IPAC2021 - List of Keywords (gun)

Paper	Title	Other Keywords	Page
MOXC02	Improved Lifetime of a High Spin Polarization Superlattice Photocathode	electron, cathode, polarization, 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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MOPAB107	RF Plans for the Diamond-II Upgrade	cavity, HOM, linac, booster	391
	C. Christou, P. Gu, P.J. Marten, S.A. Pande, A.F. Rankin DLS, Oxfordshire, United Kingdom
	The RF system for the proposed Diamond-II upgrade will be based on normal-conducting EU HOM-damped cavities powered by high powered solid state amplifiers and controlled by digital low level RF systems built on the microTCA platform. Reasons for these design choices are discussed, and experience of the selected technologies in the Diamond-I ring are reviewed. The storage ring will also include a third harmonic cavity, and the different design options for this device are discussed. RF design of the booster ring is presented, and details are given of an upgraded linac and gun design intended to improve the charge delivered for top-up.
	Poster MOPAB107 [1.703 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB107
About •	paper received ※ 18 May 2021 paper accepted ※ 20 May 2021 issue date ※ 20 August 2021
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MOPAB255	Demonstration of a Novel Longitudinal Phase Space Linearization Method without Higher Harmonics	cavity, electron, 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	emittance, simulation, electron, 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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MOPAB314	Surrogate Modeling for MUED with Neural Networks	electron, experiment, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB314
About •	paper received ※ 20 May 2021 paper accepted ※ 07 June 2021 issue date ※ 15 August 2021
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MOPAB348	Portable 2.5 MeV X-Band Linear Accelerator Structure	linac, GUI, radiation, target	1084
	A.V. Mishin, K. Brown, M. Denney, D. Fischer, N.P. Hanson, S. Proskin, J. Stammetti Varex Imaging, Salt Lake City, USA
	Two versions of 2.5 MeV X-Band linear accelerator structure have been designed and tested. The first is a traditional single input linac, and the other one is a dual input, two section linac with power input through a 3 dB coupler. The linac is designed for a portable linac system, which can be used for security screening, non-destructive testing, medical and industrial CT, and, perhaps, some other applications.
	Poster MOPAB348 [1.490 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB348
About •	paper received ※ 15 May 2021 paper accepted ※ 28 May 2021 issue date ※ 28 August 2021
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MOPAB349	New Accelerator Beam Centerline (ABC) Production Line at Varex Imaging Corporation	linac, betatron, detector, GUI	1087
	A.V. Mishin Varex Imaging, Salt Lake City, USA
	In January 2017, a Salt Lake City Component Division of Varian Medical (Varian), producer of X-ray tubes, detectors, and imaging panels has been spun off, giving birth to a new public company Varex Imaging Corporation (Varex), which also includes the Security and Inspection Products (SIP) linac producer in Las Vegas. Based on Varian asset acquisition of two small LLCs** in May 2016, 8 months prior to the transition, a new business branch within Varex has been established, which included distribution of the betatrons and detector arrays as well as pilot production line for Accelerator Beam Centerlines (ABC). In 3 years, we moved ABC production from Fremont, CA to Salt Lake in Utah and improved it; several ABCs have been designed, produced, and qualified. A number of new products in energy range of 1-20 MeV are under development, based on the new ABCs used as components for SIP linear accelerator systems and ABCs sold to third parties for applications other than Security and NDT. The new products will brag broad energy and dose rate regulation, smooth and reliable operation, providing extended benefits to our customers. * - https://www.varian.com/ - https://www.vareximaging.com/ * - both Thought One LLC and Radmedex LLC have been dissolved in 2018 upon completion of the transition process
	Poster MOPAB349 [2.182 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB349
About •	paper received ※ 13 May 2021 paper accepted ※ 27 May 2021 issue date ※ 14 August 2021
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MOPAB351	Using an RFQ to Transport Intense Heavy Ion Beams from an ECR Ion Source	rfq, ECR, ion-source, focusing	1093
	G.O. Rodrigues IUAC, New Delhi, India R.W. Hamm R&M Technical Enterprises, Pleasanton, California, USA
	In the transport of high intensity, heavy ions from an ECR ion source through a low energy beam transport (LEBT) section, space charge can limit the transmission. It has been proposed to use a Radio Frequency Quadrupole (RFQ) to efficiently address this problem. The stray magnetic field of the ECR ion source can be used to provide focusing against the space charge blow-up when using the Direct Plasma Injection Scheme (DPIS) developed for laser ion sources. The RFQ will focus and transport the injected beam, eliminating most of the charge states extracted from the ECR ion source. This narrowing of the charge state distribution is a filter, reducing the low energy beam transport problem, as well as the emittance growth for the desired beam. A combined extraction/matching system has been designed for direct injection into a 48.5 MHz RFQ for the production of 238U⁴⁰⁺ (0.52 mA) and 209Bi³⁰⁺ (1.047 mA) beams. The IGUN code has been used to design the injection directly into the RFQ. The RFQ design has been modified with a pre-buncher built into the vanes to narrow the transmitted charge state distribution as much as possible. The design details of this system will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB351
About •	paper received ※ 20 May 2021 paper accepted ※ 15 August 2021 issue date ※ 17 August 2021
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MOPAB415	Failure Rates and Downtimes of Multi-Leaf Collimators in Indonesia	linac, radiation, target, power-supply	1248
	G.S. Peiris, S.L. Sheehy The University of Melbourne, Melbourne, Victoria, Australia M.F. Kasim, S.A. Pawiro University of Indonesia, Depok, Jawa Barat, Indonesia
	One of the greatest barriers to cancer treatment in Low and Middle-Income Countries (LMICs) is the access to Radiotherapy Linear Accelerators (LINACs). Not only are the LINACs complex, the harsh environment of LMICs cause frequent breakdowns resulting in downtimes ranging from days to months. Recent research has identified a disparity between LMICs and High Income Countries (HICs) and determined the Multi-Leaf Collimator (MLC) as a component needing re-evaluation. The MLC causes over 30% of the problems in RT LINACs, but the modes of failure and quantify the extent of the damage done are yet to be quantified. Using data from across Indonesia, we show the pathways to failure of RT Machines and frequency of breakdowns over time. A component of the MLC needs to be replaced every 9.98 faults per 1000 patients treated and the MLC itself breaks down on average every 36±1.8 days. When comparing the downtime by leaf width, the data shows 5mm leaves contribute 18.27±6.5% to all breakdowns while 10mm makes up 15.87±4.3%. These results outline the need to reassess the current generation of RT LINACs and ultimately work towards guiding future designs to be robust enough for all environments.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB415
About •	paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 10 August 2021
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TUXB01	A 3 MeV All Optical Terahertz-Driven Electron Source at Tsinghua University	electron, acceleration, laser, 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
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXB01
About •	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	electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXB04
About •	paper received ※ 18 May 2021 paper accepted ※ 22 June 2021 issue date ※ 28 August 2021
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TUPAB033	Photocathode Stress Test Bench at INFN LASA	cathode, laser, electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB033
About •	paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 16 August 2021
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TUPAB037	The Design of a High Charge Polarized Preinjector for the Electron-Ion Collider	cathode, cavity, linac, electron	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB037
About •	paper received ※ 16 May 2021 paper accepted ※ 15 June 2021 issue date ※ 31 August 2021
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TUPAB045	The Low Energy Injector Design for the Southern Advanced Photon Source	electron, linac, cavity, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB045
About •	paper received ※ 17 May 2021 paper accepted ※ 09 June 2021 issue date ※ 21 August 2021
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TUPAB046	Preliminary design of the Full Energy Linac Injector for the Southern Advanced Photon Source	linac, FEL, injection, photon	1454
	X. Liu Institute of High Energy Physics, CAS, Guangdong, People’s Republic of China Y. Jiao, B. Li, S. Wang IHEP, Beijing, People’s Republic of China
	A 4th generation mid-energy range diffraction limited storage ring, named as the Southern Advanced Photon Source (SAPS), is under consideration to be built at the same campus as China Spallation Neutron Source (CSNS), providing a charming one-stop solution for fundamental sciences and industrial applications. While the design of the ring is still under study, a full energy Linac has been proposed as one candidate option for its injector, with the capability of being used as an X-ray Free Electron Laser (XFEL) in the near future. In this paper, an overview of the preliminary design of the Linac is given and simulation results are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB046
About •	paper received ※ 18 May 2021 paper accepted ※ 10 June 2021 issue date ※ 24 August 2021
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TUPAB127	Spare Gun Multi-Physics Analysis for LCLS-II	cavity, cathode, simulation, electron	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB127
About •	paper received ※ 19 May 2021 paper accepted ※ 20 August 2021 issue date ※ 25 August 2021
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TUPAB167	Status of Conduction Cooled SRF Photogun for UEM/UED	SRF, cavity, cryomodule, shielding	1773
	R.A. Kostin, C. Jing Euclid Beamlabs, Bolingbrook, USA P.V. Avrakhov, A. Liu, Y. Zhao Euclid TechLabs, Solon, Ohio, USA
	Funding: DOE #DE-SC0018621 Benefiting from the rapid progress on RF photogun technologies in the past two decades, the development of MeV range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation. UEM or UED use low power electron beams with modest energies of a few MeV to study ultrafast phenomena in a variety of novel and exotic materials. SRF photoguns become a promising candidate to produce highly stable electrons for UEM/UED applications because of the ultrahigh shot-to-shot stability compared to room temperature RF photoguns. SRF technology was prohibitively expensive for industrial use until two recent advancements: Nb₃Sn and conduction cooling. The use of Nb₃Sn allows to operate SRF cavities at higher temperatures (4K) with low power dissipation which is within the reach of commercially available closed-cycle cryocoolers. Euclid is developing a continuous wave (CW), 1.5-cell, MeV-scale SRF conduction cooled photogun operating at 1.3 GHz. In this paper, the technical details of the design and first experimental data are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB167
About •	paper received ※ 29 May 2021 paper accepted ※ 21 June 2021 issue date ※ 31 August 2021
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TUPAB182	The Electron Cooling for High Energy	electron, high-voltage, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB182
About •	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	electron, 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
About •	paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 17 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)	electron, 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]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB236
About •	paper received ※ 19 May 2021 paper accepted ※ 19 July 2021 issue date ※ 25 August 2021
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TUPAB248	A Parallel Time Domain Thermal Solver for Transient Analysis of Accelerator Cavities	cavity, simulation, background, software	2030
	C.-K. Ng, L. Ge, Z. Li, L. Xiao SLAC, Menlo Park, California, USA
	Funding: Work supported by US DOE under contract AC02-76SF00515. Simulation of thermal effects in accelerator cavity is normally performed assuming steady state solution where a static thermal solver suffices to evaluate temperature gradients and impacts on mechanical design. However, during the rf pulse ramp up or the machine system cool-down process, when the field in the cavity changes rapidly, transient effects need to be taken into account. A parallel time domain thermal solver has been developed in the finite element multi-physics code suite ACE3P with integrated electromagnetic, thermal and mechanical modeling capabilities. The implementation takes advantage of the parallel computation infrastructure of ACE3P and shares most of the ingredients in mesh generation, matrix assembly, time advancement scheme and postprocessing. In this paper, we will outline the finite element formulation of the transient thermal problem and verify the implementation against analytical solutions and existing numerical results. The thermal solver has also been coupled to ACE3P mechanical solver, allowing stress and strain analysis during the transient stage. Application of the transient thermal solver to realistic accelerator cavities will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB248
About •	paper received ※ 19 May 2021 paper accepted ※ 18 August 2021 issue date ※ 25 August 2021
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TUPAB286	Experience with On-line Optimizers for APS Linac Front End Optimization	linac, operation, controls, injection	2151
	H. Shang, M. Borland, X. Huang, Y. Sun ANL, Lemont, Illinois, USA M. Song, Z. Zhang SLAC, Menlo Park, California, USA
	Funding: * Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 and BES R&D project FWP 2020-ANL-34573 While the APS linac lattice is set up using a model developed with ELEGANT, the thermionic RF gun front end beam dynamics has been difficult to model. One of the issues is that beam properties from the thermionic gun can vary from time to time. As a result, linac front end beam tuning is required to establish good matching and maximize the charge transported through the linac. We have been using a traditional simplex optimizer to find the best settings for the gun front end magnets and steering magnets. However, it takes a long time and requires some fair initial conditions. Therefore, we imported other on-line optimizers, such as robust conjugate direction search (RCDS) which is a classic optimizer as simplex, multi-objective particle swarm (MOPSO), and multi-generation gaussian process optimizer (MG-GPO) which is based on machine learning technique. In this paper we report our experience with these on-line optimizers for maximum bunch charge transportation efficiency through the linac.
	Poster TUPAB286 [2.964 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB286
About •	paper received ※ 12 May 2021 paper accepted ※ 08 July 2021 issue date ※ 02 September 2021
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TUPAB290	Demonstration of Machine Learning Front-End Optimization of the Advanced Photon Source Linac	linac, controls, electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB290
About •	paper received ※ 09 May 2021 paper accepted ※ 28 July 2021 issue date ※ 19 August 2021
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TUPAB366	Design and Realization of New Solenoids for High Brightness Electron Beam Injectors	solenoid, electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB366
About •	paper received ※ 19 May 2021 paper accepted ※ 18 June 2021 issue date ※ 12 August 2021
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TUPAB387	Superconducting Solenoid Field Measurement and Optimization	solenoid, quadrupole, emittance, multipole	2425
	S. Ma, A. Arnold, P. Murcek, A.A. Ryzhov, J. Schaber, J. Teichert, R. Xiang, P.Z. Zwartek HZDR, Dresden, Germany H.J. Qian DESY Zeuthen, Zeuthen, Germany
	The solenoid is a significant part of an electron injector to provide a proper focusing, and preserve the beam projected emittance. A superconducting solenoid is applied for the SRF photoinjector at HZDR. The solenoid itself can degrade electron beam quality due to magnetic field imperfections like multipole components. In order to determine the field aberrations in the solenoid, we measured the superconducting solenoid magnetic field in the cryomodule. A simple and effective method is used to analyze the multipole field components, which will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB387
About •	paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 25 August 2021
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TUPAB393	Study of Remote Helium Mass Spectrometer Leak Detection in Accelerator	vacuum, detector, operation, controls	2441
	H.Y. He, D.H. Zhu IHEP CSNS, Guangdong Province, People’s Republic of China J.M. Liu DNSC, Dongguan, People’s Republic of China
	In order to solve the problem that the vacuum system of the accelerator can’t be close to the operation for a long time, a long-distance helium mass spectrometer leak detection system is explored by studying the structure of the conventional round tube vacuum box of the vacuum system, which integrates the online vacuum leak detection, defect diagnosis and process design, improves the digital operation, realizes the accurate and effective detection of the leak location range and leak rate, and provides the technology for the remote leak detection of the vacuum system. Support.
	Poster TUPAB393 [0.666 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB393
About •	paper received ※ 13 May 2021 paper accepted ※ 31 May 2021 issue date ※ 15 August 2021
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TUPAB405	Design of High Energy Linac for Generation of Isotopes for Medical Applications	linac, electron, target, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB405
About •	paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 21 August 2021
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TUPAB412	New 3 MeV and 7 MeV Accelerators for Cargo Screening and NDT	electron, target, 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*
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB412
About •	paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 30 August 2021
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TUPAB417	Pushing Spatial Resolution Limits In Single-Shot Time-Resolved Transmission Electron Microscopy at the UCLA Pegasus Laboratory	electron, space-charge, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB417
About •	paper received ※ 19 May 2021 paper accepted ※ 28 July 2021 issue date ※ 12 August 2021
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WEXC03	Review of Superconducting Radio Frequency Gun	cathode, SRF, cavity, operation	2556
	R. Xiang HZDR, Dresden, Germany
	The success of proposed high power free-electron lasers (FELs) and energy recovery linac (ERL) largely depends on the development of the electron source, which requires the best beam quality and CW operation. An elegant way to realize this average brilliance is to combine the high beam quality of mature normal conducting radio frequency photoinjector with the quick developing superconducting radio frequency technology, to build superconducting rf photoinjectors (SRF guns). In last decade, several SRF gun programs based on different approaches have achieved promising progress, even succeeded in routine operation at BNL and HZDR [,]. In the near future SRF guns are expected to play an important role for hard X-ray FEL facilities. In this contribution, we will review the design concepts, parameters, and the status of the major SRF gun projects. I. Petrushina et al., Phys. Rev. Lett. 124, 244801 **J. Teichert at al., Phys. Rev. Accel. Beams 24, 033401
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXC03
About •	paper received ※ 19 May 2021 paper accepted ※ 28 June 2021 issue date ※ 11 August 2021
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WEPAB020	The Relation Between Field Flatness and the Passband Frequency in the Elliptical Cavities	cavity, SRF, simulation, accelerating-gradient	2636
	G.-T. Park, R.A. Rimmer, H. Wang JLab, Newport News, Virginia, USA
	A technique that predicts the field flatness of the operating pi-mode based on the passband frequency is highly desirable when the direct measurement of the field is not available. Such a technique was developed for the SNS-PPU cavity, a 6-cell SRF cavity whose field flatness is important for cold operation. In this paper, we will present the theory on the relations between field profile and passband frequencies of the arbitrary deformed cavities, the simulation studies, and comparison with the experimental measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB020
About •	paper received ※ 17 May 2021 paper accepted ※ 24 June 2021 issue date ※ 31 August 2021
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WEPAB042	Linac-200: A New Electron Test Beam Facility at JINR	electron, controls, linac, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB042
About •	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, electron, 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
About •	paper received ※ 18 May 2021 paper accepted ※ 24 June 2021 issue date ※ 29 August 2021
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WEPAB048	Design of an Optical Cavity for Generating Intense THz Pulse Based on Coherent Cherenkov Radiation	electron, radiation, cavity, 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
About •	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	electron, emittance, cathode, linac	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
About •	paper received ※ 18 May 2021 paper accepted ※ 01 July 2021 issue date ※ 22 August 2021
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WEPAB054	Electromagnetic and Beam Dynamics Studies of the ThomX LINAC	HOM, linac, electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB054
About •	paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 31 August 2021
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WEPAB056	Advanced Photoinjector Development at the UCLA SAMURAI Laboratory	FEL, emittance, linac, simulation	2728
	A. Fukasawa, G. Andonian, O. Camacho, C.E. Hansel, G.E. Lawler, W.J. Lynn, N. Majernik, P. Manwani, B. Naranjo, J.B. Rosenzweig, Y. Sakai, O. Williams UCLA, Los Angeles, California, USA Z. Li, R. Robles, S.G. Tantawi SLAC, Menlo Park, California, USA J.I. Mann PBPL, Los Angeles, USA M. Yadav The University of Liverpool, Liverpool, United Kingdom
	Funding: This work was supported by the US Department of Energy under the contract No. DE-SC0017648, DE-SC0009914, and DE-SC0020409, and by National Science Foundation Grant No. PHY-1549132 UCLA has recently constructed SAMURAI, a new radiation bunker and laser infrastructure for advanced accelerator research. In its first phase, we will build a 30 MeV photoinjector with an S-band hybrid gun. The beam dynamics simulation for this beamline showed the generation of the beam with the emittance 2.4 um and the peak current 270 A. FIR-FEL experiments are planned in this beamline. The saturation peak power was expected at 170 MW.
	Poster WEPAB056 [0.939 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB056
About •	paper received ※ 28 May 2021 paper accepted ※ 01 July 2021 issue date ※ 25 August 2021
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WEPAB067	High Duty Cycle EUV Radiation Source Based on Inverse Compton Scattering	laser, electron, 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]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB067
About •	paper received ※ 23 May 2021 paper accepted ※ 24 June 2021 issue date ※ 11 August 2021
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WEPAB092	Redesign of the Jefferson Lab -300 kV DC Photo-Gun for High Bunch Charge Operations	cathode, high-voltage, simulation, electron	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB092
About •	paper received ※ 20 May 2021 paper accepted ※ 02 June 2021 issue date ※ 19 August 2021
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WEPAB096	RF Testbed for Cryogenic Photoemission Studies	cathode, cryogenics, electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB096
About •	paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 21 August 2021
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WEPAB098	Cryogenic Component and Material Testing for Compact Electron Beamlines	cryogenics, cavity, cathode, electron	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).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB098
About •	paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 18 August 2021
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WEPAB104	Improving the Operational Lifetime of the CEBAF Photo-Gun by Anode Biasing	cathode, laser, simulation, electron	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB104
About •	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	electron, simulation, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB105
About •	paper received ※ 20 May 2021 paper accepted ※ 25 June 2021 issue date ※ 02 September 2021
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WEPAB109	Initial Study of GaN Thin Films for Photocathodes Prepared by Magnetron Sputtering on Copper Substrates	cathode, electron, plasma, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB109
About •	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	electron, cavity, linac, simulation	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
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB110
About •	paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 19 August 2021
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WEPAB138	Superconducting RF Gun with High Current and the Capability to Generate Polarized Electron Beams	SRF, electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB138
About •	paper received ※ 25 May 2021 paper accepted ※ 29 July 2021 issue date ※ 23 August 2021
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WEPAB149	The RF Gun for the Siberian Circular Light Source "SKIF"	cavity, cathode, electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB149
About •	paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 10 August 2021
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WEPAB158	Compact Terahertz-Powered Electron Photo-Gun	electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB158
About •	paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 10 August 2021
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WEPAB163	An X-Band Ultra-High Gradient Photoinjector	experiment, emittance, linac, solenoid	2986
	S.V. Kuzikov, S.P. Antipov, P.V. Avrakhov, E. Dosov, C.-J. Jing, E.W. Knight Euclid TechLabs, Solon, Ohio, USA G. Ha, C.-J. Jing, W. Liu, P. Piot, J.G. Power, D.S. Scott, J.H. Shao, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing Euclid Beamlabs, Bolingbrook, USA X. Lu MIT/PSFC, Cambridge, Massachusetts, USA X. Lu SLAC, Menlo Park, California, USA P. Piot Fermilab, Batavia, Illinois, USA P. Piot, W.H. Tan Northern Illinois University, DeKalb, Illinois, USA E.E. Wisniewski IIT, Chicago, Illinois, USA
	Funding: This work was supported by DoE SBIR grant # DE-SC0018709. High brightness beams appealing for XFELs and UEM essentially imply a high current and a low emittance. To obtain such beams we propose to raise the accelerating voltage in the gun mitigating repealing Coulomb forces. An ultra-high gradient is achieved utilizing a short-pulse technology. We have designed a room temperature X-band 1,5 cell gun that is able to inject 4 MeV, 100 pC bunches with as low as 0.15 mcm normalized transverse emittance. The gun is operated with as high gradients as 400 MV/m and fed by 200 MW, 10 ns RF pulses generated with Argonne Wakefield Accelerator (AWA) power extractor. We report results of low RF power tests, laser alignment test results, and successful gun conditioning results carried out at nominal RF power.
	Poster WEPAB163 [5.427 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB163
About •	paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 13 August 2021
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WEPAB274	Numerical Study of Beam Dynamics in PITZ Bunch Compressor	simulation, laser, booster, FEL	3285
	A. Lueangaramwong, Z. Aboulbanine, G.D. Adhikari, N. Aftab, P. Boonpornprasert, N. Chaisueb, G.Z. Georgiev, J. Good, M. Groß, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, D. Melkumyan, H.J. Qian, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach DESY Zeuthen, Zeuthen, Germany H. Shaker CLS, Saskatoon, Saskatchewan, Canada
	A magnetic bunch compressor has been recently designed for an accelerator-based THz source which is under development at the Photo Injector Test facility at DESY in Zeuthen (PITZ). The THz source is assumed to be a prototype for an accelerator-based THz source for pump-probe experiments at the European XFEL. As an electron bunch is compressed to achieve higher bunch currents for the THz source, we investigate the beam dynamics in the bunch compressor by numerical simulations. A start-to-end simulation optimizer has been developed by combining the use of ASTRA, IMPACT-T, and OCELOT to support the design of the THz source prototype. Coherent synchrotron radiation effects degrade the compression performance for our study cases with bunch charges up to 4 nC and beam energy of 17 MeV at a bending angle of 19 degrees. Simulation and preliminary beam characteristic results will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB274
About •	paper received ※ 11 May 2021 paper accepted ※ 06 July 2021 issue date ※ 15 August 2021
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WEPAB287	Upgrade of the ELBE Timing System	timing, operation, hardware, GUI	3326
	M. Kuntzsch, M. Justus, A. Schwarz, K. Zenker HZDR, Dresden, Germany L. Krmpotic, U. Legat, U. Rojec Cosylab, Ljubljana, Slovenia Ž. Oven COSYLAB, Control System Laboratory, Ljubljana, Slovenia
	At the ELBE accelerator center a superconducting linac is operated to drive manifold secondary radiation sources like two infrared FELs, a positron source and a THz facility. The machine uses two injectors as electron sources that are accelerated in the main linac. The user experiments demand a large variety of bunch patterns from single shot to macro pulsed and cw beam at up to 26 MHz repetition rate. At ELBE a new timing system is being developed based on the MRF hardware platform and the MRF Timing System IOC. It uses two masters and a scalable number of connected receivers to generate the desired pulse patterns for operating the machine and to control user experiments. The contribution will show the architecture of the timing system, the control interfacing and performance measurements acquired on the test bench.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB287
About •	paper received ※ 21 May 2021 paper accepted ※ 01 July 2021 issue date ※ 29 August 2021
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WEPAB294	LLRF Control and Synchronization System of the ARES Facility	LLRF, laser, experiment, distributed	3347
	S. Pfeiffer, J. Branlard, F. Burkart, M. Hoffmann, T. Lamb, F. Ludwig, H. Schlarb, S. Schulz, B. Szczepanski, M. Titberidze DESY, Hamburg, Germany
	The linear accelerator ARES (Accelerator Research Experiment at SINBAD) is a new research facility at DESY. Electron bunches with a maximum repetition rate of 50 Hz are accelerated up to 155 MeV. The facility aims for ultra-stable sub-femtosecond arrival-times and high peak-currents at the experiment, placing high demands on the reference distribution and field regulation of the S-band RF structures. In this paper, we report on the current status of the RF reference generation, facility-wide distribution, and the LLRF systems of the RF structures.
	Poster WEPAB294 [2.394 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB294
About •	paper received ※ 18 May 2021 paper accepted ※ 05 July 2021 issue date ※ 11 August 2021
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WEPAB295	Parameter Estimation of Short Pulse Normal-Conducting Standing Wave Cavities	cavity, coupling, RF-structure, resonance	3351
	S. Pfeiffer, J. Branlard, F. Burkart, M. Hoffmann, H. Schlarb DESY, Hamburg, Germany
	The linear accelerator ARES (Accelerator Research Experiment at SINBAD) is a new research facility at DESY. Electron bunches with a maximum repetition rate of 50 Hz are accelerated to a target energy of 155 MeV. The facility aims for ultra-stable sub-femtosecond arrival-times and high peak-currents at the experiment, placing high demands on the reference distribution and field regulation of the RF structure. In this contribution, we present the physical parameter estimation of key RF properties such as cavity detuning not directly measurable on the RF field decay. The method can be used as a fast monitor of inner cell temperature. The estimated properties are finally compared with the measured ones.
	Poster WEPAB295 [0.860 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB295
About •	paper received ※ 19 May 2021 paper accepted ※ 05 July 2021 issue date ※ 10 August 2021
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WEPAB371	Numerical Analysis on Nitrogen Injection Fire Extinguishing System in the LINAC Area at TPS	simulation, linac, injection, GUI	3578
	J.-C. Chang, W.S. Chan, Y.F. Chiu NSRRC, Hsinchu, Taiwan
	The Linear accelerator (LINAC) of Taiwan Photon Source (TPS) could generate electrons to 150 MeV. The main subsystems including an electron gun, buncher, accelerating sections, vacuum system, and focusing and steering magnets are located in the LINAC area of 223.5 m2 and 3 m in height. We designed a nitrogen injection fire extinguishing system for the LINAC area and performed Computational Fluid Dynamic (CFD) simulation to analyse the fire extinguishing performance with and without fresh air supplied from the air conditioning system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB371
About •	paper received ※ 16 May 2021 paper accepted ※ 21 June 2021 issue date ※ 19 August 2021
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WEPAB374	The Southern Hemisphere’s First X-Band Radio-Frequency Test Facility at the University of Melbourne	electron, klystron, 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
About •	paper received ※ 18 May 2021 paper accepted ※ 06 July 2021 issue date ※ 12 August 2021
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WEPAB385	Beam Dynamic Analysis of RF Modulated Electron Beam Produced by Gridded Thermionic Guns	electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB385
About •	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, electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB387
About •	paper received ※ 18 May 2021 paper accepted ※ 23 July 2021 issue date ※ 13 August 2021
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WEPAB418	The Power Supply System for 10 MeV & 20 kW Industry Irradiation Facility	power-supply, radiation, electron, 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]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB418
About •	paper received ※ 15 May 2021 paper accepted ※ 23 June 2021 issue date ※ 29 August 2021
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THXC06	Design and Measurements of an X-Band 8 MeV Standing-Wave Electron Accelerator	electron, bunching, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXC06
About •	paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 22 August 2021
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THPAB082	Recent Operational Experience with Thermionic RF Guns at the APS	linac, operation, cathode, injection	3959
	Y. Sun, M. Borland, G.I. Fystro, X. Huang, H. Shang 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 electron beam at the Argonne Advanced Photon Source (APS) is generated from an S-band thermionic RF gun. There are two locations at the frontend of the linac where thermionic RF guns are installed – RG1 and RG2. Three so-called generation-III guns are available, two are installed at RG1 and RG2, one is a spare. In recent years, these guns are showing signs of aging after over a couple of decades of operations. RF trips started to occur, and we had to reduce the nominal operating rf power to alleviate the problem. In addition, beam generated by RG1 suffers from low transportation efficiency from the gun to the linac, and beam trajectory is unstable which results in charge instabilities. Recently, APS obtained a new type of prototype gun and it was beam commissioned in the linac. In this paper, we report our operational experience with these thermionic rf guns including thermionic-cathode beam extraction, gun front-end optimization for maximum charge transmission through the linac, linac lattice setup to match beam for injection into the Particle Accumulator Ring (PAR) and optimization for maximum PAR injection efficiency.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB082
About •	paper received ※ 19 May 2021 paper accepted ※ 28 July 2021 issue date ※ 16 August 2021
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THPAB083	Measurement of the Longitudinal Phase-Space of the APS Photo-Injector Beam	linac, cavity, dipole, lattice	3963
	Y. Sun 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. An S-band photo-cathode RF gun (PCG) exists at the front of the linac. The high-brightness photoinjector beam is accelerated by the linac and and can be used for accelerator technology and beam physics R&D experiments in the Linac Extension Area (LEA). For some applications, the beam needs to be compressed by a magnetic bunch compressor in the middle of the linac. An S-band transverse-mode cavity (Tcav) is available at the end of the linac for beam longitudinal phase-space diagnostics. Beam commissioning experience of the Tcav is reported in this paper. The cavity rf conditioning and calibration was performed. There is a horizontally bending dipole magnet downstream of the Tcav, which kicks beam in the vertical plane. Beam image on a YAG screen downstream of the Tcav and dipole magnet contains the single-shot information of the longitudinal phase-space of the photo-injector beam. The first measurements of the longitudinal phase-space of the compressed and non-compressed photoinjector beam are discussed. Improvements of the measurement resolution are planned.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB083
About •	paper received ※ 25 May 2021 paper accepted ※ 12 July 2021 issue date ※ 26 August 2021
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THPAB119	Many-Objective Beam Dynamics Optimization for High-Repetition-Rate XFEL Photoinjector	emittance, FEL, electron, 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]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB119
About •	paper received ※ 17 May 2021 paper accepted ※ 07 July 2021 issue date ※ 30 August 2021
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THPAB129	Beam Dynamics Simulations in a High-Gradient X-Band Photoinjector	emittance, cathode, electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB129
About •	paper received ※ 20 May 2021 paper accepted ※ 14 July 2021 issue date ※ 31 August 2021
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THPAB141	Novel Design of a HVDC Magnetized Electron Source	cathode, solenoid, permanent-magnet, simulation	4034
	O.H. Rahman, J. Skaritka, E. Wang 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 hadron beam in EIC is flat with a transverse size ratio of about 1:3. The cooling rate of the hadron beam can be maximized if the electron beam from the strong hadron cooler fully overlaps with the hadron beam. Therefore, generating a flat electron beam is essential. The most efficient way to generate a flat electron beam is to produce a magnetized beam first, and then convert it to flat to the desired transverse size ratio. Using a Magnetized electron beam is a promising way to cool high-energy hadrons. One of the major challenges in producing magnetized beams is fine-tuning the longitudinal magnetic field on the cathode surface and maintaining the desired field uniformity over the emission area. In this paper, we discuss the design of a novel high voltage DC gun capable of fine-tuning the B field on the cathode. This is achieved by installing a permanent magnet inside the cathode puck, with a solenoid field at the front of the cathode. We show magnetostatic simulation to prove the feasibility of this idea. We also show preliminary beam dynamics simulations showing emittance from the gun as the permanent magnet and solenoidal fields are tuned for minimum emittance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB141
About •	paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 25 August 2021
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THPAB145	Cold Test of a Novel S-Band 1.6 Cell Photocathode RF Gun	cavity, coupling, cathode, simulation	4045
	Zh.X. Tang, S.X. Dong, Y.J. Pei, B.F. Wei USTC/NSRL, Hefei, Anhui, People’s Republic of China
	Funding: Work supported by National Natural Science Foundation of China(Grant No. 11805199 and U1832135) and Fundamental Research Funds for the Central Universities (Grant No. WK2310000072) The photocathode RF gun is one of the most critical components for high quality electron beam sources. The asymmetric multi-pole field contributes to the transverse emittance growth and degrades the beam quality. In order to overcome the problem, we propose a novel rotationally symmetric 1.6 cell RF gun to construct the symmetric field in this paper. The concrete proposal is that a coaxial cell cavity with a symmetrical distribution of four grooves is concatenated to the photocathode end of the traditional 0.6 cell cavity to form the novel 0.6 cell cavity. Through the detailed design study, the profile of the RF gun is optimized to improve the shunt impedance and mode separation and make the surface peak electric field at the photocathode end. Considering the filling time, a coupling slot is designed to couple input power into the RF gun. The RF cavity is machined by numerical control machine tool, and the tuning and low power RF measurement are carried out. The experimental results are consistent with the simulation results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB145
About •	paper received ※ 09 May 2021 paper accepted ※ 30 August 2021 issue date ※ 02 September 2021
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THPAB146	Preliminary Study of Femtosecond Electron Source Based on THz Acceleration and Field Emission	electron, cavity, FEM, cathode	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB146
About •	paper received ※ 09 May 2021 paper accepted ※ 18 August 2021 issue date ※ 02 September 2021
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THPAB156	Built-in Thermionic Electron Source for an SRF Linacs	cathode, cavity, electron, 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
About •	paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 28 August 2021
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THPAB290	Evolution of the LHC Beam Screen Surface Conditioning Upon Electron Irradiation	electron, radiation, ECR, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB290
About •	paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 26 August 2021
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THPAB331	High-Power Test of a Highly Over-Coupled X-Band RF Gun Driven by Short RF Pulses	cathode, electron, 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB331
About •	paper received ※ 25 May 2021 paper accepted ※ 14 July 2021 issue date ※ 10 August 2021
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THPAB344	Magneto-Optical Trap Cathode for High Brightness Applications	electron, laser, emittance, cathode	4466

Paper

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MOXC02

Improved Lifetime of a High Spin Polarization Superlattice Photocathode

electron, cathode, polarization, 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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MOPAB107

RF Plans for the Diamond-II Upgrade

cavity, HOM, linac, booster

391

C. Christou, P. Gu, P.J. Marten, S.A. Pande, A.F. Rankin
DLS, Oxfordshire, United Kingdom

The RF system for the proposed Diamond-II upgrade will be based on normal-conducting EU HOM-damped cavities powered by high powered solid state amplifiers and controlled by digital low level RF systems built on the microTCA platform. Reasons for these design choices are discussed, and experience of the selected technologies in the Diamond-I ring are reviewed. The storage ring will also include a third harmonic cavity, and the different design options for this device are discussed. RF design of the booster ring is presented, and details are given of an upgraded linac and gun design intended to improve the charge delivered for top-up.

Poster MOPAB107 [1.703 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB107

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

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MOPAB255

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

cavity, electron, 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

emittance, simulation, electron, 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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MOPAB314

Surrogate Modeling for MUED with Neural Networks

electron, experiment, 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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MOPAB348

Portable 2.5 MeV X-Band Linear Accelerator Structure

linac, GUI, radiation, target

1084

A.V. Mishin, K. Brown, M. Denney, D. Fischer, N.P. Hanson, S. Proskin, J. Stammetti
Varex Imaging, Salt Lake City, USA

Two versions of 2.5 MeV X-Band linear accelerator structure have been designed and tested. The first is a traditional single input linac, and the other one is a dual input, two section linac with power input through a 3 dB coupler. The linac is designed for a portable linac system, which can be used for security screening, non-destructive testing, medical and industrial CT, and, perhaps, some other applications.

Poster MOPAB348 [1.490 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB348

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

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MOPAB349

New Accelerator Beam Centerline (ABC) Production Line at Varex Imaging Corporation

linac, betatron, detector, GUI

1087

A.V. Mishin
Varex Imaging, Salt Lake City, USA

In January 2017, a Salt Lake City Component Division of Varian Medical (Varian)*, producer of X-ray tubes, detectors, and imaging panels has been spun off, giving birth to a new public company Varex Imaging Corporation (Varex)**, which also includes the Security and Inspection Products (SIP) linac producer in Las Vegas. Based on Varian asset acquisition of two small LLCs*** in May 2016, 8 months prior to the transition, a new business branch within Varex has been established, which included distribution of the betatrons and detector arrays as well as pilot production line for Accelerator Beam Centerlines (ABC). In 3 years, we moved ABC production from Fremont, CA to Salt Lake in Utah and improved it; several ABCs have been designed, produced, and qualified. A number of new products in energy range of 1-20 MeV are under development, based on the new ABCs used as components for SIP linear accelerator systems and ABCs sold to third parties for applications other than Security and NDT. The new products will brag broad energy and dose rate regulation, smooth and reliable operation, providing extended benefits to our customers.
* - https://www.varian.com/
** - https://www.vareximaging.com/
*** - both Thought One LLC and Radmedex LLC have been dissolved in 2018 upon completion of the transition process

Poster MOPAB349 [2.182 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB349

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paper received ※ 13 May 2021 paper accepted ※ 27 May 2021 issue date ※ 14 August 2021

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MOPAB351

Using an RFQ to Transport Intense Heavy Ion Beams from an ECR Ion Source

rfq, ECR, ion-source, focusing

1093

G.O. Rodrigues
IUAC, New Delhi, India
R.W. Hamm
R&M Technical Enterprises, Pleasanton, California, USA

In the transport of high intensity, heavy ions from an ECR ion source through a low energy beam transport (LEBT) section, space charge can limit the transmission. It has been proposed to use a Radio Frequency Quadrupole (RFQ) to efficiently address this problem. The stray magnetic field of the ECR ion source can be used to provide focusing against the space charge blow-up when using the Direct Plasma Injection Scheme (DPIS) developed for laser ion sources. The RFQ will focus and transport the injected beam, eliminating most of the charge states extracted from the ECR ion source. This narrowing of the charge state distribution is a filter, reducing the low energy beam transport problem, as well as the emittance growth for the desired beam. A combined extraction/matching system has been designed for direct injection into a 48.5 MHz RFQ for the production of 238U⁴⁰⁺ (0.52 mA) and 209Bi³⁰⁺ (1.047 mA) beams. The IGUN code has been used to design the injection directly into the RFQ. The RFQ design has been modified with a pre-buncher built into the vanes to narrow the transmitted charge state distribution as much as possible. The design details of this system will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB351

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paper received ※ 20 May 2021 paper accepted ※ 15 August 2021 issue date ※ 17 August 2021

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MOPAB415

Failure Rates and Downtimes of Multi-Leaf Collimators in Indonesia

linac, radiation, target, power-supply

1248

G.S. Peiris, S.L. Sheehy
The University of Melbourne, Melbourne, Victoria, Australia
M.F. Kasim, S.A. Pawiro
University of Indonesia, Depok, Jawa Barat, Indonesia

One of the greatest barriers to cancer treatment in Low and Middle-Income Countries (LMICs) is the access to Radiotherapy Linear Accelerators (LINACs). Not only are the LINACs complex, the harsh environment of LMICs cause frequent breakdowns resulting in downtimes ranging from days to months. Recent research has identified a disparity between LMICs and High Income Countries (HICs) and determined the Multi-Leaf Collimator (MLC) as a component needing re-evaluation. The MLC causes over 30% of the problems in RT LINACs, but the modes of failure and quantify the extent of the damage done are yet to be quantified. Using data from across Indonesia, we show the pathways to failure of RT Machines and frequency of breakdowns over time. A component of the MLC needs to be replaced every 9.98 faults per 1000 patients treated and the MLC itself breaks down on average every 36±1.8 days. When comparing the downtime by leaf width, the data shows 5mm leaves contribute 18.27±6.5% to all breakdowns while 10mm makes up 15.87±4.3%. These results outline the need to reassess the current generation of RT LINACs and ultimately work towards guiding future designs to be robust enough for all environments.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB415

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 10 August 2021

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TUXB01

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

electron, acceleration, laser, 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

electron, 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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TUPAB033

Photocathode Stress Test Bench at INFN LASA

cathode, laser, electron, 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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TUPAB037

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

cathode, cavity, linac, electron

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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TUPAB045

The Low Energy Injector Design for the Southern Advanced Photon Source

electron, linac, cavity, 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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TUPAB046

Preliminary design of the Full Energy Linac Injector for the Southern Advanced Photon Source

linac, FEL, injection, photon

1454

X. Liu
Institute of High Energy Physics, CAS, Guangdong, People’s Republic of China
Y. Jiao, B. Li, S. Wang
IHEP, Beijing, People’s Republic of China

A 4th generation mid-energy range diffraction limited storage ring, named as the Southern Advanced Photon Source (SAPS), is under consideration to be built at the same campus as China Spallation Neutron Source (CSNS), providing a charming one-stop solution for fundamental sciences and industrial applications. While the design of the ring is still under study, a full energy Linac has been proposed as one candidate option for its injector, with the capability of being used as an X-ray Free Electron Laser (XFEL) in the near future. In this paper, an overview of the preliminary design of the Linac is given and simulation results are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB046

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paper received ※ 18 May 2021 paper accepted ※ 10 June 2021 issue date ※ 24 August 2021

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TUPAB127

Spare Gun Multi-Physics Analysis for LCLS-II

cavity, cathode, simulation, electron

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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TUPAB167

Status of Conduction Cooled SRF Photogun for UEM/UED

SRF, cavity, cryomodule, shielding

1773

R.A. Kostin, C. Jing
Euclid Beamlabs, Bolingbrook, USA
P.V. Avrakhov, A. Liu, Y. Zhao
Euclid TechLabs, Solon, Ohio, USA

Funding: DOE #DE-SC0018621
Benefiting from the rapid progress on RF photogun technologies in the past two decades, the development of MeV range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation. UEM or UED use low power electron beams with modest energies of a few MeV to study ultrafast phenomena in a variety of novel and exotic materials. SRF photoguns become a promising candidate to produce highly stable electrons for UEM/UED applications because of the ultrahigh shot-to-shot stability compared to room temperature RF photoguns. SRF technology was prohibitively expensive for industrial use until two recent advancements: Nb₃Sn and conduction cooling. The use of Nb₃Sn allows to operate SRF cavities at higher temperatures (4K) with low power dissipation which is within the reach of commercially available closed-cycle cryocoolers. Euclid is developing a continuous wave (CW), 1.5-cell, MeV-scale SRF conduction cooled photogun operating at 1.3 GHz. In this paper, the technical details of the design and first experimental data are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB167

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paper received ※ 29 May 2021 paper accepted ※ 21 June 2021 issue date ※ 31 August 2021

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TUPAB182

The Electron Cooling for High Energy

electron, high-voltage, 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

electron, 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]

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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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TUPAB236

Progress on the Electron Gun Design for a McMillan Electron Lens in the Fermilab Integrable Optics Test Accelerator (IOTA)

electron, 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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TUPAB248

A Parallel Time Domain Thermal Solver for Transient Analysis of Accelerator Cavities

cavity, simulation, background, software

2030

C.-K. Ng, L. Ge, Z. Li, L. Xiao
SLAC, Menlo Park, California, USA

Funding: Work supported by US DOE under contract AC02-76SF00515.
Simulation of thermal effects in accelerator cavity is normally performed assuming steady state solution where a static thermal solver suffices to evaluate temperature gradients and impacts on mechanical design. However, during the rf pulse ramp up or the machine system cool-down process, when the field in the cavity changes rapidly, transient effects need to be taken into account. A parallel time domain thermal solver has been developed in the finite element multi-physics code suite ACE3P with integrated electromagnetic, thermal and mechanical modeling capabilities. The implementation takes advantage of the parallel computation infrastructure of ACE3P and shares most of the ingredients in mesh generation, matrix assembly, time advancement scheme and postprocessing. In this paper, we will outline the finite element formulation of the transient thermal problem and verify the implementation against analytical solutions and existing numerical results. The thermal solver has also been coupled to ACE3P mechanical solver, allowing stress and strain analysis during the transient stage. Application of the transient thermal solver to realistic accelerator cavities will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB248

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paper received ※ 19 May 2021 paper accepted ※ 18 August 2021 issue date ※ 25 August 2021

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TUPAB286

Experience with On-line Optimizers for APS Linac Front End Optimization

linac, operation, controls, injection

2151

H. Shang, M. Borland, X. Huang, Y. Sun
ANL, Lemont, Illinois, USA
M. Song, Z. Zhang
SLAC, Menlo Park, California, USA

Funding: * Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 and BES R&D project FWP 2020-ANL-34573
While the APS linac lattice is set up using a model developed with ELEGANT, the thermionic RF gun front end beam dynamics has been difficult to model. One of the issues is that beam properties from the thermionic gun can vary from time to time. As a result, linac front end beam tuning is required to establish good matching and maximize the charge transported through the linac. We have been using a traditional simplex optimizer to find the best settings for the gun front end magnets and steering magnets. However, it takes a long time and requires some fair initial conditions. Therefore, we imported other on-line optimizers, such as robust conjugate direction search (RCDS) which is a classic optimizer as simplex, multi-objective particle swarm (MOPSO), and multi-generation gaussian process optimizer (MG-GPO) which is based on machine learning technique. In this paper we report our experience with these on-line optimizers for maximum bunch charge transportation efficiency through the linac.

Poster TUPAB286 [2.964 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB286

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paper received ※ 12 May 2021 paper accepted ※ 08 July 2021 issue date ※ 02 September 2021

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TUPAB290

Demonstration of Machine Learning Front-End Optimization of the Advanced Photon Source Linac

linac, controls, electron, 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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TUPAB366

Design and Realization of New Solenoids for High Brightness Electron Beam Injectors

solenoid, electron, 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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TUPAB387

Superconducting Solenoid Field Measurement and Optimization

solenoid, quadrupole, emittance, multipole

2425

S. Ma, A. Arnold, P. Murcek, A.A. Ryzhov, J. Schaber, J. Teichert, R. Xiang, P.Z. Zwartek
HZDR, Dresden, Germany
H.J. Qian
DESY Zeuthen, Zeuthen, Germany

The solenoid is a significant part of an electron injector to provide a proper focusing, and preserve the beam projected emittance. A superconducting solenoid is applied for the SRF photoinjector at HZDR. The solenoid itself can degrade electron beam quality due to magnetic field imperfections like multipole components. In order to determine the field aberrations in the solenoid, we measured the superconducting solenoid magnetic field in the cryomodule. A simple and effective method is used to analyze the multipole field components, which will be presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB387

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

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TUPAB393

Study of Remote Helium Mass Spectrometer Leak Detection in Accelerator

vacuum, detector, operation, controls

2441

H.Y. He, D.H. Zhu
IHEP CSNS, Guangdong Province, People’s Republic of China
J.M. Liu
DNSC, Dongguan, People’s Republic of China

In order to solve the problem that the vacuum system of the accelerator can’t be close to the operation for a long time, a long-distance helium mass spectrometer leak detection system is explored by studying the structure of the conventional round tube vacuum box of the vacuum system, which integrates the online vacuum leak detection, defect diagnosis and process design, improves the digital operation, realizes the accurate and effective detection of the leak location range and leak rate, and provides the technology for the remote leak detection of the vacuum system. Support.

Poster TUPAB393 [0.666 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB393

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paper received ※ 13 May 2021 paper accepted ※ 31 May 2021 issue date ※ 15 August 2021

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TUPAB405

Design of High Energy Linac for Generation of Isotopes for Medical Applications

linac, electron, target, 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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TUPAB412

New 3 MeV and 7 MeV Accelerators for Cargo Screening and NDT

electron, target, 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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TUPAB417

Pushing Spatial Resolution Limits In Single-Shot Time-Resolved Transmission Electron Microscopy at the UCLA Pegasus Laboratory

electron, space-charge, 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.

DOI •

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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WEXC03

Review of Superconducting Radio Frequency Gun

cathode, SRF, cavity, operation

2556

R. Xiang
HZDR, Dresden, Germany

The success of proposed high power free-electron lasers (FELs) and energy recovery linac (ERL) largely depends on the development of the electron source, which requires the best beam quality and CW operation. An elegant way to realize this average brilliance is to combine the high beam quality of mature normal conducting radio frequency photoinjector with the quick developing superconducting radio frequency technology, to build superconducting rf photoinjectors (SRF guns). In last decade, several SRF gun programs based on different approaches have achieved promising progress, even succeeded in routine operation at BNL and HZDR [*,**]. In the near future SRF guns are expected to play an important role for hard X-ray FEL facilities. In this contribution, we will review the design concepts, parameters, and the status of the major SRF gun projects.
*I. Petrushina et al., Phys. Rev. Lett. 124, 244801
**J. Teichert at al., Phys. Rev. Accel. Beams 24, 033401

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXC03

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

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WEPAB020

The Relation Between Field Flatness and the Passband Frequency in the Elliptical Cavities

cavity, SRF, simulation, accelerating-gradient

2636

G.-T. Park, R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA

A technique that predicts the field flatness of the operating pi-mode based on the passband frequency is highly desirable when the direct measurement of the field is not available. Such a technique was developed for the SNS-PPU cavity, a 6-cell SRF cavity whose field flatness is important for cold operation. In this paper, we will present the theory on the relations between field profile and passband frequencies of the arbitrary deformed cavities, the simulation studies, and comparison with the experimental measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB020

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paper received ※ 17 May 2021 paper accepted ※ 24 June 2021 issue date ※ 31 August 2021

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WEPAB042

Linac-200: A New Electron Test Beam Facility at JINR

electron, controls, linac, 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, electron, 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.

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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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WEPAB048

Design of an Optical Cavity for Generating Intense THz Pulse Based on Coherent Cherenkov Radiation

electron, radiation, cavity, 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.

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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

electron, emittance, cathode, linac

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]

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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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WEPAB054

Electromagnetic and Beam Dynamics Studies of the ThomX LINAC

HOM, linac, electron, 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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WEPAB056

Advanced Photoinjector Development at the UCLA SAMURAI Laboratory

FEL, emittance, linac, simulation

2728

A. Fukasawa, G. Andonian, O. Camacho, C.E. Hansel, G.E. Lawler, W.J. Lynn, N. Majernik, P. Manwani, B. Naranjo, J.B. Rosenzweig, Y. Sakai, O. Williams
UCLA, Los Angeles, California, USA
Z. Li, R. Robles, S.G. Tantawi
SLAC, Menlo Park, California, USA
J.I. Mann
PBPL, Los Angeles, USA
M. Yadav
The University of Liverpool, Liverpool, United Kingdom

Funding: This work was supported by the US Department of Energy under the contract No. DE-SC0017648, DE-SC0009914, and DE-SC0020409, and by National Science Foundation Grant No. PHY-1549132
UCLA has recently constructed SAMURAI, a new radiation bunker and laser infrastructure for advanced accelerator research. In its first phase, we will build a 30 MeV photoinjector with an S-band hybrid gun. The beam dynamics simulation for this beamline showed the generation of the beam with the emittance 2.4 um and the peak current 270 A. FIR-FEL experiments are planned in this beamline. The saturation peak power was expected at 170 MW.

Poster WEPAB056 [0.939 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB056

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paper received ※ 28 May 2021 paper accepted ※ 01 July 2021 issue date ※ 25 August 2021

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WEPAB067

High Duty Cycle EUV Radiation Source Based on Inverse Compton Scattering

laser, electron, 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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WEPAB092

Redesign of the Jefferson Lab -300 kV DC Photo-Gun for High Bunch Charge Operations

cathode, high-voltage, simulation, electron

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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WEPAB096

RF Testbed for Cryogenic Photoemission Studies

cathode, cryogenics, electron, 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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WEPAB098

Cryogenic Component and Material Testing for Compact Electron Beamlines

cryogenics, cavity, cathode, electron

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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WEPAB104

Improving the Operational Lifetime of the CEBAF Photo-Gun by Anode Biasing

cathode, laser, simulation, electron

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

electron, simulation, 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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WEPAB109

Initial Study of GaN Thin Films for Photocathodes Prepared by Magnetron Sputtering on Copper Substrates

cathode, electron, plasma, 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

electron, cavity, linac, simulation

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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WEPAB138

Superconducting RF Gun with High Current and the Capability to Generate Polarized Electron Beams

SRF, electron, 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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WEPAB149

The RF Gun for the Siberian Circular Light Source "SKIF"

cavity, cathode, electron, 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.

DOI •

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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WEPAB158

Compact Terahertz-Powered Electron Photo-Gun

electron, 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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WEPAB163

An X-Band Ultra-High Gradient Photoinjector

experiment, emittance, linac, solenoid

2986

S.V. Kuzikov, S.P. Antipov, P.V. Avrakhov, E. Dosov, C.-J. Jing, E.W. Knight
Euclid TechLabs, Solon, Ohio, USA
G. Ha, C.-J. Jing, W. Liu, P. Piot, J.G. Power, D.S. Scott, J.H. Shao, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing
Euclid Beamlabs, Bolingbrook, USA
X. Lu
MIT/PSFC, Cambridge, Massachusetts, USA
X. Lu
SLAC, Menlo Park, California, USA
P. Piot
Fermilab, Batavia, Illinois, USA
P. Piot, W.H. Tan
Northern Illinois University, DeKalb, Illinois, USA
E.E. Wisniewski
IIT, Chicago, Illinois, USA

Funding: This work was supported by DoE SBIR grant # DE-SC0018709.
High brightness beams appealing for XFELs and UEM essentially imply a high current and a low emittance. To obtain such beams we propose to raise the accelerating voltage in the gun mitigating repealing Coulomb forces. An ultra-high gradient is achieved utilizing a short-pulse technology. We have designed a room temperature X-band 1,5 cell gun that is able to inject 4 MeV, 100 pC bunches with as low as 0.15 mcm normalized transverse emittance. The gun is operated with as high gradients as 400 MV/m and fed by 200 MW, 10 ns RF pulses generated with Argonne Wakefield Accelerator (AWA) power extractor. We report results of low RF power tests, laser alignment test results, and successful gun conditioning results carried out at nominal RF power.

Poster WEPAB163 [5.427 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB163

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paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 13 August 2021

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WEPAB274

Numerical Study of Beam Dynamics in PITZ Bunch Compressor

simulation, laser, booster, FEL

3285

A. Lueangaramwong, Z. Aboulbanine, G.D. Adhikari, N. Aftab, P. Boonpornprasert, N. Chaisueb, G.Z. Georgiev, J. Good, M. Groß, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, D. Melkumyan, H.J. Qian, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach
DESY Zeuthen, Zeuthen, Germany
H. Shaker
CLS, Saskatoon, Saskatchewan, Canada

A magnetic bunch compressor has been recently designed for an accelerator-based THz source which is under development at the Photo Injector Test facility at DESY in Zeuthen (PITZ). The THz source is assumed to be a prototype for an accelerator-based THz source for pump-probe experiments at the European XFEL. As an electron bunch is compressed to achieve higher bunch currents for the THz source, we investigate the beam dynamics in the bunch compressor by numerical simulations. A start-to-end simulation optimizer has been developed by combining the use of ASTRA, IMPACT-T, and OCELOT to support the design of the THz source prototype. Coherent synchrotron radiation effects degrade the compression performance for our study cases with bunch charges up to 4 nC and beam energy of 17 MeV at a bending angle of 19 degrees. Simulation and preliminary beam characteristic results will be presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB274

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paper received ※ 11 May 2021 paper accepted ※ 06 July 2021 issue date ※ 15 August 2021

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WEPAB287

Upgrade of the ELBE Timing System

timing, operation, hardware, GUI

3326

M. Kuntzsch, M. Justus, A. Schwarz, K. Zenker
HZDR, Dresden, Germany
L. Krmpotic, U. Legat, U. Rojec
Cosylab, Ljubljana, Slovenia
Ž. Oven
COSYLAB, Control System Laboratory, Ljubljana, Slovenia

At the ELBE accelerator center a superconducting linac is operated to drive manifold secondary radiation sources like two infrared FELs, a positron source and a THz facility. The machine uses two injectors as electron sources that are accelerated in the main linac. The user experiments demand a large variety of bunch patterns from single shot to macro pulsed and cw beam at up to 26 MHz repetition rate. At ELBE a new timing system is being developed based on the MRF hardware platform and the MRF Timing System IOC. It uses two masters and a scalable number of connected receivers to generate the desired pulse patterns for operating the machine and to control user experiments. The contribution will show the architecture of the timing system, the control interfacing and performance measurements acquired on the test bench.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB287

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paper received ※ 21 May 2021 paper accepted ※ 01 July 2021 issue date ※ 29 August 2021

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WEPAB294

LLRF Control and Synchronization System of the ARES Facility

LLRF, laser, experiment, distributed

3347

S. Pfeiffer, J. Branlard, F. Burkart, M. Hoffmann, T. Lamb, F. Ludwig, H. Schlarb, S. Schulz, B. Szczepanski, M. Titberidze
DESY, Hamburg, Germany

The linear accelerator ARES (Accelerator Research Experiment at SINBAD) is a new research facility at DESY. Electron bunches with a maximum repetition rate of 50 Hz are accelerated up to 155 MeV. The facility aims for ultra-stable sub-femtosecond arrival-times and high peak-currents at the experiment, placing high demands on the reference distribution and field regulation of the S-band RF structures. In this paper, we report on the current status of the RF reference generation, facility-wide distribution, and the LLRF systems of the RF structures.

Poster WEPAB294 [2.394 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB294

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paper received ※ 18 May 2021 paper accepted ※ 05 July 2021 issue date ※ 11 August 2021

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WEPAB295

Parameter Estimation of Short Pulse Normal-Conducting Standing Wave Cavities

cavity, coupling, RF-structure, resonance

3351

S. Pfeiffer, J. Branlard, F. Burkart, M. Hoffmann, H. Schlarb
DESY, Hamburg, Germany

The linear accelerator ARES (Accelerator Research Experiment at SINBAD) is a new research facility at DESY. Electron bunches with a maximum repetition rate of 50 Hz are accelerated to a target energy of 155 MeV. The facility aims for ultra-stable sub-femtosecond arrival-times and high peak-currents at the experiment, placing high demands on the reference distribution and field regulation of the RF structure. In this contribution, we present the physical parameter estimation of key RF properties such as cavity detuning not directly measurable on the RF field decay. The method can be used as a fast monitor of inner cell temperature. The estimated properties are finally compared with the measured ones.

Poster WEPAB295 [0.860 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB295

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paper received ※ 19 May 2021 paper accepted ※ 05 July 2021 issue date ※ 10 August 2021

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WEPAB371

Numerical Analysis on Nitrogen Injection Fire Extinguishing System in the LINAC Area at TPS

simulation, linac, injection, GUI

3578

J.-C. Chang, W.S. Chan, Y.F. Chiu
NSRRC, Hsinchu, Taiwan

The Linear accelerator (LINAC) of Taiwan Photon Source (TPS) could generate electrons to 150 MeV. The main subsystems including an electron gun, buncher, accelerating sections, vacuum system, and focusing and steering magnets are located in the LINAC area of 223.5 m2 and 3 m in height. We designed a nitrogen injection fire extinguishing system for the LINAC area and performed Computational Fluid Dynamic (CFD) simulation to analyse the fire extinguishing performance with and without fresh air supplied from the air conditioning system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB371

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

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WEPAB374

The Southern Hemisphere’s First X-Band Radio-Frequency Test Facility at the University of Melbourne

electron, klystron, 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.

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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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WEPAB385

Beam Dynamic Analysis of RF Modulated Electron Beam Produced by Gridded Thermionic Guns

electron, 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, electron, 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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WEPAB418

The Power Supply System for 10 MeV & 20 kW Industry Irradiation Facility

power-supply, radiation, electron, 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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THXC06

Design and Measurements of an X-Band 8 MeV Standing-Wave Electron Accelerator

electron, bunching, 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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THPAB082

Recent Operational Experience with Thermionic RF Guns at the APS

linac, operation, cathode, injection

3959

Y. Sun, M. Borland, G.I. Fystro, X. Huang, H. Shang
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 electron beam at the Argonne Advanced Photon Source (APS) is generated from an S-band thermionic RF gun. There are two locations at the frontend of the linac where thermionic RF guns are installed – RG1 and RG2. Three so-called generation-III guns are available, two are installed at RG1 and RG2, one is a spare. In recent years, these guns are showing signs of aging after over a couple of decades of operations. RF trips started to occur, and we had to reduce the nominal operating rf power to alleviate the problem. In addition, beam generated by RG1 suffers from low transportation efficiency from the gun to the linac, and beam trajectory is unstable which results in charge instabilities. Recently, APS obtained a new type of prototype gun and it was beam commissioned in the linac. In this paper, we report our operational experience with these thermionic rf guns including thermionic-cathode beam extraction, gun front-end optimization for maximum charge transmission through the linac, linac lattice setup to match beam for injection into the Particle Accumulator Ring (PAR) and optimization for maximum PAR injection efficiency.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB082

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paper received ※ 19 May 2021 paper accepted ※ 28 July 2021 issue date ※ 16 August 2021

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THPAB083

Measurement of the Longitudinal Phase-Space of the APS Photo-Injector Beam

linac, cavity, dipole, lattice

3963

Y. Sun
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.
An S-band photo-cathode RF gun (PCG) exists at the front of the linac. The high-brightness photoinjector beam is accelerated by the linac and and can be used for accelerator technology and beam physics R&D experiments in the Linac Extension Area (LEA). For some applications, the beam needs to be compressed by a magnetic bunch compressor in the middle of the linac. An S-band transverse-mode cavity (Tcav) is available at the end of the linac for beam longitudinal phase-space diagnostics. Beam commissioning experience of the Tcav is reported in this paper. The cavity rf conditioning and calibration was performed. There is a horizontally bending dipole magnet downstream of the Tcav, which kicks beam in the vertical plane. Beam image on a YAG screen downstream of the Tcav and dipole magnet contains the single-shot information of the longitudinal phase-space of the photo-injector beam. The first measurements of the longitudinal phase-space of the compressed and non-compressed photoinjector beam are discussed. Improvements of the measurement resolution are planned.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB083

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paper received ※ 25 May 2021 paper accepted ※ 12 July 2021 issue date ※ 26 August 2021

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THPAB119

Many-Objective Beam Dynamics Optimization for High-Repetition-Rate XFEL Photoinjector

emittance, FEL, electron, 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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THPAB129

Beam Dynamics Simulations in a High-Gradient X-Band Photoinjector

emittance, cathode, electron, 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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THPAB141

Novel Design of a HVDC Magnetized Electron Source

cathode, solenoid, permanent-magnet, simulation

4034

O.H. Rahman, J. Skaritka, E. Wang
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 hadron beam in EIC is flat with a transverse size ratio of about 1:3. The cooling rate of the hadron beam can be maximized if the electron beam from the strong hadron cooler fully overlaps with the hadron beam. Therefore, generating a flat electron beam is essential. The most efficient way to generate a flat electron beam is to produce a magnetized beam first, and then convert it to flat to the desired transverse size ratio. Using a Magnetized electron beam is a promising way to cool high-energy hadrons. One of the major challenges in producing magnetized beams is fine-tuning the longitudinal magnetic field on the cathode surface and maintaining the desired field uniformity over the emission area. In this paper, we discuss the design of a novel high voltage DC gun capable of fine-tuning the B field on the cathode. This is achieved by installing a permanent magnet inside the cathode puck, with a solenoid field at the front of the cathode. We show magnetostatic simulation to prove the feasibility of this idea. We also show preliminary beam dynamics simulations showing emittance from the gun as the permanent magnet and solenoidal fields are tuned for minimum emittance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB141

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

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THPAB145

Cold Test of a Novel S-Band 1.6 Cell Photocathode RF Gun

cavity, coupling, cathode, simulation

4045

Zh.X. Tang, S.X. Dong, Y.J. Pei, B.F. Wei
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by National Natural Science Foundation of China(Grant No. 11805199 and U1832135) and Fundamental Research Funds for the Central Universities (Grant No. WK2310000072)
The photocathode RF gun is one of the most critical components for high quality electron beam sources. The asymmetric multi-pole field contributes to the transverse emittance growth and degrades the beam quality. In order to overcome the problem, we propose a novel rotationally symmetric 1.6 cell RF gun to construct the symmetric field in this paper. The concrete proposal is that a coaxial cell cavity with a symmetrical distribution of four grooves is concatenated to the photocathode end of the traditional 0.6 cell cavity to form the novel 0.6 cell cavity. Through the detailed design study, the profile of the RF gun is optimized to improve the shunt impedance and mode separation and make the surface peak electric field at the photocathode end. Considering the filling time, a coupling slot is designed to couple input power into the RF gun. The RF cavity is machined by numerical control machine tool, and the tuning and low power RF measurement are carried out. The experimental results are consistent with the simulation results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB145

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paper received ※ 09 May 2021 paper accepted ※ 30 August 2021 issue date ※ 02 September 2021

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THPAB146

Preliminary Study of Femtosecond Electron Source Based on THz Acceleration and Field Emission

electron, cavity, FEM, cathode

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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THPAB156

Built-in Thermionic Electron Source for an SRF Linacs

cathode, cavity, electron, 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]

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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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THPAB290

Evolution of the LHC Beam Screen Surface Conditioning Upon Electron Irradiation

electron, radiation, ECR, 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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THPAB331

High-Power Test of a Highly Over-Coupled X-Band RF Gun Driven by Short RF Pulses

cathode, electron, 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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THPAB344

Magneto-Optical Trap Cathode for High Brightness Applications

electron, laser, 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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THPAB369

Research and Design of an X-Band 100-MeV Compact Electron Accelerator for Very High Energy Electron Therapy in Tsinghua University

cavity, electron, 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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FRXB07

Injector Optimization for the IR-FEL Operation at the Compact ERL at KEK

emittance, FEL, operation, laser

4531

O.A. Tanaka, N. Higashi, T. Miyajima
KEK, Ibaraki, 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) at KEK is a test accelerator to develop ERL technologies and to operate with a high average beam current and a high beam quality. cERL consists of a photoinjector, a main linac for energy recovery, a recirculation loop and a beam dump. A recent upgrade of the cERL to the middle Infrared Free Electron Laser (IR-FEL) imposed new conditions to maintain beam parameters. Therefore, the injector should be optimized to meet the following requirements at the exit of the main linac. The rms bunch length should be 2 ps, the rms longitudinal emittance should be kept the least, and simultaneously the rms transverse emittance should be kept less than 3 c mm mrad. In this work we describe the strategy and results of the injector optimization to achieve the better performance of the cERL-FEL.

Slides FRXB07 [3.450 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXB07

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paper received ※ 19 May 2021 paper accepted ※ 22 July 2021 issue date ※ 27 August 2021

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