received ※ 19 May 2021 paper accepted ※ 29 July 2021 issue date ※ 24 August 2021

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WEPAB331

Application of KALYPSO as a Diagnostic Tool for Beam and Spectral Analysis

detector, laser, synchrotron, experiment

3451

M.M. Patil, E. Bründermann, M. Caselle, A. Ebersoldt, S. Funkner, B. Kehrer, A.-S. Müller, M.J. Nasse, G. Niehues, J.L. Steinmann, M. Weber, C. Widmann
KIT, Karlsruhe, Germany

Funding: This work is supported by the BMBF project 05K19VKD STARTRAC and DFG-funded Doctoral School ’Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology’
KALYPSO is a novel detector capable of operating at frame rates up to 12 MHz developed and tested at the institute of data processing and electronics (IPE) and employed at Karlsruhe Research Accelerator (KARA) which is part of the Test Facility and Synchrotron Radiation Source KIT. This detector consists of silicon, InGaAs, PbS, or PbSe line array sensor with spectral sensitivity from 350 nm to 5000 nm. The unprecedented frame rate of this detector is achieved by a custom-designed ASIC readout chip. The FPGA-readout architecture enables continuous data acquisition and real-time data processing. Such a detector has various applications in the fields of beam diagnostics and spectral analysis. KALYPSO is currently employed at various synchrotron facilities for electro-optical spectral decoding (EOSD) to study the longitudinal profile of the electron beam, to study the energy spread of the electron beam, tuning of free-electron lasers (FELs), and also in characterizing laser spectra. This contribution will present an overview of the results from the mentioned applications.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB331

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paper received ※ 19 May 2021 paper accepted ※ 22 July 2021 issue date ※ 02 September 2021

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WEPAB337

Some Methods of Making Titanium Vacuum Chamber Act as Getter Pump for UHV/XHV

vacuum, ECR, experiment, hadron

3471

J. Kamiya, T. Takano, H. Yuza
JAEA/J-PARC, Tokai-mura, Japan
K. Wada
Tokyo Electronics Co. Ltd., Kokubunji, Tokyo, Japan

Funding: JSPS KAKENHI Grant Number JP18K11925
The non-evaporable getter (NEG) coating has been developed in CERN to make a beam pipe act as a distributed vacuum pump by coating the getter materials with the ability to adsorb/absorb gas molecules on the beam pipe surface. The NEG coating materials used in the LHC are alloys of titanium, zirconium, and vanadium. In high-power beam accelerators, titanium has been used as the beam pipe chamber material due to its low radio activation characteristics. The ordinal titanium surface has no getter function because it is covered with a titanium oxide film. The new technique, which removes the titanium-oxide surface by some methods, such as baking or sputtering, has been investigated. The dependence of the surface oxide film and the getter characteristics on the baking temperature have been measured. Also, by sputtering the inner surface of the titanium chamber, clear evidence that shows the chamber acts as a vacuum pump has been obtained. Furthermore, the NEG coating on the pure titanium surface can suppress the rapid decrease of the sticking probability by the repeated air purge and reactivation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB337

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paper received ※ 14 May 2021 paper accepted ※ 25 June 2021 issue date ※ 22 August 2021

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WEPAB338

Amorphous Carbon Coating in SPS

vacuum, target, operation, multipactoring

3475

W. Vollenberg, P. Chiggiato, P. Costa Pinto, P. Cruikshank, H. Moreno, C. Pasquino, J. Perez Espinos, M. Taborelli
CERN, Meyrin, Switzerland

Within the LHC Injector Upgrade (LIU) project, the Super Proton Synchrotron (SPS) needs to be upgraded to inject into the LHC higher intensity and brighter 25-ns bunch spaced beams. To mitigate the Electron Multipacting (E.M.) phenomenon, a well-known limiting factor for high-intensity positively charged beams, CERN developed carbon coatings with a low Secondary Electron Yield (SEY). During the 2016 & 2017 year-end technical stops, such coatings were deposited on the inner wall of the vacuum chambers of some SPS quadrupole and dipole magnets by a dedicated in-situ setup. A much larger scale deployment was implemented during the Long Shutdown 2 (2019-2020) to coat all beam pipes of focussing quadrupoles (QF) and their adjacent short straight sections. In this contribution, we remind the motivation of the project, and present the results and the quality control of the carbon coating campaign during the latter phase of implementation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB338

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paper received ※ 19 May 2021 paper accepted ※ 16 June 2021 issue date ※ 16 August 2021

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WEPAB339

Beam-Induced Surface Modification of the LHC Beam Screens: The Reason for the High Heat Load in Some LHC Arcs?

dipole, cryogenics, hadron, ECR

3479

V. Petit, P. Chiggiato, M. Himmerlich, G. Iadarola, H. Neupert, M. Taborelli, D.A. Zanin
CERN, Geneva, Switzerland

All over Run 2, the LHC beam-induced heat load exhibited a wide scattering along the ring. Studies ascribed the heat source to electron cloud build-up, indicating an unexpectedly high Secondary Electron Yield (SEY) of the beam screen surface in some LHC regions. During the Long Shutdown 2, the beam screens of a low and a high heat load dipole were extracted. Their inner copper surface was analysed in the laboratory to compare their SEY and surface composition. While findings on the low heat load beam screens are compatible with expectations from laboratory studies of copper conditioning and deconditioning mechanisms, an extremely low carbon amount and the presence of CuO (non-native surface oxide) are observed on the high heat-load beam screens. The azimuthal distribution of CuO correlates with the density and energy of electron impingement. Such chemical modifications increase the SEY and inhibit the full conditioning of affected surfaces. This work shows a direct correlation between the abnormal LHC heat load and the surface properties of its beam screens, opening the door to the development of curative solutions to overcome this critical limitation.

Poster WEPAB339 [2.247 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB339

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paper received ※ 19 May 2021 paper accepted ※ 22 June 2021 issue date ※ 26 August 2021

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WEPAB340

Pressure Simulations for the EIC Interaction Region

vacuum, photon, detector, simulation

3483

M.L. Stutzman
JLab, Newport News, Virginia, USA

Background detector rates in the Electron Ion Collider depend in part on the pressure in the interaction region. Materials choice, synchrotron radiation induced desorption, conditioning time and pumping configuration all affect the pressure in the system. Simulations of the region using Synrad and Molflow+ coupled simulation codes will be presented for various configruations and conditioning times.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB340

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paper received ※ 18 May 2021 paper accepted ※ 20 July 2021 issue date ※ 27 August 2021

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WEPAB344

Studies for Mitigating Flashover of CERN-LHC Dilution Kicker Magnets

kicker, simulation, vacuum, high-voltage

3498

A.M. Loebner, M.J. Barnes, W. Bartmann, C. Bracco, L. Ducimetière, V. Namora, V. Senaj
CERN, Geneva 23, Switzerland

The LHC beam dump system is used for extracting beam from the LHC and, as such, is a safety critical system whose proper functionality must be assured. Dilution kicker magnets (MKBs) sweep the extracted beam over the cross-sectional area of a dump block as the energy density would otherwise be too high and damage the block. In 2018, a high voltage flashover occurred in a vertical MKB (MKBV) vacuum tank, during a beam dump, which resulted in non-ideal sweep of the beam over the block. The location of the flashover could not be identified during a subsequent inspection of the magnet. Hence, electrical field simulations have been carried out to identify potentially critical regions, to determine the most probable region of the flashover. One potentially critical region is a rectangular beam pipe (RBP) between the end of the tank and the MKBV magnet, whose purpose is to reduce plasma propagation to the adjacent tank in the event of a flashover. Mitigating measures were studied and are reported in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB344

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paper received ※ 16 May 2021 paper accepted ※ 06 July 2021 issue date ※ 27 August 2021

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WEPAB358

Development of Low-Z Collimator for SuperKEKB

impedance, cavity, positron, operation

3537

S. Terui, T. Abe, Y. Funakoshi, T. Ishibashi, H.N. Nakayama, K. Ohmi, D. Zhou
KEK, Ibaraki, Japan
A. Natochii
University of Hawaii, Honolulu,, USA

Collimator jaws for SuperKEKB main ring, which is an electron-positron collider, installed to suppress background noise in a particle detector complex named Belle II. The collimators are successful to reduce backgrounds when the collimator was closed. But, in high current operations with 500 mA or more, jaws were occasionally damaged by hitting abnormal beams. This trouble is a low-frequency, which is once-a-commissioning period currently, but a high-consequence one because we are not able to apply high voltage on detectors in Belle II by high backgrounds. Low-Z collimator jaw, that is durable through hitting uncontrollable beam, have been designed due to protect important component as the solution of the trouble. The low-Z collimator jaws are installable in a present collimator chamber, have a pair of vertically opposed movable jaws. One pair of low-Z collimator jaws was installed. The paper is to describe what did we calculate and measure to make a low-Z collimator, how did we make a low-Z collimator, the impact of the installed low-Z collimator, mainly transverse mode coupling instability.

Poster WEPAB358 [0.788 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB358

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paper received ※ 16 May 2021 paper accepted ※ 22 July 2021 issue date ※ 31 August 2021

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WEPAB359

Report on Collimator Damaged Event in SuperKEKB

detector, positron, MMI, operation

3541

S. Terui, Y. Funakoshi, H. Hisamatsu, T. Ishibashi, K. Kanazawa, Y. Ohnishi, K. Shibata, M. Shirai, Y. Suetsugu, M. Tobiyama
KEK, Ibaraki, Japan

Collimator jaws for SuperKEKB main ring, which is an electron-positron collider, installed to suppress background noise in a particle detector complex named Belle II. In high current operations with 500 mA or more, jaws were occasionally damaged by hitting abnormal beams. This trouble is a low-frequency, which is once-a-commissioning period currently, but high-consequence one because we are not able to apply high voltage on detectors in Belle II by high backgrounds. At this moment this jaw damage event occurs, we observed pressure burst near the collimator with the beam abort, there was no sign of beam oscillation indicating instability, and the beam intensity suddenly decreased a few turns before the abort. I predict that the cause of this jaw damage was that a sudden change of the beam energy by the collision with dust. In this paper, the explanation of the observation result of this events and tracking simulation of beam colliding with dust are reported.

Poster WEPAB359 [3.869 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB359

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paper received ※ 17 May 2021 paper accepted ※ 22 July 2021 issue date ※ 19 August 2021

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WEPAB370

Study of an L-Band CW Linac

radiation, linac, emittance, solenoid

3575

J. Gao, H.B. Chen, J.Y. Liu, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China

We have studied an L-band linac based on a cheap industrial magnetron, which works at CW mode with 75kW averaged output-power. The designed energy-gain of electrons is 500keV. Low accelerating gradient was the dominant problem encountered during the structure design. We adopted a standing-wave structure with magnetically coupling and nose cones to increase the effective shunt impedance. A 7-cell design has been completed, of which the transverse dynamics and thermodynamics were simulated. Results showed that this accelerating structure could work stably at 59 C and 100 mA output beam current was achieved. This L-band design provided a cheap and efficient way to generate low-energy electrons for industrial irradiation processing.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB370

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 02 September 2021

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WEPAB374

The Southern Hemisphere’s First X-Band Radio-Frequency Test Facility at the University of Melbourne

klystron, gun, network, GUI

3588

M. Volpi, R.P. Rassool, S.L. Sheehy, G. Taylor, S.D. Williams
The University of Melbourne, Melbourne, Victoria, Australia
M.J. Boland
CLS, Saskatoon, Saskatchewan, Canada
M.J. Boland
University of Saskatchewan, Saskatoon, Canada
N. Catalán Lasheras, S. Gonzalez Anton, G. McMonagle, S. Stapnes, W. Wuensch
CERN, Meyrin, Switzerland
R.T. Dowd, K. Zingre
AS - ANSTO, Clayton, Australia

The first Southern Hemisphere X-band Laboratory for Accelerators and Beams (X-LAB) is under construction at the University of Melbourne, and it will operate CERN X-band test stand containing two 12GHz 6MW klystron amplifiers. By power combination through hybrid couplers and the use of pulse compressors, up to 50 MW of peak power can be sent to any of 2 test slots at pulse repetition rates up to 400 Hz. The test stand is dedicated to RF conditioning and testing CLIC’s high gradient accelerating structures beyond 100 MV/m. It will also form the basis for developing a compact accelerator for medical applications, such as radiotherapy and compact light sources. Australian researchers working as part of a collaboration between the University of Melbourne, international universities, national industries, the Australian Synchrotron -ANSTO, Canadian Light Source and the CERN believe that creating a laboratory for novel accelerator research in Australia could drive technological and medical innovation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB374

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paper received ※ 18 May 2021 paper accepted ※ 06 July 2021 issue date ※ 12 August 2021

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WEPAB378

Near-Infrared Laser System for Dielectric Laser Acceleration Experiments at SINBAD

laser, experiment, timing, acceleration

3596

C. Mahnke, U. Grosse-Wortmann, I. Hartl, C.M. Heyl, Y. Hua, T. Lamb, Y. Ma, C. Mohr, J. Müller, S.H. Salman, S. Schulz, C. Vidoli
DESY, Hamburg, Germany
H. Çankaya
CFEL, Hamburg, Germany

The technique of dielectric laser acceleration (DLA) utilizes the strong field gradients generated by intense laser light near the surfaces of microscopic photonic structures, possibly allowing compact accelerator devices. We report on the infrared laser system at the SINBAD facility at DESY, where first DLA experiments with relativistic electrons pre-accelerated by the ARES linear accelerator started in late 2020. We constructed a low-noise Holmium fiber oscillator producing pulses at a wavelength of 2050 nm, seeding a Ho:YLF regenerative amplifier. Pulses of 2 mJ and 2 ps duration from the amplifier are transported over a distance of about 30 m to the DLA interaction point. The laser system is synchronized to the accelerator by locking the laser repetition rate to an RF master oscillator using an all-digital phase-locked loop, giving a residual timing jitter of about 45 fs. The digital locking scheme allows precise shifting of the relative timing between laser pulses and electrons without need for a dedicated optical delay line. It is planned to lock the system to the UV photocathode laser by means of an optical cross correlator further to improve the locking performance.

Poster WEPAB378 [1.445 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB378

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paper received ※ 19 May 2021 paper accepted ※ 22 June 2021 issue date ※ 01 September 2021

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WEPAB379

Photocathode Laser Development for Superconducting X-Ray Free Electron Lasers at DESY

laser, FEL, operation, cathode

3599

C. Li, O. Akcaalan, U. Grosse-Wortmann, I. Hartl, C. Mohr, M. Seidel, H. Tuennermann, C. Vidoli, L. Winkelmann
DESY, Hamburg, Germany
M. Frede, O. Puncken
neoLASE GmbH, Hanover, Germany

Funding: Deutsches Elektronen-Synchrotron, Hamburg, 22609, Germany
Modern X-Ray Free-Electron Lasers (XFEL) are a key tool to enable a variety of scientific research. Those large-scale machines rely on robust and reliable deep ultraviolet (DUV) laser sources to drive electrons from their RF photocathode gun. In this paper we present a new photocathode laser prototype, which offers more flexibility in duration and shape of the 257.5 nm pulses for driving the CsTe Photocathodes of DESY’s superconducting burst-mode FELs. The laser matches the FEL pulse structure, which are 800 µs bursts at up to 4.5 MHz intraburst-rate with 10 Hz burst-repetition-rate. In a first version the system will offer variable DUV pulse durations, tunable from 1 ps to 20 ps to address different operational regimes of the XFEL. The laser system comprises a high-resolution spectral shaper with the option of generating flat-top DUV pulses for reducing electron-beam emittance at a later version. The laser is constructed in a hybrid Yb:fiber and Yb:YAG architecture. Our prototype delivers 180 uJ pulse energy at 1030 nm and 1 MHz intra-burst rate and we demonstrated conversion of 50µJ of the NIR beam to DUV, resulting 11.5µJ at 21ps (FWHM) and 6.15 µJ at 1.05 ps (FWHM) pulse duration.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB379

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paper received ※ 27 May 2021 paper accepted ※ 02 July 2021 issue date ※ 29 August 2021

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WEPAB380

Measurements of Field Emission Induced Optical Spectra

alignment, radiation, site, experiment

3602

R.C. Peacock, G. Burt
Lancaster University, Lancaster, United Kingdom
S. Calatroni, W. Wuensch
CERN, Meyrin, Switzerland

Field emission induced optical spectra in a dc electrode system have been measured using a spectrometer and CCD camera system in order to gain insight into the nature of field emissions sites. Spectra were measured from between 2 ridged parallel copper electrodes with a gap ranging from 60µm to 100µm and a bias voltage of up to 8000V under high vacuum conditions. A strong correlation between the light intensity of the spectra and the measured field emitted current was observed as a function of applied voltage. A characteristic broadband spectrum ranging from 550nm and 850nm wavelength was observed but there were important features which varied as a function of observation angle, polarity, and conditioning state and also with time. Possible causes of the optical spectra being considered include black body radiation, optical transition radiation and cathode luminescence of copper. Further experiments are ongoing with an improved optical setup to increase optical alignment for measurements with different materials of electrodes, developing further understanding of the cause of the optical spectra, to provide understanding into characteristics and evolution of emission sites.

Poster WEPAB380 [1.158 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB380

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paper received ※ 11 May 2021 paper accepted ※ 24 June 2021 issue date ※ 31 August 2021

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WEPAB381

Multipactor Simulations for MYRRHA Spoke Cavity: Comparison Between SPARK3D, MUSICC3D, CST PIC and Measurement

multipactoring, simulation, cavity, niobium

3606

N. Hu, M. Chabot, J.-L. Coacolo, D. Longuevergne, G. Olry
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
M.B. Belhaj
ONERA, Toulouse, France

The multipactor effect can lead to thermal breakdown (quench), high field emission and limited accelerating gradient in superconducting accelerator devices. To determine the multipactor breakdown power level, multipactor simulations can be performed. The objective of this study is to compare the results given by different simulation codes with the results of vertical testing of SRF cavities. In this paper, Spark3D, MUSICC3D and CST Studio PIC solver have been used to simulate the multipactor effect in Spoke cavity developed within the framework of MYRRHA project. Then, a benchmark of these three simulation codes has been made. The breakdown power level, the multipactor order and the most prominent location of multipactor are presented. Finally, the simulation results are compared with the measurements done during the vertical tests.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB381

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 30 August 2021

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WEPAB384

Design and Beam Dynamics of the Electron Lens for Space Charge Compensation in SIS18

space-charge, simulation, solenoid, dipole

3614

S. Artikova, D. Ondreka, K. Schulte-Urlichs, P.J. Spiller
GSI, Darmstadt, Germany

An electron lens for space charge compensation is being developed at GSI to increase the ion beam intensities in SIS18 for the FAIR project. It uses an electron beam of 10A maximum current at 30keV. The maximum magnetic field on-axis is 0.6T, considerably higher than the field of the existing electron cooler. The magnetic system of the lens consists of solenoids and toroids. The toroids’ vertical field component creates a significant horizontal orbit deflection in the circulating low rigidity ion beam. To correct this deflection, four correction dipoles have been introduced. As common for electron lenses, the high-power electron beam is not dumped at ground potential, but rather in a collector with a small bias potential with respect to the cathode. The present design foresees a collector at -27kV, leading to a power dissipation of 30kW, distributed over a large surface area by placing the collector in an appropriately shaped magnetic field of a pre-collector solenoid. This contribution reports on the design of the lens and presents the results of beam transport simulations for the electron beam (with space charge) and a representative ion beam, performed using the 3D CST STUDIO.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB384

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paper received ※ 20 May 2021 paper accepted ※ 05 July 2021 issue date ※ 15 August 2021

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WEPAB385

Beam Dynamic Analysis of RF Modulated Electron Beam Produced by Gridded Thermionic Guns

gun, cathode, emittance, linac

3618

G. Adam
University of Strathclyde, Glasgow, United Kingdom
A.W. Cross, L. Zhang
USTRAT/SUPA, Glasgow, United Kingdom
B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
B.L. Militsyn
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: Science and Technology Facilities Council (STFC) U.K training grant, industrial case with TMD Ltd, UK ST/R002141/1 "Accelerators for Security, healthcare and Environmental applications ".
A thermionic cathode gridded electron gun used in injectors for different types of circular and linear particle accelerators and for energy recovery configurations was studied. Both theory and numerical simulation were used to explore the relationship between the bunch charge and bunch length. The electron gun is based on a Pierce-type geometry. It was initially designed using Vaughan synthesis followed by optimization using a 2D electron trajectory solver TRAK. After optimization, the grid in front of the cathode was inserted and the RF field was introduced through a coaxial waveguide structure. The complete gun was simulated using the PIC code MAGIC. High duty cycle operations at frequencies 1.5 GHz and 3.0 GHz, were investigated using different combinations of both the bias and the RF voltage applied between the cathode and the grid. The beam dynamics results from the PIC showed that a minimum bunch length of 10⁶ ps could be achieved with a bunch charge of 33 pC when the driving RF frequency was 1.5 GHz. Operating at the higher RF frequency of 3GHz did not significantly reduce the bunch length. The normalized emittance of about 5.6 mm-mrad was demonstrated in PIC simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB385

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paper received ※ 19 May 2021 paper accepted ※ 02 July 2021 issue date ※ 24 August 2021

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WEPAB387

Study of Failure Modes in Electron Linac-Based X-Ray Sources for Industrial Applications

linac, gun, operation, vacuum

3622

K.P. Dixit, G. Vinod
BARC, Mumbai, India

Electron linac-based X-ray sources (XRS) have an increased demand in industrial applications, mainly for their advantages of compactness and ease of use. In order to achieve reliable operation, it is necessary to have rugged components in the linac system. Hence, this study focusses on achieving high reliability design; also in formulating a preventive maintenance programme to optimise the availability and prognostic methods for performance monitoring of components. This paper investigates the failure modes in the important sub-systems of a 6 MeV electron linac, including electron gun, RF power source, vacuum system, x-ray target, control system, etc. Electron guns suffer from problems related to the filament heater damage and high voltage insulation failure. In the RF source, major components (line-type pulsed modulators, magnetrons, circulator and RF window) are studied to assess their life. Fault tree analysis of the individual sub-systems and the effect of individual failures on the linac down-time are studied. A few mitigation techniques used in practical systems are also discussed here.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB387

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paper received ※ 18 May 2021 paper accepted ※ 23 July 2021 issue date ※ 13 August 2021

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WEPAB396

First Measurements on Multipactor Study

multipactoring, vacuum, simulation, ECR

3633

Y. Gómez Martínez, J. Angot, M.A. Baylac, T. Cabanel, P.-O. Dumont, N. Emeriaud, O. Zimmermann
LPSC, Grenoble Cedex, France
D. Longuevergne
FLUO, Orsay, France
G. Sattonnay
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

Multipactor (MP) is an undesired phenomenon of resonant electron build up encountered on particle accelerators. It can induce anomalous thermal losses, higher than the Joule losses, inducing a decrease of the superconducting cavities quality factor, it can even lead to a cavity quench. On couplers, it can produce irreversible damages or generate a breakdown of their vacuum window. Multipactor may lead to Electron Cloud build up as well. The accelerator group at LPSC has developed a test bench dedicated to the multipactor studies. This paper presents the experimental set-up and its first measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB396

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paper received ※ 18 May 2021 paper accepted ※ 14 July 2021 issue date ※ 30 August 2021

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WEPAB405

Supercontinuum Generation for the Improvement of Pulse Radiolysis System

laser, radiation, polarization, photon

3657

M. Sato, Y. Kaneko, Y. Koshiba, M. Washio
RISE, Tokyo, Japan
K. Sakaue
The University of Tokyo, Graduate School of Engineering, Bunkyo, Japan

Pulse radiolysis is one of the absorption measurement methods for investigating the fundamental, ultrafast process of radiation chemical reactions. Analytical light is transmitted simultaneously with the timing of electron beam irradiation, and its absorption by reactive species is detected. Since the target reactions arise in pico second time scale or even shorter, analytical light is required to have such duration. Besides, so as not to be buried in noise of the radiation source, the optical power of the analytical light must be high enough. Furthermore, it is desirable that the analytical light covers visible region because important absorptions caused by irradiation products such as hydrated electron, hydroxyl radical, or so exist in the region. We considered that the supercontinuum light generated from an ultrashort pulse laser is suitable as an analytical light because it has all these characteristics. In this study, we generate the second harmonic (775 nm) of an erbium fiber laser (1550 nm) as a seed laser for supercontinuum generation. In this presentation, we report the current situation of our laser system and prospects.

Poster WEPAB405 [0.734 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB405

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paper received ※ 18 May 2021 paper accepted ※ 24 August 2021 issue date ※ 01 September 2021

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WEPAB418

The Power Supply System for 10 MeV & 20 kW Industry Irradiation Facility

power-supply, gun, radiation, high-voltage

3678

F.L. Shang, L. Shang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by National Key R&D Program of China 2018YFF0109204
The 10 MeV and 20 kW industry irradiation facility (IIF) has been designed by National Synchrotron Radiation Laboratory (NSRL) for years. Modular design power supplies are employed for the latest version, depend on the performance of these power supplies with high precision and high stability, the operating reliability of the IIF has been greatly improved.

Poster WEPAB418 [0.991 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB418

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paper received ※ 15 May 2021 paper accepted ※ 23 June 2021 issue date ※ 29 August 2021

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THXA02

Overview of the Micro-Bunching Instability in Electron Storage Rings and Evolving Diagnostics

operation, bunching, simulation, diagnostics

3686

M. Brosi
KIT, Karlsruhe, Germany

The micro-bunching instability is a longitudinal instability that leads to dynamical deformations of the charge distribution in the longitudinal phase space. It affects the longitudinal charge distribution, and thus the emitted coherent synchrotron radiation spectra, as well as the energy distribution of the electron bunch. Not only the threshold in the bunch current above which the instability occurs, but also the dynamics above the instability threshold strongly depends on machine parameters, e.g., natural bunch length, accelerating voltage, momentum compaction factor, and beam energy. All this makes the understanding and potential mitigation or control of the micro-bunching instability an important topic for the next generation of light sources and circular e⁺/e⁻ colliders. This presentation will give a review on the micro-bunching instability and discuss how technological advances in the turn-by-turn and bunch-by-bunch diagnostics are leading to a deeper understanding of this intriguing phenomenon.

Slides THXA02 [23.626 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXA02

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paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 02 September 2021

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THXA04

Microbunching Instability in the Presence of Intrabeam Scattering for Single-Pass Accelerators

bunching, scattering, FEL, simulation

3692

C.-Y. Tsai
HUST, Wuhan, People’s Republic of China
W. Qin
Lund University, Lund, Sweden

Funding: This work is supported by the Fundamental Research Funds for the Central Universities under Project No. 5003131049 and National Natural Science Foundation of China under project No. 11905073.
Intrabeam scattering (IBS) has long been studied in lepton or hadron storage rings as a slow diffusion process, while the effects of IBS on single-pass or recirculating electron accelerators have drawn attention only in the recent two decades due to the emergence of linac-based or ERL-based 4th-generation light sources, which require high-quality electron beams during the beam transport. Recent experimental measurements indicate that in some parameter regimes, IBS can have a significant influence on microbunched beam dynamics. Here we develop a theoretical formulation* of microbunching instability (MBI) in the presence of IBS for single-pass accelerators. We start from the Vlasov-Fokker-Planck (VFP) equation, combining both collective longitudinal space charge and incoherent IBS effects. The linearized VFP equation with the corresponding coefficients is derived. The evolutions of the phase space density and energy modulations are formulated as a set of coupled integral equations. The formulation** is then applied to a simplified single-pass transport line. The results from the semi-analytical calculation are compared and show good agreement with particle tracking simulations.
* C.-Y. Tsai et al., Phys. Rev. Accel. Beams 23, 124401 (2020)
** C.-Y. Tsai and W. Q, Phys. Plasmas (2021), accepted for publication

Slides THXA04 [2.718 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXA04

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paper received ※ 13 May 2021 paper accepted ※ 19 July 2021 issue date ※ 01 September 2021

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THXA05

A Fast Method of 2D Calculation of Coherent Synchrotron Radiation Wakefield in Relativistic Beams

radiation, dipole, synchrotron, synchrotron-radiation

3696

J. Tang, Z. Huang, G. Stupakov
SLAC, Menlo Park, California, USA

Coherent Synchrotron Radiation (CSR) is regarded as one of the most important reasons that limit beam brightness in modern accelerators. CSR wakefield is often computed in a 1D assuming a line charge, which can become invalid when the beam has a large transverse extension and small bunch length. On the other hand, the existing 2D or 3D codes are often computationally inefficient or incomplete. In our previous work * we developed a new model for fast computation of 2D CSR wakefield in relativistic beams with Gaussian distribution. Here we further generalize this model to achieve self-consistent computation compatible with arbitrary beam distribution and nonlinear magnetic lattice with particle tracking. These new features can enable us to perform realistic simulations and study the physics of CSR beyond 1D in electron beams with extreme short bunch length and high peak current.
* J. Tang and G. Stupakov. NAPAC2019, paper WEPLS09 (2019).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXA05

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paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 23 August 2021

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THXA06

The Effect of Beam Velocity Distribution on Electron-Cooling at Elena

proton, emittance, antiproton, simulation

3700

B. Veglia, A. Farricker, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
A. Farricker
UMAN, Manchester, United Kingdom
B. Veglia, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: Work supported by EU Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 721559.
ELENA is a novel storage ring at CERN, designed to deliver low energy, high-quality antiprotons to antimatter experiments. The electron cooler is a key component of this decelerator, which counters the beam blow-up as the antiproton energy is reduced from 5.3 MeV to 100 keV. Typical numerical approximations on electron cooling processes assume that the density distribution of electrons in analytical form and the velocity distribution space to be Maxwellian. However, it is useful to have an accurate description of the cooling process based on a realistic electron distribution. In this contribution, BETACOOL simulations of the ELENA antiproton beam phase space evolution were performed using uniform, Gaussian, and "hollow beam" electron velocity distributions. The results are compared with simulations considering a custom electron beam distribution obtained with G4beamline. The program was used to simulate the interaction of an initially Gaussian electron beam with the magnetic field measured inside the electron cooler interaction chamber. The resulting beam lifetime and equilibrium parameters are then compared with measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXA06

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paper received ※ 18 May 2021 paper accepted ※ 01 July 2021 issue date ※ 17 August 2021

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THXB01

3D Tracking of a Single Electron in IOTA

experiment, synchrotron, storage-ring, radiation

3708

A.L. Romanov, S. Nagaitsev, J.K. Santucci, G. Stancari, A. Valishev
Fermilab, Batavia, Illinois, USA
N. Kuklev, I. Lobach
University of Chicago, Chicago, Illinois, USA

High-resolution observations of single-particle dynamics have potential as a powerful tool in the diagnostics, tuning and design of storage rings. We are presenting the results of experiments with single electrons that were conducted at Fermilab’s IOTA ring to explore the feasibility of this approach. A set of sensitive, high-resolution digital cameras was used to detect the synchrotron radiation emitted by an electron, and the resulting images were used to reconstruct the time evolution of oscillation amplitudes in all three degrees of freedom. From the evolution of the oscillation amplitudes, we deduce transverse emittances, momentum spread, damping times, beam energy and estimated residual-gas density and composition. To our knowledge, this is the first time that the dynamics of a single particle in a storage ring has been tracked in all three dimensions. We discuss farther development of a single particle diagnostics that may allow reconstruction of its turn-by-turn coordinates over macroscopic periods of time facilitating ultra-precise lattice diagnostics and direct benchmarking of tracking codes.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB01

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paper received ※ 24 May 2021 paper accepted ※ 29 July 2021 issue date ※ 14 August 2021

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THXB02

Beam Arrival Stability at the European XFEL

FEL, laser, timing, feedback

3714

M.K. Czwalinna, J. Kral, B. Lautenschlager, J. Müller, H. Schlarb, S. Schulz, B. Steffen
DESY, Hamburg, Germany
R. Boll, H. Kirkwood, J. Koliyadu, R. Letrun, J. Liu, F. Pallas, D.E. Rivas, T. Sato
EuXFEL, Schenefeld, Germany

Free electron laser facilities, such as the European XFEL, make increasingly high demands on the longterm temporal stability and uniformity of the electron bunches, as pump-probe experiments meanwhile aim for timing stabilities of few femtoseconds residual jitter only. For a beam-based feedback control of the linear accelerator, electro-optical bunch arrival-time monitors are deployed, achieving a time resolution better than 3 fs. In a first attempt, we recently demonstrated a beam-based feedback system, reducing the arrival time jitter of the electron bunches to the 10 fs level with stable operation over hours. For pump-probe experiments it is crucial to equally verify this new level of precision in the FEL pulse arrival time with independent methods. In this work, we are discussing first results from examining the facility-wide temporal stability at the European XFEL, with attention to the contributions of various sub-systems and on the different time scales.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB02

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paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 29 August 2021

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THXB07

Coherent Radiation From Inverse Compton Scattering Sources by Means of Particle Trapping

laser, radiation, undulator, FEL

3732

A. Fallahi, L. Novotny
ETH Zurich, Photonics Laboratory, Zurich, Switzerland
N. Kuster
ETH, Zurich, Switzerland

Funding: This work is supported by the Swiss National Science Foundation (SNSF) under the Spark grant CRSK-2-190840.
Inverse Compton scattering (ICS) sources are one of the promising compact tools to generate short wavelength radiation from electron beams based on the relativistic Doppler effect. Nonetheless, these sources suffer from a few shortcomings such as incoherent radiation and low-efficiency in radiation generation. This contribution presents a novel scheme based on the scattering of an optical beam from a trapped electron beam inside an optical cavity. Inverse-Compton scattering off both free and trapped electrons are simulated using a full-wave solution of first-principle equations based on FDTD/PIC in the co-moving frame of electron beams. It is shown that the strong space-charge effect in low-energies is the main obstacle in acquiring coherent gain through the ICS mechanism. Subsequently, it is shown that by trapping the electron beam to the high-intensity spots, the space-charge effect is compensated, and additionally, the ultrahigh charge density enables high FEL-gain at trapping spots, thereby augmenting the coherence of the output radiation and concurrently increasing the source efficiency by three orders of magnitude.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB07

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paper received ※ 28 May 2021 paper accepted ※ 01 July 2021 issue date ※ 18 August 2021

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THXC06

Design and Measurements of an X-Band 8 MeV Standing-Wave Electron Accelerator

bunching, gun, experiment, linac

3744

F. Liu, H.B. Chen, J. Shi, C.-X. Tang, H. Zha
TUB, Beijing, People’s Republic of China

X-band low-energy electron linear accelerators are attractive to industrial and medical applications due to the compact size. In this work we present tests of an 8 MeV X-band accelerator for industrial use. It adopts the coaxial coupling standing wave structure working at 9300 MHz. The accelerator length is 50 cm including the cavity, thermal gun, and electron window. Dedicated bunching cells are designed to reduce the energy spread. In the high power tests, the accelerator was able to generate the electron beam with RMS energy spread less than 1% (beam energy: 8.1 MeV, peak current: 45 mA). Combining features of compact size and the low energy spread, this X-band accelerator design is valuable for various applications.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXC06

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 22 August 2021

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THPAB002

Lattice Design for BEPCII Upgrade

cavity, lattice, quadrupole, dynamic-aperture

3756

H. Geng, W.B. Liu, J. Qiu, J. Xing, C.H. Yu, Y. Zhang
IHEP, Beijing, People’s Republic of China

The Beijing Electron Positron Collider II (BEPCII) has achieved a series of achievements in high-energy physics study. Along with the deepening of the research, more important physics is expected in higher energy regions (>2.1 GeV). As the upper limit of BEPCII design energy is 2.1GeV, an urgent upgrade is required for BEPCII. To achieve a higher luminosity at higher energy, the number of RF cavities is expected to be doubled. In this paper, the lattice design for the upgrade of BEPCII is studied. The dynamic aperture tracking result shows that the lattice could meet the injection requirement of the BEPCII beam with a reasonable margin.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB002

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paper received ※ 14 May 2021 paper accepted ※ 17 June 2021 issue date ※ 01 September 2021

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THPAB003

Application of Generalized Gaussian Distribution in the Processing the Wire Scanner Data

emittance, hadron, linac, background

3759

H. Geng, C. Meng, F. Yan, Y. Zhang, Y.L. Zhao
IHEP, Beijing, People’s Republic of China

Wire scanners are widely used for measuring beam emittance in both electron and hadron accelerators. Gaussian fitting is the most commonly used method in processing the wire scanner data. But in hadron machines, beams are normally not gaussian distribution due to the action of nonlinear forces such as space charge effect. Under these circumstances, there would be big deviations if the wire scanner data was still fitted with gaussian distributions. This paper introduces generalized Gaussian distribution in the processing the wire scanner data measured in the ADS injector-I. The results using different fitting method will be compared.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB003

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paper received ※ 14 May 2021 paper accepted ※ 18 June 2021 issue date ※ 31 August 2021

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THPAB009

A Hard X-Ray Compton Source at CBETA

photon, laser, scattering, brilliance

3765

K.E. Deitrick, C. Franck, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J. Crone, H.L. Owen
UMAN, Manchester, United Kingdom
G.A. Krafft
JLab, Newport News, Virginia, USA
G.A. Krafft, B. Terzić
ODU, Norfolk, Virginia, USA
B.D. Muratori, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
B.D. Muratori, P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Inverse Compton scattering (ICS) holds the potential for future high flux, narrow bandwidth x-ray sources driven by high quality, high repetition rate electron beams. CBETA, the Cornell-BNL Energy recovery linac (ERL) Test Accelerator, is the world’s first superconducting radiofrequency multi-turn ERL, with a maximum energy of 150 MeV, capable of ICS production of x-rays above 400 keV. We present an update on the bypass design and anticipated parameters of a compact ICS source at CBETA. X-ray parameters from the CBETA ICS are compared to those of leading synchrotron radiation facilities, demonstrating that, above a few hundred keV, photon beams produced by ICS outperform those produced by undulators in term of flux and brilliance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB009

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paper received ※ 19 May 2021 paper accepted ※ 06 July 2021 issue date ※ 24 August 2021

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THPAB012

The Magnetic Compensation Scheme of the FCC-ee Detectors

solenoid, detector, emittance, quadrupole

3773

M. Koratzinos, K. Oide
CERN, Meyrin, Switzerland

A crucial part of the design of an FCC-ee detector is the minimisation of the disruption of the beam due to the presence of a large and powerful detector magnet. Indeed, the emittance blow-up of the few meters around the interaction point (IP) at lower energies is comparable to the emittance introduced by the rest of the 100 km ring. Vertical emittance is the single most important factor in achieving high performance (luminosity, in this case) in a modern e⁺ e⁻ storage ring such as the FCC-ee. The design adopted is the simplest possible arrangement that can nevertheless deliver high performance: two additional coils per IP side. The performance achieved is such that vertical emittance blow-up will not be a limiting performance factor even in the case of a ring with four experiments, and even in the most demanding energy regime, that of the Z running (about 45 GeV beam energy).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB012

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paper received ※ 10 May 2021 paper accepted ※ 28 July 2021 issue date ※ 17 August 2021

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THPAB015

Studies of the Imperfection in Crab Crossing Scheme for Electron-Ion Collider

cavity, solenoid, luminosity, proton

3784

Y. Hao, J.S. Berg, D. Holmes, Y. Luo, C. Montag
BNL, Upton, New York, USA
V.S. Morozov
JLab, Newport News, Virginia, USA
J. Qiang
LBNL, Berkeley, California, USA
D. Xu
FRIB, East Lansing, Michigan, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
Crab crossing scheme is the essential scheme that accommodates large crossing angle without loss of luminosity in the design of Electron-Ion collider (EIC). The ideal optics and phase advances of the crab cavity pair are set to create a local crabbing bump in the interaction region (IR). However, there are always small errors in the actual lattice of IR. In this article, we will present the simulation and analytical studies on the imperfections in the crab crossing scheme in the EIC design. The tolerance of the imperfection and the possible remedies can be concluded from these studies.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB015

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paper received ※ 17 May 2021 paper accepted ※ 16 July 2021 issue date ※ 30 August 2021

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THPAB021

Status of VEPP-5 Injection Complex

injection, positron, damping, linac

3796

F.A. Emanov, A.V. Andrianov, K.V. Astrelina, V.V. Balakin, A.M. Barnyakov, A.M. Batrakov, O.V. Belikov, D.E. Berkaev, Y.M. Boimelshtain, D. Bolkhovityanov, A. Butakov, A.R. Frolov, G.V. Karpov, A.S. Kasaev, A.A. Kondakov, N.Kh. Kot, E.S. Kotov, G.Y. Kurkin, R.M. Lapik, N.N. Lebedev, A.E. Levichev, Yu.I. Maltseva, P.V. Martyshkin, S.V. Motygin, A.A. Murasev, V. Muslivets, D.A. Nikiforov, A.V. Pavlenko, A.M. Pilan, Yu.A. Rogovsky, S.L. Samoylov, A.G. Tribendis, S. Vasiliev, V.D. Yudin
BINP SB RAS, Novosibirsk, Russia

VEPP-5 injection complex is being put into operation as beam source of VEPP-2000 and VEPP-4 colliders at the end of 2016. Since then injection complex demonstrated maximum positron storage rate 1.7·10¹⁰ e+/s and stable operation at the energy of 430 MeV. Latest operation results and prospects are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB021

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paper received ※ 20 May 2021 paper accepted ※ 27 July 2021 issue date ※ 23 August 2021

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THPAB022

Possibilities for Upgrading to Polarized SuperKEKB

polarization, experiment, lattice, cathode

3799

Z.J. Liptak, M. Kuriki
HU/AdSM, Higashi-Hiroshima, Japan
J.M. Roney
Victoria University, Victoria, B.C., Canada

The SuperKEKB accelerator is currently in operation in Tsukuba, Japan, with a planned long shutdown in 2026. Among the possible upgrades being considered during this period is the change to a polarized electron beam in the High Energy Ring. Such a change would require modifications in the source generation and transport, geometrical and lattice variations to provide spin rotation, and polarimetry. A Polarized SuperKEKB Working Group has been formed from members of the Belle II experiment and the SuperKEKB accelerator team to investigate the possibilities and challenges of these modifications. This talk lays out the goals of the proposed upgrade, considers the necessary changes to the existing accelerator and their feasibility and lays out the physics motivation behind such an effort.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB022

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paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 15 August 2021

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THPAB025

A Proposed Beam-Beam Test Facility COMBINE

collider, experiment, linac, beam-beam-effects

3802

E.A. Nissen, G.A. Krafft
JLab, Newport News, Virginia, USA
J.R. Delayen
ODU, Norfolk, Virginia, USA

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, license to publish or reproduce this manuscript.
The COmpact Machine for Beam-beam Interactions in Non-Equilibrium systems (COMBINE) is a proposed, dedicated, beam-beam test facility. The base design would make use of a pair of identical octagonal rings (2.5 meters per side) one rotated 180 degrees from the other, meeting at their common interaction point. These would be fed by an electron gun producing up to 125 keV electrons. The low energy will allow for beam-beam tune shifts commensurate with existing colliders, some linac-ring type systems, and will also allow for an exploration of the predicted effects of gear-changing, which would be performed using a variable pathlength scheme. The low energy, and small size will allow for cost effective research, simulation code benchmarking, as well as training opportunities for students.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB025

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paper received ※ 20 May 2021 paper accepted ※ 31 August 2021 issue date ※ 01 September 2021

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THPAB026

Final Booster Complex Design for the Jefferson Lab Electron Ion Collider

collider, booster, solenoid, dipole

3805

E.A. Nissen
JLab, Newport News, Virginia, USA

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. retains a license to publish or reproduce this manuscript for U.S. Government purposes.
In this work we show the final iteration of the design for the booster complex of the Jefferson Lab EIC, which would have brought the ions from an energy (proton) of 150 MeV up to 12.1 GeV. This complex would have consisted of two figure-8 rings. The Low Energy Booster (LEB) which would have accelerated its protons from 150 MeV to 8 GeV, and has had its lattice tweaked to increase the effectiveness of chromaticity cancellations. The High Energy Booster (HEB) would have brought the 8 GeV protons up to 12.1 GeV. The HEB would in the tunnel that was designed for the collider rings, sitting on top of them. It has had a bypass around the interaction region added, as well as a cooling solenoid installed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB026

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paper received ※ 19 May 2021 paper accepted ※ 22 June 2021 issue date ※ 31 August 2021

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THPAB028

Beam-Beam Related Design Parameter Optimization for the Electron-Ion Collider

proton, simulation, betatron, luminosity

3808

Y. Luo, J.S. Berg, M. Blaskiewicz, W. Fischer, X. Gu, H. Lovelace III, C. Montag, R.B. Palmer, S. Peggs, V. Ptitsyn, F.J. Willeke
BNL, Upton, New York, USA
Y. Hao, D. Xu
FRIB, East Lansing, Michigan, USA
H. Huang
ODU, Norfolk, Virginia, USA
E.A. Nissen, T. Satogata
JLab, Newport News, Virginia, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The design luminosity goal for the Electron-Ion Collider (EIC) is 1e34 cm^-2s⁻¹. To achieve such a high luminosity, the EIC design adopts high bunch intensities, flat beams at the interaction point (IP) with a small vertical β^*-function, and a high collision frequency, together with crab cavities to compensate the geometrical luminosity loss due to the large crossing angle of 25mrad. In this article, we present our strategies and approaches to obtain the design luminosity by optimizing some key beam-beam related design parameters. Through our extensive strong-strong and weak-strong beam-beam simulations, we found that beam flatness, electron and proton beam size matching at the IP, electron and proton working points, and synchro-betatron resonances arising from the crossing angle collision play a crucial role in proton beam size growth and luminosity degradation. After optimizing those parameters, we found a set of beam-beam related design parameters to reach the design luminosity with an acceptable beam-beam performance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB028

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paper received ※ 17 May 2021 paper accepted ※ 28 July 2021 issue date ※ 30 August 2021

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THPAB029

Dynamic Aperture Evaluation for the Hadron Storage Ring in the Electron-Ion Collider

dynamic-aperture, cavity, proton, dipole

3812

Y. Luo, J.S. Berg, M. Blaskiewicz, W. Fischer, X. Gu, H. Lovelace III, C. Montag, R.B. Palmer, S. Peggs, V. Ptitsyn, F.J. Willeke, H. Witte
BNL, Upton, New York, USA
Y. Hao, D. Xu
FRIB, East Lansing, Michigan, USA
H. Huang
ODU, Norfolk, Virginia, USA
V.S. Morozov, E.A. Nissen, T. Satogata
JLab, Newport News, Virginia, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The Electron-Ion Collider (EIC) is aiming at a design luminosity of 1e34 cm^-2s⁻¹. To maintain such a high luminosity, both beams in the EIC need an acceptable beam lifetime in the presence of the beam-beam interaction. For this purpose, we carried out weak-strong element-by-element particle tracking to evaluate the long-term dynamic aperture for the hadron ring lattice design. We improved our simulation code SimTrack to treat some new lattice design features, such as radially offset on-momentum orbits, coordinate transformations in the interaction region, etc. In this article, we will present the preliminary dynamic aperture calculation results with β^*- function scan, radial orbit shift, crossing angle collision, and magnetic field errors.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB029

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paper received ※ 17 May 2021 paper accepted ※ 31 August 2021 issue date ※ 01 September 2021

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THPAB035

Study of the Tolerances for Superconducting Undulators at the European XFEL

undulator, FEL, simulation, photon

3819

B. Marchetti, S. Casalbuoni, V. Grattoni, S. Serkez
EuXFEL, Schenefeld, Germany

European XFEL is investing in the development of superconducting undulators (SCUs) for future upgrade of its beamlines SCUs made of NbTi, working at 2K, with a period length of 15 mm and a vacuum gap of 5 mm allow covering a range between 54 keV and 100 keV for 17.5 GeV electron energy. The effect of mechanical errors in the distribution of K along the undulators is more relevant for working points at lower photon energy, which are obtained using a higher magnetic field in the undulator. In this article we investigate the effect of error distribution in the K-parameter for a working point at 50keV photon energy obtained injecting an electron beam with 16.5 GeV energy from the XFEL linear accelerator in a undulator line composed by SCUs with 1.58 T peak magnetic field.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB035

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paper received ※ 12 May 2021 paper accepted ※ 05 July 2021 issue date ※ 19 August 2021

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THPAB036

Superconducting Phase Shifter Design for the Afterburner at the European XFEL

FEL, undulator, photon, operation

3823

V. Grattoni, J.E. Baader, S. Casalbuoni
EuXFEL, Schenefeld, Germany

At the European XFEL, a superconducting afterburner is under design for the SASE2 hard X-ray beamline. It will consist of 5 undulator modules. One module corresponds to two superconducting undulator (SCU) coils of 2 m length plus one phase shifter. Such an afterburner will enable photon energies above 30 keV. Superconducting (SC) phase shifters will be installed in each undulator module to keep the correct phase delay between the electron beam and photon beam. In this contribution, we present the required SC phase shifter parameters to enable operation in the electron beam energy range 11.5-17.5 GeV. We also analyze different magnetic designs satisfying the calculated specifications.

Poster THPAB036 [0.991 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB036

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paper received ※ 18 May 2021 paper accepted ※ 06 July 2021 issue date ※ 20 August 2021

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THPAB040

A Phase Shifter for Inline Undulators at the Advanced Photon Source Upgrade Project

undulator, photon, permanent-magnet, radiation

3830

E.R. Moog, R.J. Dejus, A.T. Donnelly, Y. Piao, M.F. Qian, I. Vasserman, J.Z. Xu
ANL, Lemont, Illinois, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, under contract number DE AC02-06CH11357.
Several undulator lines for the Advanced Photon Source Upgrade (APS-U) will consist of two inline undulators. In order to keep the undulators operating with optimal phasing over the full range of gaps, a phase shifter will be included between the undulators. A design has been developed for a phase shifter that will serve for a variety of undulator period lengths and gap ranges. The permanent-magnet phase shifter will use SmCo magnets to reduce the risk of radiation-induced demagnetization. The available space between the undulators is tight, so magnetic shields are placed between the undulators, the phase shifter, and the corrector magnet that is also located in the inter-undulator space. While these shields guard against magnetic cross-talk between the devices as the undulator and phase shifter gaps change, they do have an effect on the end fields of the devices. These end-field effects are examined and relevant tolerances are set and presented.

Poster THPAB040 [0.429 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB040

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paper received ※ 23 May 2021 paper accepted ※ 21 June 2021 issue date ※ 12 August 2021

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THPAB043

A Superconducting Undulator for CompactLight: Resistive Wall Wakefield Analysis

undulator, wakefield, impedance, FEL

3841

K.B. Marinov
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The CompactLight project is an advanced X-ray FEL light source, with high-frequency, high-gradient linacs and compact undulators. Lower electron energies give higher energy efficiency and a smaller environmental footprint. The extremely short bunch lengths (few fs) and narrow undulator gaps (4 mm) drastically increase the impact of resistive wall wakefields on the lasing process. The longitudinal resistive wall wakefield impedance is calculated in the framework of the surface impedance approach, in accordance with anomalous skin effect (ASE) theory. The dependence of the electron energy loss factor and the correlated energy spread of the bunch on the residual resistivity ratio (RRR) for both copper and aluminum is much higher for long (100 fs) than for ultra-short (6 fs) bunches. This is due to a known property of the longitudinal wakefield impedance - the field acting on a single particle traversing a resistive vessel does not depend on the conductivity of the vessel. The wakefields generated by the ultra-short bunch are already close to that of a single-particle regime and this leads to interesting consequences which are discussed in the present work.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB043

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 13 August 2021

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THPAB045

Design of a Short Period Helical Superconducting Undulator

undulator, FEL, photon, simulation

3844

A.G. Hinton
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
J. Boehm, L. Cooper, B. Green, T. Hayler, P. Jeffery, C.P. Macwaters
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
S. Milward
DLS, Oxfordshire, United Kingdom
B.J.A. Shepherd
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
B.J.A. Shepherd
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Superconducting technology provides the possibility to develop short period, small bore undulators that can generate much larger magnetic fields than alternative technologies. This may allow an XFEL with optimised superconducting undulators to cover a broader range of wavelengths than traditional undulators. At STFC, we have undertaken work to design and build a prototype helical superconducting undulator (HSCU) module with parameters suitable for use on a future XFEL facility. This work includes the design of a full 2 m long undulator module, including an undulator with 13 mm period and 5 mm inner winding diameter, the supporting cryogenic and vacuum systems required for operation, and quadrupoles, phase shifters and correction magnets for use between undulator sections. We present here the magnetic and mechanical design of the HSCU. The choice of undulator parameters and their influence on the design is discussed. A turnaround scheme to allow continuous winding of the undulator without the need for superconducting joints is also presented. Techniques for winding the undulator are currently being investigated and a short prototype will soon be wound and tested.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB045

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paper received ※ 17 May 2021 paper accepted ※ 18 June 2021 issue date ※ 12 August 2021

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THPAB051

Vertical Septum Magnet Design for the APS Upgrade

septum, simulation, magnet-design, photon

3862

M. Abliz, M. Borland, H. Cease, G. Decker, A.K. Jain, M.S. Jaski, M. Kasa, J.S. Kerby, U. Wienands, A. Xiao
ANL, Lemont, Illinois, USA
J.W. Amann
SLAC, Menlo Park, California, USA
D.J. Harding
Fermilab, Batavia, Illinois, USA

The vertical injection scheme proposed for the APS Upgrade (APS-U) Project requires a challenging septum magnet that must meet stringent beam physics, magnetic field leakage, and vacuum requirements. The current iteration of this magnet design includes an enlarged stored-beam chamber aperture of 9 mm x 12 mm and a reduction of the septum thickness to 1.5 mm. The enlarged aperture accommodates a non-evaporable getter (NEG)-coated stored beam chamber to better achieve the required vacuum. A prototype septum magnet has been built and measurements confirm the cancellation of a peak leakage field even though the value is six times larger than the design. The leakage field measured at the upstream (US) end cancels the downstream (DS) end as was expected by design. The measured and simulated leakage field and the stored beam trajectories are reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB051

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paper received ※ 14 May 2021 paper accepted ※ 18 August 2021 issue date ※ 01 September 2021

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THPAB056

Conceptual Design of a Multiple Period Staggered Undulator

undulator, solenoid, radiation, synchrotron

3879

I. Asparuhov, J. Chavanne, G. Le Bec
ESRF, Grenoble, France

In staggered undulators, a ferromagnetic pole structure paired to a solenoid generates a sinusoidal field. Interest of such insertion devices has been studied for application to FEL systems in the end of the previous century. However, the concept has never been used in synchrotron radiation sources due to the undesirable magnetic effect of the solenoid on electron beam parameters in storage rings. Advent of fourth-generation low emittance light sources is foreseen to change this situation. Indeed, consequent electron beam transverse size and divergence reduction for such new storage rings give promise for a beam less sensitive to the presence of a longitudinal solenoidal field. Relating to this, a staggered concept can be an adequate design choice for short-period undulators producing high-energy photon flux. Such undulators would have a low K value a priori limiting their photon energy tunability. Considering integration of separate magnetic arrays of distinct periods in a solenoid to compose a global assembly can help suppress this possible drawback. Magnetic design and radiative performance of such an insertion device are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB056

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paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 13 August 2021

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THPAB060

Dispersion Controlled Temporal Shaping of Photoinjector Laser Pulses for Electron Emittance Reduction in X-Ray Free Electron Lasers

laser, emittance, simulation, bunching

3886

R.A. Lemons, S. Carbajo, J.P. Duris, A. Marinelli, N.R. Neveu
SLAC, Menlo Park, California, USA
C.G. Durfee
Colorado School of Mines, Golden, USA

Funding: Office of Science DE-SC0014664
Temporal shaping of photocathode excitation laser pulses is a long-sought-after challenge to tailor the phase-space of electrons. The temporal profile of lasers, typically up-converted from infrared to ultraviolet, have significant impact on the distribution and time-evolution of the collective electron bunches. Towards this end, we present a method combining efficient nonlinear up-conversion with simultaneous and adaptable temporal profile shaping through dispersion-controlled sum-frequency generation* resulting in temporal profiles with sharp rise-fall times and flat top profiles. Using the LCLS-II photoinjector as a case study, we demonstrate a reduction in generated electron transverse emittance by upwards of 30% over conventionally implemented temporal profiles. Additionally, we discuss the ongoing experimental implementation of this method and preliminary results.
* R. Lemons, et al. arXiv:2012.00957 [physics.optics] (2020)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB060

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paper received ※ 17 May 2021 paper accepted ※ 08 July 2021 issue date ※ 15 August 2021

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THPAB061

Pulse-Burst CO₂ Laser for High-Brilliance Compton Light Sources

laser, photon, synchrotron, brightness

3890

I. Pogorelsky, M.N. Polyanskiy, T.V. Shaftan
BNL, Upton, New York, USA

Funding: U.S. Department of Energy under contract DE-SC0012704
We propose a novel architecture for a mid-IR, high-repetition, kilowatt-class, CO₂ laser system operating in a pulse-burst regime and its implementation in In-verse Compton Scattering (ICS) sources of x-ray and gamma-ray radiation. Different types of particle accelerators are considered for conversion to such ICS sources, including energy recovery linacs and synchrotron storage rings. The expected ICS performance parameters are compared with earlier proposals where CBETA and DAΦNE accelerators have been paired with near-IR, mode-locked solid-state lasers operating at a multi-megahertz repetition rate. A considerable increase in acting laser energy attainable in our CO₂ laser-based scheme, combined with an order of magnitude higher number of laser photons per Joule of energy allows maintaining a similarly high average flux of produced hard x-rays while the peak flux and brilliance will be raised by three to four orders of magnitude compared to aforementioned schemes based on near-IR lasers.

Poster THPAB061 [1.082 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB061

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paper received ※ 12 May 2021 paper accepted ※ 21 June 2021 issue date ※ 17 August 2021

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THPAB064

LUMOS: A Visible Diagnostic Beamline for the Solaris Storage Ring

diagnostics, emittance, synchrotron, storage-ring

3901

R. Panaś, A. Curcio, A.I. Wawrzyniak
NSRC SOLARIS, Kraków, Poland

LUMOS is a diagnostic beamline which operates in the visible region. It was installed in the Solaris storage ring during summer 2019. The first light was observed at the beginning of December 2019. During 2020 the beamline was commissioned and equipped with a streak camera setup. Currently, LUMOS allows to analyze far-field and near field images of synchrotron light for transverse beam profile measurements. Moreover, using the streak camera setup, it is also possible to investigate the bunch length, the filling pattern and the longitudinal beam profile changes with respect to the different condition (ramping, 3rd harmonic cavities tuning, etc.). During the presentation the optical setup to be presented along with the measurements conducted with it.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB064

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paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 01 September 2021

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THPAB066

Ground Diffusion Measurement and Its Effect on APS-U Orbit Stability

ground-motion, alignment, simulation, quadrupole

3907

V. Sajaev
ANL, Lemont, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Spatial and temporal ground diffusion can be approximately described by the ATL law*,**. Ground diffusion can have an important effect on the long-term stability of the accelerator alignment. To estimate the possible consequences of the ground diffusion on the APS Upgrade performance, the ground diffusion constant of the existing APS tunnel was measured using historical data of the orbit correction effort and then used to estimate the ground diffusion effect on the orbit stability of the APS Upgrade. In this paper, we will describe the diffusion constant measurement and present the estimations of the expected APS-U alignment and orbit stability.
* B.A. Baklakov et. al., Technical Physics, v.38(10), pp.894-898(1993)
** V. Shiltsev, Physical Review Letters, 104(23), p.238501 (2010).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB066

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paper received ※ 12 May 2021 paper accepted ※ 13 July 2021 issue date ※ 27 August 2021

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THPAB069

Design Concepts for a High-Gradient C-Band Linac

cavity, FEL, linac, accelerating-gradient

3919

T.B. Bolin, S.I. Sosa Guitron
UNM-ECE, Albuquerque, USA
S. Biedron
UNM-ME, Albuquerque, New Mexico, USA
J.R. Cary
Tech-X, Boulder, Colorado, USA
M. Dal Forno
SLAC, Menlo Park, California, USA

Funding: This work was performed under Contract No. 89233218CNA000001, supported by the U.S. DOE’s National Nuclear Security Administration, for the operation of Los Alamos National Laboratory (LANL).
During the last decade, the production of soft to hard x-rays (up to 25 keV) at XFEL facilities has enabled new developments in a broad range of disciplines. One caveat is that these instruments can require a large amount of real estate. For example, the XFEL driver is typically an electron beam linear accelerator (LINAC) and the need for higher electron beam energies capable of generating higher energy X-rays can require longer linacs; costs quickly become prohibitive, requiring state of art methods. One cost-saving measure is to produce a high accelerating gradient while reducing cavity size. Compact accelerating structures are also high-frequency. Here, we describe design concepts for a high-gradient, cryo-cooled LINAC for XFEL facilities in the C-band regime (~4-8 GHz). We are also exploring C-band for different applications including drivers for security applications. We investigate 2 different traveling wave (TW) geometries optimized for high-gradient operation as modeled with VSim software.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB069

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paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 13 August 2021

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THPAB079

Design Study on Beam Size Measurement System Using SR Interferometry for Low Beam Current

synchrotron, radiation, synchrotron-radiation, storage-ring

3949

W. Li, P. Liu, Y.K. Wu, J. Yan
FEL/Duke University, Durham, North Carolina, USA

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
To enable reliable measurements of the small vertical size of the electron beam in the Duke storage ring, a measurement system is being developed using synchrotron radiation interferometry (SRI). By relating the transverse beam size to the transverse spatial coherence of synchrotron radiation from a dipole magnet according to the Van Cittert-Zernike theorem, the transverse beam size can be inferred by recording and fitting the interference fringe as a function of the characteristic features of the interference filter used. In this paper, we describe the preliminary design of such a measurement system and present design considerations to make it possible to measure the electron beam vertical size for a wide range of electron beam energies and currents. Especially this system will be optimized to measure the electron beam size for low current operation down to 50 to 100~μA. This beam size measurement system will be used as an important beam diagnostic for the intrabeam scattering research at the Duke storage ring.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB079

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paper received ※ 27 May 2021 paper accepted ※ 12 July 2021 issue date ※ 14 August 2021

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THPAB080

Correcting the Magnetic Field Offsets Inside the Undulators of the EuXFEL Using the K-Monochromator

undulator, FEL, radiation, synchrotron

3953

F. Brinker
DESY, Hamburg, Germany
S. Casalbuoni, W. Freund
EuXFEL, Schenefeld, Germany

Hard X-ray free-electron lasers (XFELs) generate intense coherent X-ray beams by passing electrons through undulators, i.e. very long periodic magnet structures, which extend over hundreds of meters. A crucial condition for the lasing process is the spatial overlap of the electrons with the electromagnetic field. Well-established electron beam-based procedures allow finding a straight trajectory for the electrons defined by the beam position monitors (BPM) between the undulators. A bending of the trajectory in between the BPMs cannot be seen by these methods. A general field offset inside the undulators has the effect that the synchrotron radiation is emitted at a different angle at the beginning and the end of the undulator which can result in a degradation of the FEL-gain especially for very short wavelengths. We report on how the spectral and spatial characteristics of the monochromatized radiation of a single undulator can be used to minimize the field offset in situ with the help of correction coils.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB080

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paper received ※ 19 May 2021 paper accepted ※ 25 June 2021 issue date ※ 23 August 2021

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THPAB097

Towards Arbitrary Pulse Shapes in the Terahertz Domain

laser, radiation, storage-ring, controls

3977

C. Mai, B. Büsing, A. Held, S. Khan, D. Krieg
DELTA, Dortmund, Germany

Funding: Work supported by the BMBF (05K19PEC).
The TU Dortmund University operates the 1.5-GeV electron storage ring DELTA as a synchrotron light source in user operation and for accererator physics research. At a dedicated beamline, experiments with (sub-)THz radiation are carried out. Here, an interaction of short laser pulses with electron bunches is used to modulate the electron energy which causes the formation of a dip in the longitudinal electron density, giving rise to the coherent emission of radiation between 75 GHz and 6 THz. The standard mode of operation is the generation of broadband radiation. However, more sophisticated energy modulation schemes were implemented using a liquid-crystal phase modulator. Here, a modulation of the spectral phase of the laser is used to control the spectral shape of the THz pulses. The resulting THz spectra have a relative bandwidth of about 2 %. Measurement results from the different THz generation schemes are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB097

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paper received ※ 18 May 2021 paper accepted ※ 12 July 2021 issue date ※ 19 August 2021

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THPAB119

Many-Objective Beam Dynamics Optimization for High-Repetition-Rate XFEL Photoinjector

emittance, FEL, gun, laser

3991

Z.H. Zhu, J.W. Yan
SINAP, Shanghai, People’s Republic of China
D. Gu
SARI-CAS, Pudong, Shanghai, People’s Republic of China
Q. Gu
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China

SHINE, as the first hard x-ray free-electron-laser (FEL) facility in China, is design to provide high-brightness FEL lasing under high-repetition-rate operation. In order to drive x-ray FEL pulses with high qualities, the photoinjector section is deployed to provide the specified electron beam with low transverse emittance and high brightness. Normally the multi-objective optimization algorithm is employed in the injector beam dynamics design. In this paper, the many-objective optimization algorithm NSGA-III is introduced to the injector physical design for optimizing the 4 detailed beam quality properties using 17 variables for the first time. The results of the optimization are presented and the correlations are analyzed. This approach can provide guidance for further physical research as well as improve the beam dynamics optimization efficiency.

Poster THPAB119 [0.936 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB119

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paper received ※ 17 May 2021 paper accepted ※ 07 July 2021 issue date ※ 30 August 2021

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THPAB120

Beam on Demand for High-Repetition-Rate X-Ray Free-Electron Lasers

laser, FEL, SRF, linac

3995

Z. Zhang, Y. Ding, Z. Huang
SLAC, Menlo Park, California, USA

High-repetition-rate (HRR) free-electron lasers (FELs) with multiple undulator beamlines will advance the frontiers of X-ray science significantly from the remarkable success of existing X-ray FEL facilities. The wide-ranging requirements for the photon properties from multiple beamlines are extremely challenging to satisfy by the same electron beam from a single superconducting radio-frequency (SRF) accelerator. To realize the full potential of an HRR FEL facility, a new emerging concept of "beam on demand" is proposed here. The concept is based on advanced beam dynamics and radio-frequency (RF) techniques to provide beam properties tailored to each undulator line at the desired repetition rate. The beam properties that will be pursued in this proposal include, but are not limited to, beam energy, bunch charge, bunch length, beam current, and its profile. The realization of "beam on demand" will allow optimization of photon properties of individual beamlines to maximize their performance and drastically improve the multiplexing capabilities of Linac Coherent Light Source II and its high-energy upgrade.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB120

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paper received ※ 17 May 2021 paper accepted ※ 23 July 2021 issue date ※ 26 August 2021

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THPAB126

Operational Experience and Characterization of a Superconducting Transverse Gradient Undulator for Compact Laser Wakefield Accelerator-Driven FEL

laser, undulator, FEL, experiment

4009

K. Damminsek, A. Bernhard, J. Gethmann, A.W. Grau, A.-S. Müller, Y. Nie, M.S. Ning, S.C. Richter, R. Rossmanith
KIT, Karlsruhe, Germany

A 40-period superconducting transverse gradient undulator (TGU) has been designed and fabricated at Karlsruhe Institute of Technology (KIT). Combining a TGU with a Laser Wakefield Accelerator (LWFA) is a potential key for realizing an extremely compact Free Electron Laser (FEL) radiation source. The TGU scheme is a viable option to compensate the challenging properties of the LWFA electron beam in terms of beam divergence and energy spread. In this contribution, we report on the operational experience of this TGU inside its own cryostat and show the current status of the TGU and the further plan for experiments. This work is supported by the BMBF project 05K19VKA PlasmaFEL (Federal Ministry of Education and Research).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB126

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paper received ※ 19 May 2021 paper accepted ※ 25 August 2021 issue date ※ 28 August 2021

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THPAB129

Beam Dynamics Simulations in a High-Gradient X-Band Photoinjector

gun, emittance, cathode, linac

4013

W.H. Tan, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
G. Chen, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
G. Chen
IIT, Chicago, Illinois, USA
G. Ha, C.-J. Jing
ANL, Lemont, Illinois, USA
C.-J. Jing
Euclid Beamlabs, Bolingbrook, USA

A high-gradient X-band (11.7-GHz) photoinjector was recently developed by Euclid Techlabs and is in its commissioning phase at the Argonne Wakefield Accelerator (AWA). This contribution discuss the beam-dynamics modeling of the photoinjector system comprising an RF gun and linac section. We especially discuss beam-dynamics optimization of setup for an integrated proof-of-principle experiments. We also discuss the use of such a photoinjector as a witness-bunch source for a future high-gradient collinear-wakefield accelerator experiments at the AWA.
* S. V. Kuzikov, et al. these proceedings.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB129

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paper received ※ 20 May 2021 paper accepted ※ 14 July 2021 issue date ※ 31 August 2021

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THPAB131

Spatio-Temporal Measurements of THz Pulses

polarization, radiation, laser, FEM

4021

G.A. Hine
ORNL, Oak Ridge, Tennessee, USA

Funding: This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory under Contract No. DEAC05-00OR22725.
The 3D characterization of single-cycle Terahertz (THz) pulses in its transverse and temporal dimensions is presented. The high fields and short wavelengths of THz pulses make them an intriguing prospect for novel accelerator technologies. Effective application for free-space THz pulses requires high beam quality and concomitant measuring techniques. The combination of conventional electro-optic sampling to measure the temporal profile and detectors like microbolometer focal plane arrays to measure the transverse profile does not capture the correlations that can arise in single-cycle THz pulses. To capture these correlations, a modified version electro-optic sampling using a CCD is implemented. THz pulses generated by optical rectification in organic crystals are measured using this technique and their spatiotemporal correlations characterized.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB131

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paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 01 September 2021

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THPAB134

Development and Analysis of Software for the Numerical Simulation of Field Emission Electron Sources

simulation, injection, software, electronics

4024

N.S. Kakorin, K.A. Nikiforov
Saint Petersburg State University, Saint Petersburg, Russia
N.V. Egorov
St. Petersburg State University, St. Petersburg, Russia

Funding: The reported study was funded by RFBR, project number 20-07-01086.
The open-source DAISI C++ package (Design of Accelerators, optImizations and SImulations) is extended with the ability to simulate the operation of electron sources in the field emission mode, with the user-defined initial distribution of emitted electrons velocities, as a model parameter, and with the automated calculation of current-voltage characteristics. Particles injection scheme is suggested. Computational experiments are performed for silicon carbide field emission electron source nanostructure with bimodal energy spectrum, revealed from experimental study, and comparative analysis with Maxwell distribution is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB134

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paper received ※ 20 May 2021 paper accepted ※ 27 July 2021 issue date ※ 26 August 2021

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THPAB142

Optical and Surface Characterization of Alkali-Antimonide Photocathodes

cathode, photon, emittance, vacuum

4037

P. Saha, O. Chubenko, G.S. Gevorkyan, A.H. Kachwala, S.S. Karkare, C.J. Knill
Arizona State University, Tempe, USA
E.J. Montgomery, S. Poddar
Euclid Beamlabs, Bolingbrook, USA
H.A. Padmore
LBNL, Berkeley, California, USA

Alkali-antimonides, characterized by high quantum efficiency and low mean transverse energy in visible light, are excellent electron sources to drive x-ray free electron lasers, electron cooling and ultrafast electron diffraction applications etc. Existing studies of alkali-antimonides have focused on quantum efficiency and emittance, but information is lacking on the fundamental aspects of the electronic structure, such as the energy gap of the semiconductor and the density of defects as well as the overall nano-structure of the materials. We are, therefore, conducting photoconductivity measurements to measure fundamental semiconductor properties as well as using atomic force microscope (AFM) and kelvin probe force microscope (KPFM) to measure the nanostructure variations in structure and surface potential.

Poster THPAB142 [1.211 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB142

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paper received ※ 16 May 2021 paper accepted ※ 14 July 2021 issue date ※ 15 August 2021

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THPAB146

Preliminary Study of Femtosecond Electron Source Based on THz Acceleration and Field Emission

cavity, FEM, cathode, gun

4048

Zh.X. Tang, G. Feng, B.F. Wei
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by National Natural Science Foundation of China (Grant No. U1832135 and 11805199) and Fundamental Research Funds for the Central Universities (Grant No. WK2310000072)
In this paper, we propose a novel electron gun based on THz acceleration and field emission to generate femtosecond electron bunches. The field emission cathode is placed in the center of the cavity, and the standing wave field is established in the cavity to achieve the field emission conditions and extract the electron beam. Because the period of THz band is about picosecond, the femtosecond bunch is formed by controlling the field strength and the pulse width of the extracted beam. We analyzed the feasibility of field emission and the length of the pulse beam. The surface peak field intensity of the structure of the cavity with different emitters are simulated by CST software.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB146

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paper received ※ 09 May 2021 paper accepted ※ 18 August 2021 issue date ※ 02 September 2021

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THPAB151

The Advantage of Cold Electron Source in Electron Diffraction

simulation, experiment, FEL, ion-source

4053

J. Liu, H. Luo
SWUST, Mianyang City, Sichuan Province, People’s Republic of China

In this paper, a model for discussing the influence of transverse coherence of electron beams on electron diffraction is established. With reference to Fedele’s thermal-wave model, the transverse coherence length is introduced into this model to characterize the transverse coherence of electron beams. The simulation results show that the transverse coherence of electron beams has a significant influence on electron diffraction, and the cold electron source with high transverse coherence has an obvious advantage in electron diffraction.

Poster THPAB151 [0.647 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB151

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paper received ※ 15 May 2021 paper accepted ※ 21 June 2021 issue date ※ 20 August 2021

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THPAB155

Strong Quadrupole Wakefield Based Focusing in Dielectric Wakefield Accelerators

wakefield, controls, focusing, simulation

4059

W.J. Lynn, G. Andonian, N. Majernik, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

Funding: Grant number: DOE HEP Grants DE-SC0017648, DE-SC0009914, and National Science Foundation Grant No. PHY-1549132.
We propose here to exploit the quadrupole wakefields in an alternating symmetry slab-based dielectric wakefield accelerator (DWA) to produce second-order focusing. The resultant focusing is found to be strongly dependent on longitudinal position in the bunch. We analyze this effect with analytical estimates and electromagnetic PIC simulations. We examine the use of this scenario to induce beam stability in very high gradient DWA, with positive implications for applications in linear colliders and free-electron lasers.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB155

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paper received ※ 20 May 2021 paper accepted ※ 27 July 2021 issue date ※ 15 August 2021

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THPAB156

Built-in Thermionic Electron Source for an SRF Linacs

cathode, cavity, gun, SRF

4062

I.V. Gonin, S. Kazakov, R.D. Kephart, T.N. Khabiboulline, T.H. Nicol, N. Solyak, J.C.T. Thangaraj, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

The design of a thermionic electron source connected directly to a superconducting cavity, the key part of an SRF gun, is described. The results of beam dynamics optimization are presented which allow lack of beam current intercepting in the superconducting cavity. The electron source concept is presented including the cathode-grid assembly, thermal insulation of the cathode from the cavity, and the gun resonator design. The cavity thermal load caused by the gun is analyzed including the static heat load, black body radiation, backward electron heating, etc.

Poster THPAB156 [0.670 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB156

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paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 28 August 2021

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THPAB157

Studying X-Ray Spectra of the SIS18 Electrostatic Septa to Measure Their Electric Field

extraction, septum, injection, detector

4065

B. Gålander, E. Kozlova, D. Ondreka, A. Sokolov, P.J. Spiller, J. Stadlmann
GSI, Darmstadt, Germany

The synchrotron SIS18 at GSI uses resonant extraction for slow beam extraction on the order of seconds. For some time, there has been an unexplained discrepancy of the slow extraction with a lower extraction efficiency than expected at the highest beam energies. Recent machine studies have indicated that the deflection by the electrostatic septum might be less than the nominal 2.5 mrad, leading to increased losses at the magnetic septum. In this paper, we pursue an idea to directly measure the voltage of the electrode gap by utilizing the fact that dark current electrons accelerated in the gap of the electrostatic extraction septum generate Bremsstrahlung X-rays when hitting the anode. The high-energy cut-off of the X-ray spectra then corresponds to the voltage of the electrode gap. Measurements of the X-ray spectra at the extraction septum of SIS18 have been performed using a solid-state CdTe detector. This technique provides an in-situ measurement of the voltage applied to the electrostatic extraction channel and has proven to be a useful diagnostics tool.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB157

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paper received ※ 19 May 2021 paper accepted ※ 24 August 2021 issue date ※ 02 September 2021

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THPAB171

mm-Wave Linac Design for Next Generation VHEE Cancer Therapy Systems

linac, simulation, impedance, coupling

4090

E.J.C. Snively, K.C. Deering, E.A. Nanni
SLAC, Menlo Park, California, USA

Direct electron therapy offers an attractive method for providing the high dose rates necessary for FLASH radiation therapy, a new treatment modality with the potential for enhanced healthy tissue sparing. Direct electron therapy has been limited by the low beam energies, up to 20 MeV, provided by today’s medical linacs, restricting the achievable dose depth to superficial tumors. Very High Energy Electron (VHEE) therapy could reach deep-seated tumors throughout the body. A clinically viable VHEE system must provide electron energies of around 100 MeV in a compact footprint, roughly 1 to 2 meters, with modest power requirements. We investigate the development of mm-wave linacs to provide the necessary beam energies on the sub-meter scale, taking advantage of the favorable scaling of high-frequency operation to support gradients well above 100 MeV/m. We discuss the design parameters necessary for high-efficiency structures, with shunt impedance on the order of 1 GOhm/m, producing high gradients with only a few megawatts of power. We present simulations of cavity performance in the mm-wave operating regime, with an emphasis on compatibility with the requirements of VHEE therapy.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB171

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paper received ※ 19 May 2021 paper accepted ※ 26 July 2021 issue date ※ 11 August 2021

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THPAB209

Tracking Complex Re-Circulating Machines with PLACET2

wakefield, radiation, synchrotron-radiation, synchrotron

4197

R.A.J. Costa, A. Latina
CERN, Geneva, Switzerland

We present the latest version of the multi-particle tracking package PLACET2. This software was designed to track multiple electron bunches through re-circulating machines with complex topologies, such as the recombination complex of the Compact Linear Collider (CLIC), energy-recovery linacs such as the Large Hadron-Electron Collider (LHeC), racetracks and others. This update also expands the capabilities of PLACET2 to track heavier particles such as muons. In addition to simulation, PLACET2 was also developed to allow beamline optimization scans, evaluating beam properties and tuning the beamline parameters at runtime either standalone or accessing the optimization tools present in the Octave and Python packages, with which it interfaces. This paper presents and benchmarks PLACET2’s latest features, such as coherent and incoherent synchrotron radiation, long and short wakefields and power extraction.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB209

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paper received ※ 18 May 2021 paper accepted ※ 13 July 2021 issue date ※ 31 August 2021

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THPAB210

Extrapolated Range for Low Energy Electrons (< 1 keV)

simulation, experiment, multipactoring, GUI

4201

C. Inguimbert, M.B. Belhaj, Q. Gibaru
ONERA, Toulouse, France
Q. Gibaru, D. Lambert, M. Raine
CEA, Arpajon, France
Q. Gibaru
CNES, PARIS, France

Funding: ONERA- DPHY, 2 avenue E. Belin, 31055 Toulouse, France CEA, DAM, DIF, 91297 Arpajon, France CNES, 18 av. E. Belin, 31055 Toulouse, France
The Secondary Electron Emission (SEE) process plays an important role in the performance of various devices. Mitigating the multipactor phenomenon that may occur in radio-frequency components is a concern in many fields such as space technologies or electron microscopy. SEE is also a concern in the accelerator physics community, where the beam lines stability can strongly be affected by this phenomenon*,**. In that scope, the escaped depth and thus the range of emitted electrons is of great interest. Our goal, by means of simulations is to provide a better knowledge of SEE. We have developed a Monte Carlo electron transport code for low energy electrons [~eV, ~10keV], that is part of the Dec. 2020 release of GEANT4***. It has been used to study the practical range of low energy electrons. Our goal is to formulate, below ~10 keV, an analytic range vs. energy expression, and to relate it to fundamental physcial parameters such as the mean free paths of electrons in matter. The goal is to provide simple practical extrapolated range formula that can help to understand SEE phenomenon.
* M. Mostajeran et al. J. of Instr. 5 (2010)
** C. Y. Vallgren et al. Phys. Rev. Accel. Beam 14 (2011)
*** Q. Gibaru et al. Nuc. Inst. And Met. 487 (2021)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB210

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paper received ※ 10 May 2021 paper accepted ※ 23 June 2021 issue date ※ 02 September 2021

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THPAB211

Monte Carlo Simulation of 3D Surface Morphologies for Secondary Electron Emission Reduction

simulation, multipactoring, GUI, experiment

4204

Q. Gibaru, M.B. Belhaj, C. Inguimbert
ONERA, Toulouse, France
Q. Gibaru, D. Lambert, M. Raine
CEA, Arpajon, France
Q. Gibaru
CNES, PARIS, France

Low energy electrons of few tens of eV may cause Multipactor breakdowns in waveguides driven by the Secondary Electron Emission Yield (SEY) of the walls. This risk is lowered by using low emissive surfaces and this topic has been studied experimentally and with numerical simulations. The dependence of the SEY on surface properties is well known*. Surface morphology has been widely used to reduce the SEY by forming roughness patterns on the surface**. All patterns do not have the same efficiency so their analysis in terms of SEY is relevant. Monte-Carlo simulation codes can be used to study the processes behind the SEY. The MicroElec module of GEANT4 has recently been extended with more materials and processes and validated with experimental data for SEY calculations**. In this work, simulation results are shown for a bulk sample capped with different roughness patterns. The effects of the shape parameters on the SEY are studied for typical dimensions between 20 µm and 100 µm. The results are checked with experimental SEY measurements on samples with similar roughness patterns.
*:T Gineste et al, Appl Surf Sci 359 (2015) 398-404
**:J Pierron et al, J Appl Phys 124 (2018) 095101
***:Q. Gibaru, C. Inguimbert, P. Caron, M. Raine, D. Lambert, J. Puech, NIM B. 487 (2021) 66-77

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB211

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paper received ※ 12 May 2021 paper accepted ※ 23 June 2021 issue date ※ 16 August 2021

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THPAB217

Lightsource Unified Modeling Environment (LUME), a Start-to-End Simulation Ecosystem

simulation, interface, FEL, software

4212

C.E. Mayes, A.L. Edelen, P. Fuoss, J.R. Garrahan, A. Halavanau, F. Ji, J. Krzywiński, W. Lou, N.R. Neveu, H.H. Slepicka
SLAC, Menlo Park, California, USA
J.C. E, C. Fortmann-Grote
EuXFEL, Schenefeld, Germany
C.M. Gulliford, D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
L. Gupta
University of Chicago, Chicago, Illinois, USA
A. Huebl, R. Lehé
LBNL, Berkeley, USA

SLAC is developing the Lightsource Unified Modeling Environment (LUME) for efficient modeling of X-ray free electron laser (XFEL) performance. This project takes a holistic approach starting with the simulation of the electron beams, to the production of the photon pulses, to their transport through the optical components of the beamline, to their interaction with the samples and the simulation of the detectors, and finally followed by the analysis of simulated data. LUME leverages existing, well-established simulation codes, and provides standard interfaces to these codes via open-source Python packages. Data are exchanged in standard formats based on openPMD and its extensions. The platform is built with an open, well-documented architecture so that science groups around the world can contribute specific experimental designs and software modules, advancing both their scientific interests and a broader knowledge of the opportunities provided by the exceptional capabilities of X-ray FELs.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB217

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paper received ※ 20 May 2021 paper accepted ※ 20 July 2021 issue date ※ 28 August 2021

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THPAB219

Beam Dynamics in Coherent Electron Cooling Accelerator

simulation, linac, cavity, emittance

4216

Y.C. Jing, V. Litvinenko, I. Petrushina, I. Pinayev, K. Shih, Y.H. Wu
BNL, Upton, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA
I. Petrushina, Y.H. Wu
SUNY SB, Stony Brook, New York, USA
K. Shih
SBU, Stony Brook, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Coherent electron Cooling (CeC) has the potential to substantially reduce the cooling time of the high-energy hadrons and hence to boost luminosity in high-intensity hadron-hadron and electron-hadron colliders. Recent development in CeC cooling theory requires the accelerator to deliver high-quality electron bunches with low beam noise. In this paper, we present our design of the CeC accelerator to achieve the electron beam requirements and compare our findings with the experimental observations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB219

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paper received ※ 27 May 2021 paper accepted ※ 27 July 2021 issue date ※ 20 August 2021

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THPAB228

Study on Laser Modulator for Electron Beam Density Modulation

laser, undulator, bunching, simulation

4241

K. Kan, M. Gohdo, J. Yang, Y. Yoshida
ISIR, Osaka, Japan

Ultrashort electron beams are essential for light sources and time-resolved measurements. Laser modulation using an undulator and pulsed near infrared light is expected for attosecond density modulation of electron beam. In this study, simulation of laser modulation using undulator with period length of 6.6 mm and optical pulse with a wavelength of 800 nm was performed by ELEGANT* code. Simulation results of laser modulation for electron beam with an energy of 32.5 MeV will be presented from a view point of the density modulation.
* M. Borland, elegant: A Flexible SDDS-Compliant Code for Accelerator Simulation, Advanced Photon Source LS-287, September 2000.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB228

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paper received ※ 19 May 2021 paper accepted ※ 28 July 2021 issue date ※ 12 August 2021

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THPAB229

Energy-Binning Fast Multipole Method for Electron Injector Simulations

space-charge, simulation, multipole, cathode

4244

S.A. Schmid, H. De Gersem, E. Gjonaj
TEMF, TU Darmstadt, Darmstadt, Germany

In a high brilliance electron injector, small beam energy and large charge density give rise to strong space charge effects. Furthermore, a large relative energy spread during the beam generation modifies the space charge interaction between different regions of the particle bunch. Therefore, modeling the phase space evolution in an electron injector requires a numerically efficient particle tracking code that can handle space charge interactions of spatially and energetically strongly inhomogeneous particle distributions. We implemented an energy-binning scheme for a meshless fast multipole method (FMM). The energy-binning approximates the momentum distribution of the beam by assigning particles to adaptive tree structures defined at different Lorentz frames. Based on the tree structures, the FMM computes a hierarchical approximation for the space charge interaction of the particle bunch. We use the energy-binning FMM to simulate the beam generation in the photoinjector of the European XFEL developed at DESY-PITZ. Furthermore, we present numerical convergence and performance studies and compare the simulation results to direct particle-particle methods.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB229

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paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 13 August 2021

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THPAB230

Design of Split Permanent Magnet Quadrupoles for Small Aperture Implementation

quadrupole, permanent-magnet, focusing, simulation

4247

I.I. Gadjev, G. Andonian, T.J. Campese, M. Ruelas
RadiaBeam, Santa Monica, California, USA
C.C. Hall
RadiaSoft LLC, Boulder, Colorado, USA

Permanent magnet quadrupoles are ideal for strong focusing in compact footprints. Recent research in the use of permanent magnet based quadrupole magnets has enabled very high-gradient uses approaching 800T/m in final focus systems. However, in order to achieve high quality field profiles with strong fields, small diameter bore magnets must be used necessitating in vacuum operation, or very small beampipes. For small beampipe geometry, we have developed a hybrid-permanent magnet quadrupole, with steel and permanent magnet wedges, that is able to maintain high quality fields but also readily machinable in a separable design. The split design allows for accurate and reproducible reconfiguration on a beam pipe. In this paper, we will discuss the design, engineering, fabrication and first measurements of the split permanent magnet quadrupole.

Poster THPAB230 [1.605 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB230

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paper received ※ 15 May 2021 paper accepted ※ 08 July 2021 issue date ※ 20 August 2021

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THPAB233

Could "Flakes" of Neutral Paramagnetic or Dipolar Molecules Explain Beam Losses in the LHC?

solenoid, dipole, vacuum, electromagnetic-fields

4254

G. Franchetti
GSI, Darmstadt, Germany
F. Zimmermann
CERN, Meyrin, Switzerland

"Flakes" of neutral water or oxygen molecules carrying an electric or magnetic dipole moment can be attracted and trapped by the electromagnetic field of the circulating LHC proton beam. The possible presence of such flakes in the vacuum system could explain beam losses and beam instabilities encountered during the 2017 and 2018 LHC runs, and the observed effect of an external magnetic field.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB233

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paper received ※ 09 May 2021 paper accepted ※ 12 July 2021 issue date ※ 02 September 2021

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THPAB238

An Overview of the Collective Effects and Impedance Calculation for the EIC

vacuum, simulation, wakefield, dipole

4266

A. Blednykh, D.M. Gassner, B. Podobedov, S. Verdú-Andrés
Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA
M. Blaskiewicz, C. Hetzel, B. Lepore, V.H. Ranjbar, M.P. Sangroula, P. Thieberger, G. Wang, Q. Wu
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
A new high-luminosity Electron-Ion Collider (EIC) is being designed at Brookhaven National Laboratory (BNL). Stable operation of the electron beam at an average current of 2.5A within 1100 bunches with a 7mm bunch length is one of the challenging tasks in achieving an electron-proton luminosity of 1033-1034 cm^-2 ses⁻¹ range. Beam induced heating, short-range and long-range wakefield analysis is discussed for some of the vacuum components of the electron storage ring (ESR), the hadron storage ring (HSR), and the rapid cycling synchrotron (RCS) and as well as the impact of the collective effects on the beam stability.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB238

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paper received ※ 15 May 2021 paper accepted ※ 24 June 2021 issue date ※ 25 August 2021

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THPAB239

Impedance Optimization of the EIC Interaction Region Vacuum Chamber

vacuum, impedance, detector, wakefield

4270

A. Blednykh
Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA
E.C. Aschenauer, M. Blaskiewicz, C. Hetzel, M.P. Sangroula, G. Wang, H. Witte
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The interaction region chamber has a complex geometry at the crossing location of electron and proton beam pipes. In the direction of the electron beam, the pipe is designed in a way to avoid joints with cavity characteristics. The horizontal slot on the upstream side and the tapered transition on the downstream side are applied to minimize the IR chamber contribution to the total impedance of the electron ring and to avoid generating Higher Order Modes and heating-related issues. The synchrotron radiation mask is included to protect the IR chamber from synchrotron radiation without significant aperture reduction. In the direction of the proton beam, the main area for optimization is the transition area right after the detector.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB239

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paper received ※ 15 May 2021 paper accepted ※ 24 June 2021 issue date ※ 18 August 2021

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THPAB251

Efficient Terahertz Generation by Tilted-Pulse-Front Pumping in Lithium Niobate for the Split-Ring Resonator Experiment at FLUTE

laser, experiment, diagnostics, vacuum

4299

M. Nabinger, E. Bründermann, S. Funkner, B. Härer, A.-S. Müller, M.J. Nasse, G. Niehues, R. Ruprecht, J. Schäfer, T. Schmelzer, N.J. Smale
KIT, Karlsruhe, Germany
M.M. Dehler, R. Ischebeck, M. Moser, V. Schlott
PSI, Villigen PSI, Switzerland
T. Feurer, M. Hayati, Z. Ollmann
Universität Bern, Institute of Applied Physics, Bern, Switzerland

Funding: This work is co-funded via the European Union’s H2020 research and innovation program, GA No 730871, ARIES.
A compact, longitudinal diagnostics for fs-scale electron bunches using a THz electric-field transient in a split-ring resonator (SRR) for streaking will be tested at the Ferninfrarot Linac- Und Test- Experiment (FLUTE). For this new streaking technique, intensive THz pulses are required, which will be generated by laser-based optical rectification. We present a setup for generating THz pulses using tilted-pulse-front pumping in lithium niobate at room temperature. Excited by an 800 nm Ti:Sa pump laser with 35 fs bandwidth-limited pulse length, conversion efficiencies up to 0.027% were achieved. Furthermore, the status of the SRR experiment is shown.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB251

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paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 12 August 2021

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THPAB265

New RF BPM Electronics for the 560 Beam Position Monitors of the APS-U Storage Ring

storage-ring, electronics, site, instrumentation

4325

P. Leban, L. Bogataj, M. Cargnelutti, U. Dragonja, P. Paglovec
I-Tech, Solkan, Slovenia
A.R. Brill, J. Carwardine, W.X. Cheng, N. Sereno
ANL, Lemont, Illinois, USA

Within the upgrade of the APS storage ring to a multi-bend achromat lattice, 560 RF Beam Position Monitors will be required. The projected beam sizes are below 10 microns in both horizontal and vertical planes, putting stringent requirements on the BPM electronics resolution, long-term stability, beam current dependency, and instrument reproducibility. For the APS-U project, the Libera Brilliance⁺ instrument has been upgraded in technology and capabilities, including the independent multi-bunch turn-by-turn processing and an improved algorithm to further reduce the crossbar-switch artifacts. More than 140 instruments, equipped with 4 BPM electronics each, are being delivered to Argonne National Laboratory, consisting of the largest scale production for Instrumentation Technologies. In this contribution, the extensive test conditions to which the instruments were exposed and their results will be presented, as well as the beam-based long-term drift measurements with different fill patterns.

Poster THPAB265 [9.272 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB265

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paper received ※ 16 May 2021 paper accepted ※ 22 June 2021 issue date ※ 12 August 2021

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THPAB269

Compton Spectrometer for FACET-II

detector, simulation, plasma, wakefield

4332

B. Naranjo, G. Andonian, A. Fukasawa, W.J. Lynn, N. Majernik, J.B. Rosenzweig, Y. Sakai, O. Williams, M. Yadav, Y. Zhuang
UCLA, Los Angeles, California, USA

Funding: DARPA GRIT Contract 20204571, DOE HEP Grant DE-SC0009914
We present the design of a Compton spectrometer for use at FACET-II. A sextupole is used for magnetic spectral analysis, giving a broad dynamic range (180 keV through 28 MeV) and the capability to capture an energy-angular double-differential spectrum in a single shot. At low gamma energies, below 1 MeV, Compton spectroscopy becomes increasingly challenging as the scattering cross-section becomes more isotropic. To extend the range of the spectrometer down to around 180 keV, we use a 3D-printed tungsten collimator at the detector plane to preferentially select forward-scattered electrons at the Compton edge.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB269

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paper received ※ 20 May 2021 paper accepted ※ 22 July 2021 issue date ※ 12 August 2021

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THPAB270

Pair Spectrometer for FACET-II

positron, scattering, detector, photon

4336

B. Naranjo, G. Andonian, A. Fukasawa, N. Majernik, M.H. Oruganti, J.B. Rosenzweig, Y. Sakai, O. Williams, M. Yadav
UCLA, Los Angeles, California, USA
N. Cavanagh, G. Sarri
Queen’s University of Belfast, Belfast, Northern Ireland, United Kingdom
A. Di Piazza, C.H. Keitel
MPI-K, Heidelberg, Germany
E. Gerstmayr, S. Meuren, D.A. Reis, D.W. Storey, V. Yakimenko
SLAC, Menlo Park, California, USA
R. Holtzapple
CalPoly, San Luis Obispo, California, USA
C. Nielsen
AU, Aarhus, Denmark

Funding: DARPA GRIT Contract 20204571, DOE HEP Grant DE-SC0009914
We present the design of a pair spectrometer for use at FACET-II, where there is a need for spectroscopy of photons having energies up to 10 GeV. Incoming gammas are converted to high-energy positron-electron pairs, which are then subsequently analyzed in a dipole magnet. These charged particles are then recorded in arrays of acrylic Cherenkov counters, which are significantly less sensitive to background x-rays than scintillator counters in this case. To reconstruct energies of single high-energy photons, the spectrometer has a sensitivity to single positron-electron pairs. Even in this single-photon limit, there is always some low-energy continuum present, so spectral deconvolution is not trivial, for which we demonstrate a maximum likelihood reconstruction. Finally, end-to-end simulations of experimental scenarios, together with anticipated backgrounds, are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB270

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paper received ※ 20 May 2021 paper accepted ※ 28 July 2021 issue date ※ 13 August 2021

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THPAB273

Spectral Reconstruction for FACET-II Compton Spectrometer

photon, network, site, positron

4346

Y. Zhuang, B. Naranjo, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, USA

Funding: This work was supported by DOE Contract DE-SC0009914, NSF Grant No. PHY-1549132, and DARPA GRIT Contract 20204571.
The Compton spectrometer under development at UCLA for FACET-II is a versatile tool to analyze gamma-ray spectra in a single shot, in which the energy and angular position of the incoming photons are recorded by observing the momenta and position of Compton scattered electrons. We present methods to reconstruct the primary spectrum from these data via machine learning and the EM Algorithm. A multi-layer fully connected neural network is used to perform the regression task of reconstructing both the double-differential spectrum and the photon energy spectrum incident with zero angular offset. We present the expected performance of these techniques, concentrating on the achievable energy resolution.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB273

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paper received ※ 20 May 2021 paper accepted ※ 28 July 2021 issue date ※ 29 August 2021

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THPAB284

Analytical and Numerical Characterization of Cherenkov Diffraction Radiation as a Longitudinal Electron Bunch Profile Monitor for AWAKE Run 2

radiation, plasma, proton, wakefield

4355

C. Davut, G.X. Xia
UMAN, Manchester, United Kingdom
O. Apsimon
The University of Liverpool, Liverpool, United Kingdom
O. Apsimon
Cockcroft Institute, Warrington, Cheshire, United Kingdom
P. Karataev
Royal Holloway, University of London, Surrey, United Kingdom
P. Karataev
JAI, Egham, Surrey, United Kingdom
T. Lefèvre, S. Mazzoni
CERN, Geneva, Switzerland

In this paper, CST simulations of the coherent Cherenkov Diffraction Radiation with a range of parameters for different dielectric target materials and geometries are discussed and compared with the theoretical investigation of the Polarization Current Approach to design a prototype of a radiator for the bunch length/profile monitor for AWAKE Run 2. It was found that the result of PCA theory and CST simulation are consistent with each other regarding the shape of the emitted ChDR cone.
* Karlovets, D. V. (2011). JETP, 113(1), 27-45.
** Shevelev, M. V., & Konkov, A. S. (2014). JETP, 118(4), 501-511.
*** Curcio, A., et al.(2020). PRAB, 23(2), 022802.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB284

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paper received ※ 16 May 2021 paper accepted ※ 14 July 2021 issue date ※ 14 August 2021

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THPAB290

Evolution of the LHC Beam Screen Surface Conditioning Upon Electron Irradiation

radiation, ECR, gun, vacuum

4370

S. Bilgen, S. Della-Negra, D. Jacquet, B. Mercier, I. Ribaud, G. Sattonnay
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
V. Baglin
CERN, Meyrin, Switzerland

For the vacuum scientists and the accelerator community, finding solutions to mitigate pressure rises induced by electron, photon, and ion desorption, and also beam instabilities induced by ion and electron clouds is a major issue. Moreover, it is worth noting that the OFE copper beam screen of the LHC is initially cleaned with standard industrial processes, leading to residual chemical contamination. Along the time, changes in the surface chemistry of vacuum chambers are observed during beam operations, leading to modifications of outgassing rates, stimulated desorption processes, and secondary emission yields (SEY). The impact of ions on molecule desorption and electron production was investigated to identify their influence on the global pressure rises and to quantify the ion conditioning effect on copper surfaces: (i) SEY evolution was measured to understand the changes of surface conditioning upon particle irradiation; (ii) surface chemistry evolution after electron irradiation was investigated by both XPS and TOF-SIMS analyses using the ANDROMEDE facility at IJCLab. Finally, the relationship between surface chemistry and the conditioning phenomenon will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB290

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paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 26 August 2021

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THPAB291

DYVACS (DYnamic VACuum Simulation) Code: Gas Density Profiles in Presence of Electron Cloud in the LHC

proton, vacuum, injection, photon

4373

S. Bilgen, B. Mercier, G. Sattonnay
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
V. Baglin
CERN, Meyrin, Switzerland

The computation of residual gas density profiles in particle accelerators is an essential task to optimize beam pipes and vacuum system design. In a hadron collider such as the LHC, the beam induces dynamic effects due to ion, electron, and photon-stimulated gas desorption. The well-known VASCO* code developed at CERN in 2004 is already used to estimate vacuum stability and density profiles in steady-state conditions. Nevertheless, some phenomena are not taken into account such as the ionization of residual gas by the electron clouds and the evolution of the electronic density related to the electron cloud build-up. Therefore, we propose an upgrade of this code by introducing electron cloud maps** to estimate the electron density and the ionization of gas by electrons leading to an increase of induced desorption. The pressure evolution computed with DYVACS reproduces with good accuracy the experimental pressure recorded in the VPS beam pipes sector*** of the LHC from the proton beam injection to the stable beam period. Additionally, DYVACS can also be used as a predictive tool to compute the pressure evolution in the beam pipes for Future Circular Colliders (FCC-hh or -ee).
* A. Rossi, Tech. Report, LHC Project Note 341
** T. Demma et al Phys. Rev. Acceler. and Beams 10, 114401 (2007)
*** B. Henrist et al, Proc. IPAC2014, Dresden

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB291

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paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 02 September 2021

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THPAB292

Dynamic Pressure in the LHC: Detection of Ions Induced by Ionization of Residual Gas by the Proton Beam and by the Electron-Cloud

proton, experiment, vacuum, ECR

4377

S. Bilgen, B. Mercier, G. Sattonnay
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
V. Baglin
CERN, Meyrin, Switzerland

Ultra-High Vacuum is an essential requirement to achieve design performances and high luminosities in high-energy particle colliders. Consequently, the understanding of the dynamic pressure evolution during accelerator operation is fundamental to provide solutions to mitigate pressure rises induced by multiple effects leading to beam instabilities. For the LHC, the appearance of instabilities may be due to the succession of several phenomena: (i) the induced desorption of gases adsorbed on the surfaces leading to pressure rises; (ii) the creation of secondary particles (ions, electrons); (iii) the production of the so-called Electron Cloud build-up by multipacting effect. This work aims to investigate some fundamental phenomena which drive the dynamic pressure in the LHC, namely the effects induced by electrons and ions interacting with the copper surface of the beam screens. Electron and ion currents, as well as pressure, were recorded in situ in the Vacuum Pilot Sector (VPS*) located on the LHC ring during the RUN II. By analyzing the results, more ions than expected were detected and the interplay between electrons, ions, and pressure changes was investigated.
* The LHC Vacuum Pilot-Sector Project, B. Henrist, V. Baglin, G. Bregliozzi, and P. Chiggiato, CERN, Geneva, Switzerland, Proceedings of IPAC2014, Dresden, Germany

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB292

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 22 August 2021

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THPAB310

Automatic Correction System for the TLS Booster Linac Klystron Modulator

klystron, booster, acceleration, linac

4396

S.J. Huang, Y.K. Lin
NSRRC, Hsinchu, Taiwan

The aim of this article is to analyse the performance output of the klystron modulator, which is based on the observation of the output voltage and current performance of the linear-accelerator klystron modulator; we modify the operating-point parameters based on those results or assess whether the klystron needs to be replaced. For this purpose, we collect the observation data of the klystron performance; we then develop a program to adjust automatically the high-voltage setting of the klystron to ensure that the storage current maintains beam current 360 mA in the top-up mode operation.

Poster THPAB310 [0.785 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB310

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paper received ※ 16 May 2021 paper accepted ※ 02 July 2021 issue date ※ 14 August 2021

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THPAB311

Using Linear Regression to Model the Parameters of the Flat Wires in TLS-EPU56

feedback, injection, undulator, hardware

4399

S.J. Huang, Y.H. Chang, T.Y. Chung
NSRRC, Hsinchu, Taiwan
Y.W. Chen
Academia Sinica, Taipei, Taiwan

Although a theoretical calculation might predict the set currents of the flat wires, which are used to compensate the deviation in the Betatron tune caused by the elliptically polarized undulator (EPU), those set currents must still be tuned in reality. To approach this reality, a strategy of Machine Learning was adopted, which included collecting real-condition data and using a linear-regression model to adjust the parameters of the flat wires. After training the model, the predictions in variables tune x, tune y and beam size x were compared with the required amount of correction of the EPU at various gaps and phases. To prove the feasibility of this method, a test was performed under the real conditions of accelerator Taiwan Light Source (TLS).

Poster THPAB311 [1.226 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB311

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paper received ※ 13 May 2021 paper accepted ※ 28 June 2021 issue date ※ 25 August 2021

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THPAB313

Drive Laser System for Shanghai Soft X-Ray Free Electron Laser

laser, FEL, cathode, free-electron-laser

4403

L. Feng, C.L. Li, B. Liu, J.G. Wang
SARI-CAS, Pudong, Shanghai, People’s Republic of China
X. Lu
ANL, Lemont, Illinois, USA
X.T. Wang, W.Y. Zhang
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China

In this paper, we introduce the design and layout of the drive laser of Shanghai Soft X-ray Free Electron Laser (SXFEL). It is known that the temporal and spatial distribution of the drive laser is crucial for high-quality electron beams. The drive laser provides the laser pulse of 266nm wavelength and 8ps pulse duration for the photocathode, as well as 400nm wavelength, 2-20ps tunable pulse duration for the laser heater. For this purpose, there are mainly four parts in such system, including a third-harmonic generation device, pulse stretcher, image transmitted system, and laser optical module for laser heater. Finally, the measured results of the electron beam under this drive laser system are presented and discussed.

Poster THPAB313 [0.691 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB313

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paper received ※ 20 May 2021 paper accepted ※ 15 July 2021 issue date ※ 10 August 2021

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THPAB331

High-Power Test of a Highly Over-Coupled X-Band RF Gun Driven by Short RF Pulses

gun, cathode, wakefield, flattop

4432

J.H. Shao, D.S. Doran, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
X. Lu, P. Piot, W.H. Tan
Northern Illinois University, DeKalb, Illinois, USA

Beam brightness, a key figure of merit of RF photocathode guns, can be improved by increasing the cathode surface field which suppresses emittance growth from space charge. The surface field in normal-conducting structures is mainly limited by RF breakdown and it has been experimentally discovered that RF breakdown rate exponentially depends on RF pulse length. A highly over-coupled 1.5-cell X-band photocathode gun has been developed to be powered by 9 ns RF pulses with 3 ns rising time, 3 ns flat-top, and 3 ns falling time generated by an X-band metallic power extractor. In the recent experiment at Argonne Wakefield Accelerator facility, cathode surface field up to ~350 MV/m with a low breakdown rate has been obtained under ~250 MW input power. Strong beam loading from dark current was observed during RF conditioning and quickly recovered to a negligible level after the gun reached the maximum gradient. Detailed high-power test results and data analysis will be reported in this manuscript.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB331

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paper received ※ 25 May 2021 paper accepted ※ 14 July 2021 issue date ※ 10 August 2021

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THPAB332

Development of a Pair of 182 GHz Two-Half Power Extractor and Accelerator for Short Pulse RF Breakdown Study

acceleration, GUI, wakefield, alignment

4435

J.H. Shao, J.G. Power
ANL, Lemont, Illinois, USA
R.B. Agustsson, S.V. Kutsaev, A.Yu. Smirnov
RadiaBeam, Santa Monica, California, USA

High-frequency structures are favorable in structure wakefield acceleration for their strong beam-structure interaction. Recent progress of advanced fabrication technologies, such as high-precision two-half milling and additive machining, has enabled experimental research of mm-wave/THz structures. In this work, we have designed a pair of 182 GHz two-half copper power extractor and accelerator for short pulse RF breakdown study. When driven by a 182 GHz 4-bunch train with 4 nC total charge and 0.3 mm rms bunch length, the power extractor will generate 0.4 ns ~8 MW RF pulses and the corresponding gradient in the single-cell accelerator will reach ~460 MV/m. RF and mechanical design of the proof-of-concept structures will be reported in this manuscript.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB332

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paper received ※ 26 May 2021 paper accepted ※ 19 July 2021 issue date ※ 24 August 2021

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THPAB340

Sub-Nanosecond Switching of HV SiC MOS Transistors for Impact Ionisation Triggering

plasma, kicker, laser, high-voltage

4454

V. Senaj, T. Kramer, A.A. del Barrio Montañés
CERN, Geneva 23, Switzerland
M. Sack
KIT, Karlsruhe, Germany

Pulse generators with multi kV/kA pulses are necessary for the particle accelerator environment for beam transfer magnets. Traditionally these generators are using thyratrons - until recently the only switches capable of switching such pulses within tens of ns. There is a strong demand to replace thyratrons with semiconductor switches to avoid their future obsolescence. Very promising candidates are components from the family of fast ionization dynistors triggered by impact ionization. Their sub-nanosecond switching time and extreme current densities can provide performances superior to that of thyratrons. Recent investigations showed that impact ionization triggering is feasible also in cheap industrial thyristors. The main issue is the generation of triggering pulses with slew rates in the multi kV/ns region and with the required output current for charging the parasitic capacitance of the thyristor. We present an approach of generating > 1 kV/ns pulses by ultra-boosted gate driving of HV SiC MOS transistors. We found that the MOS lifetime under these extreme triggering conditions can still reach more than 10⁸ pulses, enough for kicker generator applications.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB340

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paper received ※ 18 May 2021 paper accepted ※ 01 July 2021 issue date ※ 27 August 2021

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THPAB341

TiN Metalizing and Coating for Multi-Megawatt RF Vacuum Windows

Windows, vacuum, multipactoring, high-voltage

4457

M.L. Neubauer, A. Dudas, R.P. Johnson
Muons, Inc, Illinois, USA

Coatings on microwave windows and high-voltage ceramics are required to eliminate secondary electron emission (SEE), which initiates multipactoring discharge causing local heating and ceramic failures due to cracking and loss of vacuum. The region surrounding the triple junction (ceramic+metal+vacuum) is the primary source of free electrons and in microwave windows and high-voltage ceramics. This region is located at the metalizing and braze joint of the ceramic support structure making the vacuum seal. On very large microwave windows typically at low frequencies, this critical region is difficult to coat by the traditional techniques of sputter coating anti-multipactoring titanium nitride or other materials. The novel processes proposed here include a means for applying and controlling the thickness of titanium nitride both in the metallizing (controlling the source) and on the surface of the window, eliminating SEE and the multipactoring discharge.

Poster THPAB341 [0.845 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB341

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paper received ※ 23 May 2021 paper accepted ※ 21 July 2021 issue date ※ 18 August 2021

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THPAB344

Magneto-Optical Trap Cathode for High Brightness Applications

laser, gun, emittance, cathode

4466

V.S. Yu, C.E. Hansel, G.E. Lawler, M. Mills, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
J.I. Mann
PBPL, Los Angeles, USA

Funding: This work was performed with support of the US Department of Energy under Contract No. DE-SC0020409 and the National Science Foundation under Grant No. PHY-1549132
Electron bunches extracted from magneto-optical traps (MOTs) via femtosecond photo-ionization and electrostatic acceleration can have significantly lower transverse emittance than emissions from traditional metal cathodes. Such MOT cathodes, however, have two drawbacks: the need for multiple trapping lasers and the limit to ~MV/m fields. Designs exist for MOTs which only require one trapping laser. Our RF simulations in High-Frequency Structure Simulator (HFSS) indicate that the cone MOT is the only one compatible with high gradient RF cavities. We present the combination of the two, an RF cavity with a cone-MOT as part of its geometry. It only requires one trapping laser and can use much higher fields. The geometry of the chamber is compatible with a wide range of MOT species, which allows the search for one which is compatible with copper cavities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB344

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paper received ※ 19 May 2021 paper accepted ※ 29 July 2021 issue date ※ 31 August 2021

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THPAB349

Feed-Forward Neural Network Based Modelling of an Ultrafast Laser for Enhanced Control

laser, network, controls, cathode

4478

A. Aslam, M. Martínez-Ramón, S.D. Scott
UNM-ECE, Albuquerque, USA
S. Biedron
Argonne National Laboratory, Office of Naval Research Project, Argonne, Illinois, USA
S. Biedron
Element Aero, Chicago, USA
S. Biedron
UNM-ME, Albuquerque, New Mexico, USA
M. Burger, J. Murphy
NERS-UM, Ann Arbor, Michigan, USA
K.M. Krushelnick, J. Nees, A.G.R. Thomas
University of Michigan, Ann Arbor, Michigan, USA
Y. Ma
IHEP, Beijing, People’s Republic of China
Y. Ma
Michigan University, Ann Arbor, Michigan, USA

Funding: Acknowledgements: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under award number DE-SC0019468.
The applications of machine learning in today’s world encompass all fields of life and physical sciences. In this paper, we implement a machine learning based algorithm in the context of laser physics and particle accelerators. Specifically, a neural network-based optimisation algorithm has been developed that offers enhanced control over an ultrafast femtosecond laser in comparison to the traditional Proportional Integral and derivative (PID) controls. This research opens a new potential of utilising machine learning and even deep learning techniques to improve the performance of several different lasers and accelerators systems.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB349

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paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 19 August 2021

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THPAB369

Research and Design of an X-Band 100-MeV Compact Electron Accelerator for Very High Energy Electron Therapy in Tsinghua University

cavity, gun, linac, klystron

4502

X. Lin, H.B. Chen, J. Shi, C.-X. Tang, H. Zha, L.Y. Zhou
TUB, Beijing, People’s Republic of China

A 100-MeV Compact Electron Accelerator scheme based on the Tsinghua X-band (11.424 GHz) High Power Test stand (TPot-X) was proposed for Very High Energy Electron (VHEE) radiotherapy. A pulse compressor with correction cavity chain was designed to compress the 50 MW, 1500 ns microwave pulse from the X-band klystron to 120 MW, 300 ns. The acceleration system consists of 3 parts, a buncher which bunches and boosts the electron from a thermionic cathode gun to 8 MeV, and two accelerating structure which further boost the electron energy to 100MeV. The detailed design and consideration are presented in this article.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB369

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 17 August 2021

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THPAB372

SABINA: A Research Infrastructure at LNF

laser, radiation, experiment, focusing

4505

L. Sabbatini, D. Alesini, M.P. Anania, M. Bellaveglia, A. Biagioni, B. Buonomo, S. Cantarella, F. Cardelli, E. Chiadroni, G. Costa, G. Di Pirro, F. Dipace, A. Esposito, M. Ferrario, M. Galletti, A. Gallo, A. Ghigo, L. Giannessi, A. Giribono, S. Incremona, L. Pellegrino, L. Piersanti, R. Pompili, R. Ricci, J. Scifo, A. Stecchi, A. Stella, C. Vaccarezza, A. Vannozzi, S. Vescovi, F. Villa
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
A. Cianchi
INFN-Roma II, Roma, Italy
A. Doria, A. Petralia
ENEA C.R. Frascati, Frascati (Roma), Italy
L. Giannessi
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
S. Lupi
Sapienza University of Rome, Roma, Italy
S. Macis
La Sapienza University of Rome, Rome, Italy
V. Petrillo
Universita’ degli Studi di Milano, Milano, Italy
V. Petrillo
INFN-Milano, Milano, Italy

Funding: SABINA is a project co-funded by Regione Lazio within POR-FESR 2014-2020 program.
SABINA (Source of Advanced Beam Imaging for Novel Applications) is a project aimed at the enhancement of the SPARC_LAB research facility. This enhancement is carried out through the following actions: first, the increase of the uptime through the consolidation of technological systems and the replacement of some critical equipment in order to limit the number and extent of faults; then, the improvement of the accelerator performances, by replacing some devices with updated ones. The effect will be greater reliability of the accelerator, which will allow it to be opened as a facility for external users, both industrial and scientific, with the goal of increasing the competitiveness of industries in a broad range of technological areas and enhancing collaborations with research institutions. The two user lines that will be implemented are a power laser target area and a THz radiation line, by using a dedicated undulator. The undulator and the THz line are also described in other contributions to this conference. A brief description of the project and potential exploitations are reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB372

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paper received ※ 24 May 2021 paper accepted ※ 01 July 2021 issue date ※ 18 August 2021

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FRXA01

Full Energy On-Demand Beam Injection from SACLA into the SPring-8 Storage Ring

injection, FEL, operation, linac

4508

H. Maesaka, T. Fukui, T. Hara, T. Hiraiwa, T. Inagaki, E. Iwai, H. Tanaka, K. Togawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
H. Dewa, T. Fujita, K. Fukami, N. Hosoda, A. Kiyomichi, M. Masaki, S. Matsubara, T. Ohshima, M. Oishi, K. Soutome, S. Takano, T. Watanabe
JASRI/SPring-8, Hyogo-ken, Japan
C. Kondo
JASRI, Hyogo, Japan

The beam injector for the SPring-8 storage ring (SR) was switched from the booster synchrotron to the SACLA linac, a driver for X-ray free-electron laser (XFEL). The low-emittance beam from SACLA (~100 pm rad, 8 GeV) is delivered to the SR through a 600m-long beam transport line. This low-emittance beam can be applied to the new low-emittance storage ring after the SPring-8 upgrade planed in the coming years. The shutdown of the booster synchrotron and 1-GeV linac saves energy consumption and operation cost. To provide the electron beam injected to the SR on demand for the top-up injection during the XFEL operation, the SACLA linac must be synchronized to the desired bucket of the SR, the beam energy and route must be switched shot-to-shot, and the XFEL performance must not be degraded. We developed a precise synchronization system, on-demand beam route and parameter switching system, a pulsed magnet for the switchyard, isolated bunch purification system, etc. In this presentation, we will show the design and performance of each component for the beam injection and the results from beam commissioning of the accelerator and transport line.

Slides FRXA01 [3.446 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXA01

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 22 August 2021

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FRXA06

Mitigation of Beam Instabilities in the Echo-Enabled Harmonic Generation Beamline for FLASH²⁰²⁰⁺

bunching, laser, FEL, free-electron-laser

4514

F. Pannek, W. Hillert, D. Samoilenko
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Ackermann, E. Allaria, P. Niknejadi, G. Paraskaki, L. Schaper
DESY, Hamburg, Germany
M.A. Pop
MAX IV Laboratory, Lund University, Lund, Sweden

With the FLASH²⁰²⁰⁺ upgrade, one of the beamlines of the free-electron laser FLASH at DESY will be based on the Echo-Enabled Harmonic Generation (EEHG) seeding scheme and provide high-repetition-rate, coherent radiation down to 4 nm. To reach this wavelength, it is necessary to imprint intricate structures on the longitudinal phase space of the electron bunch at a very high harmonic of the seed laser wavelength, making the scheme potentially vulnerable to beam instabilities. Part of the beamline is a strong chicane, which is necessary to create the dispersion required by EEHG. Resulting effects such as Coherent Synchrotron Radiation (CSR) can be very detrimental for the bunching process and have to be taken into account already in the design of the beamline to ensure optimum FEL performance. We investigate and propose possible mitigation solutions to such instabilities in the FLASH²⁰²⁰⁺ parameter range.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXA06

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paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 29 August 2021

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FRXC03

Modern Ultra-Fast Detectors for Online Beam Diagnostics

detector, laser, experiment, FPGA

4540

M.M. Patil, E. Bründermann, M. Caselle, A. Ebersoldt, S. Funkner, B. Kehrer, A.-S. Müller, M.J. Nasse, G. Niehues, J.L. Steinmann, W. Wang, M. Weber, C. Widmann
KIT, Karlsruhe, Germany

Funding: This work is supported by the BMBF project 05K19VKD STARTRAC and DFG-funded Doctoral School ’Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology’
Synchrotron light sources operate with bunch repetition rates in the MHz regime. The longitudinal and transverse beam dynamics of these electron bunches can be investigated and characterized by experiments employing linear array detectors. To improve the performance of modern beam diagnostics and overcome the limitations of commercially available detectors, we have at KIT developed KALYPSO, a detector system operating with an unprecedented frame rate of up to 12 MHz. To facilitate the integration in different experiments, a modular architecture has been utilized. Different semiconductor microstrip sensors based on Si, InGaAs, PbS, and PbSe can be connected to the custom-designed low noise front-end ASIC to optimize the quantum efficiency at different photon energies, ranging from near-UV, visible, and up to near-IR. The front-end electronics are integrated within a heterogeneous DAQ consisting of FPGAs and GPUs, which allows the implementation of real-time data processing. This detector is currently installed at KARA, European XFEL, FLASH, Soleil, DELTA. In this contribution, we present the detector architecture, the performance results, and the ongoing technical developments.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXC03

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paper received ※ 19 May 2021 paper accepted ※ 22 July 2021 issue date ※ 24 August 2021

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FRXC06

Development of the Prototype of the Cavity BPM System for SHINE

cavity, FEL, experiment, controls

4552

J. Chen, Y.B. Leng, R.X. Yuan
SSRF, Shanghai, People’s Republic of China
S.S. Cao
SINAP, Shanghai, People’s Republic of China
L.W. Lai
SARI-CAS, Pudong, Shanghai, People’s Republic of China

The Shanghai high repetition rate XFEL and extreme light facility (SHINE) under construction is designed as one of the most advanced FEL facilities in the world, which will produce coherent x-rays with wavelengths from 0.05 to 3 nm and maximum repetition rate of 1MHz. In order to achieve precise, stable alignment of the electron and photo beams in the undulator, the prototype of the cavity beam position monitors (CBPM) including C-band and X-band have been designed and fabricated for the SHINE. And the requirement of the transverse position resolution is better than 200 nm for a single bunch of 100 pC at the dynamic range of ±100 µm. In this paper, we present the design of the cavity with high loaded Q and the RF front-end with low noise-figure, adjustable gain, single-stage down-conversion and phase-locked with reference clock, and also described the structure and specifications of the home-made data acquisition (DAQ) system. The construction of the experiment platform and preliminary measurement result with beam at Shanghai Soft X-ray FEL facility (SXFEL) will be addressed as well.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXC06

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paper received ※ 20 May 2021 paper accepted ※ 06 July 2021 issue date ※ 14 August 2021

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