IPAC2021 - List of Keywords (laser)

Paper	Title	Other Keywords	Page
MOPAB040	Gain of Hard X-Ray Fel at 3 GeV and Required Parameters	FEL, electron, undulator, focusing	178
	L.H. Yu BNL, Upton, New York, USA
	We develop a tool for the calculation to study the conditions for a hard x-ray FEL oscillator based on an electron beam in the medium energy range from 3 to 4.5 GeV. We show that the approach developed by K.J. Kim et al. for the small-signal low gain formula can be modified so that the gain can be derived without taking the "no focusing approximation" adopted in the approach so that a strong focusing can be applied. We also derive the formula to allow for the gain calculation of harmonic lasing. The gain in this formula can be cast in the form of a product of two factors with one of them only depends on the harmonic number, undulator period, and gap. Thus this factor can be used to show that it is favorable to use harmonic lasing to achieve hard x-ray FEL working in the medium energy range and in the small-signal low gain regime.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB040
About •	paper received ※ 09 May 2021 paper accepted ※ 26 May 2021 issue date ※ 10 August 2021
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MOPAB042	Beam Dynamics Investigation for a New Project of Compton Back Scattering Photon Source at NRNU MEPhI	linac, photon, electron, scattering	186
	V.S. Dyubkov, I.A. Ashanin, M. Gusarova, Yu.D. Kliuchevskaia, M.V. Lalayan, S.M. Polozov, A.I. Pronikov, V.I. Rashchikov MEPhI, Moscow, Russia
	Funding: This project is supported by Russian Foundation for Basic Research, Grant no. 19-29-12036. The activities on physical models design of a compact monochromatic radiation source in the x-ray range based on inverse Compton scattering are started at NRNU MEPhI. There are comparison of two schemes of the photon source here: one of them is considered to be based on linac with variable energy of 20-60 MeV only and the other one is considered as accelerator complex where linac is supposed to be used as injector to medium size storage ring (energy up to 60 MeV). Preliminary results of linac structures and storage ring design as well as electron dynamics simulation are discussed
	Poster MOPAB042 [0.962 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB042
About •	paper received ※ 13 May 2021 paper accepted ※ 20 May 2021 issue date ※ 10 August 2021
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MOPAB054	Start-to-End Simulation of a Free-Electron Laser Driven by a Laser-Plasma Wakefield Accelerator	plasma, bunching, electron, radiation	233
	W. Liu, Y. Jiao, S. Wang IHEP, Beijing, People’s Republic of China
	The rapid development of laser-plasma wakefield accelerator (LPA) has opened up a new possible way to achieve ultra-compact free-electron laser (FEL). To this end, LPA experts have made many efforts to generate electron beams with sub-micrometer emittance and low energy spread. Recently, a new laser modulation method was proposed for generating EUV coherent pulse in an LPA-driven FEL. The simulation demonstration of this scheme is based on the Gaussian beam. However, the distribution of the LPA beam is not Gaussian. To further verify the feasibility of the method mentioned above, a start-to-end simulation is required.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB054
About •	paper received ※ 18 May 2021 paper accepted ※ 27 May 2021 issue date ※ 22 August 2021
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MOPAB055	Generation of Coherent Attosecond X-ray Pulses in the Southern Advanced Photon Source	electron, storage-ring, emittance, photon	237
	W. Liu, Y. Zhao IHEP CSNS, Guangdong Province, People’s Republic of China Y. Jiao, S. Wang IHEP, Beijing, People’s Republic of China
	Southern Advanced Photon Source (SAPS) is a fourth-generation storage ring light source that has been considered for construction in Guangdong province of China, adjacent to the China Spallation Neutron Source. As a low-emittance storage ring, the natural emittance of SAPS is below 100 pm. One of the benefits is that the brightness is about 2 orders high than 3rd generation light sources. However, like many other storage ring-based light sources, the time resolution is limited by the electron bunch length in the range of picoseconds. In this work, we propose a new scheme for the generation of coherent attoseconds X-ray pulses with a high repetition rate in SAPS. A numerical demonstration of the scheme is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB055
About •	paper received ※ 17 May 2021 paper accepted ※ 26 May 2021 issue date ※ 26 August 2021
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MOPAB097	Two Color Grating design for Soft X-Ray Self-Seeding at LCLS-II	FEL, electron, simulation, photon	361
	A. Halavanau, D. Cocco, E. Hemsing, G. Marcus, D.S. Morton SLAC, Menlo Park, California, USA G.R. Wilcox Cornell University, Ithaca, New York, USA
	A new grating design is examined for the soft x-ray self-seeding system (SXRSS) at LCLS-II to ultimately produce stable two-color XFEL pulses. The grating performance is analyzed with Fourier optics methods. The final XFEL performance is assessed via full numerical XFEL simulations that substantiate the feasibility of the proposed design.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB097
About •	paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 21 August 2021
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MOPAB098	LCLS Multi-Bunch Improvement Plan	FEL, linac, electron, experiment	365
	A. Halavanau, S. Carbajo, F.-J. Decker, A.K. Krasnykh, A.A. Lutman, A. Marinelli, C.E. Mayes, D.C. Nguyen SLAC, Menlo Park, California, USA
	Current and future experiments at LCLS require XFEL pulse trains of variable time separation. The cavity based XFEL (CBXFEL) project requires multiple pulses separated by 220 ns, the X-ray Laser Oscillator (XLO) uses 15 ns spaced pulse trains and Matter under Extreme Conditions (MEC) experiments need a shortly spaced (less than 5 ns) pulse trains. In this proceeding, we discuss the LCLS multi-bunch improvement plan and report on its recently status and progress.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB098
About •	paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 20 August 2021
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MOPAB099	Intensity Fluctuations Reduction in the Double-Bunch FEL at LCLS	FEL, electron, free-electron-laser, undulator	369
	G. Zhou, A. Halavanau, C. Pellegrini SLAC, Menlo Park, California, USA
	In this paper we explore the possibility of reducing the intensity fluctuations of a hard X-ray double-bunch free-electron laser (DBFEL) by using an ultra-short, high peak current electron bunch to generate the seed signal, as studied recently for soft X-ray single bunch self-seeding. The ultra-short, nearly single-spike, SASE pulse is amplified to saturation, where a four-crystal monochromator selects a narrow bandwidth seed for the second bunch. Start-to-end simulation results for 7 keV photon energy are presented here for a DBFEL already studied for LCLS using the HXR undulator. We show that using this enhanced DBFEL (EDBFEL) system; the seed signal intensity fluctuations can be reduced from 85% to about 30%, and the second bunch intensity fluctuation at saturation to about 15%.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB099
About •	paper received ※ 24 May 2021 paper accepted ※ 16 July 2021 issue date ※ 31 August 2021
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MOPAB100	Progress Report on Population Inversion-Based X-Ray Laser Oscillator	FEL, electron, experiment, radiation	373
	A. Halavanau, R. Alonso-Mori, A. Aquila, U. Bergmann, D. DePonte, F.-J. Decker, F. Fuller, M. Liang, A.A. Lutman, C. Pellegrini SLAC, Menlo Park, California, USA M. Doyle UCB, Berkeley, USA
	The population inversion X-ray Laser Oscillator (XLO) is a fully coherent, transform limited hard X-ray source. It operates by repetitively pumping inner-shell atomic transitions with an XFEL, in a closed Bragg cavity. XLO will produce very bright monochromatic X-ray pulses for applications in quantum optics, X-ray interferometry and metrology. We report the progress to build the first XLO operating at the copper alpha line, using LCLS 9 keV SASE X-ray pulses as a pump.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB100
About •	paper received ※ 20 May 2021 paper accepted ※ 29 July 2021 issue date ※ 02 September 2021
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MOPAB121	Progress Towards Soft X-Ray Beam Position Monitor Development	detector, undulator, radiation, synchrotron	438
	B. Podobedov, C. Eng, S. Hulbert, C. Mazzoli BNL, Upton, New York, USA D. Donetski, K. Kucharczyk, J. Liu, R. Lutchman Stony Brook University, Stony Brook, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. X-ray beam position monitors (BPMs) are instrumental for storage ring light sources, where they reliably provide positional measurements of high-power beams in hard X-ray beamlines. However, despite a growing need, coming especially from coherent soft X-ray beamlines, non-invasive soft X-ray BPMs have not been demonstrated yet. We are presently working on a funded R&D proposal to develop a non-invasive soft X-ray BPM with micron-scale resolution for high-power white beams. In our approach, multi-pixel GaAs detector arrays are placed into the beam halo and beam position is inferred from the pixel photocurrent levels. Presently, the first detector array prototypes have been manufactured and are being prepared for low-power beam tests. The mechanical design of a BPM test-stand, which will be installed in the 23-ID canted soft X-ray undulator beamline at NSLS-II, is well under way. In addition, we are developing new algorithms of beam position calculation which take full advantage of extended multi-pixel detector arrays. In this paper we will review our design choices and discuss recent progress.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB121
About •	paper received ※ 03 June 2021 paper accepted ※ 13 July 2021 issue date ※ 28 August 2021
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MOPAB138	Dielectric Wakefield Acceleration with a Laser Injected Witness Beam	wakefield, experiment, cathode, simulation	481
	G. Andonian, T.J. Campese RadiaBeam, Santa Monica, California, USA N.M. Cook RadiaSoft LLC, Boulder, Colorado, USA D.S. Doran, G. Ha, J.G. Power, J.H. Shao, E.E. Wisniewski ANL, Lemont, Illinois, USA W.J. Lynn, N. Majernik, J.B. Rosenzweig, V.S. Yu UCLA, Los Angeles, California, USA
	Funding: Work supported by DOE grant DE-SC0017690 The plasma photocathode concept, whereby a two-species gas mixture is used to generate a beam -driven accelerating wakefield and a laser-ionized generation of a witness beam, was recently experimentally demonstrated. In a variation of this concept, a beam-driven dielectric wakefield accelerator is employed, filled with a neutral gas for laser-ionization and creation of a witness beam. The dielectric wakefields, in the terahertz regime, provide comparatively modest timing requirements for the injection phase of the witness beam. In this paper, we provide an update on the progress of the experimental realization of the hybrid dielectric wakefield accelerator with laser injected witness beam at the Argonne Wakefield Accelerator (AWA), including engineering considerations for gas delivery, and preliminary simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB138
About •	paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 31 August 2021
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MOPAB141	Terahertz Driven Compression and Time-Stamping Technique for Single-Shot Ultrafast Electron Diffraction	electron, FEM, radiation, resonance	492
	M.A.K. Othman, A.E. Gabriel, M.C. Hoffmann, F. Ji, E.A. Nanni, X. Shen, E.J.C. Snively, X.J. Wang SLAC, Menlo Park, California, USA
	Funding: This research has been supported by the U.S. Department of Energy (DOE) under Contract No. DE-AC02-76SF00515 and DE-AC02-05-CH11231. Ultrafast structural dynamics are well understood through pump-probe characterization using ultrafast electron diffraction (UED). Advancements in electron diffraction and spectroscopy techniques open new frontiers for scientific discovery through interrogation of ultrafast phenomena, such as quantum phase transitions. Previously, we have demonstrated that strong-field THz radiation can be utilized to efficiently manipulate and compress ultrafast electron probes , and also offer temporal diagnostics with sub-femtosecond resolution * enabled by the inherent phase locking of THz radiation to the photoemission optical drive. In this work, we demonstrate a novel THz compression and time-stamping technique to probe solid-state materials at time scales previously inaccessible with standard UED. A high-frequency THz generation method using the organic OH-1 crystals is employed to enable a threefold reduction in the electron probes length and overall timing jitter. These time-stamped probes are used to demonstrate a substantial enhancement in the UED temporal resolution using pump-probe measurement in both photoexcited single crystal and polycrystalline samples. * E. C. Snively et al., Phys. Rev. Lett, vol. 124, no. 6, p. 054801, 2020. ** R. K. Li et al., Phys. Rev. Accel. Beams, vol. 22, no. 1, p. 012803, Jan. 2019.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB141
About •	paper received ※ 20 May 2021 paper accepted ※ 21 June 2021 issue date ※ 19 August 2021
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MOPAB143	Simulations for MeV Energy Gain in Multi-Micron Vacuum Channel Dielectric Structures Driven by a CO₂ Laser	electron, simulation, vacuum, acceleration	499
	G. Yadav, O. Apsimon, Y. Wei, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom O. Apsimon, C.P. Welsch, G.X. Xia Cockcroft Institute, Warrington, Cheshire, United Kingdom G.X. Xia The University of Manchester, Manchester, United Kingdom
	Funding: This work was supported by STFC LIV. DAT under grant agreement ST/P006752/1. This research used the resources of the Supercomputing Laboratory at KAUST in Thuwal, Saudi Arabia. Dielectric Laser Accelerators (DLAs) have been demonstrated as a novel scheme for producing high acceleration gradients (~1 GV/m) within the damage threshold of the dielectric. The compactness of the DLAs and the low emittance of the output electron beam make it an attractive candidate for future endoscopic devices to be used in tumor irradiation. However, due to the small accelerating distances(sub-mm), the total energy gain is limited to sub-MeV which remains an obstacle for its realistic applications. Also, these DLAs operate under solid-state lasers with wavelengths near IR (800 nm to 2 um), where required sub-micron vacuum channel at such wavelengths imposes major aperture restrictions for the amount of charge to be accelerated. Here, we present numerical simulation results for a dielectric structure excited by a CO₂ laser with a wavelength of 10.6 um. Upon injecting a 50 MeV electron bunch through a 5.3 um diameter of vacuum channel width, our simulation suggests an energy gain beyond 1 MeV. These results are the initial steps for the realization of an mm-scale DLA capable of producing MeV energy electron beams.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB143
About •	paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 11 August 2021
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MOPAB144	Investigation of Optimization of Dielectric Terahertz Acceleration Structures	simulation, acceleration, radiation, impedance	502
	A.E. Gabriel, E.A. Nanni SLAC, Menlo Park, California, USA
	Funding: This work was supported by the Department of Energy Contract No. DE-AC02-76SF00515 (SLAC) and by NSF Grant No. PHY-1734015. THz-frequency accelerating structures could provide the accelerating gradients needed for next generation particle accelerators with compact, GV/m-scale devices. Current THz accelerators are limited by significant losses during transport of THz radiation from the generating nonlinear crystal to the electron acceleration structure. In addition, the spectral properties of high-field THz sources make it difficult to couple THz radiation into accelerating structures. Dielectric accelerator structures reduce these losses because THz radiation can be coupled laterally into the structure, as opposed to metallic structures where THz radiation must be coupled along the beam path. In order to utilize these advantages, we are investigating the optimization of THz accelerating structures for comparison between metallic and dielectric devices. These results will help to inform future designs of improved dielectric THz acceleration structures.
	Poster MOPAB144 [6.524 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB144
About •	paper received ※ 20 May 2021 paper accepted ※ 27 May 2021 issue date ※ 22 August 2021
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MOPAB150	Optimization of the Gain Medium Delivery System for an X-Ray Laser Oscillator	electron, target, free-electron-laser, FEL	524
	M. Yadav, N. Majernik, P. Manwani, B. Naranjo, C. Pellegrini, J.B. Rosenzweig UCLA, Los Angeles, California, USA E.C. Galtier, A. Halavanau, C. Pellegrini SLAC, Menlo Park, California, USA A. Malinouski ASC HMTI, Minsk, Belarus
	Funding: This work was supported by DE-SC0009914. X-ray laser oscillator, dubbed XLO, is a recently proposed project at SLAC to build the first population inversion X-ray laser. XLO utilizes a train of XFEL SASE pulses to pump atomic core-states. The resulting amplified spontaneous emission radiation is recirculated in a backscattering Bragg cavity and subsequently amplified. XLO could provide fully coherent, transform-limited X-ray pulses with 50 meV bandwidth and 1e10 photons. Currently, XLO is being considered for operation at the copper K-alpha line at 8048 eV. In this work, we focus on the optimization of gain medium delivery in the XLO cavity. We consider a fast, subsonic jet of copper nitrate solution, moving through a cylindrical nozzle. We focus on the nozzle geometry optimization and possible diagnostics of the jet-XFEL interaction point.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB150
About •	paper received ※ 24 May 2021 paper accepted ※ 18 June 2021 issue date ※ 27 August 2021
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MOPAB153	Laser Microfabrication for Accelerator Applications	FEM, simulation, emittance, cathode	535
	S.P. Antipov, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia
	Laser microfabrication allows high precision ablation of materials at sub-mm scale. When laser pulse length is shorter than about 10 picoseconds the heat affected zone is minimized and ablation occurs without melting. Work-pieces processed in this fashion exhibit less structural damage and are expected to have a higher damage thresholds. In this paper we will review several case studies of laser-microfabricated components for accelerator and x-ray applications. Ablated materials include diamond, quartz, tungsten, copper, YAG:Ce and silicon.
	Poster MOPAB153 [2.781 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB153
About •	paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 29 August 2021
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MOPAB154	Multi-Cell Accelerating Structure Driven by a Lens-Focused Picosecond THz Pulse	focusing, electron, timing, acceleration	537
	S.P. Antipov, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia
	Recently, gradients on the order of 1 GV/m level have been obtained in a form of a single cycle (~1 ps) THz pulses produced by conversion of a high peak power laser radiation in nonlinear crystals (~1 mJ, 1 ps, up to 3% conversion efficiency). Such high-intensity radiation can be utilized for charged particle acceleration. However, these pulses are short in time (~1ps) and broadband, therefore a new accelerating structure type is required. In this paper, we propose a novel structure based on focusing of THz radiation in accelerating cell and stacking such cells to achieve a long-range interaction required for an efficient acceleration process. We present an example in which a 100 microJoule THz pulse produces a 600 keV energy gain in 5 mm long 10 cell accelerating structure for an ultra-relativistic electron. This design can be readily extended to non-relativistic particles. Such structure had been laser microfabricated and appropriate dimensions were achieved.
	Poster MOPAB154 [1.283 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB154
About •	paper received ※ 27 May 2021 paper accepted ※ 05 July 2021 issue date ※ 14 August 2021
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MOPAB164	Miniature, High Strength Transport Line Design for Laser Plasma Accelerator-Driven FELs	quadrupole, electron, plasma, undulator	561
	S. Fatehi, A. Bernhard, A.-S. Müller, M.S. Ning KIT, Karlsruhe, Germany
	Funding: This work is supported by the BMBF project 05K19VKA PlasmaFEL (Federal Ministry of Education and Research). Laser-plasma acceleration is an outstanding candidate to drive the next-generation compact light sources and FELs. To compensate large chromatic effects using novel compact beam optic elements in the beam transport line is required. We aim at designing miniature, high strength, normal conducting and superconducting transport line magnets and optics for capturing and matching LPA-generated electron bunches to given applications. Our primary application case is a demonstration experiment for transverse gradient undulator (TGU) FELs, to be performed at the JETI laser facility, Jena, Germany. In this contribution, we present the current design of the beam transport line magnets and the beam optics calculations. Laser Plasma Accelerators, FELs, Magnets, Beam Dynamics, Superconductivity, transverse gradient undulator
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB164
About •	paper received ※ 19 May 2021 paper accepted ※ 25 May 2021 issue date ※ 20 August 2021
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MOPAB166	Wakefield Excitation by a Sequence of Laser Pulses in Plasma	wakefield, plasma, simulation, acceleration	568
	D.S. Bondar KhNU, Kharkov, Ukraine V.I. Maslov, I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine
	Funding: The study is supported by the National Research Fundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299). PIC simulation by means of 2.5D UMKA code * of the wakefield excitation by a sequence of three Gaussian laser pulses in plasma was carried out. The dependence of excited wakefield intensity on power and width of laser pulses was investigated. It was shown the coherent addition of wakefield, excited by each laser pulse of the sequence, for linear case, while for the nonlinear case the coherency was destroyed. The profiled sequence of laser pulses was also considered. The possibility to obtain the same total wakefield excited by the profiled sequence of laser pulses with decreasing intensity, as for the uniform sequence was studied. * G. I. Dudnikova et al. Comp. Techn. 10 (2005) 37.
	Poster MOPAB166 [2.638 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB166
About •	paper received ※ 17 May 2021 paper accepted ※ 20 May 2021 issue date ※ 15 August 2021
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MOPAB167	Wakefield Excitation in Plasma of Metallic Density by a Laser Pulse	plasma, wakefield, electron, acceleration	571
	D.S. Bondar KhNU, Kharkov, Ukraine V.I. Maslov, I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine
	Funding: The study is supported by the National Research Foundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299). Recently the proposal to use X-ray Exawatt pulse for particle acceleration in a crystal has been declared . Short X-ray high-power pulse excites wakefield in electron plasma of metallic density which can be used for high gradient acceleration of charged particles. This wakefield is suited for laser wakefield acceleration. In this paper there are simulated with PIC code UMKA: excitation of the large wakefield amplitude up to several TV/m in electron plasma of metallic density by a powerful X-ray laser pulse; laser-plasma wakefield acceleration of self-injected electron bunch in such setup; combined acceleration by plasma wakefield driven by a laser pulse (LPWA) and by self-injected electron bunch (PWFA). T.Tajima. Eur. Phys. J. Special Topics 223 (2014) 1037.
	Poster MOPAB167 [2.054 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB167
About •	paper received ※ 17 May 2021 paper accepted ※ 21 May 2021 issue date ※ 22 August 2021
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MOPAB171	Numerical Simulation on Plasma-Based Beam Dumps Using Smilei	plasma, electron, wakefield, acceleration	582
	S. Kumar, C. Davut, G.X. Xia UMAN, Manchester, United Kingdom A. Bonatto, C. Davut, L. Liang The University of Manchester, Manchester, United Kingdom A. Bonatto Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil B.S. Nunes IF-UFRGS, Porto Alegre, Brazil R.P. Nunes UFRGS, Porto Alegre, Brazil
	The active plasma beam dump utilizes a laser to generate a plasma wakefield and decelerate an externally injected beam to low energy. We use the particle-in-cell code "Smi-lei" for the investigation of electron beam energy loss in plasma. In this research work, we optimize the laser and plasma parameters to investigate the active plasma beam dump scheme. In doing so, most of the beam energy will be deposited in the plasma. The optimization strategy for the beam energy loss in plasma is presented. A. Bonatto, C. B. Schroeder et al., Physics of Plasmas 22 (8) 083106 (2015). G. Xia, A. Bonatto et al., Instruments 4 (2) 10 (2020). *A Bonatto et al., J. Phys.: Conf. Ser. 1596 012058, 2020.
	Poster MOPAB171 [0.756 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB171
About •	paper received ※ 15 May 2021 paper accepted ※ 24 May 2021 issue date ※ 26 August 2021
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MOPAB175	Advanced Concepts and Technologies for Heavy Ion Synchrotrons	synchrotron, heavy-ion, electron, space-charge	594
	P.J. Spiller, O. Boine-Frankenheim, L.H.J. Bozyk, S. Klammes, H. Kollmus, D. Ondreka, I. Pongrac, N. Pyka, C. Roux, K. Sugita, St. Wilfert, T. Winkler, D.F.A. Winters GSI, Darmstadt, Germany
	New concepts and technologies are developed to advance the performance of heavy ion synchrotrons. Besides fast ramping of superconducting magnets, extreme UHV technologies to stabilize dynamic vacuum and charge related loss, broad band MA cavities, space charge compensation by means of electron lenses and new cooling technologies, e.g. laser cooling, show great promise to advance the forefront of beam parameters. Several of these technologies and concepts are developed and tested at GSI/FAIR. Progress and plans will be reported.
	Poster MOPAB175 [1.367 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB175
About •	paper received ※ 11 May 2021 paper accepted ※ 21 May 2021 issue date ※ 20 August 2021
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MOPAB255	Demonstration of a Novel Longitudinal Phase Space Linearization Method without Higher Harmonics	cavity, electron, gun, simulation	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 ※ 16 August 2021
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MOPAB266	Start-to-End Study on Laser and RF Jitter Effects for MAX-IV SXL	FEL, radiation, linac, simulation	844
	S.P. Pirani, B.S. Kyle MAX IV Laboratory, Lund University, Lund, Sweden F. Curbis, M.A. Pop, S. Werin Lund University, Lund, Sweden W. Qin DESY, Hamburg, Germany
	A Soft X-ray free electron laser (FEL) for the MAX IV Laboratory is currently in the design phase and it will use the existing 3 GeV linac. Present stability limits in the RF and the photocathode laser will affect the performance of the FEL. One of the critical elements for the design of a FEL is to have an estimation on jitter effects of the accelerator parameters on the X-ray radiation. In this regard, we implemented a start-to-end study using Astra, Elegant and Genesis in order to assess possible variations in pulse energy, photon pulse length and spectral width in the Soft X-ray Laser (SXL) radiation. This investigation provides insights on the final SXL performance variation due to RF and laser related jitter affecting the electron beam.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB266
About •	paper received ※ 19 May 2021 paper accepted ※ 26 July 2021 issue date ※ 24 August 2021
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MOPAB278	Prototype of the Bunch Arrival Time Monitor for SHINE	pick-up, FEL, electron, controls	881
	X.Q. Liu, L.W. Lai SARI-CAS, Pudong, Shanghai, People’s Republic of China Y.B. Leng, R.X. Yuan, N. Zhang, Y.M. Zhou SSRF, Shanghai, People’s Republic of China
	Funding: Youth Innovation Promotion Association, CAS (Grant No. 2019290) Bunch arrival time monitor (BAM) is an important tool to investigate the temporal characteristic of electron bunch in free electron lasers (FEL). Since the timing jitter of electron bunch will affect the FEL’s stability and the resolution of time-resolved experiment at FELs, it is nec-essary to precisely measure the electron bunch’s arrival time information to stabilize the electron bunch’s timing jitter using beam-based feedback. The BAM based on electro-optic modulator (EOM) is currently being devel-oping for Shanghai high-repetition-rate XFEL and Ex-treme light facility (SHINE). And the first BAM prototype has been installed on SXFEL for beam test. The beam test result shows that the estimated resolution of the pro-totype is about 27.5 fs rms.
	Poster MOPAB278 [1.166 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB278
About •	paper received ※ 20 May 2021 paper accepted ※ 23 June 2021 issue date ※ 30 August 2021
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MOPAB280	Split Ring Resonator Experiment - Simulation Results	simulation, electron, experiment, solenoid	888
	J. Schäfer, B. Härer, A. Malygin, A.-S. Müller, M. Nabinger, M.J. Nasse, T. Schmelzer, M. Schuh, T. Windbichler KIT, Karlsruhe, Germany
	Funding: Supported by "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology (KSETA)" and European Union’s Horizon 2020 Research and Innovation programme. FLUTE (Ferninfrarot Linac- Und Test-Experiment) is a compact linac-based test facility for accelerator and diagnostics R&D. An example for a new accelerator diagnostics tool currently studied at FLUTE is the split-ring-resonator (SRR) experiment, which aims to measure the longitudinal bunch profile of fs-scale electron bunches. Laser-generated THz radiation is used to excite a high frequency oscillating electromagnetic field in the SRR. Particles passing through the SRR gap are time-dependently deflected in the vertical plane, which allows a vertical streaking of an electron bunch. This principle allows a diagnosis of the longitudinal bunch profile in the femtosecond time domain and will be tested at FLUTE. This contribution presents an overview of the SRR experiment and the results of various tracking simulations for different scenarios as a function of laser pulse length and bunch charge. Based on these results possible working points for the experiments at FLUTE will be proposed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB280
About •	paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 01 September 2021
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MOPAB286	Towards a Data Science Enabled MeV Ultrafast Electron Diffraction System	electron, network, experiment, real-time	906
	M.A. Fazio, S. Biedron, M. Martínez-Ramón, D.J. Monk, S.I. Sosa Guitron UNM-ECE, Albuquerque, USA M. Babzien, K.A. Brown, M.G. Fedurin, J.J. Li, M.A. Palmer, J. Tao BNL, Upton, New York, USA S. Biedron, T. Talbott UNM-ME, Albuquerque, New Mexico, USA J. Chen, A.J. Hurd, N.A. Moody, R. Prasankumar, C. Sweeney LANL, Los Alamos, New Mexico, USA D. Martin, M.E. Papka ANL, Lemont, Illinois, USA
	Funding: US DOE, SC, BES, MSE, award DE-SC0021365 and DOE NNSA award 89233218CNA000001 through DOE’s EPSCoR program in Office of BES with resources of DOE SC User Facilities BNL’s ATF and ALCF. A MeV ultrafast electron diffraction (MUED) instrument is a unique characterization technique to study ultrafast processes in materials by a pump-probe technique. This relatively young technology can be advanced further into a turn-key instrument by using data science and artificial intelligence (AI) mechanisms in conjunctions with high-performance computing. This can facilitate automated operation, data acquisition and real time or near- real time processing. AI based system controls can provide real time feedback on the electron beam which is currently not possible due to the use of destructive diagnostics. Deep learning can be applied to the MUED diffraction patterns to recover valuable information on subtle lattice variations that can lead to a greater understanding of a wide range of material systems. A data science enabled MUED facility will also facilitate the application of this technique, expand its user base, and provide a fully automated state-of-the-art instrument. We will discuss the progress made on the MUED instrument in the Accelerator Test Facility of Brookhaven National Laboratory.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB286
About •	paper received ※ 20 May 2021 paper accepted ※ 09 June 2021 issue date ※ 25 August 2021
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MOPAB293	Electro-Optical Diagnostics at KARA and FLUTE - Results and Prospects	diagnostics, electron, storage-ring, experiment	927
	G. Niehues, E. Bründermann, M. Caselle, S. Funkner, A.-S. Müller, M.J. Nasse, M.M. Patil, R. Ruprecht, M. Schuh, M. Weber, C. Widmann KIT, Karlsruhe, Germany
	Funding: S.F. was funded by BMBF contract No. 05K16VKA, C. W. by BMBF contract number 05K19VKD. G.N. and E.B. acknowledge support by the Helmholtz President’s strategic fund IVF "Plasma Accelerators". Electro-optical (EO) methods are nowadays well-proven diagnostic tools, which are utilized to detect THz fields in countless experiments. The world’s first near-field EO sampling monitor at an electron storage ring was developed and installed at the KIT storage ring KARA (Karlsruhe Research Accelerator) and optimized to detect longitudinal bunch profiles. This experiment with other diagnostic techniques builds a distributed, synchronized sensor network to gain comprehensive data about the phase-space of electron bunches as well as the produced coherent synchrotron radiation (CSR). These measurements facilitate studies of physical conditions to provide, at the end, intense and stable CSR in the THz range. At KIT, we also operate FLUTE (Ferninfrarot Linac- und Test-Experiment), a new compact versatile linear accelerator as a test facility for novel techniques and diagnostics. There, EO diagnostics will be implemented to open up possibilities to evaluate and compare new techniques for longitudinal bunch diagnostics. In this contribution, we will give an overview of results achieved, the current status of the EO diagnostic setups at KARA and FLUTE and discuss future prospects.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB293
About •	paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 17 August 2021
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MOPAB294	Implementing Electro-Optical Diagnostics for Measuring the CSR Far-Field at KARA	radiation, detector, synchrotron, storage-ring	931
	C. Widmann, E. Bründermann, M. Caselle, S. Funkner, A.-S. Müller, M.J. Nasse, G. Niehues, M.M. Patil, C. Sax, J.L. Steinmann, M. Weber KIT, Karlsruhe, Germany C. Mai DELTA, Dortmund, Germany
	Funding: This work was supported by BMBF ErUM-Pro project 05K19 STARTRAC, C.W. was funded under contract No. 05K19VDK, C.M. under contract No. 05K19PEC, S.F. under contract No. 05K16VKA. For measuring the temporal profile of the coherent synchrotron radiation (CSR) at the KIT storage ring KARA (Karlsruhe Research Accelerator) an experimental setup based on electro-optical spectral decoding (EOSD) is currently being implemented. The EOSD technique allows single-shot, phase-sensitive measurements of the far-field radiation on a turn-by-turn basis at rates in the MHz range. Therefore, the resulting THz radiation from the dynamics of the bunch evolution, e.g. the microbunching, can be observed with high temporal resolution. This far-field setup is part of the distributed sensor network at KARA. Additionally to the information acquired from the near-field EOSD spectral decoding and the horizontal bunch profile monitor, it enables to monitor the longitudinal phase-space of the bunch. In this contribution, the characterization of the far-field setup is summarized and its implementation is discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB294
About •	paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 18 August 2021
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MOPAB321	Schlieren Imaging for Flow Visualisation of Gas Jet in Vacuum for Accelerator Applications	vacuum, controls, solenoid, linac	989
	S. Rosily, B. Dikshit, S. Krishnagopal Homi Bhbha National Institute (HBNI), DAE, Mumbai, India S. Krishnagopal, S. Rosily BARC, Mumbai, India
	Schlieren imaging was explored for flow visualising of a gas jet in vacuum for beam profile monitor application. In supersonic gas jet based beam profile monitors, the high density jet flows through various differentially pumped skimmer stages before being shaped into a sheet. Schlieren imaging is a well known technique used in aerodynamic studies to visualise gas flow. This technique is explained in the paper along with a gist of other flow visualisation techniques. An Z-type schlieren imaging setup used to view the high density flow features of a pulsed supersonic gas jet inside vacuum is described in detail. Flow around a Pitot probe in supersonic flow was simulated and the resultant density profile obtained was compared with the image obtained using schlieren imaging. The flow features including a detached shock around the tip of the probe was observable at medium and high vacuum after processing the image. Image processing algorithms and tools useful for this application are also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB321
About •	paper received ※ 20 May 2021 paper accepted ※ 26 May 2021 issue date ※ 29 August 2021
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MOPAB325	Development of Bunch Width Monitor with High Time Resolution for Low Emittance Muon Beam in the J-PARC Muon g-2 / EDM Experiment	emittance, experiment, acceleration, linac	1004
	M. Yotsuzuka, T. Iijima, K. Inami, Y. Sue, K. Sumi Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan T. Iijima KMI, Nagoya, AIchi Prefecture, Japan Y. Kondo JAEA, Ibaraki-ken, Japan T. Mibe KEK, Tsukuba, Japan Y. Nakazawa Ibaraki University, Ibaraki, Japan M. Otani, N. Saito J-PARC, KEK & JAEA, Ibaraki-ken, Japan Y. Takeuchi Kyushu University, Fukuoka, Japan H.Y. Yasuda University of Tokyo, Tokyo, Japan
	The J-PARC muon g-2/EDM experiment plans to measure the muon anomalous magnetic moment and electric dipole moment sensitive to new physics with high precision. This experiment uses a novel method using the low-emittance muon beam achieved by cooling and re-acceleration. In the muon linac consisting of four different accelerating cavities, the main cause of the emittance growth is the beam mismatch between the different cavities. Especially for the cavity in the low-beta section (ß=0.08-0.27), the longitudinal acceptance is narrow and beam mismatch has a significant impact. In order to perform beam matching in the low-beta cavity, a new beam monitor that can measure the low-emittance muon beam with high time resolution is required. Therefore, we developed a bunch width monitor (BWM) using a microchannel plate. The time resolution of the BWM was measured to be 40 picoseconds on the test bench using a picosecond pulse laser. It means that the BWM is possible to perform diagnosis with a phase accuracy of 1% for the acceleration phase of 324 MHz. We also evaluated factors that limit the current time resolution. In this presentation, the results of an evaluation of the BWM are reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB325
About •	paper received ※ 19 May 2021 paper accepted ※ 08 June 2021 issue date ※ 10 August 2021
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MOPAB326	Maximum Entropy Reconstruction of 4D Transverse Phase Space from 2D Projections: with Application to Laser Wire Measurements in the SNS HEBT	emittance, neutron, coupling, linac	1008
	C.Y. Wong, A.P. Shishlo ORNL, Oak Ridge, Tennessee, USA
	We employ the principle of maximum entropy (MENT) to reconstruct 4D transverse phase space from its 2D projections. Emittance devices commonly measure two specific 2D projections, i.e. the horizontal and vertical phase space distributions. We show that: 1) given only these two 2D projections, their product is the analytic MENT solution to the 4D distribution; and 2) additional 2D projections provide information on inter-plane coupling in the MENT reconstruction of the 4D phase space which can be solved numerically. At the Spallation Neutron Source (SNS), laser wires in the high energy beam transport (HEBT) enable non-invasive two-slit type transverse phase space measurements. Laser wires play the role of the first slit whereas physical wires downstream of a drift act as the second slit. We reconstruct the 4D phase space in the HEBT using all four horizontal/vertical permutations of the two slits where: 1) the two configurations with parallel slits constitute ordinary 2D phase space measurements in either plane; and 2) the two configurations with perpendicular slits carry coupling information.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB326
About •	paper received ※ 20 May 2021 paper accepted ※ 19 July 2021 issue date ※ 17 August 2021
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MOPAB394	Preliminary BCP Flow Field Investigation by CFD Simulations and PIV in a Transparent Model of a SRF Elliptical Low Beta Cavity	cavity, experiment, simulation, SRF	1204
	A. D’Ambros, M. Bertucci, A. Bosotti, A.T. Grimaldi, P. Michelato, L. Monaco, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy F. Cozzi, G. Pianello Politecnico di Milano, Milano, Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	Standard vertical Buffered Chemical Polishing (BCP) is one of the main surface treatment for Superconducting Radiofrequency (SRF) cavities. A finite element Computational Fluid Dynamic (CFD) model has been developed. Uncertainties in the solution of fluid simulations are not negligible due to the complex geometry of a SRF cavity; thus without an experimental validation, results from this type of simulations cannot be confidently used to improve the process. To this aim, an experimental study was started to investigate the fluid dynamics of the BCP process by means of Particle Image Velocimetry (PIV) technique. Similitude on Reynolds number and Refractive Index Matching (RIM) technique were also implemented to replace the dangerous BCP mixture with a glycerine-water mixture. The paper describes the preliminary results from simulations and experiment.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB394
About •	paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 13 August 2021
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TUXB01	A 3 MeV All Optical Terahertz-Driven Electron Source at Tsinghua University	electron, acceleration, gun, GUI	1294
	H. Xu, Y.-C. Du, W.-H. Huang, R.K. Li, C.-X. Tang, L.X. Yan TUB, Beijing, People’s Republic of China
	Funding: Science Challenge Project No.TZ2018005 Efficient acceleration and manipulation of high-brightness electron beams using terahertz waves in a compact setup has been recently a hot research topic in acceleration community. Previous works have achieved multi-MV/m acceleration gradient and dozens of keV energy gain while leaving room for further improvements in the high-energy regime. Here, we experimentally demonstrate whole-bunch acceleration and cascaded terahertz-driven acceleration of a relativistic beam with a record energy gain of 204 keV. A terahertz-driven all-optical electron source is now under development, which hold great potential for terahertz-driven ultrafast electron diffraction and related scientific discoveries. * Xu, H., Yan, L., Du, Y. et al. Cascaded high-gradient terahertz-driven acceleration of relativistic electron beams. Nat. Photonics (2021). https://doi.org/10.1038/s41566-021-00779-x
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 ※ 10 August 2021
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TUXC06	Visualizing Lattice Dynamic Behavior by Acquiring a Single Time-Resolved MeV	electron, lattice, detector, experiment	1311
	X. Yang, T.V. Shaftan, V.V. Smaluk, J. Tao, L. Wu, Y. Zhu BNL, Upton, New York, USA W. Wan ShanghaiTech University, Shanghai, People’s Republic of China
	We explore the possibility of visualizing the lattice dynamic behavior by acquiring a single time-resolved MeV UED image. Conventionally, multiple UED shots with varying time delays are needed to map out the entire dynamic process. The measurement precision is limited by the timing jitter between the pulses of laser pump and UED probe. We show that, by converting the longitudinal time of an electron bunch to the transverse position of a Bragg peak on the detector, one can obtain the full lattice dynamic process in a single electron pulse. We propose a novel design of a time-resolved UED with the capability of capturing a wide range of dynamic features in a single diffraction image. The work presented here is not only an extension of the ultrashort-pulse pump/long-pulse probe scheme being used in transient spectroscopy studies for decades but also advances the capabilities of MeV UED for future applications with tunable electron probe profile and detecting time range with femtosecond resolution. Furthermore, we present numerical simulations illustrating the capability of acquiring a single time-resolved diffraction image based on the case-by-case studies of lattice dynamic behavior.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXC06
About •	paper received ※ 14 May 2021 paper accepted ※ 28 July 2021 issue date ※ 31 August 2021
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TUPAB033	Photocathode Stress Test Bench at INFN LASA	cathode, gun, 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 ※ 19 August 2021
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TUPAB034	Development of Multi-Alkali Antimonides Photocathodes for High-Brightness RF Photoinjectors	cathode, electron, emittance, site	1416
	S.K. Mohanty, M. Krasilnikov, A. Oppelt, H.J. Qian, F. Stephan DESY Zeuthen, Zeuthen, Germany G. Guerini Rocco, C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany P. Michelato, L. Monaco, D. Sertore INFN/LASA, Segrate (MI), Italy
	Multi-alkali antimonide-based photocathodes are suitable candidate for the electron sources of next-generation high brightness RF photoinjectors due to their excellent photoemissive properties especially, like low thermal emittances and high sensitivity to visible light. The former stands out, paving the way towards CW operations. Based on the previous successful development of Cesium Telluride photocathodes, we are now channelling our efforts toward an R&D activity focused on KCsSb and NaKSb(Cs) photocathodes. Parallel to that R&D activity, we have installed a new dedicated photocathode production system at the INFN-LASA to start the preparation of these photocathodes for their test in the PITZ photoinjector at DESY in Zeuthen. In this paper, detailed experimental results obtained from the KCsSb, along with a preliminary result from the NaKSb(Cs) photocathode material as well as the status of the overall project are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB034
About •	paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 31 August 2021
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TUPAB047	Bunch Compressor Design in the Full Energy Linac Injector for the Southern Advanced Photon Source	linac, electron, simulation, bunching	1458
	B. Li IHEP CSNS, Guangdong Province, People’s Republic of China Y. Jiao, X. Liu, S. Wang IHEP, Beijing, People’s Republic of China
	A mid-energy fourth-generation storage ring light source named the Southern Advanced Photon Source (SAPS), has been considered to be built neighboring the China Spallation Neutron Source (CSNS). A full energy linac has been proposed as an injector to the storage ring, with the capability to generate high brightness electron beams to feed a Free Electron Laser (FEL) at a later stage. To achieve the high peak current in FELs, space charge, RF structure wakefield, coherent synchrotron radiation (CSR), RF curvature, and the second-order momentum compaction factor should be carefully considered and optimized during the bunch compression processes. In this paper, physic design and simulation results of the bunch compressors are described.
	Poster TUPAB047 [1.918 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB047
About •	paper received ※ 15 May 2021 paper accepted ※ 09 June 2021 issue date ※ 28 August 2021
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TUPAB057	Carbon Beam at I-3 Injector for Semiconductor Implantation	radiation, target, plasma, ion-source	1489
	A.A. Losev, P.N. Alekseev, N.N. Alexeev, T. Kulevoy, A.D. Milyachenko, Yu.A. Satov, A. Shumshurov ITEP, Moscow, Russia P.B. Lagov NUST MISIS, Moscow, Russia M.E. Letovaltseva MIREA, Moscow, Russia Y.S. Pavlov IPCE RAS, Moscow, Russia
	Carbon implantation can be effectively used for axial minority charge carriers lifetime control in various silicon bulk and epitaxial planar structures. When carbon is implanted, more stable recombination centers are formed and silicon is not doped with additional impurities, as for example, when irradiated with protons or helium ions. Economically, such a process competes with alternative methods, and is more efficient for obtaining small lifetimes (several nanoseconds). I-3 ion injector with laser-plasma ion source in Institute for theoretical and experimental physics (ITEP) is used as ion implanter in semiconductors. The ion source uses pulsed CO₂ laser setup with radiation-flux density of 10¹¹ W/cm² at target surface. The ion source produces beams of various ions from solid targets. The generated ion beam is accelerated in the two gap RF resonator at voltage of up to 2 MV per gap. Resulting beam energy is up to 4 MV per charge. Parameters of carbon ion beam generated and used for semiconductor samples irradiation during experiments for axial minority charge carriers lifetime control in various silicon bulk and epitaxial planar structures are presented.
	Poster TUPAB057 [0.630 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB057
About •	paper received ※ 15 May 2021 paper accepted ※ 28 May 2021 issue date ※ 01 September 2021
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TUPAB066	Status of the Short-Pulse Source at DELTA	electron, undulator, bunching, simulation	1518
	A. Held, B. Büsing, H. Kaiser, S. Khan, D. Krieg, A.R. Krishnan, C. Mai DELTA, Dortmund, Germany
	Funding: Work supported by BMBF (05K19PEB). At the synchrotron light source DELTA operated by the TU Dortmund University, the short-pulse source employs the seeding scheme coherent harmonic generation (CHG) and provides ultrashort pulses in the vacuum ultraviolet and terahertz regime. Here, the interaction of laser pulses with the stored electron bunches result in a modulation of the longitudinal electron density which gives rise to coherent emission at harmonics of the laser wavelength. Recently, investigations of the influence of the Gouy phase shift at the focal point of the laser pulses on the laser-electron interaction have been performed. For the planned upgrade towards the more sophisticated seeding scheme echo-enabled harmonic generation (EEHG) featuring a twofold laser-electron interaction, simulations of the ideal parameters of the laser beams have been carried out.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB066
About •	paper received ※ 19 May 2021 paper accepted ※ 22 July 2021 issue date ※ 28 August 2021
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TUPAB069	The Sabina Terahertz/Infrared Beamline at SPARC-Lab Facility	radiation, electron, experiment, photon	1525
	S. Macis La Sapienza University of Rome, Rome, Italy M. Bellaveglia, M. Cestelli Guidi, E. Chiadroni, F. Dipace, A. Ghigo, L. Giannessi, A. Giribono, L. Sabbatini, C. Vaccarezza INFN/LNF, Frascati, Italy A. Doria, A. Petralia ENEA C.R. Frascati, Frascati (Roma), Italy S. Lupi Sapienza University of Rome, Roma, Italy V. Petrillo INFN-Milano, Milano, Italy
	Funding: SABINA is a project co-funded by Regione Lazio within POR-FESR 2014-2020 program. Following the EU Terahertz (THz) Road Map, high-intensity, ps-long, THz)/Infrared (IR) radiation is going to become a fundamental spectroscopy tool for probing and control low-energy quantum systems ranging from graphene, and Topological Insulators, to novel superconductors* **. In the framework of the SABINA project, a novel THz/IR beamline based on an APPLE-X undulator emission will be developed at the SPARC-Lab facility at LNF-INFN. Light will be propagated from the SPARC-Lab to a new user lab facility nearly 20 m far away. This beamline will cover a broad spectral region from 3 THz to 30 THz, showing ps- pulses and energy of tens of µJ with variable polarization from linear to circular. The corresponding electric fields up to 10 MV/cm, are able to induce non-linear phenomena in many quantum systems. The beamline, open to user experiments, will be equipped with a 5 T magnetic cryostat and will be synchronized with a fs laser for THz/IR pump, VIS/UV probe experiments. [] S.S. Dhillon et al., J. Phys. D: Appl. Phys. 50, 043001 (2017); [] F. Giorgianni et al., Nature Commun. 7, 11421 (2016); [*] P. Di Pietro et al., Phys. Rev. Lett. 124, 226403 (2020);
	Poster TUPAB069 [0.884 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB069
About •	paper received ※ 16 May 2021 paper accepted ※ 21 June 2021 issue date ※ 25 August 2021
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TUPAB072	The Status of a Grating Monochromator for Soft X-Ray Self-Seeding Experiment at SHINE	electron, FEL, free-electron-laser, cavity	1532
	K.Q. Zhang SSRF, Shanghai, People’s Republic of China H.X. Deng, C. Feng, B. Liu, T. Liu SARI-CAS, Pudong, Shanghai, People’s Republic of China
	The research status of a grating monochromator for soft X-ray self-seeding experiment at SHINE has been presented in this paper. The monochromator system includes the vacuum cavity, optical elements, and mechanical movement devices. Until now, the vacuum cavity has finished the manufactured process completely, the optical mirrors have finished machining and measured by the longitudinal trace profiler (LTP) and atomic force microscope (AFM). To make sure the monochromator system can achieve an optical resolution of 1/10000 at the photon energy of 700-1300eV, the system has been integrated and tested recently. In this year, the previous online experiment will be performed in the shanghai soft X-ray free-electron laser (FEL) user facility.
	Poster TUPAB072 [0.717 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB072
About •	paper received ※ 11 May 2021 paper accepted ※ 09 June 2021 issue date ※ 01 September 2021
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TUPAB073	The Design of EEHG Cascaded Harmonic Lasing for SXFEL User Facility	FEL, undulator, electron, radiation	1536
	K.Q. Zhang, C. Feng SSRF, Shanghai, People’s Republic of China H.X. Deng, B. Liu, T. Liu SARI-CAS, Pudong, Shanghai, People’s Republic of China
	The preliminary design and simulation results of EEHG cascaded harmonic lasing for the SXFEL user facility have been presented in this paper. Using the basic seeded beamline of the SXFEL user facility, the designed parameters are optimized to obtain full coherent FEL output at the 90th harmonic of a 265 nm seed laser. According to the designed parameters and the layout of the SXFEL user facility, the detailed simulations are carried out, the results show that the seeded beamline of the SXFEL user facility can generate 2.93 nm full coherent radiation by the proposed method, which indicates that the method can extend the photon energy range of a seeded FEL and the method can be achieved at the SXFEL user facility.
	Poster TUPAB073 [0.955 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB073
About •	paper received ※ 11 May 2021 paper accepted ※ 10 June 2021 issue date ※ 27 August 2021
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TUPAB078	Relative Timing Jitter Effects on Two-stage Seeded FEL at SHINE	FEL, electron, timing, radiation	1551
	H.X. Yang SINAP, Shanghai, People’s Republic of China H.X. Deng, B. Liu, D. Wang, K.S. Zhou SARI-CAS, Pudong, Shanghai, People’s Republic of China
	Funding: The National Key Research and Development Program of China (Grants No. 2016YFA0401901, No. 2018YFE0103100) and the National Natural Science Foundation of China (Grants No. 11935020, No. 11775293). The synchronization between the ultrashort electron beam and external seed laser is essential for seeded FELs, especially for a multi-stage one. In this paper, we demonstrate a simple method to obtain the correlations between the pulse energy and relative timing jitter for evaluating the corresponding effects. In this method, the sensitivity of the output FEL performance against electron beam properties is demonstrated by scanning the electron beam and seed lasers, and the fitted curve is used to predict the pulse energy in different timing jitter by random sampling. The results indicate that the pulse energy of the first-stage EEHG is more stable than the second-stage HGHG. Meanwhile, the rise of bunch charge from 100 pC to 300 pC can reduce the timing control requirement by a factor of least 3 for the RMS timing jitter in our numerical simulations based on the parameters of Shanghai High-Repetition-Rate XFEL and Extreme Light Facility. The timing jitter study can demonstrate the feasibility of the EEHG-HGHG cascading scheme in different current profiles for generating Fourier-transform-limited soft X-ray FEL.
	Poster TUPAB078 [0.866 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB078
About •	paper received ※ 11 May 2021 paper accepted ※ 11 June 2021 issue date ※ 21 August 2021
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TUPAB084	An Empirically-Derived ABCD Matrix for Transverse Dynamics Studies in Seeded Free-Electron Lasers	FEL, radiation, electron, free-electron-laser	1573
	R. Robles Stanford University, Stanford, California, USA Z. Huang, G. Marcus SLAC, Menlo Park, California, USA
	Funding: DOE Contract DE-AC02-76SF00515. We present a simple empirical method for deriving an ABCD matrix for studying the transverse dynamics of the radiation field in seeded, high-gain free-electron lasers before saturation. In spite of the inherently nonlinear nature of FEL optical guiding, the ABCD matrix we find is able to predict the evolution of the FEL mode size and centroid to a high degree of accuracy across a large range of input mode characteristics. This scheme enables extremely fast simulation of transverse dynamics, which in turn greatly simplifies numerical studies of seeded FEL systems. Of particular interest in that regard is the x-ray regenerative amplifier free-electron laser, in which the x-ray beam propagates through an optical cavity many hundreds of times, thereby making traditional simulation methods cumbersome and time consuming.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB084
About •	paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 11 August 2021
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TUPAB085	Three-Dimensional Radiative Effects in the Compression of Ultra-Short Electron Micro-Bunches	emittance, FEL, electron, simulation	1577
	R. Robles, J.B. Rosenzweig UCLA, Los Angeles, California, USA S.B. van der Geer Pulsar Physics, Eindhoven, The Netherlands
	Funding: DOE Contract DE-SC0009914 DOE Contract DE-SC0020409 National Science Foundation Grant No. PHY-1549132 Micro-bunched current profiles have recently gained traction as an alternative to bulk compression in certain free-electron laser applications. The attraction of the micro-bunched structure is owed in part to its promise to minimize deleterious effects associated with coherent synchrotron radiation during compression. Simultaneously, these profiles push the boundaries of traditional one-dimensional CSR simulation models which assume the bunch length to far exceed the transverse beam size in the bunch rest frame - an assumption which may be violated by the sub-micron length micro-bunches. Here we present simulation studies of the impact of three-dimensional CSR effects on micro-bunching based compression schemes using the General Particle Tracer code.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB085
About •	paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 13 August 2021
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TUPAB086	FLASH2020+ Plans for a New Coherent Source at DESY	FEL, electron, experiment, undulator	1581
	E. Allaria, N. Baboi, K. Baev, M. Beye, G. Brenner, F. Christie, C. Gerth, I. Hartl, K. Honkavaara, B. Manschwetus, J. Mueller-Dieckmann, R. Pan, E. Plönjes-Palm, O. Rasmussen, J. Rönsch-Schulenburg, L. Schaper, E. Schneidmiller, S. Schreiber, K.I. Tiedtke, M. Tischer, S. Toleikis, R. Treusch, M. Vogt, L. Winkelmann, M.V. Yurkov, J. Zemella DESY, Hamburg, Germany
	With FLASH2020+, a major upgrade of the FLASH facility has started to meet the new requirements of the growing soft-x ray user community. The design of the FEL beamlines aims at photon properties suitable to the needs of future user experiments with high repetition rate XUV and soft X-ray radiation. By the end of the project, both existing FEL lines at FLASH will be equipped with fully tunable undulators capable of delivering photon pulses with variable polarization. The use of the external seeding at 1 MHz in burst mode is part of the design of the new FLASH1 beamline, while FLASH2 will exploit novel lasing concepts based on different undulator configurations. The new FLASH2020+ will rely on an electron beam energy of 1.35 GeV that will extend the accessible wavelength range to the oxygen K-edge with variable polarization. The facility will be completed with new laser sources for pump and probe experiment and new experimental stations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB086
About •	paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 23 August 2021
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TUPAB089	Proof-of-Principle Experiment Design for PEHG-FEL in SXFEL User Facility	FEL, electron, radiation, experiment	1589
	Z. Qi, H.X. Deng, C. Feng, B. Liu SARI-CAS, Pudong, Shanghai, People’s Republic of China S. Chen, Z.T. Zhao SSRF, Shanghai, People’s Republic of China
	In this paper, we demonstrate a proof-of-principle experimental design for phase-merging enhanced harmonic generation (PEHG) free electron laser (FEL) in Shanghai Soft X-ray Free Electron Laser (SXFEL) user facility. The simulation results indicate that, taking advantage of the beam switchyard, the normal modulator and the seeded FEL line in SXFEL user facility, together with an oblique incident seed laser, we can perform the phase-merging effect in PEHG and finally get an 8.86nm FEL radiation through the undulator, which is the 30th harmonic of the seed laser.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB089
About •	paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 02 September 2021
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TUPAB092	Demonstration FELs Using UC-XFEL Technologies at the SAMURAI Laboratory	FEL, undulator, cryogenics, electron	1592
	N. Majernik, G. Andonian, O. Camacho, A. Fukasawa, G.E. Lawler, W.J. Lynn, B. Naranjo, J.B. Rosenzweig, Y. Sakai, O. Williams UCLA, Los Angeles, California, USA R. Robles SLAC, Menlo Park, California, USA
	Funding: DOE HEP Grant DE-SC0020409, National Science Foundation Grant No. PHY-1549132 The ultra-compact x-ray free-electron laser (UC-XFEL), described in [J. B. Rosenzweig, et al. 2020 New J. Phys. 22 093067], combines several cutting edge beam physics techniques and technologies to realize an x-ray free electron laser at a fraction of the cost and footprint of existing XFEL installations. These elements include cryogenic, normally conducting RF structures for both the gun and linac, IFEL bunch compression, and short-period undulators. In this work, several stepping-stone, demonstrator scenarios under discussion for the UCLA SAMURAI Laboratory are detailed and simulated, employing different subsets of these elements. The cost, footprint, and technology risk for these scenarios are considered in addition to the anticipated engineering and physics experience gained.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB092
About •	paper received ※ 19 May 2021 paper accepted ※ 11 August 2021 issue date ※ 02 September 2021
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TUPAB095	Arbitrary Longitudinal Pulse Shaping with a Multi-Leaf Collimator and Emittance Exchange	wakefield, acceleration, plasma, emittance	1600
	N. Majernik, G. Andonian, J.B. Rosenzweig UCLA, Los Angeles, California, USA D.S. Doran, G. Ha, J.G. Power, E.E. Wisniewski ANL, Lemont, Illinois, USA R.J. Roussel Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
	Funding: DOE HEP Grant DE-SC0017648, and National Science Foundation Grant No. PHY-1549132 Drive and witness beams with variable current profiles and bunch spacing can be generated using an emittance exchange beamline (EEX) in conjunction with transverse masks. Recently, this approach was used to create advanced driver profiles and demonstrate record-breaking plasma wakefield transformer ratios [Roussel, R., et al., Phys. Rev. Lett. 124, 044802 (2020)], a crucial advancement for effective witness acceleration. Presently, these transverse masks are individually laser cut, making the refinement of beam profiles a slow process. Instead, we have proposed the used of a UHV compatible multileaf collimator (MLC) to replace these masks. An MLC permits real-time adjustment of the beam masking, permitting faster optimization in a manner highly synergistic with machine learning. Beam dynamics simulations have shown that practical MLCs offer resolution that is functionally equivalent to that offered by the laser cut masks. In this work, the engineering considerations and practical implementation of such a system at the AWA facility are discussed and the results of benchtop tests are presented. * Roussel, Ryan, et al. PRL 124.4 (2020): 044802
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB095
About •	paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 29 August 2021
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TUPAB099	Construction of an Infrared FEL at the Compact ERL	FEL, undulator, operation, electron	1608
	R. Kato, M. Adachi, S. Eguchi, K. Harada, N. Higashi, Y. Honda, T. Miyajima, S. Nagahashi, N. Nakamura, K.N. Nigorikawa, T. Nogami, T. Obina, H. Sagehashi, H. Sakai, M. Shimada, T. Shioya, M. Tadano, R. Takai, O.A. Tanaka, Y. Tanimoto, K. Tsuchiya, T. Uchiyama, A. Ueda, M. Yamamoto KEK, Ibaraki, Japan R. Hajima QST, Tokai, Japan N.P. Norvell SLAC, Menlo Park, California, USA F. Sakamoto Akita National College of Technology, Akita, Japan M. Shimada HSRC, Higashi-Hiroshima, Japan
	Funding: Work supported by NEDO project "Development of advanced laser processing with intelligence based high-brightness and high-efficiency laser technologies (TACMI project)". The compact Energy Recovery Linac (cERL) has been in operation at KEK since 2013 to demonstrate ERL performance and develop ERL technology. Recently KEK has launched an infrared FEL project with a competitive funding. The purpose of this project is to build a mid-infrared FEL at the cERL, and to use that FEL as a light source for construction of the processing database required for industrial lasers. The FEL system is composed of two 3-m undulators and a matching section between them, and generates light with a maximum pulse energy of 0.1 micro-J at the wavelength of 20 microns with an 81.25 MHz repetition rate. The FEL is also expected to become a proof-of-concept machine for ERL base FELs for future EUV lithography.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB099
About •	paper received ※ 20 May 2021 paper accepted ※ 14 June 2021 issue date ※ 29 August 2021
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TUPAB103	Discussion on CSR instability in EEHG Simulation	electron, bunching, FEL, simulation	1622
	D. Samoilenko, W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany F. Curbis, M.A. Pop, S. Werin MAX IV Laboratory, Lund University, Lund, Sweden P. Niknejadi, G. Paraskaki DESY, Hamburg, Germany F. Pannek University of Hamburg, Hamburg, Germany
	Echo-Enabled Harmonic Generation (EEHG) is an external seeding technique for XUV and soft X-ray Free Electron Lasers (FEL). It has recently been experimentally demonstrated and currently many facilities worldwide intend to incorporate it in user operation. The EEHG process relies on very accurate and complex transformations of electron beam phase space by means of a series of undulators coupled to lasers and dispersive chicanes. As a result of the phase space manipulation, electrons are bunched at a high harmonic of the seed laser wavelength allowing coherent emission at few nm wavelength. Dispersion occurring in strong chicanes is imperative for implementation of this scheme and effective electron bunching generation. However, strong chicanes at the same time can be source of beam instability effects, such as Coherent Synchrotron Radiation (CSR), that can significantly grow in these conditions and suppress the bunching process. Therefore, there is a common need to investigate such effects in detail. Here, we discuss their treatment with simulation codes applied to a typical EEHG setup.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB103
About •	paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 12 August 2021
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TUPAB111	Layout of the Laser Heater for FLASH2020+	electron, undulator, FEL, free-electron-laser	1647
	C. Gerth, E. Allaria, A. Choudhuri, L. Schaper, E. Schneidmiller, S. Schreiber, M. Tischer, P. Vagin, M. Vogt, L. Winkelmann, M.V. Yurkov, J. Zemella DESY, Hamburg, Germany
	The major upgrade FLASH2020+ of the FEL user facility FLASH includes an improved injector layout for the generation of the high-brightness electron beam as well as an externally seeded FEL beamline. Microbunching gain of initial modulations or shot-noise fluctuations degrade the electron beam quality, which is in particular harmful to the external seed process. To minimize the microbunching gain by a controlled increase of the uncorrelated energy spread, the installation of a laser heater is foreseen directly upstream of the first bunch compression chicane. In this paper, we present the layout of the laser heater section, which follows the original proposal published almost 20 years ago and differs in several aspects from the common layout implemented at many other FEL facilities. The considerations that have been made for the optimisation of the laser heater parameters are described in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB111
About •	paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 01 September 2021
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TUPAB113	Highlights From the Conceptual Design Report of the Soft X-Ray Laser at MAX IV	FEL, undulator, electron, linac	1651
	F. Curbis, J. Andersson, L. Isaksson, B.S. Kyle, F. Lindau, E. Mansten, H. Tarawneh, P.F. Tavares, S. Thorin, A.S. Vorozhtsov MAX IV Laboratory, Lund University, Lund, Sweden S. Bonetti Stockholm University, Stockholm, Sweden V.A. Goryashko, P.M. Salén Uppsala University, Uppsala, Sweden P. Johnsson, S.P. Pirani, M.A. Pop, W. Qin, S. Werin Lund University, Lund, Sweden M. Larsson Stockholm University, Department of Physics, Stockholm, Sweden A. Nilsson FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden J.A. Sellberg KTH Physics, Stockholm, Sweden
	Funding: Knut and Alice Wallenberg Foundation The SXL (Soft X-ray Laser) project developed a conceptual design for a soft X-ray Free Electron Laser in the 1–5 nm wavelength range, driven by the existing MAX IV 3 GeV linac. In this contribution we will focus on the FEL operation modes developed for the first phase of the project based on two different linac modes. The design work was supported by the Knut and Alice Wallenberg foundation and by several Swedish universities and organizations (Stockholm, Uppsala, KTH Royal Institute of Technology, Stockholm-Uppsala FEL center, MAX IV laboratory and Lund University).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB113
About •	paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 19 August 2021
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TUPAB117	Eigenmode Decomposition for Free-Electron Lasers Using Bayesian Analysis	optics, FEL, simulation, distributed	1666
	P. Liu, W. Li, Y.K. Wu, J. Yan FEL/Duke University, Durham, North Carolina, USA
	Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. Laser beams from an optical cavity, such as free-electron laser (FEL) resonators, are typically a mixture of the cavity’s eigenmodes, such as the Hermite-Gaussian (HG) modes or Laguerre-Gaussian (LG) modes. Robust evaluation of the eigenmode spectrum of a multimode laser beam has various applications in laser development, research, and utilization. In this work, a general eigenmode decomposition method for a multimode laser beam has been developed based on Bayesian analysis. This problem is transformed into a linear system and then solved using a Gaussian probabilistic model. Using Bayesian analysis, prior knowledge about the mode content is further incorporated into the solution to improve the results for laser beams contaminated with complex disturbances. The decomposition of the beam image from the incoherent intensity addition of HG modes is discussed with different types of noise or disturbances. The simulation results have been used to show the robustness of this method. This method can be straightforwardly extended into other cases such as the wavefront decomposition into the coherent superposition of HG and LG modes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB117
About •	paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 01 September 2021
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TUPAB121	Photoinjector Drive Laser Temporal Shaping for Shanghai Soft X-Ray Free Electron Laser	electron, cathode, FEL, flattop	1674
	C.L. Li, X.T. Wang, W.Y. Zhang Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China X.L. Dai SSRF, Shanghai, People’s Republic of China H.X. Deng, L. Feng, B. Liu, J.G. Wang SARI-CAS, Pudong, Shanghai, People’s Republic of China
	Shanghai soft X ray free electron laser (SXFEL) initial designed shape of the photocathode driver laser is flattop produced by α-BBO stacking. The advantage of this design is attractive in producing electron bunch with low initial emittance and high uniformity along the electron bunch. However, some unavoidable modulations are generated along the laser pulse which trigger the electron bunch modulation generated at the source, which is due to the fast response time (tens of femtosecond) of copper cathode. In order to eliminate the modulation of electron bunch, temporal Gaussian driver laser was designed and tested, measurement results show the electron bunch longitudinal modulation was removed. In this paper, we present two kinds of driver laser pulse temporal shaping methods based on α-BBO stacking and UV grating pair shaping. Moreover, corresponding electron bunch temporal profile are also presented.
	Poster TUPAB121 [2.469 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB121
About •	paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 25 August 2021
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TUPAB126	Spectral Gap in the Middle Infrared FEL Oscillator of FELiCHEM	FEL, GUI, electron, free-electron-laser	1685
	Y.P. Zhu, H.T. Li, Z. Zhao USTC/NSRL, Hefei, Anhui, People’s Republic of China
	A phenomenon of spectral gap is observed in the Middle Infrared FEL Oscillator of FELiCHEM: the laser power falls down at the particular wavelength. Starting with the experimental data, this paper focuses on the simulation calculation and analysis of the effect from using the partial waveguide. The relationship between waveguide and spectral gap is revealed.
	Poster TUPAB126 [1.063 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB126
About •	paper received ※ 17 May 2021 paper accepted ※ 14 June 2021 issue date ※ 21 August 2021
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TUPAB141	On the Development of a Low Peak-Power, High Repetition-Rate Laser Plasma Accelerator at IPEN	plasma, electron, experiment, photon	1713
	A. Bonatto Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil E.P. Maldonado ITA, São José dos Campos, Brazil R.P. Nunes UFRGS, Porto Alegre, Brazil R.E. Samad, F.B.D. Tabacow, N.D. Vieira, A.V.F. Zuffi IPEN-CNEN/SP, São Paulo, Brazil
	Funding: FAPESP (Grant #2018/25961), CNPq and CAPES. In this work, the current status on the development of a laser plasma accelerator at the Nuclear and Energy Research Institute (Instituto de Pesquisas Nucleares e Energéticas, IPEN/CNEN), in São Paulo, Brazil, is presented. Short pulses to be produced by an under-development near-TW, kHz laser system will be used to ionize a gas jet, with a density profile designed to optimize the self-injection of plasma electrons. The same laser pulse will also drive a plasma wakefield, which will allow for electron acceleration in the self-modulated regime. The current milestone is to develop the experimental setup, including electron beam and plasma diagnostics, required to produce electron bunches with energies of a few MeV. Once this has been achieved, the next milestone is to produce beams with energies higher than 50 MeV. Besides kickstarting the laser wakefield accelerator (LWFA) technology in Brazil, this project aims to pave the way for conducting research on the production of radioisotopes by photonuclear reactions, triggered by LWFA-accelerated beams.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB141
About •	paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 10 August 2021
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TUPAB142	Simulation Study of Laser Wakefield Acceleration Varying the Down-Ramp Length of a Gas Jet	electron, plasma, simulation, injection	1717
	R.P. Nunes UFRGS, Porto Alegre, Brazil A. Bonatto Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil E.P. Maldonado ITA, São José dos Campos, Brazil R.E. Samad, N.D. Vieira IPEN-CNEN/SP, São Paulo, Brazil
	In this work, particle-in-cell simulations were carried out to investigate the role of the down-ramp length of a H\textsubscript{2} gas jet in accelerating electrons ionized by the laser pulse. The laser and plasma density were chosen so that the system is operating in the self-modulated regime. Preliminary results show how the down-ramp length can control the injection of electrons in the first bubble induced in the plasma by the laser pulse.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB142
About •	paper received ※ 20 May 2021 paper accepted ※ 15 June 2021 issue date ※ 13 August 2021
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TUPAB143	Laser Pulse Dynamics in the Self-Modulated Regime	electron, plasma, wakefield, simulation	1721
	R.P. Nunes UFRGS, Porto Alegre, Brazil A. Bonatto Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil E.P. Maldonado ITA, São José dos Campos, Brazil R.E. Samad, N.D. Vieira IPEN-CNEN/SP, São Paulo, Brazil
	In this work, particle-in-cell simulations were carried out to investigate the dynamics of a laser pulse propagating along a H₂ gas jet. The laser-driven wakefield and the density of ionized electrons are analyzed during the pulse propagation through the gas jet. The laser and plasma quantities were chosen in order to have the system operating in the self-modulated regime. Results show how the self-modulation fragments the laser pulse, originating higher-amplitude pulses that can induce bubble formation with wave-breaking and particle injection.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB143
About •	paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 21 August 2021
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TUPAB146	High Brightness Electron Beams from Dragon Tail Injection and the E-312 Experiment at FACET-II	plasma, injection, electron, experiment	1728
	P. Manwani, N. Majernik, J.B. Rosenzweig UCLA, Los Angeles, California, USA D.L. Bruhwiler RadiaSoft LLC, Boulder, Colorado, USA B. Hidding USTRAT/SUPA, Glasgow, United Kingdom M.D. Litos Colorado University at Boulder, Boulder, Colorado, USA
	Funding: This work was performed with support of the US Department of Energy under Contract No. DE-SC0009914 The advent of optically triggered injection in multi component plasma wakefield accelerators has been shown to enable a substantial increase in witness electron beam quality. Here we present a novel way of using the overlap of laser and beam radial fields to locally liberate electrons from the tunneling ionization of the non-ionized gas species. These liberated ultracold electrons gain sufficient energy to be trapped in the accelerating phase at the back of the plasma blowout. This method of controlled injection has advantages in precision timing since injection is locked to peak beam current and has the potential of generating beams with very low emittance and energy spread. This method has been investigated using particle-in-cell (PIC) simulations. This scenario corresponds to a planned experiment, E-312, at SLAC’s FACET-II facility.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB146
About •	paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 22 August 2021
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TUPAB153	Modeling of Capillary Discharge Plasmas for Wakefield Accelerators and Beam Transport	plasma, simulation, electron, GUI	1740
	N.M. Cook, J.A. Carlsson, S.J. Coleman, A. Diaw, J.P. Edelen RadiaSoft LLC, Boulder, Colorado, USA E.C. Hansen, P. Tzeferacos Flash Center for Computational Science, Chicago, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0018719. Next generation accelerators demand sophisticated beam sources to reach ultra-low emittances at large accelerating gradients, along with improved optics to transport these beams without degradation. Capillary discharge plasmas can address each of these challenges. As sources, capillaries have been shown to increase the energy and quality of wakefield accelerators, and as active plasma lenses they provide orders-of-magnitude increases in peak magnetic field. Capillaries are sensitive to energy deposition, heat transfer, ionization dynamics, and magnetic field penetration; therefore, capillary design requires careful modeling. We present simulations of capillary discharge plasmas using FLASH, a publicly-available multi-physics code developed at the University of Chicago. We report on the implementation of 2D and 3D models of capillary plasma density and temperature evolution with realistic boundary and discharge conditions. We then demonstrate laser energy deposition to model channel formation for guiding intense laser pulses. Lastly, we examine active capillary plasmas with varying fill species and compare our simulations against experimental studies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB153
About •	paper received ※ 24 May 2021 paper accepted ※ 29 July 2021 issue date ※ 30 August 2021
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TUPAB163	Developing a 50 MeV LPA-Based Injector at ATHENA for a Compact Storage Ring	plasma, electron, storage-ring, target	1765
	E. Panofski, J. Dirkwinkel, T. Hülsenbusch, A.R. Maier, J. Osterhoff, G. Palmer, T. Parikh, P.A. Walker, P. Winkler DESY, Hamburg, Germany C. Braun, T.F.J. Eichner, L. Hübner, S. Jalas, L. Jeppe, M. Kirchen, P. Messner, M. Schnepp, M. Trunk, C.M. Werle University of Hamburg, Hamburg, Germany E. Bründermann, B. Härer, A.-S. Müller, C. Widmann KIT, Karlsruhe, Germany M. Kaluza, A. Sävert HIJ, Jena, Germany
	The laser-driven generation of relativistic electron beams in plasma and their acceleration to high energies with GV/m-gradients has been successfully demonstrated. Now, it is time to focus on the application of laser-plasma accelerated (LPA) beams. The "Accelerator Technology HElmholtz iNfrAstructure" (ATHENA) of the Helmholtz Association fosters innovative particle accelerators and high-power laser technology. As part of the ATHENAe pillar several different applications driven by LPAs are to be developed, such as a compact FEL, medical imaging and the first realization of LPA-beam injection into a storage ring. The latter endeavor is conducted in close collaboration between Deutsche Elektronen-Synchrotron (DESY), Karlsruhe Institute of Technology (KIT) and Helmholtz Institute Jena. In the cSTART project at KIT, a compact storage ring optimized for short bunches and suitable to accept LPA-based electron bunches is in preparation. In this conference contribution we will introduce the 50 MeV LPA-based injector and give an overview about the project goals. The key parameters of the plasma injector will be presented. Finally, the current status of the project will be summarized.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB163
About •	paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 21 August 2021
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TUPAB246	Numerical Simulation and Beam-Dynamics Study of a Hollow-Core Woodpile Coupler for Dielectric Laser Accelerators	GUI, photon, acceleration, electron	2022
	G.S. Mauro, D. Mascali, G. Sorbello, G. Torrisi INFN/LNS, Catania, Italy A. Bacci INFN/LASA, Segrate (MI), Italy C. De Angelis, A. Locatelli University of Brescia, Brescia, Italy A.R. Rossi INFN-Milano, Milano, Italy G. Sorbello University of Catania, Catania, Italy
	Hollow core dielectric microstructures powered by lasers represent a new and promising area of accelerator research thanks to the higher damage threshold and accelerating gradients with respect to metals at optical wavelengths. In this paper we present the design of a dielectric Electromagnetic Band Gap (EBG) mode converter for high-power coupling of the accelerating mode in Dielectric Laser Accelerators (DLAs). The design is wavelength-independent, and here we propose an implementation operating at 90.505 GHz (wavelength 3.3 mm) based on a silicon woodpile structure. The coupler is composed by two perpendicularly coupled hollow-core waveguides: a TE-like mode waveguide (excited from RF/laser power) and a TM-like mode accelerating waveguide. The structure has been numerically designed and optimized, presenting Insertion Losses (IL) < 0.3 dB and an efficient mode conversion in the operating bandwidth. The properties and effectiveness of the confined accelerating mode have been optimized in order to derive the needed accelerating gradient. The simulated electric field has been used as input for Astra beam-dynamics simulations in order to compute the beam properties.
	Poster TUPAB246 [2.209 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB246
About •	paper received ※ 18 May 2021 paper accepted ※ 27 July 2021 issue date ※ 13 August 2021
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TUPAB247	Influence of the Profile of the Dielectric Structure on the Electric Fields Excited by a Laser in Dielectric Accelerators Based on Chip	electron, acceleration, experiment, simulation	2026
	A. Vasyliev, O.O. Bolshov, K. Galaydych, A.I. Povrozin, G.V. Sotnikov NSC/KIPT, Kharkov, Ukraine
	Funding: The National Research Foundation of Ukraine, program "Leading and Young Scientists Research Support" (project # 2020.02/0299). To provide experimental researches at the NSC KIPT theoretical studies and computations of the electron acceleration in a dielectric laser accelerator have been carried out. Laser accelerator consists of two periodic quartz structures on diffraction gratings or Chips, symmetrically located along both sides of the vacuum accelerating channel. Using PIC numerical simulations, electromagnetic fields excited by laser radiation with a wavelength of 800 nm in dielectric laser accelerators were investigated. The influence of the shape and depth of the profile of diffraction gratings or Chip structures on the distribution of the electric field in the interaction space has been studied. For modeling, different types of profiles were taken, both in serial and a unique structure. In consequence of the analysis of the obtained results, estimated efficiency of acceleration was defined for each type of profile. The rectangular profile of the diffraction grating with the maximum accelerating gradient was selected as optimal for the next experiments.
	Poster TUPAB247 [1.195 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB247
About •	paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 11 August 2021
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TUPAB267	Investigation of Beam Impedance and Heat Load in a High Temperature Superconducting Undulator	undulator, impedance, simulation, site	2089
	D. Astapovych, H. De Gersem, E. Gjonaj TEMF, TU Darmstadt, Darmstadt, Germany T.A. Arndt, E. Bründermann, N. Glamann, A.W. Grau, B. Krasch, A.-S. Müller, R. Nast, D. Saez de Jauregui, A. Will KIT, Eggenstein-Leopoldshafen, Germany
	The use of high temperature superconducting (HTS) materials can enhance the performance of superconducting undulators (SCU), which can later be implemented in free electron laser facilities, synchrotron storage rings and light sources. In particular, the short period < 10 mm undulators with narrow magnetic gap < 4 mm are relevant. One of the promising approaches considers a 10 cm meander-structured HTS tapes stacked one above the other. Then, the HTS tape is wound on the SCU. The idea of this jointless undulator has been proposed by, and is being further developed at KIT. Since minimizing the different sources of heat load is a critical issue for all SCUs, a detailed analysis of the impedance and heat load is required to meet the cryogenic system design. The dominant heat source is anticipated to be the resistive surface loss, which is one of the subjects of this study. Considering the complexity of the HTS tape, the impedance model includes the geometrical structure of the HTS tapes as well as the anomalous skin effect. The results of the numerical investigation performed by the help of the CST PS solver will be presented and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB267
About •	paper received ※ 18 May 2021 paper accepted ※ 26 July 2021 issue date ※ 12 August 2021
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TUPAB273	Observations on Submicropulse Electron-Beam Effects From Short-Range Wakefields in Tesla-Type Superconducting Rf Cavities	cavity, electron, wakefield, HOM	2105
	A.H. Lumpkin, D.R. Edstrom, P.S. Prieto, J. Ruan, R.M. Thurman-Keup Fermilab, Batavia, Illinois, USA J.A. Diaz Cruz UNM-ECE, Albuquerque, USA J.A. Diaz Cruz, A.L. Edelen, B.T. Jacobson, F. Zhou SLAC, Menlo Park, California, USA
	Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. In previous experiments at the Fermilab Accelerator Science and Technology (FAST) facility, the effects of higher-order modes (HOMs) in TESLA-type cavities on submacropulse centroid motion were elucidated. We now have extended our investigations to short-range wakefields (SRWs) in these cavities. The latter result in submicropulse effects where the transverse wakefields cause head-tail centroid shifts. We used a Hamamatsu C5680 UV-visible synchroscan streak camera to synchronously sum the OTR from each of the 50 micropulses in the macropulse. We generated the y-t effect in the 41-MeV beam by purposely steering the beam off axis in y at the entrance of the first capture cavity. The head-tail transverse kicks within the 11-ps-long micropulses of 500 pC each were observed at the 100-micron level for steering off-axis in one cavity and several 100 microns for two cavities. These SRW results will be compared to simulations from the ASTRA model of a single micropulse in FAST. Since the SRW kicks go inversely with energy, these emittance-dilution effects are particularly relevant to the LCLS-II injector commissioning plans where <1 MeV beam will be injected into a TESLA-type cryomodule. A.H. Lumpkin et al, Phys. Rev. Accel. and Beams 23, 054401 (2020).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB273
About •	paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 28 August 2021
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TUPAB275	Enhanced Orthogonal Polarization Component Treatment in COTRI Model for Microbunched Beam Diagnostics	bunching, radiation, diagnostics, polarization	2113
	D.W. Rule Private Address, Silver Spring, USA A.H. Lumpkin ANL, Lemont, Illinois, USA
	Funding: Work supported by U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. We present the results of modifying our coherent optical transition radiation interferometry (COTRI) model’s treatment of the perpendicular polarization of OTR, Iperp. Our previous analytic approximation for Iperp was for beam divergences, sy << 1/g, where g is the Lorentz factor and sy is the rms y-component of the beam divergence. We have replaced our analytical form with a Gaussian quadrature for the convolution of Iperp with the divergence in theta-y. This extends the range of divergences we reliably model to sy > 1/g. Ipar, the parallel polarization in the model, is unchanged. Iperp is polarized along the y-axis and is proportional to the square of the y-component of the beam’s velocity distribution. We illustrate our results with two cases: 1) beam energy E=1 GeV, OTR wavelength 633 nm, Q=235 pC, microbunching fraction, bf=1%, divergences of 0.1-0.7 mrad, and rms beam sizes 2,10, and 30 microns; 2) E=375 MeV, wavelength 266 nm, Q=300 pC, bf=10%, divergences of 0.1-0,7 mrad, and rms beam sizes of 10,25,50, and 100 microns. We will present two cases that would be of interest for the diagnostics of laser-plasma accelerator beams* and pre-bunched FELs*, respectively. A. H. Lumpkin et al., Phys. Rev. Lett. 125, 014801 (2020). ** A. H. Lumpkin and D. W. Rule, in Proc., 39th International FEL Conference, FEL 2019 (JACoW Pub., Hamburg, Germany, 2019), pp. 408-411.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB275
About •	paper received ※ 22 May 2021 paper accepted ※ 10 June 2021 issue date ※ 20 August 2021
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TUPAB291	Subsystem Level Data Acquisition for the Optical Synchronization System at European XFEL	FEL, controls, data-acquisition, database	2167
	M. Schütte, A. Eichler, T. Lamb, V. Rybnikov, H. Schlarb, T. Wilksen DESY, Hamburg, Germany
	The optical synchronization system for the European X-Ray Free-Electron Laser provides sub-10 femtosecond timing precision * for the accelerator subsystems and experiments. This is achieved by phase locking a mode-locked laser oscillator to the main RF reference and distributing the optical pulse train carrying the time information via actively propagation-time stabilized optical fibers to multiple end-stations. Making up roughly one percent of the entire European XFEL, it is the first subsystem to receive a large-scale data acquisition system [2] for storing not just hand-selected information, but in fact all diagnostic, monitoring, and configuration data relevant to the optical synchronization available from the distributed control system infrastructure. A minimum of 100 TB per year may be stored in a persistent archive for long-term health monitoring and data mining whereas excess data is stored in a short-term ring buffer for high-resolution fault analysis and feature extraction algorithm development. This paper describes scale, challenges and first experiences from the optical synchronization data acquisition system. * S. Schulz et al., "Few-Femtosecond Facility-Wide Sync. of the European XFEL," in Proc. FEL’19 ** T. Wilksen et al., "A Bunch-Sync. DAQ System for the European XFEL," in Proc. ICALEPCS’17
	Poster TUPAB291 [0.281 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB291
About •	paper received ※ 14 May 2021 paper accepted ※ 17 June 2021 issue date ※ 24 August 2021
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TUPAB296	LLRF Upgrade at the Argonne Wakefield Accelerator Test Facility	LLRF, controls, klystron, pick-up	2176
	W. Liu, D.S. Doran, G. Ha, P. Piot, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA L.R. Doolittle, D. Filippetto, D. Li, S. Paiagua, C. Serrano, V.K. Vytla LBNL, Berkeley, California, USA
	Funding: US Department of Energy, Office of Science The Argonne Wakefiled Accelerator (AWA) Test Facility designed and operated a homemade LLRF system for the last 20 years. It is based on NI-PXI products that has now become obsolete. The AWA’s LLRF cannot keep up with the increasing stability demands of AWA’s upgraded facility. An overhaul of the system is strongly desired. With the support from DOE-HEP, the AWA is collaborating with Lawrence Berkeley National Laboratory (LBNL)to upgrade its LLRF system with modern instrumentation to meet the growing stability demands. An overview of AWA’s current LLRF system performance is presented together with the upgrade plan and expectations.
	Poster TUPAB296 [1.943 MB]

Paper

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MOPAB040

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

FEL, electron, undulator, focusing

178

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

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

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

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paper received ※ 09 May 2021 paper accepted ※ 26 May 2021 issue date ※ 10 August 2021

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MOPAB042

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

linac, photon, electron, scattering

186

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

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

Poster MOPAB042 [0.962 MB]

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

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paper received ※ 13 May 2021 paper accepted ※ 20 May 2021 issue date ※ 10 August 2021

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MOPAB054

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

plasma, bunching, electron, radiation

233

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

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

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

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paper received ※ 18 May 2021 paper accepted ※ 27 May 2021 issue date ※ 22 August 2021

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MOPAB055

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

electron, storage-ring, emittance, photon

237

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

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

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

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

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MOPAB097

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

FEL, electron, simulation, photon

361

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

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

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

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paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 21 August 2021

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MOPAB098

LCLS Multi-Bunch Improvement Plan

FEL, linac, electron, experiment

365

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

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

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

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

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MOPAB099

Intensity Fluctuations Reduction in the Double-Bunch FEL at LCLS

FEL, electron, free-electron-laser, undulator

369

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

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

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

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paper received ※ 24 May 2021 paper accepted ※ 16 July 2021 issue date ※ 31 August 2021

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MOPAB100

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

FEL, electron, experiment, radiation

373

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

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

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

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paper received ※ 20 May 2021 paper accepted ※ 29 July 2021 issue date ※ 02 September 2021

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MOPAB121

Progress Towards Soft X-Ray Beam Position Monitor Development

detector, undulator, radiation, synchrotron

438

B. Podobedov, C. Eng, S. Hulbert, C. Mazzoli
BNL, Upton, New York, USA
D. Donetski, K. Kucharczyk, J. Liu, R. Lutchman
Stony Brook University, Stony Brook, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
X-ray beam position monitors (BPMs) are instrumental for storage ring light sources, where they reliably provide positional measurements of high-power beams in hard X-ray beamlines. However, despite a growing need, coming especially from coherent soft X-ray beamlines, non-invasive soft X-ray BPMs have not been demonstrated yet. We are presently working on a funded R&D proposal to develop a non-invasive soft X-ray BPM with micron-scale resolution for high-power white beams. In our approach, multi-pixel GaAs detector arrays are placed into the beam halo and beam position is inferred from the pixel photocurrent levels. Presently, the first detector array prototypes have been manufactured and are being prepared for low-power beam tests. The mechanical design of a BPM test-stand, which will be installed in the 23-ID canted soft X-ray undulator beamline at NSLS-II, is well under way. In addition, we are developing new algorithms of beam position calculation which take full advantage of extended multi-pixel detector arrays. In this paper we will review our design choices and discuss recent progress.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB121

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paper received ※ 03 June 2021 paper accepted ※ 13 July 2021 issue date ※ 28 August 2021

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MOPAB138

Dielectric Wakefield Acceleration with a Laser Injected Witness Beam

wakefield, experiment, cathode, simulation

481

G. Andonian, T.J. Campese
RadiaBeam, Santa Monica, California, USA
N.M. Cook
RadiaSoft LLC, Boulder, Colorado, USA
D.S. Doran, G. Ha, J.G. Power, J.H. Shao, E.E. Wisniewski
ANL, Lemont, Illinois, USA
W.J. Lynn, N. Majernik, J.B. Rosenzweig, V.S. Yu
UCLA, Los Angeles, California, USA

Funding: Work supported by DOE grant DE-SC0017690
The plasma photocathode concept, whereby a two-species gas mixture is used to generate a beam -driven accelerating wakefield and a laser-ionized generation of a witness beam, was recently experimentally demonstrated. In a variation of this concept, a beam-driven dielectric wakefield accelerator is employed, filled with a neutral gas for laser-ionization and creation of a witness beam. The dielectric wakefields, in the terahertz regime, provide comparatively modest timing requirements for the injection phase of the witness beam. In this paper, we provide an update on the progress of the experimental realization of the hybrid dielectric wakefield accelerator with laser injected witness beam at the Argonne Wakefield Accelerator (AWA), including engineering considerations for gas delivery, and preliminary simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB138

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 31 August 2021

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MOPAB141

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

electron, FEM, radiation, resonance

492

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

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

DOI •

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

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

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MOPAB143

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

electron, simulation, vacuum, acceleration

499

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

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

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

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paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 11 August 2021

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MOPAB144

Investigation of Optimization of Dielectric Terahertz Acceleration Structures

simulation, acceleration, radiation, impedance

502

A.E. Gabriel, E.A. Nanni
SLAC, Menlo Park, California, USA

Funding: This work was supported by the Department of Energy Contract No. DE-AC02-76SF00515 (SLAC) and by NSF Grant No. PHY-1734015.
THz-frequency accelerating structures could provide the accelerating gradients needed for next generation particle accelerators with compact, GV/m-scale devices. Current THz accelerators are limited by significant losses during transport of THz radiation from the generating nonlinear crystal to the electron acceleration structure. In addition, the spectral properties of high-field THz sources make it difficult to couple THz radiation into accelerating structures. Dielectric accelerator structures reduce these losses because THz radiation can be coupled laterally into the structure, as opposed to metallic structures where THz radiation must be coupled along the beam path. In order to utilize these advantages, we are investigating the optimization of THz accelerating structures for comparison between metallic and dielectric devices. These results will help to inform future designs of improved dielectric THz acceleration structures.

Poster MOPAB144 [6.524 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB144

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paper received ※ 20 May 2021 paper accepted ※ 27 May 2021 issue date ※ 22 August 2021

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MOPAB150

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

electron, target, free-electron-laser, FEL

524

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

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

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

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paper received ※ 24 May 2021 paper accepted ※ 18 June 2021 issue date ※ 27 August 2021

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MOPAB153

Laser Microfabrication for Accelerator Applications

FEM, simulation, emittance, cathode

535

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

Laser microfabrication allows high precision ablation of materials at sub-mm scale. When laser pulse length is shorter than about 10 picoseconds the heat affected zone is minimized and ablation occurs without melting. Work-pieces processed in this fashion exhibit less structural damage and are expected to have a higher damage thresholds. In this paper we will review several case studies of laser-microfabricated components for accelerator and x-ray applications. Ablated materials include diamond, quartz, tungsten, copper, YAG:Ce and silicon.

Poster MOPAB153 [2.781 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB153

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paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 29 August 2021

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MOPAB154

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

focusing, electron, timing, acceleration

537

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

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

Poster MOPAB154 [1.283 MB]

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

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

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MOPAB164

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

quadrupole, electron, plasma, undulator

561

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

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

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

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

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MOPAB166

Wakefield Excitation by a Sequence of Laser Pulses in Plasma

wakefield, plasma, simulation, acceleration

568

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

Funding: The study is supported by the National Research Fundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299).
PIC simulation by means of 2.5D UMKA code * of the wakefield excitation by a sequence of three Gaussian laser pulses in plasma was carried out. The dependence of excited wakefield intensity on power and width of laser pulses was investigated. It was shown the coherent addition of wakefield, excited by each laser pulse of the sequence, for linear case, while for the nonlinear case the coherency was destroyed. The profiled sequence of laser pulses was also considered. The possibility to obtain the same total wakefield excited by the profiled sequence of laser pulses with decreasing intensity, as for the uniform sequence was studied.
* G. I. Dudnikova et al. Comp. Techn. 10 (2005) 37.

Poster MOPAB166 [2.638 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB166

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

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MOPAB167

Wakefield Excitation in Plasma of Metallic Density by a Laser Pulse

plasma, wakefield, electron, acceleration

571

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

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

Poster MOPAB167 [2.054 MB]

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

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paper received ※ 17 May 2021 paper accepted ※ 21 May 2021 issue date ※ 22 August 2021

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MOPAB171

Numerical Simulation on Plasma-Based Beam Dumps Using Smilei

plasma, electron, wakefield, acceleration

582

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

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

Poster MOPAB171 [0.756 MB]

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

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paper received ※ 15 May 2021 paper accepted ※ 24 May 2021 issue date ※ 26 August 2021

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MOPAB175

Advanced Concepts and Technologies for Heavy Ion Synchrotrons

synchrotron, heavy-ion, electron, space-charge

594

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

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

Poster MOPAB175 [1.367 MB]

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

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paper received ※ 11 May 2021 paper accepted ※ 21 May 2021 issue date ※ 20 August 2021

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MOPAB255

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

cavity, electron, gun, simulation

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 ※ 16 August 2021

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MOPAB266

Start-to-End Study on Laser and RF Jitter Effects for MAX-IV SXL

FEL, radiation, linac, simulation

844

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

A Soft X-ray free electron laser (FEL) for the MAX IV Laboratory is currently in the design phase and it will use the existing 3 GeV linac. Present stability limits in the RF and the photocathode laser will affect the performance of the FEL. One of the critical elements for the design of a FEL is to have an estimation on jitter effects of the accelerator parameters on the X-ray radiation. In this regard, we implemented a start-to-end study using Astra, Elegant and Genesis in order to assess possible variations in pulse energy, photon pulse length and spectral width in the Soft X-ray Laser (SXL) radiation. This investigation provides insights on the final SXL performance variation due to RF and laser related jitter affecting the electron beam.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB266

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paper received ※ 19 May 2021 paper accepted ※ 26 July 2021 issue date ※ 24 August 2021

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MOPAB278

Prototype of the Bunch Arrival Time Monitor for SHINE

pick-up, FEL, electron, controls

881

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

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

Poster MOPAB278 [1.166 MB]

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

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paper received ※ 20 May 2021 paper accepted ※ 23 June 2021 issue date ※ 30 August 2021

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MOPAB280

Split Ring Resonator Experiment - Simulation Results

simulation, electron, experiment, solenoid

888

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

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

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

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 01 September 2021

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MOPAB286

Towards a Data Science Enabled MeV Ultrafast Electron Diffraction System

electron, network, experiment, real-time

906

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

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

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

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paper received ※ 20 May 2021 paper accepted ※ 09 June 2021 issue date ※ 25 August 2021

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MOPAB293

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

diagnostics, electron, storage-ring, experiment

927

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

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

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

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paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 17 August 2021

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MOPAB294

Implementing Electro-Optical Diagnostics for Measuring the CSR Far-Field at KARA

radiation, detector, synchrotron, storage-ring

931

C. Widmann, E. Bründermann, M. Caselle, S. Funkner, A.-S. Müller, M.J. Nasse, G. Niehues, M.M. Patil, C. Sax, J.L. Steinmann, M. Weber
KIT, Karlsruhe, Germany
C. Mai
DELTA, Dortmund, Germany

Funding: This work was supported by BMBF ErUM-Pro project 05K19 STARTRAC, C.W. was funded under contract No. 05K19VDK, C.M. under contract No. 05K19PEC, S.F. under contract No. 05K16VKA.
For measuring the temporal profile of the coherent synchrotron radiation (CSR) at the KIT storage ring KARA (Karlsruhe Research Accelerator) an experimental setup based on electro-optical spectral decoding (EOSD) is currently being implemented. The EOSD technique allows single-shot, phase-sensitive measurements of the far-field radiation on a turn-by-turn basis at rates in the MHz range. Therefore, the resulting THz radiation from the dynamics of the bunch evolution, e.g. the microbunching, can be observed with high temporal resolution. This far-field setup is part of the distributed sensor network at KARA. Additionally to the information acquired from the near-field EOSD spectral decoding and the horizontal bunch profile monitor, it enables to monitor the longitudinal phase-space of the bunch. In this contribution, the characterization of the far-field setup is summarized and its implementation is discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB294

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 18 August 2021

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MOPAB321

Schlieren Imaging for Flow Visualisation of Gas Jet in Vacuum for Accelerator Applications

vacuum, controls, solenoid, linac

989

S. Rosily, B. Dikshit, S. Krishnagopal
Homi Bhbha National Institute (HBNI), DAE, Mumbai, India
S. Krishnagopal, S. Rosily
BARC, Mumbai, India

Schlieren imaging was explored for flow visualising of a gas jet in vacuum for beam profile monitor application. In supersonic gas jet based beam profile monitors, the high density jet flows through various differentially pumped skimmer stages before being shaped into a sheet. Schlieren imaging is a well known technique used in aerodynamic studies to visualise gas flow. This technique is explained in the paper along with a gist of other flow visualisation techniques. An Z-type schlieren imaging setup used to view the high density flow features of a pulsed supersonic gas jet inside vacuum is described in detail. Flow around a Pitot probe in supersonic flow was simulated and the resultant density profile obtained was compared with the image obtained using schlieren imaging. The flow features including a detached shock around the tip of the probe was observable at medium and high vacuum after processing the image. Image processing algorithms and tools useful for this application are also discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB321

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paper received ※ 20 May 2021 paper accepted ※ 26 May 2021 issue date ※ 29 August 2021

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MOPAB325

Development of Bunch Width Monitor with High Time Resolution for Low Emittance Muon Beam in the J-PARC Muon g-2 / EDM Experiment

emittance, experiment, acceleration, linac

1004

M. Yotsuzuka, T. Iijima, K. Inami, Y. Sue, K. Sumi
Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan
T. Iijima
KMI, Nagoya, AIchi Prefecture, Japan
Y. Kondo
JAEA, Ibaraki-ken, Japan
T. Mibe
KEK, Tsukuba, Japan
Y. Nakazawa
Ibaraki University, Ibaraki, Japan
M. Otani, N. Saito
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
Y. Takeuchi
Kyushu University, Fukuoka, Japan
H.Y. Yasuda
University of Tokyo, Tokyo, Japan

The J-PARC muon g-2/EDM experiment plans to measure the muon anomalous magnetic moment and electric dipole moment sensitive to new physics with high precision. This experiment uses a novel method using the low-emittance muon beam achieved by cooling and re-acceleration. In the muon linac consisting of four different accelerating cavities, the main cause of the emittance growth is the beam mismatch between the different cavities. Especially for the cavity in the low-beta section (ß=0.08-0.27), the longitudinal acceptance is narrow and beam mismatch has a significant impact. In order to perform beam matching in the low-beta cavity, a new beam monitor that can measure the low-emittance muon beam with high time resolution is required. Therefore, we developed a bunch width monitor (BWM) using a microchannel plate. The time resolution of the BWM was measured to be 40 picoseconds on the test bench using a picosecond pulse laser. It means that the BWM is possible to perform diagnosis with a phase accuracy of 1% for the acceleration phase of 324 MHz. We also evaluated factors that limit the current time resolution. In this presentation, the results of an evaluation of the BWM are reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB325

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paper received ※ 19 May 2021 paper accepted ※ 08 June 2021 issue date ※ 10 August 2021

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MOPAB326

Maximum Entropy Reconstruction of 4D Transverse Phase Space from 2D Projections: with Application to Laser Wire Measurements in the SNS HEBT

emittance, neutron, coupling, linac

1008

C.Y. Wong, A.P. Shishlo
ORNL, Oak Ridge, Tennessee, USA

We employ the principle of maximum entropy (MENT) to reconstruct 4D transverse phase space from its 2D projections. Emittance devices commonly measure two specific 2D projections, i.e. the horizontal and vertical phase space distributions. We show that: 1) given only these two 2D projections, their product is the analytic MENT solution to the 4D distribution; and 2) additional 2D projections provide information on inter-plane coupling in the MENT reconstruction of the 4D phase space which can be solved numerically. At the Spallation Neutron Source (SNS), laser wires in the high energy beam transport (HEBT) enable non-invasive two-slit type transverse phase space measurements. Laser wires play the role of the first slit whereas physical wires downstream of a drift act as the second slit. We reconstruct the 4D phase space in the HEBT using all four horizontal/vertical permutations of the two slits where: 1) the two configurations with parallel slits constitute ordinary 2D phase space measurements in either plane; and 2) the two configurations with perpendicular slits carry coupling information.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB326

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

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MOPAB394

Preliminary BCP Flow Field Investigation by CFD Simulations and PIV in a Transparent Model of a SRF Elliptical Low Beta Cavity

cavity, experiment, simulation, SRF

1204

A. D’Ambros, M. Bertucci, A. Bosotti, A.T. Grimaldi, P. Michelato, L. Monaco, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
F. Cozzi, G. Pianello
Politecnico di Milano, Milano, Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

Standard vertical Buffered Chemical Polishing (BCP) is one of the main surface treatment for Superconducting Radiofrequency (SRF) cavities. A finite element Computational Fluid Dynamic (CFD) model has been developed. Uncertainties in the solution of fluid simulations are not negligible due to the complex geometry of a SRF cavity; thus without an experimental validation, results from this type of simulations cannot be confidently used to improve the process. To this aim, an experimental study was started to investigate the fluid dynamics of the BCP process by means of Particle Image Velocimetry (PIV) technique. Similitude on Reynolds number and Refractive Index Matching (RIM) technique were also implemented to replace the dangerous BCP mixture with a glycerine-water mixture. The paper describes the preliminary results from simulations and experiment.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB394

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 13 August 2021

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TUXB01

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

electron, acceleration, gun, GUI

1294

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

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

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

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paper received ※ 19 May 2021 paper accepted ※ 01 June 2021 issue date ※ 10 August 2021

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TUXC06

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

electron, lattice, detector, experiment

1311

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

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

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

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paper received ※ 14 May 2021 paper accepted ※ 28 July 2021 issue date ※ 31 August 2021

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TUPAB033

Photocathode Stress Test Bench at INFN LASA

cathode, gun, 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 ※ 19 August 2021

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TUPAB034

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

cathode, electron, emittance, site

1416

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

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

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

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 31 August 2021

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TUPAB047

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

linac, electron, simulation, bunching

1458

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

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

Poster TUPAB047 [1.918 MB]

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

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paper received ※ 15 May 2021 paper accepted ※ 09 June 2021 issue date ※ 28 August 2021

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TUPAB057

Carbon Beam at I-3 Injector for Semiconductor Implantation

radiation, target, plasma, ion-source

1489

A.A. Losev, P.N. Alekseev, N.N. Alexeev, T. Kulevoy, A.D. Milyachenko, Yu.A. Satov, A. Shumshurov
ITEP, Moscow, Russia
P.B. Lagov
NUST MISIS, Moscow, Russia
M.E. Letovaltseva
MIREA, Moscow, Russia
Y.S. Pavlov
IPCE RAS, Moscow, Russia

Carbon implantation can be effectively used for axial minority charge carriers lifetime control in various silicon bulk and epitaxial planar structures. When carbon is implanted, more stable recombination centers are formed and silicon is not doped with additional impurities, as for example, when irradiated with protons or helium ions. Economically, such a process competes with alternative methods, and is more efficient for obtaining small lifetimes (several nanoseconds). I-3 ion injector with laser-plasma ion source in Institute for theoretical and experimental physics (ITEP) is used as ion implanter in semiconductors. The ion source uses pulsed CO₂ laser setup with radiation-flux density of 10¹¹ W/cm² at target surface. The ion source produces beams of various ions from solid targets. The generated ion beam is accelerated in the two gap RF resonator at voltage of up to 2 MV per gap. Resulting beam energy is up to 4 MV per charge. Parameters of carbon ion beam generated and used for semiconductor samples irradiation during experiments for axial minority charge carriers lifetime control in various silicon bulk and epitaxial planar structures are presented.

Poster TUPAB057 [0.630 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB057

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paper received ※ 15 May 2021 paper accepted ※ 28 May 2021 issue date ※ 01 September 2021

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TUPAB066

Status of the Short-Pulse Source at DELTA

electron, undulator, bunching, simulation

1518

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

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

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

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paper received ※ 19 May 2021 paper accepted ※ 22 July 2021 issue date ※ 28 August 2021

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TUPAB069

The Sabina Terahertz/Infrared Beamline at SPARC-Lab Facility

radiation, electron, experiment, photon

1525

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

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

Poster TUPAB069 [0.884 MB]

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

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paper received ※ 16 May 2021 paper accepted ※ 21 June 2021 issue date ※ 25 August 2021

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TUPAB072

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

electron, FEL, free-electron-laser, cavity

1532

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

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

Poster TUPAB072 [0.717 MB]

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

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

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TUPAB073

The Design of EEHG Cascaded Harmonic Lasing for SXFEL User Facility

FEL, undulator, electron, radiation

1536

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

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

Poster TUPAB073 [0.955 MB]

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

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paper received ※ 11 May 2021 paper accepted ※ 10 June 2021 issue date ※ 27 August 2021

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TUPAB078

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

FEL, electron, timing, radiation

1551

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

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

Poster TUPAB078 [0.866 MB]

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

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

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TUPAB084

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

FEL, radiation, electron, free-electron-laser

1573

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

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

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

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

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TUPAB085

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

emittance, FEL, electron, simulation

1577

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

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

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

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 13 August 2021

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TUPAB086

FLASH2020+ Plans for a New Coherent Source at DESY

FEL, electron, experiment, undulator

1581

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

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

DOI •

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

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

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TUPAB089

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

FEL, electron, radiation, experiment

1589

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

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

DOI •

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

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 02 September 2021

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TUPAB092

Demonstration FELs Using UC-XFEL Technologies at the SAMURAI Laboratory

FEL, undulator, cryogenics, electron

1592

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

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

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

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paper received ※ 19 May 2021 paper accepted ※ 11 August 2021 issue date ※ 02 September 2021

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TUPAB095

Arbitrary Longitudinal Pulse Shaping with a Multi-Leaf Collimator and Emittance Exchange

wakefield, acceleration, plasma, emittance

1600

N. Majernik, G. Andonian, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
D.S. Doran, G. Ha, J.G. Power, E.E. Wisniewski
ANL, Lemont, Illinois, USA
R.J. Roussel
Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA

Funding: DOE HEP Grant DE-SC0017648, and National Science Foundation Grant No. PHY-1549132
Drive and witness beams with variable current profiles and bunch spacing can be generated using an emittance exchange beamline (EEX) in conjunction with transverse masks. Recently, this approach was used to create advanced driver profiles and demonstrate record-breaking plasma wakefield transformer ratios [Roussel, R., et al., Phys. Rev. Lett. 124, 044802 (2020)], a crucial advancement for effective witness acceleration. Presently, these transverse masks are individually laser cut, making the refinement of beam profiles a slow process. Instead, we have proposed the used of a UHV compatible multileaf collimator (MLC) to replace these masks. An MLC permits real-time adjustment of the beam masking, permitting faster optimization in a manner highly synergistic with machine learning. Beam dynamics simulations have shown that practical MLCs offer resolution that is functionally equivalent to that offered by the laser cut masks. In this work, the engineering considerations and practical implementation of such a system at the AWA facility are discussed and the results of benchtop tests are presented.
* Roussel, Ryan, et al. PRL 124.4 (2020): 044802

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB095

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paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 29 August 2021

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TUPAB099

Construction of an Infrared FEL at the Compact ERL

FEL, undulator, operation, electron

1608

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

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

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

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paper received ※ 20 May 2021 paper accepted ※ 14 June 2021 issue date ※ 29 August 2021

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TUPAB103

Discussion on CSR instability in EEHG Simulation

electron, bunching, FEL, simulation

1622

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

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

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

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 12 August 2021

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TUPAB111

Layout of the Laser Heater for FLASH2020+

electron, undulator, FEL, free-electron-laser

1647

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

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

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

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paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 01 September 2021

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TUPAB113

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

FEL, undulator, electron, linac

1651

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

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

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

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

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TUPAB117

Eigenmode Decomposition for Free-Electron Lasers Using Bayesian Analysis

optics, FEL, simulation, distributed

1666

P. Liu, W. Li, Y.K. Wu, J. Yan
FEL/Duke University, Durham, North Carolina, USA

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
Laser beams from an optical cavity, such as free-electron laser (FEL) resonators, are typically a mixture of the cavity’s eigenmodes, such as the Hermite-Gaussian (HG) modes or Laguerre-Gaussian (LG) modes. Robust evaluation of the eigenmode spectrum of a multimode laser beam has various applications in laser development, research, and utilization. In this work, a general eigenmode decomposition method for a multimode laser beam has been developed based on Bayesian analysis. This problem is transformed into a linear system and then solved using a Gaussian probabilistic model. Using Bayesian analysis, prior knowledge about the mode content is further incorporated into the solution to improve the results for laser beams contaminated with complex disturbances. The decomposition of the beam image from the incoherent intensity addition of HG modes is discussed with different types of noise or disturbances. The simulation results have been used to show the robustness of this method. This method can be straightforwardly extended into other cases such as the wavefront decomposition into the coherent superposition of HG and LG modes.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB117

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paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 01 September 2021

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TUPAB121

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

electron, cathode, FEL, flattop

1674

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

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

Poster TUPAB121 [2.469 MB]

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

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

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TUPAB126

Spectral Gap in the Middle Infrared FEL Oscillator of FELiCHEM

FEL, GUI, electron, free-electron-laser

1685

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

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

Poster TUPAB126 [1.063 MB]

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

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paper received ※ 17 May 2021 paper accepted ※ 14 June 2021 issue date ※ 21 August 2021

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TUPAB141

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

plasma, electron, experiment, photon

1713

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

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

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

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paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 10 August 2021

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TUPAB142

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

electron, plasma, simulation, injection

1717

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

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

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

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paper received ※ 20 May 2021 paper accepted ※ 15 June 2021 issue date ※ 13 August 2021

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TUPAB143

Laser Pulse Dynamics in the Self-Modulated Regime

electron, plasma, wakefield, simulation

1721

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

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

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

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paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 21 August 2021

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TUPAB146

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

plasma, injection, electron, experiment

1728

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

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

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

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

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TUPAB153

Modeling of Capillary Discharge Plasmas for Wakefield Accelerators and Beam Transport

plasma, simulation, electron, GUI

1740

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

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

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

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

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TUPAB163

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

plasma, electron, storage-ring, target

1765

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

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

DOI •

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

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paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 21 August 2021

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TUPAB246

Numerical Simulation and Beam-Dynamics Study of a Hollow-Core Woodpile Coupler for Dielectric Laser Accelerators

GUI, photon, acceleration, electron

2022

G.S. Mauro, D. Mascali, G. Sorbello, G. Torrisi
INFN/LNS, Catania, Italy
A. Bacci
INFN/LASA, Segrate (MI), Italy
C. De Angelis, A. Locatelli
University of Brescia, Brescia, Italy
A.R. Rossi
INFN-Milano, Milano, Italy
G. Sorbello
University of Catania, Catania, Italy

Hollow core dielectric microstructures powered by lasers represent a new and promising area of accelerator research thanks to the higher damage threshold and accelerating gradients with respect to metals at optical wavelengths. In this paper we present the design of a dielectric Electromagnetic Band Gap (EBG) mode converter for high-power coupling of the accelerating mode in Dielectric Laser Accelerators (DLAs). The design is wavelength-independent, and here we propose an implementation operating at 90.505 GHz (wavelength 3.3 mm) based on a silicon woodpile structure. The coupler is composed by two perpendicularly coupled hollow-core waveguides: a TE-like mode waveguide (excited from RF/laser power) and a TM-like mode accelerating waveguide. The structure has been numerically designed and optimized, presenting Insertion Losses (IL) < 0.3 dB and an efficient mode conversion in the operating bandwidth. The properties and effectiveness of the confined accelerating mode have been optimized in order to derive the needed accelerating gradient. The simulated electric field has been used as input for Astra beam-dynamics simulations in order to compute the beam properties.

Poster TUPAB246 [2.209 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB246

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paper received ※ 18 May 2021 paper accepted ※ 27 July 2021 issue date ※ 13 August 2021

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TUPAB247

Influence of the Profile of the Dielectric Structure on the Electric Fields Excited by a Laser in Dielectric Accelerators Based on Chip

electron, acceleration, experiment, simulation

2026

A. Vasyliev, O.O. Bolshov, K. Galaydych, A.I. Povrozin, G.V. Sotnikov
NSC/KIPT, Kharkov, Ukraine

Funding: The National Research Foundation of Ukraine, program "Leading and Young Scientists Research Support" (project # 2020.02/0299).
To provide experimental researches at the NSC KIPT theoretical studies and computations of the electron acceleration in a dielectric laser accelerator have been carried out. Laser accelerator consists of two periodic quartz structures on diffraction gratings or Chips, symmetrically located along both sides of the vacuum accelerating channel. Using PIC numerical simulations, electromagnetic fields excited by laser radiation with a wavelength of 800 nm in dielectric laser accelerators were investigated. The influence of the shape and depth of the profile of diffraction gratings or Chip structures on the distribution of the electric field in the interaction space has been studied. For modeling, different types of profiles were taken, both in serial and a unique structure. In consequence of the analysis of the obtained results, estimated efficiency of acceleration was defined for each type of profile. The rectangular profile of the diffraction grating with the maximum accelerating gradient was selected as optimal for the next experiments.

Poster TUPAB247 [1.195 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB247

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paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 11 August 2021

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TUPAB267

Investigation of Beam Impedance and Heat Load in a High Temperature Superconducting Undulator

undulator, impedance, simulation, site

2089

D. Astapovych, H. De Gersem, E. Gjonaj
TEMF, TU Darmstadt, Darmstadt, Germany
T.A. Arndt, E. Bründermann, N. Glamann, A.W. Grau, B. Krasch, A.-S. Müller, R. Nast, D. Saez de Jauregui, A. Will
KIT, Eggenstein-Leopoldshafen, Germany

The use of high temperature superconducting (HTS) materials can enhance the performance of superconducting undulators (SCU), which can later be implemented in free electron laser facilities, synchrotron storage rings and light sources. In particular, the short period < 10 mm undulators with narrow magnetic gap < 4 mm are relevant. One of the promising approaches considers a 10 cm meander-structured HTS tapes stacked one above the other. Then, the HTS tape is wound on the SCU. The idea of this jointless undulator has been proposed by, and is being further developed at KIT. Since minimizing the different sources of heat load is a critical issue for all SCUs, a detailed analysis of the impedance and heat load is required to meet the cryogenic system design. The dominant heat source is anticipated to be the resistive surface loss, which is one of the subjects of this study. Considering the complexity of the HTS tape, the impedance model includes the geometrical structure of the HTS tapes as well as the anomalous skin effect. The results of the numerical investigation performed by the help of the CST PS solver will be presented and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB267

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paper received ※ 18 May 2021 paper accepted ※ 26 July 2021 issue date ※ 12 August 2021

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TUPAB273

Observations on Submicropulse Electron-Beam Effects From Short-Range Wakefields in Tesla-Type Superconducting Rf Cavities

cavity, electron, wakefield, HOM

2105

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

Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
In previous experiments at the Fermilab Accelerator Science and Technology (FAST) facility, the effects of higher-order modes (HOMs) in TESLA-type cavities on submacropulse centroid motion were elucidated*. We now have extended our investigations to short-range wakefields (SRWs) in these cavities. The latter result in submicropulse effects where the transverse wakefields cause head-tail centroid shifts. We used a Hamamatsu C5680 UV-visible synchroscan streak camera to synchronously sum the OTR from each of the 50 micropulses in the macropulse. We generated the y-t effect in the 41-MeV beam by purposely steering the beam off axis in y at the entrance of the first capture cavity. The head-tail transverse kicks within the 11-ps-long micropulses of 500 pC each were observed at the 100-micron level for steering off-axis in one cavity and several 100 microns for two cavities. These SRW results will be compared to simulations from the ASTRA model of a single micropulse in FAST. Since the SRW kicks go inversely with energy, these emittance-dilution effects are particularly relevant to the LCLS-II injector commissioning plans where <1 MeV beam will be injected into a TESLA-type cryomodule.
* A.H. Lumpkin et al, Phys. Rev. Accel. and Beams 23, 054401 (2020).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB273

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 28 August 2021

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TUPAB275

Enhanced Orthogonal Polarization Component Treatment in COTRI Model for Microbunched Beam Diagnostics

bunching, radiation, diagnostics, polarization

2113

D.W. Rule
Private Address, Silver Spring, USA
A.H. Lumpkin
ANL, Lemont, Illinois, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
We present the results of modifying our coherent optical transition radiation interferometry (COTRI) model’s treatment of the perpendicular polarization of OTR, Iperp. Our previous analytic approximation for Iperp was for beam divergences, sy << 1/g, where g is the Lorentz factor and sy is the rms y-component of the beam divergence. We have replaced our analytical form with a Gaussian quadrature for the convolution of Iperp with the divergence in theta-y. This extends the range of divergences we reliably model to sy > 1/g. Ipar, the parallel polarization in the model, is unchanged. Iperp is polarized along the y-axis and is proportional to the square of the y-component of the beam’s velocity distribution. We illustrate our results with two cases: 1) beam energy E=1 GeV, OTR wavelength 633 nm, Q=235 pC, microbunching fraction, bf=1%, divergences of 0.1-0.7 mrad, and rms beam sizes 2,10, and 30 microns; 2) E=375 MeV, wavelength 266 nm, Q=300 pC, bf=10%, divergences of 0.1-0,7 mrad, and rms beam sizes of 10,25,50, and 100 microns. We will present two cases that would be of interest for the diagnostics of laser-plasma accelerator beams* and pre-bunched FELs**, respectively.
* A. H. Lumpkin et al., Phys. Rev. Lett. 125, 014801 (2020).
** A. H. Lumpkin and D. W. Rule, in Proc., 39th International FEL Conference, FEL 2019 (JACoW Pub., Hamburg, Germany, 2019), pp. 408-411.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB275

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paper received ※ 22 May 2021 paper accepted ※ 10 June 2021 issue date ※ 20 August 2021

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TUPAB291

Subsystem Level Data Acquisition for the Optical Synchronization System at European XFEL

FEL, controls, data-acquisition, database

2167

M. Schütte, A. Eichler, T. Lamb, V. Rybnikov, H. Schlarb, T. Wilksen
DESY, Hamburg, Germany

The optical synchronization system for the European X-Ray Free-Electron Laser provides sub-10 femtosecond timing precision * for the accelerator subsystems and experiments. This is achieved by phase locking a mode-locked laser oscillator to the main RF reference and distributing the optical pulse train carrying the time information via actively propagation-time stabilized optical fibers to multiple end-stations. Making up roughly one percent of the entire European XFEL, it is the first subsystem to receive a large-scale data acquisition system [2] for storing not just hand-selected information, but in fact all diagnostic, monitoring, and configuration data relevant to the optical synchronization available from the distributed control system infrastructure. A minimum of 100 TB per year may be stored in a persistent archive for long-term health monitoring and data mining whereas excess data is stored in a short-term ring buffer for high-resolution fault analysis and feature extraction algorithm development. This paper describes scale, challenges and first experiences from the optical synchronization data acquisition system.
* S. Schulz et al., "Few-Femtosecond Facility-Wide Sync. of the European XFEL," in Proc. FEL’19
** T. Wilksen et al., "A Bunch-Sync. DAQ System for the European XFEL," in Proc. ICALEPCS’17

Poster TUPAB291 [0.281 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB291

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paper received ※ 14 May 2021 paper accepted ※ 17 June 2021 issue date ※ 24 August 2021

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TUPAB296

LLRF Upgrade at the Argonne Wakefield Accelerator Test Facility

LLRF, controls, klystron, pick-up

2176

W. Liu, D.S. Doran, G. Ha, P. Piot, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
L.R. Doolittle, D. Filippetto, D. Li, S. Paiagua, C. Serrano, V.K. Vytla
LBNL, Berkeley, California, USA

Funding: US Department of Energy, Office of Science
The Argonne Wakefiled Accelerator (AWA) Test Facility designed and operated a homemade LLRF system for the last 20 years. It is based on NI-PXI products that has now become obsolete. The AWA’s LLRF cannot keep up with the increasing stability demands of AWA’s upgraded facility. An overhaul of the system is strongly desired. With the support from DOE-HEP, the AWA is collaborating with Lawrence Berkeley National Laboratory (LBNL)to upgrade its LLRF system with modern instrumentation to meet the growing stability demands. An overview of AWA’s current LLRF system performance is presented together with the upgrade plan and expectations.

Poster TUPAB296 [1.943 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB296

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paper received ※ 19 May 2021 paper accepted ※ 05 July 2021 issue date ※ 26 August 2021

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TUPAB298

First Steps Toward an Autonomous Accelerator, a Common Project Between DESY and KIT

electron, controls, operation, simulation

2182

A. Eichler, F. Burkart, J. Kaiser, W. Kuropka, O. Stein
DESY, Hamburg, Germany
E. Bründermann, A. Santamaria Garcia, C. Xu
KIT, Karlsruhe, Germany

Funding: Helmholtz Artificial Cooperation Unit
Reinforcement Learning algorithms have risen in popularity in recent years in the accelerator physics community, showing potential in beam control and in the optimization and automation of tasks in accelerator operation. The Helmholtz AI project "Machine Learning toward Autonomous Accelerators" is a collaboration between DESY and KIT that works on investigating and developing RL applications for the automatic start-up of electron linear accelerators. The work is carried out in parallel at two similar research accelerators: ARES at DESY and FLUTE at KIT, giving the unique opportunity of transfer learning between facilities. One of the first steps of this project is the establishment of a common interface between the simulations and the machine, in order to test and apply various optimization approaches interchangeably between the two accelerators. In this paper we present the first results on the common interface and its application to beam focusing in ARES, and the idea of laser shaping with spatial light modulators at FLUTE.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB298

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paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 17 August 2021

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TUPAB302

Arrival Time Stabilization at Flash Using the Bunch Arrival Corrector Cavity (BACCA)

cavity, electron, feedback, SRF

2194

B. Lautenschlager, L. Butkowski, M.K. Czwalinna, B. Dursun, M. Hierholzer, S. Pfeiffer, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany

For pump-probe and seeding experiments at free electron lasers, a femtosecond precise bunch arrival time stability is mandatory. To stabilize the arrival times a fast longitudinal intra bunch-train feedback (L-IBFB) using bunch arrival time monitors is applied. The electron bunch energy prior to a bunch compression chicane is modulated by superconducting radio frequency (SRF) cavities to compensate fast arrival time fluctuations of the subsequent bunches. A broadband normal conducting RF cavity was installed in front of the first bunch compression chicane at FLASH. The L-IBFB uses the normal conducting cavity for small but fast energy corrections together with the SRF cavities for larger and slower corrections. Current measurements show arrival time stabilities of the electron bunches towards 5 fs (rms) at the end of the linac, if the normal conducting cavity acts together with the SRF cavities in the L-IBFB system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB302

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 26 August 2021

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TUPAB307

Robust Optical Instrumentation for Accelerator Alignment Using Frequency Scanning Interferometry

monitoring, target, radiation, instrumentation

2203

M. Sosin, H. Mainaud Durand, F. Micolon, V. Rude, J.M. Rutkowski
CERN, Meyrin, Switzerland

The precise alignment of components inside particle accelerators is an important engineering challenge in high-energy physics. Optical interferometry, being a precise, optical distance measurement technique, is often a method of choice in such applications. However, classical fringe-counting interferometers present several drawbacks in terms of system complexity. Due to the increasing availability of broadband, high-speed, sweeping laser sources, Frequency Scanning Interferometry (FSI) based systems, using Fourier analysis of the interference signal, are becoming a subject of growing interest. In the framework of the High-Luminosity LHC project at CERN, a range of FSI-based sensor solutions have been developed and tested. It includes the optical equipment for monitoring the position of cryogenic components inside their cryostats and FSI instrumentation like inclinometers and water-based levelling sensors. This paper presents the results of preliminary tests of these components.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB307

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paper received ※ 17 May 2021 paper accepted ※ 07 June 2021 issue date ※ 12 August 2021

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TUPAB310

Establishing a Metrological Reference Network for the Alignment of Sirius

network, alignment, survey, controls

2214

H. Geraissate, G.R. Rovigatti de Oliveira
LNLS, Campinas, Brazil
R. Junqueira Leão
CNPEM, Campinas, SP, Brazil

Sirius is the Brazilian 4th generation synchrotron light source. It consists of three electron accelerators and it has room for up to 38 beamlines. To make the alignment of Sirius components possible, there is a need for a network of points comprising the installation volume, allowing the location of portable coordinate instruments on a common reference frame. This work describes the development of such networks for the whole Sirius facility. The layout of the networks is presented together with the survey strategies. Details are given on how the calculations combined laser trackers and optical level measurements data and how the Earth curvature compensation was performed. A novel laser tracker orientation technique applied for linking networks on different environments is also presented. Finally, the uncertainty estimation for the resulting network and its deformation history is shown.

Poster TUPAB310 [4.084 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB310

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paper received ※ 20 May 2021 paper accepted ※ 07 June 2021 issue date ※ 21 August 2021

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TUPAB338

Surface Roughness Reduction of Nb₃Sn Thin Films via Laser Annealing for Superconducting Radio-Frequency Cavities

SRF, cavity, superconductivity, HOM

2283

Z. Sun, M. Ge, M. Liepe, T.E. Oseroff, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A.B. Connolly, M.O. Thompson
Cornell University, Ithaca, USA

Superconducting radio frequency (SRF) cavities, a key component of particle accelerators, await new SRF materials beyond the state-of-the-art niobium. Nb₃Sn is one of the most competitive candidates, since it increases the superheating field, allows the operation temperature up to 4K, and improves cavity efficiency. Surface roughness and grain boundaries, however, significantly affect the RF performance of current Nb₃Sn cavities. Here, we explore a post laser annealing technique to reduce the surface roughness. In doing so, we deposited a TiN laser-absorber on Nb₃Sn and Nb surfaces, and then annealed the samples by laser scanning via different laser systems. The Nb₃Sn surface roughness was minimized to 101 nm (Ra) by laser annealing via 308 nm, 35 ns pulses. Surface imaging and Fourier analysis revealed laser annealing is able to remove sharp edges and <1 um wavelength features.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB338

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paper received ※ 20 May 2021 paper accepted ※ 09 June 2021 issue date ※ 19 August 2021

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TUPAB342

Preliminary Cryogenic Cold Test Results of the First 9-Cell LSF Shape Cavity

cavity, niobium, SRF, multipactoring

2296

R.L. Geng, W.A. Clemens, R.S. Williams
JLab, Newport News, Virginia, USA
S.A. Belomestnykh
Fermilab, Batavia, Illinois, USA
Y. Fuwa
JAEA/J-PARC, Tokai-mura, Japan
H. Hayano
KEK, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
Z. Li
SLAC, Menlo Park, California, USA
V.D. Shemelin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Supplemental support by US-Japan Collaboration on HEP.
Following successful prototyping and testing of single- & 5-cell LSF shape cavities *, **, the first 9-cell LSF shape cavity LSF9-1 was successfully constructed using an innovative process at JLab with the in-house facilities. The cavity was then shipped to KEK for post-fabrication mechanical adjustment and ILC TDR style treatment and surface processing. Cold testing was carried out at the JLab VTA facility, instrumented with a suite of Kyoto instruments. Favorable values for the bath pressure detuning sensitivity and Lorentz force detuning coefficient were experimentally measured, validating the design improvement in cell stiffeners. Pass-band measurements indicate 4 out of 9 cells reaching gradient capability of > 45 MV/m, including 2 cells reaching 51 MV/m. Cornell OST detectors identified the cell and location responsible for the current hard quench limit. Multipacting-like barriers observed in end cells are investigated both analytically and numerically. The cavity was shipped to FNAL and received a light EP at the joint ANL/FNAL facility for further cold testing at Jlab. Two new 9-cell LSF cavities are being constructed including one made of large-grain niobium material.
* R. L. Geng et al.,WEPWI013, IPAC15.
** R. L. Geng et al., MOP064, SRF’19.

Poster TUPAB342 [1.600 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB342

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paper received ※ 09 May 2021 paper accepted ※ 14 June 2021 issue date ※ 20 August 2021

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TUPAB399

RF Characterisation of New Coatings for Future Circular Collider Beam Screens

impedance, collider, electron, cavity

2453

P. Krkotić, F. Pérez, M. Pont, N.D. Tagdulang
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
S. Calatroni
CERN, Meyrin, Switzerland
X. Granados, J. Gutierrez, T. Puig, A. Romanov, G.T. Telles
ICMAB, Bellatera, Spain
A.N. Hannah, O.B. Malyshev, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J.M. O’Callaghan Castella
Universitat Politécnica de Catalunya, Barcelona, Spain
D. Whitehead
The University of Manchester, Laser Processing Research Center, Manchester, United Kingdom

For the future high energy colliders being under the design at this moment, the choice of a low surface impedance beam screen coating material has become of fundamental importance to ensure sufficiently low beam impedance and consequently guaranteed stable operation at high currents. We have studied the use of high-temperature superconducting coated conductors as possible coating materials for the beam screen of the FCC-hh. In addition, amorphous carbon coating and laser-based surface treatment techniques are effective surface treatments to lower the secondary electron yield and minimise the electron cloud build-up. We have developed and adapted different experimental setups based on resonating structures at frequencies below 10 GHz to study the response of these coatings and their modified surfaces under the influence of RF fields and DC magnetic fields up to 9 T. Taking the FCC-hh as a reference, we will show that the surface resistance for REBCO-CCs is much lower than that of Cu. Further we show that the additional surface modifications can be optimised to minimise their impact on the surface impedance. Results from selected coatings will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB399

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

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WEPAB040

Characterization of Low Emittance Electron Beams Generated by Transverse Laser Beam Shaping

emittance, flattop, electron, cathode

2690

M. Groß, N. Aftab, P. Boonpornprasert, G.Z. Georgiev, J. Good, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, D. Melkumyan, S.K. Mohanty, R. Niemczyk, A. Oppelt, H.J. Qian, G. Shu, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany
Y. Chen, G. Loisch
DESY, Hamburg, Germany
I. Will
MBI, Berlin, Germany

Linac based X-ray free electron laser demand a high beam quality from the electron source, therefore RF photoinjectors are used to generate the electron bunches for state of the art beam brightness. One important figure of merit for these injectors is the transverse emittance of the generated electron beam, which can be minimized by shaping the photocathode laser pulses. Best performance can be achieved with ellipsoidal laser pulses, but 3D shaping is technically challenging. Typically, a quasi-uniform transverse laser profile is truncated from the Gaussian profile generated by the laser with an aperture to reduce the transverse nonlinear space charge forces. This is investigated in detail by optimizing the laser transverse profile at the Photoinjector Test facility at DESY in Zeuthen (PITZ), where photoinjector R&D is conducted for the E-XFEL and FLASH free electron lasers at DESY in Hamburg. In this contribution we present experimental results at high acceleration gradients (up to 60 MV/m) for both 250 pC and 500 pC. For a bunch charge of 500 pC an emittance reduction of about 30% compared to the commonly used transverse flat-top laser distribution was achieved.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB040

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paper received ※ 17 May 2021 paper accepted ※ 02 June 2021 issue date ※ 19 August 2021

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WEPAB043

Consolidation and Future Upgrades to the CLEAR User Facility at CERN

experiment, gun, 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 ※ 19 August 2021

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WEPAB052

Development of an EO Sampling System for the Analysis of THz Waves Generated by Coherent Cherenkov Radiation

radiation, electron, experiment, timing

2718

K. Murakoshi, Y. Koshiba, T. Murakami, K. Sakaue, Y. Tadenuma, P. Wang, M. Washio
Waseda University, Tokyo, Japan
R. Kuroda
AIST, Tsukuba, Japan
K. Sakaue
The University of Tokyo, Graduate School of Engineering, Bunkyo, Japan

THz waves, located between microwaves and light waves, have transparency, directionality and fingerprint spectrum of specific materials. Therefore, they are expected to be useful for various applications. We have been studying THz waves generation via Cherenkov radiation with electron beams from a photocathode rf-gun. In our early studies, we have succeeded in the generation of coherent Cherenkov radiation by tilted electron beams using an rf-deflector. Furthermore, we have generated quasi-monochromatic THz waves by spatially modulated electron beams and have succeeded in its measurement by bandpass filters. This study aims to obtain the THz wave form in time domain by electro-optic (EO) sampling, which is an useful detection system for obtaining the information of the electric field and the phase simultaneously with high S/N. In this conference, we report about our probe laser system, results of the time-domain spectroscopy measurement of THz waves by EO sampling, and future prospects.

Poster WEPAB052 [0.861 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB052

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 31 August 2021

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WEPAB055

Development of a Linac for Injection of Ultrashort Electron Bunches Into Laser Plasma Electron Accelerators

electron, plasma, acceleration, linac

2725

S. Masuda, N. Kumagai, T. Masuda, Y. Otake
JASRI, Hyogo, Japan
Y. Koshiba, S. Otsuka
Waseda University, Tokyo, Japan
T. Sakai, T. Tanaka
LEBRA, Funabashi, Japan
K. Sakaue
The University of Tokyo, The School of Engineering, Tokyo, Japan

Funding: This work is supported by JST-Mirai Program Grant Number JPMJMI17A1, Japan.
We are developing a C-band linac that produces ultrashort electron bunches as an injector for laser plasma accelerators. A plasma wave excited by a high intense ultrashort laser pulse has a wavelength of the order of 10 to 100 fs and transverse dimensions of the order of 10 to 100 um. To inject the bunch into a proper phase of the plasma wave, a length and transverse sizes of the bunch must be much smaller than the plasma wave structure. A laser triggered photo cathode electron RF-gun and a 2pi/3 mode traveling wave buncher with 24 cells for ultrashort electron bunch production have been developed based on electron beam tracking simulations that show the bunch length is less than 10 fs with a charge of 100 fC at a focus on the plasma wave. The simulations also show that sufficiently small transverse sizes of the bunch at the focus can be obtained by a Q triplet. A highly accurate timing lower than the plasma wavelength (~10fs) is required for the synchronization between the electron bunch injection and the plasma wave excitation. An RF master oscillator with low SSB phase noise (-150dBc/Hz@10MHz) has been developed for the synchronization. We will report present development status.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB055

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

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WEPAB062

Investigation of the Thomson Scattering Influence on Electron Beam Parameters in an Energy-Recovering Linear Accelerator on the Example of MESA

electron, photon, scattering, HOM

2732

C.L. Lorey, K. Aulenbacher, A. Meseck
KPH, Mainz, Germany

Funding: funded by DFG through GRK2128 ACCELENCE
At the Johannes Gutenberg University (JGU) in Mainz, the Mainz Energy-recovering Superconducting Accelerator (MESA) is currently under construction. It is designed to deliver electron beams of up to 155 MeV. As it can be operated in an energy-recovery (ER) mode thus allowing for high repetition rate, it is a promising candidate for a high flux Thomson scattering based gamma source. This paper will provide a status update on the study of the impact of Thomson scattering on electron beam parameters and the underlying mechanics. Further, the implementation into a simulation code will be discussed.

Poster WEPAB062 [1.307 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB062

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paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 02 September 2021

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WEPAB063

Status of the Polarized Source and Beam Preparation System at MESA

electron, experiment, emittance, simulation

2736

S. Friederich, K. Aulenbacher, C. Matejcek
IKP, Mainz, Germany
K. Aulenbacher
HIM, Mainz, Germany
K. Aulenbacher
GSI, Darmstadt, Germany

Funding: This work is supported by the DFG excellence initiative PRISMA+.
The MESA Low-energy Beam Apparatus (MELBA) connects the DC photoemission source STEAM with the injector accelerator MAMBO. MELBA is capable of adjusting the longitudinal phase space for the requirements of the pre-acceleration by using a chopper and buncher while providing small transverse emittances. Measurements of the transverse phase space and longitudinal beam dimension taken at a test setup are presented. These results serve now for further improvements, e.g design changes in our corrector magnets. In addition, the revised MELBA will include two Wien filters and a solenoid for spin manipulation. A double scattering Mott polarimeter for spin diagnostics and a second source for the extraction of high bunch charges is foreseen using a branched off beam line. RF-synchronized laser diodes will be used with infrared wavelength as a driver for the spin-polarized photoemission. In this report we present the latest layout of MELBA and simulation results.

Poster WEPAB063 [1.752 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB063

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

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WEPAB067

High Duty Cycle EUV Radiation Source Based on Inverse Compton Scattering

electron, gun, photon, emittance

2748

R. Huang, Q.K. Jia, C. Li
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by the National Natural Science Foundation of China Grant Number 11805200, and National Key Research and Development Program of China No. 2016YFA0401901.
ICS can obtain quasi-monochromatic and directional EUV radiation via a MeV-scale energy electron beam and a micron-scale wavelength laser beam, which enables a dramatic reduction in dimension and expense of the system, and makes it an attractive technology in research, industry, medicine and homeland security. Here we describe an EUV source based on high repetition ICS system. The scheme exploits the output from the laser-electron interaction between a MW-ps laser at MHz repetition-rate and a high quality electron beam with an energy of a few MeV at MHz repetition-rate.

Poster WEPAB067 [1.551 MB]

DOI •

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 ※ 02 September 2021

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WEPAB073

An Overview of the Radio-Frequency System for an Inverse Compton X-Ray Source Based on CLIC Technology

klystron, LLRF, controls, network

2759

T.G. Lucas, O.J. Luiten, P.H.A. Mutsaers, X.F.D. Stragier, H.A. Van Doorn, F.M. van Setten, H.J.M. van den Heuvel, M.L.M.C. van der Sluis
TUE, Eindhoven, The Netherlands

Funding: This project is financed by the "Interreg V programme Flanders-Netherlands" with financial support of the European Fund for Regional Development.
Compact inverse Compton scattering X-ray sources are gaining in popularity as the future of lab-based x-ray sources. Smart*Light is one such facility, under commissioning at Eindhoven University of Technology (TU/e), which is based on high gradient X-band technology originally designed for the Compact Linear Collider (CLIC) and its test stands located at CERN. Critical to the beam quality is the RF system which aims to deliver 10-24 MW RF pulses at repetition rates up to 1 kHz with a high amplitude and phase stability of <0.5\% and <0.65~^° allowing it to adhere to strict synchronicity conditions at the interaction point. This work overviews the design of the high power and low level RF systems for Smart*Light.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB073

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 29 August 2021

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WEPAB093

Space Charge Effects in Low Energy Magnetized Electron Beam

cathode, electron, solenoid, space-charge

2806

S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft
ODU, Norfolk, Virginia, USA
J.F. Benesch, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman, S. Zhang
JLab, Newport News, Virginia, USA

Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 and Laboratory Directed Research and Development program.
Magnetized electron cooling is one of the major approaches towards obtaining the required high luminosity in the proposed Electron-Ion Collider (EIC). In order to increase the cooling efficiency, a bunched electron beam with a high bunch charge and high repetition rate is required. At Jefferson Lab, we generated magnetized electron beams with high bunch charge using a new compact DC high voltage photogun biased at -300 kV with bialkali-antimonide photocathode and a commercial ultra-fast laser. This contribution discusses how magnetization affects space charge dominated beams as a function of magnetic field strength, gun high voltage, and laser pulse width, and spot size in comparison with simulations performed using General Particle Tracer.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB093

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paper received ※ 19 May 2021 paper accepted ※ 08 June 2021 issue date ※ 02 September 2021

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WEPAB097

Initial Nanoblade-Enhanced Laser-Induced Cathode Emission Measurements

electron, cathode, simulation, experiment

2814

G.E. Lawler, J.I. Mann, J.B. Rosenzweig, V.S. Yu
UCLA, Los Angeles, California, USA
R.J. Roussel
University of Chicago, Chicago, Illinois, USA

Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE HEP Grant DE-SC0009914
Nanostructured photocathodes offer a unique functionality not possible in traditional photocathodes, increasing beam brightness by reducing the effective emission area. Inspired by field emitter tips, we examine a possible extension for higher current operation, an extended nanoblade capable of producing asymmetric emittance electron beams. A full understanding of emission is necessary to establish the effectiveness of nanoblades as usable cathode for electron accelerators. Utilizing wet etching of silicon wafers, we arrive at a robust sample capable of dissipating incident laser fields in excess of 20 GV/m without permanent damage. Initial predictions and experiments from the nanotip case predict energies up to the keV scale from electron rescattering and fine features on the order of the photon quantum. We will present initial electron data from 800 nm Ti:S laser illumination and measurements of a focused 1 keV beam.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB097

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

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WEPAB099

Near-Threshold Nonlinear Photoemission From Cu(100)

electron, cathode, experiment, photon

2822

C.J. Knill, S.S. Karkare
Arizona State University, Tempe, USA
H.A. Padmore
LBNL, Berkeley, California, USA

Funding: National Science Foundation Grant No. PHY-1549132
Photocathodes that have a low mean transverse energy (MTE) are crucial to the development of compact X-ray Free Electron Lasers (XFEL) and ultrafast electron diffraction (UED) experiments. For FELs, low MTE cathodes result in a lower requirement for electron energy when lasing at a defined energy, and for a defined electron energy result in lasing at higher energy. For UED experiments, low MTE cathodes give a longer coherence length, allowing measurements on larger unit cell materials. A record low MTE of 5 meV has been recently demonstrated from a Cu (100) surface when measured near the photoemission threshold and cooled down to 30 K with liquid Helium [*]. For UED and XFEL applications that require a high charge density, the low quantum efficiency of Cu (100) near threshold necessitates the use of a high laser fluence to achieve the desired charge density [**]. At high laser fluences the MTE is limited by nonlinear effects, and therefore it is necessary to investigate near photoemission threshold at these high laser fluences. In this paper we report on nonlinear, near-threshold photoemission from a Cu (100) cathode, and its effect on the MTE.
* S. Karkare et al, Phys. Rev. Lett. 125, 054801 (2020)
** J. Bae et al, J. Appl. Phys., 124, 244903 (2018)

Poster WEPAB099 [0.829 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB099

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

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WEPAB100

Heat Dissipation of Photocathodes at High Laser Intensities for a New DC Electron Source

cathode, electron, experiment, operation

2826

M.A. Dehn, K. Aulenbacher
IKP, Mainz, Germany
K. Aulenbacher
HIM, Mainz, Germany
K. Aulenbacher
GSI, Darmstadt, Germany

Funding: This project was supported by the German science ministry BMBF through the Verbundforschung
Laser intensities of 1W or more are required to extract average beam currents of more than 10mA from photocathodes. Most of this laser power is converted into thermal load within the cathode and has to be dissipated to avoid excessive heating of the cathode and thus a significant reduction in lifetime. At Johannes Gutenberg-University Mainz, we are developing a new high current DC electron source operating at an energy of 100keV, where an efficient heat dissipation of the photocathode is achieved by a mechanical design of the supporting structure.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB100

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 30 August 2021

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WEPAB101

An Improved Model for Photoemission of Space Charge Dominated Picosecond Electron Bunches: Theory and Experiment

cathode, electron, experiment, space-charge

2829

S.M. Polozov, V.I. Rashchikov
MEPhI, Moscow, Russia
M. Krasilnikov
DESY Zeuthen, Zeuthen, Germany

The emission of a short highly charged electron bunch in a radiofrequency photogun is discussed. The traditional space charge limited emission numerical model is extended by an introduction of positively charged ions arising in the cathode region and dynamically changing during the emission. Estimates on the time characteristics of the charge migrating process in the semiconductor region are given. The numerical results are compared with the results of other numerical models and with experimental observations at the Photo Injector Test facility at DESY in Zeuthen (PITZ).

Poster WEPAB101 [1.601 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB101

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paper received ※ 08 May 2021 paper accepted ※ 07 June 2021 issue date ※ 19 August 2021

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WEPAB103

Systematic Beam Parameter Studies at the Injector Section of FLUTE

emittance, cathode, electron, quadrupole

2837

T. Schmelzer, E. Bründermann, D. Hoffmann, I. Križnar, S. Marsching, A.-S. Müller, M.J. Nasse, R. Ruprecht, J. Schäfer, M. Schuh, N.J. Smale, P. Wesolowski, T. Windbichler
KIT, Karlsruhe, Germany

Funding: This work is supported by the DFG-funded Doctoral School "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology (KSETA)"
FLUTE (Ferninfrarot Linac- und Test-Experiment) is a compact linac-based test facility for accelerator R&D and source of intense THz radiation for photon science. In preparation for the next experiments, the electron beam of the injector section of FLUTE has been characterized. In systematic studies the electron beam parameters, e.g., beam energy and emittance, are measured with several diagnostic systems. This knowledge allows the establishment of different operation settings and the optimization of electron beam parameters for future experiments.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB103

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paper received ※ 19 May 2021 paper accepted ※ 01 September 2021 issue date ※ 13 August 2021

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WEPAB104

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

cathode, simulation, electron, gun

2840

J.T. Yoskowitz, G.A. Krafft, G.G. Palacios Serrano, S.A.K. Wijethunga
ODU, Norfolk, Virginia, USA
J.M. Grames, J. Hansknecht, C. Hernandez-Garcia, M. Poelker, M.L. Stutzman, R. Suleiman
JLab, Newport News, Virginia, USA
S.B. van der Geer
Pulsar Physics, Eindhoven, The Netherlands

Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
The operating lifetime of GaAs-based photocathodes in DC high voltage electron photo-guns is dominated by the ionization rate of residual beamline gas molecules. In this work, experiments were performed to quantify the improvement in photocathode charge lifetime by biasing the photo-gun anode with a positive voltage, which repels ions generated downstream of the anode. The photo-cathode charge lifetime improved by almost a factor of two when the anode was biased compared to the usual grounded configuration. Simulations were performed using the particle tracking code General Particle Tracer (GPT) with a new custom element. The simulation results showed that both the number and energy of ions play a role in the pattern of QE degradation. The experiment results and conclusions supported by GPT simulations will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB104

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

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WEPAB106

Study on Durability Improvement of Cs-Te Photocathode by Means of Alkali Halide Protective Films

cathode, electron, experiment, ECR

2847

K. Ezawa, R. Fukuoka, Y. Koshiba, T. Tamba, M. Washio
Waseda University, Tokyo, Japan
K. Sakaue
The University of Tokyo, Graduate School of Engineering, Bunkyo, Japan

We have been conducting basic and applied research for generating high quality electron beams, using 1.6 cell laser photocathode RF-gun. In our laboratory, Cesium Telluride (Cs-Te), one of the semiconductor photocathodes, is used as an electron source for accelerator experiments. This semiconductor photocathode is known for high quantum efficiency (Q.E.) about 5~10% and 3-month 1/e lifetime. High Q.E. photocathodes can reduce the power requirement of the laser system, and long lifetime photocathodes can decrease the maintenance frequency, contributing to an efficient experimental environment. For these reasons, high Q.E. and long lifetime photocathodes are necessary in accelerator experiments. In order to produce robust photocathodes and extend the lifetime, we have conducted covering Cs-Te photocathodes with CsBr and CsI protective films. In this conference, we report the thickness dependency on the lifetime of Cs-Te photocathodes when we intentionally exposed oxygen gas to coated and non-coated Cs-Te photocathodes.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB106

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 15 August 2021

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WEPAB115

Beam Preparation with Temporally Modulated Photocathode Laser Pulses for a Seeded THz FEL

FEL, cathode, electron, simulation

2866

G.Z. Georgiev, N. Aftab, P. Boonpornprasert, J. Good, M. Groß, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, A. Lueangaramwong, D. Melkumyan, S.K. Mohanty, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach
DESY Zeuthen, Zeuthen, Germany
N. Chaisueb
Chiang Mai University, Chiang Mai, Thailand
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

The need for carrier-envelope-phase (CEP) stable THz pump pulses is recognized at many pump-probe experiments at the European XFEL. At the Photo Injector Test Facility at DESY in Zeuthen (PITZ), a proof-of-principle experiment of an accelerator-based THz FEL source is in preparation. Since the CEP stability of FEL pulses is not guaranteed in the SASE regime, a seeding scheme is needed. A common scheme for seeding is to drive the microbunching process with external laser pulses, which are power-limited in the THz range. Alternatively, a pre-bunched beam, generated for example by applying a temporally modulated photocathode laser pulse, can be used to drive the FEL. The beam dynamics with such a seeding method are studied with ASTRA tracking code simulations with space-charge forces as well as experimentally. The results of these studies are shown and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB115

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paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 26 August 2021

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WEPAB126

Pulsed Wire Magnetic Field Measurement System for Short-Period Long Undulators

undulator, FEL, detector, electron

2903

J.E. Baader, S. Casalbuoni
EuXFEL, Schenefeld, Germany

The pulsed wire method is an attractive option to measure the magnetic field in insertion devices, mainly for those with restricted access (e.g., small gaps, in-vacuum/cryogenic environments, etc.). Besides first and second field integrals, experiments have proved the feasibility of reconstructing the magnetic field profile. Undulators with a small gap and short period are - and are planned to be - used at diffraction-limited storage rings and free-electron lasers. This contribution outlines the pulsed wire system’s requirements to perform magnetic field reconstruction in such undulators. We examine the main expected limitations, particularly the dispersive, finite pulse-width, discretization error, and sag effects. Furthermore, we present the current status of developing the pulsed wire system at the European XFEL.

Poster WEPAB126 [1.184 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB126

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

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WEPAB139

Beam Tracking Simulations for Stage 1 of the Laser-Hybrid Accelerator for Radiobiological Applications (LhARA)

proton, simulation, target, plasma

2939

H.T. Lau
Imperial College London, London, United Kingdom

The Laser-hybrid Accelerator for Radiobiological Applications (LhARA) is a unique and flexible facility proposed for radiobiological studies. The first stage of LhARA consists of an intense laser source interacting with a thin foil target producing a large flux of protons with energies up to 15 MeV. Particles will propagate through a combination of plasma (Gabor) lenses and magnetic elements to an achromat arc delivering the beam vertically to an in-vitro end station. An end-to-end simulation from the laser source to the end station is required to verify the conceptual design of the beamline. The laser-plasma interaction is simulated with Smilei (a particle-in-cell code) to produce a two-dimensional (2D) distribution of particles. Whilst it is possible to simulate the laser-plasma interaction in three dimensions (3D), access to the computing resources needed to run highly resolved simulations was not available. A sampling routine will be described which samples the 2D distribution to generate a 3D beam. The Monte Carlo simulation programs BDSIM and GPT were used to track the beam. Results of the simulations will be shown and compared to the results of an idealized Gaussian beam.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB139

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paper received ※ 18 May 2021 paper accepted ※ 01 July 2021 issue date ※ 10 August 2021

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WEPAB140

Second Beam Test and Numerical Investigation of the Imperial College Plasma (Gabor) Lens Prototype

plasma, focusing, electron, proton

2943

T.S. Dascalu
Imperial College London, London, United Kingdom
R. Bingham, C.G. Whyte
USTRAT/SUPA, Glasgow, United Kingdom
C.L. Cheung, H.T. Lau, K.R. Long, T. Nonnenmacher, J.K. Pozimski
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

Funding: STFC through the Imperial Impact Acceleration Account
The design of the Laser-hybrid Accelerator for Radiobiological Applications (LhARA) is based on a series of plasma lenses to capture, focus, and select the energy of the ions produced in the laser-target interaction. A second beam test of the first plasma lens prototype, built at the Imperial College London, took place in October 2017 at the Ion Beam Centre of the University of Surrey. 1.4 MeV proton pencil beams were imaged 0.67m downstream of the lens on a scintillator screen over a wide range of settings. On top of the focusing effect, the electron plasma converted pencil beams into rings. The intensity of each ring shows a different degree of modulation along its circumference. Analysis of the results indicates non-uniformity and an off-axis rotation of the electron plasma. The effect on the beam is presented and compared to the results of a simulation of the plasma dynamics and proton beam transport through the lens. A particle-tracking code was used to study the impact of plasma instabilities on the focusing forces produced by the lens. The m = 1 diocotron instability was associated with the formation of rings from the pencil beams.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB140

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paper received ※ 19 May 2021 paper accepted ※ 29 August 2021 issue date ※ 18 August 2021

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WEPAB143

Sub-MeV Ion Generation by Standing Wave Excitation of Ionized Gases

electron, acceleration, plasma, simulation

2951

Sz. Turnár, G. Almási, J. Hebling, Cs. Korpa, M.I. Mechler, L. Pálfalvi, Z. Tibai
University of Pecs, Pécs, Hungary

Funding: Hungarian Scientific Research Fund (OTKA) (125808, 129134) ÚNKP-20-3 New National Excellence Program of the Ministry for Innovation and Technology from the source of the National Research
Many ion acceleration techniques have been suggested and thoroughly studied in the last two decades*. One of the promising techniques is the Coulomb explosion acceleration (CEA)**. Using CEA in clusters could result in symmetric acceleration if there are not any other significant mechanisms. We proposed a THz-driven accelerator scheme that is based on CEA in proton, deuterium and heavy water gas plasmas. Two counter-propagating THz pulses are focused to the ionized region of the gas jet. Following the ripping of the electrons from the gas plasmas by ultrafast standing waves, the Coulomb explosion accelerates the positive ions. According to our calculation, using 2 x 34 mJ THz pulses electrons and protons with 1.1 nC charge are accelerated up to 0.4 MeV and 0.1 MeV, respectively. The total energy of the particles is 0.7 % of the energy of the THz pulses. We examined the effect of the initial bunch charge, bunch size and shape on the final energy spectra and the directional distribution of the particles. Our presented technique is scalable from a few µm to a few thousand µm driving wavelengths and can be used for electron and heavy-ion acceleration.
*J. Badziak, IOP Conf. Series: J Phys: Conf. Series 959, 012001 (2018).
** M. Murakami and K. Mima, Phys. of Plasmas 16, 103108 (2009).

Poster WEPAB143 [3.467 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB143

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 15 August 2021

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WEPAB147

Simulations of Nanoblade-Enhanced Laser-Induced Cathode Emissions and Analyses of Yield, MTE, and Brightness

electron, simulation, space-charge, brightness

2957

J.I. Mann, G.E. Lawler, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
T. Arias, J.K. Nangoi
Cornell University, Ithaca, New York, USA

Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE HEP Grant DE-SC0009914.
Laser-induced field emission of electrons from metallic nanotips has been well studied. Unfortunately, nanotips suffer low damage thresholds with enhanced fields around 10 GV/m. The nanoblade, akin to a nanotip extruded in one lateral dimension, may reach upwards of 40 GV/m due to its robust thermomechanical properties. This increased surface field promises brighter electron emissions. We perform simulations of strong-field emissions from metallic nanoblades via the 1-D time-dependent Schr\"odinger equation with effective Jellium and nonlinear collective image charge potentials, including the strong field gradients induced by the nanostructure. We measure spectra and yields and compare to recent experiments. Potential analytical forms of image potential limited yield for a spectrally rich emission are presented. Calculations of mean transverse energy are provided as well as a prospective method of mitigation with the goal of increasing brightness.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB147

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paper received ※ 19 May 2021 paper accepted ※ 06 July 2021 issue date ※ 01 September 2021

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WEPAB183

Big Data Techniques for Accelerator Optimization

plasma, experiment, wakefield, radiation

3039

C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This project has received funding from STFC under grant reference ST/P006752/1.
Accelerators and the experiments that they enable are some of the largest, most data-intensive, and most complex scientific systems in existence. The interrelations between machine subsystems are complicated and often nonlinear. The system dynamics involve large parameter spaces that evolve over multiple relevant time scales and accelerator systems. Any accelerator-based experiments and applications are almost always difficult to model. LIV. DAT, the Liverpool Centre for Doctoral Training in Data-intensive science, was established in 2017 as a hub for training students in Big Data science. The centre currently has 36 PhD students that are working across nuclear, particle and astrophysics, as well as in accelerator science. This paper presents results from R&D into betatron radiation models and beam parameter reconstruction for plasma acceleration experiments at FACET-II, simulations for MeV energy gain in dielectric structures driven by a CO₂ laser, and modelling of seeded self-modulation of long elliptical bunches in plasma. It also gives an overview of the training program offered to the LIV. DAT students.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB183

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

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WEPAB198

Beam Dynamics Design of a Synchrotron Injector with Laser-Accelerated Ions

emittance, synchrotron, quadrupole, simulation

3085

M.Z. Tuo, X. Guan, W. Lu, P.F. Ma, Y. Wan, X.W. Wang, Q.Z. Xing, H.J. Yao, S.X. Zheng
TUB, Beijing, People’s Republic of China

We present, in this paper, the beam dynamics design of a linac injector with laser-accelerated carbon-ions for a medical synchrotron. In the design, the initial transverse divergence is reduced by two apertures. The beam is focused transversely through a quadrupole triplet lens downstream the apertures. The output energy spread of the extracted beam at the exit of the injector is compressed from ±6% to ±0.6% by a debuncher and a bend magnet system to meet the injection requirement for the synchrotron. By changing the width of imaging slit of the bend magnet system, the beam with energy of 4±0.024 MeV/u is extracted, and the particle number per shot and transverse emittances of the beam at the exit of the injector can be regulated through adjusting the slit height. The dynamics design can pave the way for the future concept research of the synchrotron injector.

Poster WEPAB198 [1.034 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB198

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

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WEPAB228

Modelling and Counteracting Microbunching Instability in Spreader Lines of Radiofrequency and Plasma-Based Accelerators for Free-Electron Lasers

electron, bunching, free-electron-laser, scattering

3165

G. Perosa
Università degli Studi di Trieste, Trieste, Italy
S. Di Mitri
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

High energy radiofrequency and plasma-driven accelerators target electron beam brightness suitable for x-ray free-electron lasers. Microbunching instability can be enhanced during beam transport through the spreader line from the accelerator to the undulator, degrading the brightness of the accelerated beam and therefore reducing the lasing efficiency. We present a semi-analytical model of the instability, benchmarked with experimental data at the FERMI free-electron laser, in the presence of intrabeam scattering and beam heating. Strategies for minimization of the instability both in conventional and plasma-based accelerators are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB228

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paper received ※ 19 May 2021 paper accepted ※ 08 July 2021 issue date ※ 02 September 2021

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WEPAB274

Numerical Study of Beam Dynamics in PITZ Bunch Compressor

simulation, booster, FEL, gun

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 ※ 23 August 2021

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WEPAB281

The Precision Laser Inclinometer

experiment, luminosity, detector, operation

3305

B. Di Girolamo, S. Vlachos
CERN, Geneva, Switzerland
Ju. Boudagov, M.V. Lyablin
JINR, Dubna, Moscow Region, Russia

Earth surface movements, like earthquakes or human-produced (cultural) noise, can induce a degradation of the instantaneous luminosity of particle accelerators or even sudden beam losses. In the same way the presence of seismic and cultural noise limits the detection capabilities of interferometric antennas used for the observations of gravitational waves. This contribution discusses the importance of monitoring the effects of earth vibrations using a novel multi-purpose instrument, the Precision Laser Inclinometer (PLI). Few examples of recorded events are discussed along with ideas on PLI applications.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB281

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paper received ※ 16 May 2021 paper accepted ※ 01 July 2021 issue date ※ 12 August 2021

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WEPAB285

High Resolution Arrival Time Measurement of the Seed Laser

FEL, timing, electron, experiment

3320

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

The Shanghai soft X-ray Free-Electron Laser facility (SXFEL) is a fourth-generation linac-based light source, capable of producing X-ray pulses with a duration of tens of femtosecond. The seed laser for external seeding FEL, therefore, has tight requirements for relative arrival time to the electron bunch. To reach the required energy and wavelength for external seeding FEL, further optical amplification and frequency conversion is needed. These include reflection and propagation in different material and in air, in addition, also include the long laser transport beamline to the undulator, make the laser pulses arrival time influenced by environmental variation. To reach the required specification, high-resolution measurement of the laser arrival time is necessary. In this paper, we present a general concept for the measurement of the laser arrival time.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB285

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

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WEPAB286

Design of the Laser-to-RF Synchronization at 1.3 GHz for SHINE

electron, electronics, timing, FEM

3323

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

A next-generation photo-science facility like Shanghai HIgh repetition rate XFEL aNd Extreme light facility (SHINE) is aiming to generate femtosecond X-ray pulses with unprecedented brightness to film chemical and physical reactions with sub-atomic level spatio-temporal resolution. To fulfill this scientific goal, high-precision timing synchronization is essential. The pulsed optical synchronization has become an indispensable scheme for femtosecond precision synchronization of X-ray free-electron lasers. One of the critical tasks of pulsed optical synchronization is to synchronize various microwave sources. For the future SHINE, ultralow-noise pulses generated by a mode-locked laser are distributed over large distances via stabilized fiber links to all critical facility end-stations. In order to achieve low timing jitter and long-term stability of 1.3 GHz RF reference signal for the accuracy Low-Level RF(RF) field control, an Electro-optical intensity Modulator (EOM) based scheme is being developed at SHINE. In this paper, we present the progress on the design of the optical part and the integrated electronics of the laser-to-RF synchronization.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB286

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paper received ※ 20 May 2021 paper accepted ※ 12 July 2021 issue date ※ 28 August 2021

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WEPAB289

Machine Learning Based Spatial Light Modulator Control for the Photoinjector Laser at FLUTE

electron, network, target, experiment

3332

C. Xu, E. Bründermann, A.-S. Müller, M.J. Nasse, A. Santamaria Garcia, C. Sax, C. Widmann
KIT, Karlsruhe, Germany
A. Eichler
DESY, Hamburg, Germany

Funding: C. Xu acknowledges the support by the DFG-funded Doctoral School "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology".
FLUTE (Ferninfrarot Linac- und Test-Experiment) at KIT is a compact linac-based test facility for novel accelerator technology and a source of intense THz radiation. FLUTE is designed to provide a wide range of electron bunch charges from the pC- to nC-range, high electric fields up to 1.2 GV/m, and ultra-short THz pulses down to the fs-timescale. The electrons are generated at the RF photoinjector, where the electron gun is driven by a commercial titanium sapphire laser. In this kind of setup the electron beam properties are determined by the photoinjector, but more importantly by the characteristics of the laser pulses. Spatial light modulators can be used to transversely and longitudinally shape the laser pulse, offering a flexible way to shape the laser beam and subsequently the electron beam, influencing the produced THz pulses. However, nonlinear effects inherent to the laser manipulation (transportation, compression, third harmonic generation) can distort the original pulse. In this paper we propose to use machine learning methods to manipulate the laser and electron bunch, aiming to generate tailor-made THz pulses. The method is demonstrated experimentally in a test setup.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB289

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

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WEPAB290

Pointing Stabilization Algorithms Explored and Implemented with the Low Energy RHIC Electron Cooling Laser

operation, electron, feedback, cathode

3336

L.K. Nguyen
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The electron beam for the Low Energy RHIC electron Cooler (LEReC) at Brookhaven National Laboratory (BNL) is generated by a high-power fiber laser illuminating a photocathode, with a total propagation distance of 34 m separating the laser output and the photocathode. This propagation is facilitated by three independent laser tables that have varying responses to changes in time of day, weather, and season. Alignment drifts induced by these environmental changes are mitigated by an active "slow" pointing stabilization system found along the length of the transport, and this in-house system was commissioned as part of the full laser transport in 2019, as previously reported*. In 2020, the system became fully operational alongside LEReC, the world’s first electron cooler in a collider, and helped establish the transverse stability of the electron beam required for cooling. A summary of the different slow stabilization algorithms, which were continually refined during the run in order to achieve long-term center-of-mass stability of the laser spot on the photocathode to within 10 microns RMS, is provided.
* L. K. Nguyen et al., "Active Pointing Stabilization Techniques Applied to the Low Energy RHIC Electron Cooling Laser Transport at BNL", presented at NAPAC’19, paper THYBA6.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB290

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paper received ※ 19 May 2021 paper accepted ※ 02 July 2021 issue date ※ 24 August 2021

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WEPAB294

LLRF Control and Synchronization System of the ARES Facility

LLRF, gun, 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 ※ 20 August 2021

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WEPAB308

Measurement-Based Surrogate Model of the SLAC LCLS-II Injector

simulation, network, controls, cathode

3395

L. Gupta, Y.K. Kim
University of Chicago, Chicago, Illinois, USA
A.L. Edelen, C.E. Mayes, A.A. Mishra, N.R. Neveu
SLAC, Menlo Park, California, USA

Funding: This project was funded by the DOE SCGSR Program.
There is significant effort within particle accelerator physics to use machine learning methods to improve modeling of accelerator components. Such models can be made realistic and representative of machine components by training them with measured data. These models could be used as virtual diagnostics or for model-based control when fast feedback is needed for tuning to different user settings. To prototype such a model, we demonstrate how a machine learning based surrogate model of the SLAC LCLS-II photocathode injector was developed. To create machine-based data, laser measurements were taken at the LCLS using the virtual cathode camera. These measurements were used to sample particles, resulting in realistic electron bunches, which were then propagated through the injector via the Astra space charge simulation. By doing this, the model is not only able to predict many bulk electron beam parameters and distributions which are often hard to measure or not usually available to measure, but the predictions are more realistic relative to traditionally simulated training data. The methods for training such models, as well as model capabilities and future work are presented here.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB308

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paper received ※ 26 May 2021 paper accepted ※ 27 July 2021 issue date ※ 24 August 2021

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WEPAB331

Application of KALYPSO as a Diagnostic Tool for Beam and Spectral Analysis

electron, detector, synchrotron, experiment

3451

M.M. Patil, E. Bründermann, M. Caselle, A. Ebersoldt, S. Funkner, B. Kehrer, A.-S. Müller, M.J. Nasse, G. Niehues, J.L. Steinmann, M. Weber, C. Widmann
KIT, Karlsruhe, Germany

Funding: This work is supported by the BMBF project 05K19VKD STARTRAC and DFG-funded Doctoral School ’Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology’
KALYPSO is a novel detector capable of operating at frame rates up to 12 MHz developed and tested at the institute of data processing and electronics (IPE) and employed at Karlsruhe Research Accelerator (KARA) which is part of the Test Facility and Synchrotron Radiation Source KIT. This detector consists of silicon, InGaAs, PbS, or PbSe line array sensor with spectral sensitivity from 350 nm to 5000 nm. The unprecedented frame rate of this detector is achieved by a custom-designed ASIC readout chip. The FPGA-readout architecture enables continuous data acquisition and real-time data processing. Such a detector has various applications in the fields of beam diagnostics and spectral analysis. KALYPSO is currently employed at various synchrotron facilities for electro-optical spectral decoding (EOSD) to study the longitudinal profile of the electron beam, to study the energy spread of the electron beam, tuning of free-electron lasers (FELs), and also in characterizing laser spectra. This contribution will present an overview of the results from the mentioned applications.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB331

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paper received ※ 19 May 2021 paper accepted ※ 22 July 2021 issue date ※ 13 August 2021

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WEPAB378

Near-Infrared Laser System for Dielectric Laser Acceleration Experiments at SINBAD

experiment, electron, timing, acceleration

3596

C. Mahnke, U. Grosse-Wortmann, I. Hartl, C.M. Heyl, Y. Hua, T. Lamb, Y. Ma, C. Mohr, J. Müller, S.H. Salman, S. Schulz, C. Vidoli
DESY, Hamburg, Germany
H. Çankaya
CFEL, Hamburg, Germany

The technique of dielectric laser acceleration (DLA) utilizes the strong field gradients generated by intense laser light near the surfaces of microscopic photonic structures, possibly allowing compact accelerator devices. We report on the infrared laser system at the SINBAD facility at DESY, where first DLA experiments with relativistic electrons pre-accelerated by the ARES linear accelerator started in late 2020. We constructed a low-noise Holmium fiber oscillator producing pulses at a wavelength of 2050 nm, seeding a Ho:YLF regenerative amplifier. Pulses of 2 mJ and 2 ps duration from the amplifier are transported over a distance of about 30 m to the DLA interaction point. The laser system is synchronized to the accelerator by locking the laser repetition rate to an RF master oscillator using an all-digital phase-locked loop, giving a residual timing jitter of about 45 fs. The digital locking scheme allows precise shifting of the relative timing between laser pulses and electrons without need for a dedicated optical delay line. It is planned to lock the system to the UV photocathode laser by means of an optical cross correlator further to improve the locking performance.

Poster WEPAB378 [1.445 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB378

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paper received ※ 19 May 2021 paper accepted ※ 22 June 2021 issue date ※ 18 August 2021

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WEPAB379

Photocathode Laser Development for Superconducting X-Ray Free Electron Lasers at DESY

FEL, operation, cathode, electron

3599

C. Li, O. Akcaalan, U. Grosse-Wortmann, I. Hartl, C. Mohr, M. Seidel, H. Tuennermann, C. Vidoli, L. Winkelmann
DESY, Hamburg, Germany
M. Frede, O. Puncken
neoLASE GmbH, Hanover, Germany

Funding: Deutsches Elektronen-Synchrotron, Hamburg, 22609, Germany
Modern X-Ray Free-Electron Lasers (XFEL) are a key tool to enable a variety of scientific research. Those large-scale machines rely on robust and reliable deep ultraviolet (DUV) laser sources to drive electrons from their RF photocathode gun. In this paper we present a new photocathode laser prototype, which offers more flexibility in duration and shape of the 257.5 nm pulses for driving the CsTe Photocathodes of DESY’s superconducting burst-mode FELs. The laser matches the FEL pulse structure, which are 800 µs bursts at up to 4.5 MHz intraburst-rate with 10 Hz burst-repetition-rate. In a first version the system will offer variable DUV pulse durations, tunable from 1 ps to 20 ps to address different operational regimes of the XFEL. The laser system comprises a high-resolution spectral shaper with the option of generating flat-top DUV pulses for reducing electron-beam emittance at a later version. The laser is constructed in a hybrid Yb:fiber and Yb:YAG architecture. Our prototype delivers 180 uJ pulse energy at 1030 nm and 1 MHz intra-burst rate and we demonstrated conversion of 50µJ of the NIR beam to DUV, resulting 11.5µJ at 21ps (FWHM) and 6.15 µJ at 1.05 ps (FWHM) pulse duration.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB379

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paper received ※ 27 May 2021 paper accepted ※ 02 July 2021 issue date ※ 23 August 2021

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WEPAB405

Supercontinuum Generation for the Improvement of Pulse Radiolysis System

radiation, polarization, photon, electron

3657

M. Sato, Y. Kaneko, Y. Koshiba, M. Washio
RISE, Tokyo, Japan
K. Sakaue
The University of Tokyo, Graduate School of Engineering, Bunkyo, Japan

Pulse radiolysis is one of the absorption measurement methods for investigating the fundamental, ultrafast process of radiation chemical reactions. Analytical light is transmitted simultaneously with the timing of electron beam irradiation, and its absorption by reactive species is detected. Since the target reactions arise in pico second time scale or even shorter, analytical light is required to have such duration. Besides, so as not to be buried in noise of the radiation source, the optical power of the analytical light must be high enough. Furthermore, it is desirable that the analytical light covers visible region because important absorptions caused by irradiation products such as hydrated electron, hydroxyl radical, or so exist in the region. We considered that the supercontinuum light generated from an ultrashort pulse laser is suitable as an analytical light because it has all these characteristics. In this study, we generate the second harmonic (775 nm) of an erbium fiber laser (1550 nm) as a seed laser for supercontinuum generation. In this presentation, we report the current situation of our laser system and prospects.

Poster WEPAB405 [0.734 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB405

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paper received ※ 18 May 2021 paper accepted ※ 01 September 2021 issue date ※ 20 August 2021

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WEPAB411

Ion Coulomb Crystals in Storage Rings for Quantum Information Science

storage-ring, operation, controls, rfq

3667

K.A. Brown, G.J. Mahler, T. Roser, T.V. Shaftan, Z. Zhao
BNL, Upton, New York, USA
A. Aslam, S. Biedron, T.B. Bolin, C. Gonzalez-Zacarias, S.I. Sosa Guitron
UNM-ECE, Albuquerque, USA
R. Chen, T.G. Robertazzi
Stony Brook University, Stony Brook, New York, USA
B. Huang
SBU, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
We discuss the possible use of crystalline beams in storage rings for applications in quantum information science (QIS). Crystalline beams have been created in ion trap systems and proven to be useful as a computational basis for QIS applications. The same structures can be created in a storage ring, but the ions necessarily have a constant velocity and are rotating in a circular trap. The basic structures that are needed are ultracold crystalline beams, called ion Coulomb crystals (ICC’s). We will describe different applications of ICC’s for QIS, how QIS information is obtained and can be used for quantum computing, and some of the challenges that need to be resolved to realize practical QIS applications in storage rings.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB411

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

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THXB02

Beam Arrival Stability at the European XFEL

FEL, timing, electron, feedback

3714

M.K. Czwalinna, J. Kral, B. Lautenschlager, J. Müller, H. Schlarb, S. Schulz, B. Steffen
DESY, Hamburg, Germany
R. Boll, H. Kirkwood, J. Koliyadu, R. Letrun, J. Liu, F. Pallas, D.E. Rivas, T. Sato
EuXFEL, Schenefeld, Germany

Free electron laser facilities, such as the European XFEL, make increasingly high demands on the longterm temporal stability and uniformity of the electron bunches, as pump-probe experiments meanwhile aim for timing stabilities of few femtoseconds residual jitter only. For a beam-based feedback control of the linear accelerator, electro-optical bunch arrival-time monitors are deployed, achieving a time resolution better than 3 fs. In a first attempt, we recently demonstrated a beam-based feedback system, reducing the arrival time jitter of the electron bunches to the 10 fs level with stable operation over hours. For pump-probe experiments it is crucial to equally verify this new level of precision in the FEL pulse arrival time with independent methods. In this work, we are discussing first results from examining the facility-wide temporal stability at the European XFEL, with attention to the contributions of various sub-systems and on the different time scales.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB02

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paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 23 August 2021

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THXB06

Results of the First Alignment Run for Sirius

alignment, network, operation, survey

3728

R. Junqueira Leão, R. Oliveira Neto
CNPEM, Campinas, SP, Brazil
H. Geraissate, F. Rodrigues, G.R. Rovigatti de Oliveira
LNLS, Campinas, Brazil

It is widely known that the position of particle accelerator components is critical for its performance. For the latest generation light sources, whose magnetic lattice is optimized for achieving very low emittance, the tolerable misalignments are in the order of a few dozen micrometers. Due to the perimeter of these machines, the requirements push the limits of large-volume dimensional metrology and associated instruments and techniques. Recently a fine alignment campaign of the Sirius accelerators was conducted following the pre-alignment performed during the installation phase. To conform with the strict relative positioning demands, measurement good practices were followed, and several 3D metrology procedures were developed. Also, to improve positioning resolution, high rigidity translation devices were produced. Finally, the special target holders designed as removable fiducials for the magnets were revisited to assure maximum reliability. Data processing algorithms were implemented to evaluate the alignment results in a robust and agile manner. This paper will present the final positioning errors for Sirius magnets with an expression of the estimated uncertainty.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB06

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paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 01 September 2021

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THXB07

Coherent Radiation From Inverse Compton Scattering Sources by Means of Particle Trapping

electron, radiation, undulator, FEL

3732

A. Fallahi, L. Novotny
ETH Zurich, Photonics Laboratory, Zurich, Switzerland
N. Kuster
ETH, Zurich, Switzerland

Funding: This work is supported by the Swiss National Science Foundation (SNSF) under the Spark grant CRSK-2-190840.
Inverse Compton scattering (ICS) sources are one of the promising compact tools to generate short wavelength radiation from electron beams based on the relativistic Doppler effect. Nonetheless, these sources suffer from a few shortcomings such as incoherent radiation and low-efficiency in radiation generation. This contribution presents a novel scheme based on the scattering of an optical beam from a trapped electron beam inside an optical cavity. Inverse-Compton scattering off both free and trapped electrons are simulated using a full-wave solution of first-principle equations based on FDTD/PIC in the co-moving frame of electron beams. It is shown that the strong space-charge effect in low-energies is the main obstacle in acquiring coherent gain through the ICS mechanism. Subsequently, it is shown that by trapping the electron beam to the high-intensity spots, the space-charge effect is compensated, and additionally, the ultrahigh charge density enables high FEL-gain at trapping spots, thereby augmenting the coherence of the output radiation and concurrently increasing the source efficiency by three orders of magnitude.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB07

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paper received ※ 28 May 2021 paper accepted ※ 01 July 2021 issue date ※ 24 August 2021

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THPAB009

A Hard X-Ray Compton Source at CBETA

electron, photon, scattering, brilliance

3765

K.E. Deitrick, C. Franck, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J. Crone, H.L. Owen
UMAN, Manchester, United Kingdom
G.A. Krafft
JLab, Newport News, Virginia, USA
G.A. Krafft, B. Terzić
ODU, Norfolk, Virginia, USA
B.D. Muratori, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
B.D. Muratori, P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Inverse Compton scattering (ICS) holds the potential for future high flux, narrow bandwidth x-ray sources driven by high quality, high repetition rate electron beams. CBETA, the Cornell-BNL Energy recovery linac (ERL) Test Accelerator, is the world’s first superconducting radiofrequency multi-turn ERL, with a maximum energy of 150 MeV, capable of ICS production of x-rays above 400 keV. We present an update on the bypass design and anticipated parameters of a compact ICS source at CBETA. X-ray parameters from the CBETA ICS are compared to those of leading synchrotron radiation facilities, demonstrating that, above a few hundred keV, photon beams produced by ICS outperform those produced by undulators in term of flux and brilliance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB009

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paper received ※ 19 May 2021 paper accepted ※ 06 July 2021 issue date ※ 10 August 2021

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THPAB048

Design and Fabrication Concepts of a Compact Undulator with Laser-Structured 2G-HTS Tapes

undulator, simulation, FEL, impedance

3851

A. Will, T.A. Arndt, E. Bründermann, N. Glamann, A.W. Grau, B. Krasch, A.-S. Müller, R. Nast, D. Saez de Jauregui
KIT, Karlsruhe, Germany
D. Astapovych, H. De Gersem, E. Gjonaj
TEMF, TU Darmstadt, Darmstadt, Germany

To produce small-scale high-field undulators for table-top free electron lasers (FELs), compact designs have been proposed using high temperature superconducting (HTS) tapes, which show both large critical current densities and high critical magnetic fields with a total tape thickness of about 50 μm and a width of up to 12 mm. Instead of winding coils, a meander structure can be laser-scribed directly into the superconductor layer, guiding the current path on a quasi-sinusoidal trajectory. Stacking pairs of such scribed tapes allows the generation of the desired sinusoidal magnetic fields above the tape plane, along the tape axis. Two practically feasible designs are presented, which are currently under construction at KIT: A coil concept wound from a single structured tape with a length of 15 m, which is a progression of a design that has been presented already in the past, as well as a novel stacked and soldered design, made from 25 cm long structured tapes, soldered in a zig-zag-pattern. In this contribution the designs are briefly recapped and the experimental progress is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB048

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paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 15 August 2021

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THPAB060

Dispersion Controlled Temporal Shaping of Photoinjector Laser Pulses for Electron Emittance Reduction in X-Ray Free Electron Lasers

electron, emittance, simulation, bunching

3886

R.A. Lemons, S. Carbajo, J.P. Duris, A. Marinelli, N.R. Neveu
SLAC, Menlo Park, California, USA
C.G. Durfee
Colorado School of Mines, Golden, USA

Funding: Office of Science DE-SC0014664
Temporal shaping of photocathode excitation laser pulses is a long-sought-after challenge to tailor the phase-space of electrons. The temporal profile of lasers, typically up-converted from infrared to ultraviolet, have significant impact on the distribution and time-evolution of the collective electron bunches. Towards this end, we present a method combining efficient nonlinear up-conversion with simultaneous and adaptable temporal profile shaping through dispersion-controlled sum-frequency generation* resulting in temporal profiles with sharp rise-fall times and flat top profiles. Using the LCLS-II photoinjector as a case study, we demonstrate a reduction in generated electron transverse emittance by upwards of 30% over conventionally implemented temporal profiles. Additionally, we discuss the ongoing experimental implementation of this method and preliminary results.
* R. Lemons, et al. arXiv:2012.00957 [physics.optics] (2020)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB060

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paper received ※ 17 May 2021 paper accepted ※ 08 July 2021 issue date ※ 26 August 2021

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THPAB061

Pulse-Burst CO₂ Laser for High-Brilliance Compton Light Sources

photon, electron, synchrotron, brightness

3890

I. Pogorelsky, M.N. Polyanskiy, T.V. Shaftan
BNL, Upton, New York, USA

Funding: U.S. Department of Energy under contract DE-SC0012704
We propose a novel architecture for a mid-IR, high-repetition, kilowatt-class, CO₂ laser system operating in a pulse-burst regime and its implementation in In-verse Compton Scattering (ICS) sources of x-ray and gamma-ray radiation. Different types of particle accelerators are considered for conversion to such ICS sources, including energy recovery linacs and synchrotron storage rings. The expected ICS performance parameters are compared with earlier proposals where CBETA and DAΦNE accelerators have been paired with near-IR, mode-locked solid-state lasers operating at a multi-megahertz repetition rate. A considerable increase in acting laser energy attainable in our CO₂ laser-based scheme, combined with an order of magnitude higher number of laser photons per Joule of energy allows maintaining a similarly high average flux of produced hard x-rays while the peak flux and brilliance will be raised by three to four orders of magnitude compared to aforementioned schemes based on near-IR lasers.

Poster THPAB061 [1.082 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB061

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paper received ※ 12 May 2021 paper accepted ※ 21 June 2021 issue date ※ 29 August 2021

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THPAB062

Long-Wave IR Terawatt Laser Pulse Compression to Sub-Picoseconds

simulation, experiment, FEM, plasma

3893

I. Pogorelsky, M. Babzien, M.A. Palmer, M.N. Polyanskiy
BNL, Upton, New York, USA

Funding: U.S. Department of Energy under contract DE-SC0012704
We report an experiment and simulations on post-compression of 2 ps, 0.15 TW CO₂ laser pulses to 480 fs, ~0.25 TW by means of a self-phase modulation accompanied by a negative group dispersion in KCl and BaF2 optical slabs. In addition, down to 130 fs fine pulse structure, but at lower conversion efficiency, has been observed through self-compression in a bulk NaCl crystal. The obtained results surpass by far previous achievements in the ultra-fast long-wave IR laser technology

Poster THPAB062 [2.675 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB062

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paper received ※ 12 May 2021 paper accepted ※ 18 June 2021 issue date ※ 24 August 2021

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THPAB063

Laser Transport System of Shanghai Laser Electron Gamma Source (SLEGS)

detector, controls, feedback, scattering

3897

H.H. Xu, G.T. Fan
SSRF, Shanghai, People’s Republic of China

Shanghai Laser Electron Gamma Source (SLEGS) *, based on laser Compton scattering (LCS), as one of beamlines of Shanghai Synchrotron Radiation Facility (SSRF) in phase II, is under construction now. The technical design of its laser injection system has been implemented and optimized consecutively over the last few years. In order to inject the 10640 nm CO₂ laser into the interaction point from the laser hutch outside the storage ring’s shielding, a laser transport system longer than 20 m using relay-imaging telescopes is designed. There are two operation mode in SLEGS. One is backscattering mode, which will make the laser and electron bunch collide at 180° with flux higher than 10⁷ gamma/s. The other mode is slanting mode, which mainly inherits the design used in the prototype**. In this paper, a brief summary of the laser transport system is given. The system contains several modules to perform beam expansion, combining, monitoring and real-time adjustment. The design models, simulation study of the laser quality through the transporta-tion, and the experimental results are presented.
* Y. Xu, W. Xu, et al., NIM A, 578, 457 (2007).
** H.H. Xu, J.H. Chen, et al., Transaction on Nuclear Science, IEEE, 63, 906 (2016).

Poster THPAB063 [2.508 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB063

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 27 August 2021

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THPAB097

Towards Arbitrary Pulse Shapes in the Terahertz Domain

electron, radiation, storage-ring, controls

3977

C. Mai, B. Büsing, A. Held, S. Khan, D. Krieg
DELTA, Dortmund, Germany

Funding: Work supported by the BMBF (05K19PEC).
The TU Dortmund University operates the 1.5-GeV electron storage ring DELTA as a synchrotron light source in user operation and for accererator physics research. At a dedicated beamline, experiments with (sub-)THz radiation are carried out. Here, an interaction of short laser pulses with electron bunches is used to modulate the electron energy which causes the formation of a dip in the longitudinal electron density, giving rise to the coherent emission of radiation between 75 GHz and 6 THz. The standard mode of operation is the generation of broadband radiation. However, more sophisticated energy modulation schemes were implemented using a liquid-crystal phase modulator. Here, a modulation of the spectral phase of the laser is used to control the spectral shape of the THz pulses. The resulting THz spectra have a relative bandwidth of about 2 %. Measurement results from the different THz generation schemes are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB097

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paper received ※ 18 May 2021 paper accepted ※ 12 July 2021 issue date ※ 24 August 2021

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THPAB119

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

emittance, FEL, electron, gun

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 ※ 22 August 2021

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THPAB120

Beam on Demand for High-Repetition-Rate X-Ray Free-Electron Lasers

electron, FEL, SRF, linac

3995

Z. Zhang, Y. Ding, Z. Huang
SLAC, Menlo Park, California, USA

High-repetition-rate (HRR) free-electron lasers (FELs) with multiple undulator beamlines will advance the frontiers of X-ray science significantly from the remarkable success of existing X-ray FEL facilities. The wide-ranging requirements for the photon properties from multiple beamlines are extremely challenging to satisfy by the same electron beam from a single superconducting radio-frequency (SRF) accelerator. To realize the full potential of an HRR FEL facility, a new emerging concept of "beam on demand" is proposed here. The concept is based on advanced beam dynamics and radio-frequency (RF) techniques to provide beam properties tailored to each undulator line at the desired repetition rate. The beam properties that will be pursued in this proposal include, but are not limited to, beam energy, bunch charge, bunch length, beam current, and its profile. The realization of "beam on demand" will allow optimization of photon properties of individual beamlines to maximize their performance and drastically improve the multiplexing capabilities of Linac Coherent Light Source II and its high-energy upgrade.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB120

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paper received ※ 17 May 2021 paper accepted ※ 23 July 2021 issue date ※ 27 August 2021

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THPAB126

Operational Experience and Characterization of a Superconducting Transverse Gradient Undulator for Compact Laser Wakefield Accelerator-Driven FEL

electron, undulator, FEL, experiment

4009

K. Damminsek, A. Bernhard, J. Gethmann, A.W. Grau, A.-S. Müller, Y. Nie, M.S. Ning, S.C. Richter, R. Rossmanith
KIT, Karlsruhe, Germany

A 40-period superconducting transverse gradient undulator (TGU) has been designed and fabricated at Karlsruhe Institute of Technology (KIT). Combining a TGU with a Laser Wakefield Accelerator (LWFA) is a potential key for realizing an extremely compact Free Electron Laser (FEL) radiation source. The TGU scheme is a viable option to compensate the challenging properties of the LWFA electron beam in terms of beam divergence and energy spread. In this contribution, we report on the operational experience of this TGU inside its own cryostat and show the current status of the TGU and the further plan for experiments. This work is supported by the BMBF project 05K19VKA PlasmaFEL (Federal Ministry of Education and Research).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB126

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

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THPAB131

Spatio-Temporal Measurements of THz Pulses

electron, polarization, radiation, FEM

4021

G.A. Hine
ORNL, Oak Ridge, Tennessee, USA

Funding: This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory under Contract No. DEAC05-00OR22725.
The 3D characterization of single-cycle Terahertz (THz) pulses in its transverse and temporal dimensions is presented. The high fields and short wavelengths of THz pulses make them an intriguing prospect for novel accelerator technologies. Effective application for free-space THz pulses requires high beam quality and concomitant measuring techniques. The combination of conventional electro-optic sampling to measure the temporal profile and detectors like microbolometer focal plane arrays to measure the transverse profile does not capture the correlations that can arise in single-cycle THz pulses. To capture these correlations, a modified version electro-optic sampling using a CCD is implemented. THz pulses generated by optical rectification in organic crystals are measured using this technique and their spatiotemporal correlations characterized.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB131

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paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 17 August 2021

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THPAB203

Update of the Tracking Code RF-Track

wakefield, simulation, scattering, space-charge

4180

A. Latina
CERN, Geneva, Switzerland

During the last couple of years, the RF-Track particle tracking code has seen a tremendous increase in the number of its applications: medical linacs, compact injector electron guns, and positron sources are among the main ones. Following a work of consolidation of its internal structure, new simulation capabilities have been introduced, together with several new effects: arbitrary orientation of elements in space, full element overlap, short- and long-range wakefields, and laser-beam interaction through Compton scattering are the most significant ones. In this paper, some of these new features are presented and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB203

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paper received ※ 14 May 2021 paper accepted ※ 02 August 2021 issue date ※ 01 September 2021

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THPAB214

Recent BDSIM Related Developments and Modeling of Accelerators

simulation, experiment, radiation, shielding

4208

L.J. Nevay, A. Abramov, S.E. Alden, S.T. Boogert, G. D’Alessandro, S.M. Gibson, H. Lefebvre, W. Shields, S.D. Walker
JAI, Egham, Surrey, United Kingdom
A. Abramov, G. D’Alessandro, C. Hernalsteens
CERN, Meyrin, Switzerland
E. Gnacadja, C. Hernalsteens, E. Ramoisiaux, R. Tesse
ULB, Bruxelles, Belgium
S. Liu
DESY, Hamburg, Germany

Funding: This work is supported by the STFC (UK) grants: JAI ST/P00203X/1, HL-LHC-UK1 ST/N001583/1, HL-LHC-UK2 ST/T001925/1, and ST/P003028/1.
Beam Delivery Simulation (BDSIM) is a program based on Geant4 that creates 3D radiation transport models of accelerators from a simple optical description in a vastly reduced time frame with great flexibility. It also uses ROOT and CLHEP to create a single simulation model that can accurately track all particle species in an accelerator to predict and understand beam losses, secondary radiation, dosimetric quantities and their origin. BDSIM provides a library of scalable generic geometry for a variety of applications. Our Python package, Pyg4ometry, allows rapid preparation and conversion of geometries for BDSIM and other radiation transport simulations including FLUKA. We present a broad overview of BDSIM developments related to a variety of experiments at several facilities. We present a model of the forward experiment FASER at the LHC, CERN where the geometry is composited from multiple sources using Pyg4ometry. The analysis of particle history is presented as well as production mechanisms. We also present the application of recently introduced laser interactions in Geant4 to Compton photons from a laserwire diagnostic at the ATF2.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB214

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paper received ※ 20 May 2021 paper accepted ※ 19 July 2021 issue date ※ 22 August 2021

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THPAB228

Study on Laser Modulator for Electron Beam Density Modulation

electron, undulator, bunching, simulation

4241

K. Kan, M. Gohdo, J. Yang, Y. Yoshida
ISIR, Osaka, Japan

Ultrashort electron beams are essential for light sources and time-resolved measurements. Laser modulation using an undulator and pulsed near infrared light is expected for attosecond density modulation of electron beam. In this study, simulation of laser modulation using undulator with period length of 6.6 mm and optical pulse with a wavelength of 800 nm was performed by ELEGANT* code. Simulation results of laser modulation for electron beam with an energy of 32.5 MeV will be presented from a view point of the density modulation.
* M. Borland, elegant: A Flexible SDDS-Compliant Code for Accelerator Simulation, Advanced Photon Source LS-287, September 2000.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB228

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

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THPAB251

Efficient Terahertz Generation by Tilted-Pulse-Front Pumping in Lithium Niobate for the Split-Ring Resonator Experiment at FLUTE

electron, experiment, diagnostics, vacuum

4299

M. Nabinger, E. Bründermann, S. Funkner, B. Härer, A.-S. Müller, M.J. Nasse, G. Niehues, R. Ruprecht, J. Schäfer, T. Schmelzer, N.J. Smale
KIT, Karlsruhe, Germany
M.M. Dehler, R. Ischebeck, M. Moser, V. Schlott
PSI, Villigen PSI, Switzerland
T. Feurer, M. Hayati, Z. Ollmann
Universität Bern, Institute of Applied Physics, Bern, Switzerland

Funding: This work is co-funded via the European Union’s H₂020 research and innovation program, GA No 730871, ARIES.
A compact, longitudinal diagnostics for fs-scale electron bunches using a THz electric-field transient in a split-ring resonator (SRR) for streaking will be tested at the Ferninfrarot Linac- Und Test- Experiment (FLUTE). For this new streaking technique, intensive THz pulses are required, which will be generated by laser-based optical rectification. We present a setup for generating THz pulses using tilted-pulse-front pumping in lithium niobate at room temperature. Excited by an 800 nm Ti:Sa pump laser with 35 fs bandwidth-limited pulse length, conversion efficiencies up to 0.027% were achieved. Furthermore, the status of the SRR experiment is shown.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB251

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paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 19 August 2021

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THPAB313

Drive Laser System for Shanghai Soft X-Ray Free Electron Laser

FEL, electron, cathode, free-electron-laser

4403

L. Feng, C.L. Li, B. Liu, J.G. Wang
SARI-CAS, Pudong, Shanghai, People’s Republic of China
X. Lu
ANL, Lemont, Illinois, USA
X.T. Wang, W.Y. Zhang
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China

In this paper, we introduce the design and layout of the drive laser of Shanghai Soft X-ray Free Electron Laser (SXFEL). It is known that the temporal and spatial distribution of the drive laser is crucial for high-quality electron beams. The drive laser provides the laser pulse of 266nm wavelength and 8ps pulse duration for the photocathode, as well as 400nm wavelength, 2-20ps tunable pulse duration for the laser heater. For this purpose, there are mainly four parts in such system, including a third-harmonic generation device, pulse stretcher, image transmitted system, and laser optical module for laser heater. Finally, the measured results of the electron beam under this drive laser system are presented and discussed.

Poster THPAB313 [0.691 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB313

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paper received ※ 20 May 2021 paper accepted ※ 15 July 2021 issue date ※ 24 August 2021

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THPAB314

Development of the Femtosecond Timing Distribution System for the Shanghai Soft X-Ray Free Electron Laser

FEL, timing, FEM, experiment

4406

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

High accuracy timing and synchronization system on femtosecond timescale play an important role for free-electron laser projects such as Shanghai Soft X-ray free-electron laser facility (SXFEL), and future Shanghai high repetition rate XFEL and Extreme light facility (SHINE). To meet the high precision synchronization requirements for both facilities, an optical-based timing distribution system is absolutely necessary. Such a system distributes the laser pulse train from a locked optical master oscillator through the fiber links, which stabilized by a balance optical cross-correlator based on a periodical-poled KTiOPO4 crystal. In this paper, the recent progress and experimental results of SXFEL and SHINE timing distribution system will be reported.

Poster THPAB314 [0.351 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB314

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

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THPAB340

Sub-Nanosecond Switching of HV SiC MOS Transistors for Impact Ionisation Triggering

plasma, kicker, electron, high-voltage

4454

V. Senaj, T. Kramer, A.A. del Barrio Montañés
CERN, Geneva 23, Switzerland
M. Sack
KIT, Karlsruhe, Germany

Pulse generators with multi kV/kA pulses are necessary for the particle accelerator environment for beam transfer magnets. Traditionally these generators are using thyratrons - until recently the only switches capable of switching such pulses within tens of ns. There is a strong demand to replace thyratrons with semiconductor switches to avoid their future obsolescence. Very promising candidates are components from the family of fast ionization dynistors triggered by impact ionization. Their sub-nanosecond switching time and extreme current densities can provide performances superior to that of thyratrons. Recent investigations showed that impact ionization triggering is feasible also in cheap industrial thyristors. The main issue is the generation of triggering pulses with slew rates in the multi kV/ns region and with the required output current for charging the parasitic capacitance of the thyristor. We present an approach of generating > 1 kV/ns pulses by ultra-boosted gate driving of HV SiC MOS transistors. We found that the MOS lifetime under these extreme triggering conditions can still reach more than 10⁸ pulses, enough for kicker generator applications.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB340

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paper received ※ 18 May 2021 paper accepted ※ 01 July 2021 issue date ※ 27 August 2021

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THPAB344

Magneto-Optical Trap Cathode for High Brightness Applications

electron, gun, emittance, cathode

4466

V.S. Yu, C.E. Hansel, G.E. Lawler, M. Mills, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
J.I. Mann
PBPL, Los Angeles, USA

Funding: This work was performed with support of the US Department of Energy under Contract No. DE-SC0020409 and the National Science Foundation under Grant No. PHY-1549132
Electron bunches extracted from magneto-optical traps (MOTs) via femtosecond photo-ionization and electrostatic acceleration can have significantly lower transverse emittance than emissions from traditional metal cathodes. Such MOT cathodes, however, have two drawbacks: the need for multiple trapping lasers and the limit to ~MV/m fields. Designs exist for MOTs which only require one trapping laser. Our RF simulations in High-Frequency Structure Simulator (HFSS) indicate that the cone MOT is the only one compatible with high gradient RF cavities. We present the combination of the two, an RF cavity with a cone-MOT as part of its geometry. It only requires one trapping laser and can use much higher fields. The geometry of the chamber is compatible with a wide range of MOT species, which allows the search for one which is compatible with copper cavities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB344

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paper received ※ 19 May 2021 paper accepted ※ 29 July 2021 issue date ※ 12 August 2021

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THPAB349

Feed-Forward Neural Network Based Modelling of an Ultrafast Laser for Enhanced Control

network, controls, electron, cathode

4478

A. Aslam, M. Martínez-Ramón, S.D. Scott
UNM-ECE, Albuquerque, USA
S. Biedron
Argonne National Laboratory, Office of Naval Research Project, Argonne, Illinois, USA
S. Biedron
Element Aero, Chicago, USA
S. Biedron
UNM-ME, Albuquerque, New Mexico, USA
M. Burger, J. Murphy
NERS-UM, Ann Arbor, Michigan, USA
K.M. Krushelnick, J. Nees, A.G.R. Thomas
University of Michigan, Ann Arbor, Michigan, USA
Y. Ma
IHEP, Beijing, People’s Republic of China
Y. Ma
Michigan University, Ann Arbor, Michigan, USA

Funding: Acknowledgements: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under award number DE-SC0019468.
The applications of machine learning in today’s world encompass all fields of life and physical sciences. In this paper, we implement a machine learning based algorithm in the context of laser physics and particle accelerators. Specifically, a neural network-based optimisation algorithm has been developed that offers enhanced control over an ultrafast femtosecond laser in comparison to the traditional Proportional Integral and derivative (PID) controls. This research opens a new potential of utilising machine learning and even deep learning techniques to improve the performance of several different lasers and accelerators systems.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB349

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paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 17 August 2021

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THPAB359

Simulations of the Stage 2 FFA Injection Line of LhARA for Evaluating Beam Transport Performance

space-charge, injection, simulation, target

4495

W. Shields
JAI, Egham, Surrey, United Kingdom
A. Kurup, H.T. Lau, K.R. Long, J. Pasternak
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

A new, novel facility for radiobiological research, the Laser-hybrid Accelerator for Radiobiological Applications (LhARA), has recently been proposed. LhARA will be a two-stage facility with the first stage employing laser-target acceleration to produce intense proton bunches of energies up to 15 MeV. The second stage will accelerate the beam in an FFA ring up to 127 MeV. Optimal performance of stage 2, however, will require an emittance reduction of the stage 1 beam due to the FFA’s nominal dynamical acceptance. Here, we demonstrate a new optical configuration of LhARA’s stage 1 lattice that will provide this reduced emittance. The profile of the laser-target generated beam is far from an ideal Gaussian, therefore two start-to-end Monte Carlo particle tracking codes have been used to model beam transport performance from the laser-target source through to the end of the stage 2 FFA injection line. The Geant4-based Beam Delivery Simulation (BDSIM) was used to model beam losses and the collimation that is crucial to LhARA’s energy selection system, and General Particle Tracer (GPT) was used to model the space-charge effects that may impact performance given the emittance reduction.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB359

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paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 18 August 2021

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THPAB372

SABINA: A Research Infrastructure at LNF

radiation, experiment, electron, focusing

4505

L. Sabbatini, D. Alesini, M.P. Anania, M. Bellaveglia, A. Biagioni, B. Buonomo, S. Cantarella, F. Cardelli, E. Chiadroni, G. Costa, G. Di Pirro, F. Dipace, A. Esposito, M. Ferrario, M. Galletti, A. Gallo, A. Ghigo, L. Giannessi, A. Giribono, S. Incremona, L. Pellegrino, L. Piersanti, R. Pompili, R. Ricci, J. Scifo, A. Stecchi, A. Stella, C. Vaccarezza, A. Vannozzi, S. Vescovi, F. Villa
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
A. Cianchi
INFN-Roma II, Roma, Italy
A. Doria, A. Petralia
ENEA C.R. Frascati, Frascati (Roma), Italy
L. Giannessi
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
S. Lupi
Sapienza University of Rome, Roma, Italy
S. Macis
La Sapienza University of Rome, Rome, Italy
V. Petrillo
Universita’ degli Studi di Milano, Milano, Italy
V. Petrillo
INFN-Milano, Milano, Italy

Funding: SABINA is a project co-funded by Regione Lazio within POR-FESR 2014-2020 program.
SABINA (Source of Advanced Beam Imaging for Novel Applications) is a project aimed at the enhancement of the SPARC_LAB research facility. This enhancement is carried out through the following actions: first, the increase of the uptime through the consolidation of technological systems and the replacement of some critical equipment in order to limit the number and extent of faults; then, the improvement of the accelerator performances, by replacing some devices with updated ones. The effect will be greater reliability of the accelerator, which will allow it to be opened as a facility for external users, both industrial and scientific, with the goal of increasing the competitiveness of industries in a broad range of technological areas and enhancing collaborations with research institutions. The two user lines that will be implemented are a power laser target area and a THz radiation line, by using a dedicated undulator. The undulator and the THz line are also described in other contributions to this conference. A brief description of the project and potential exploitations are reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB372

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paper received ※ 24 May 2021 paper accepted ※ 01 July 2021 issue date ※ 20 August 2021

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FRXA06

Mitigation of Beam Instabilities in the Echo-Enabled Harmonic Generation Beamline for FLASH2020+

bunching, electron, FEL, free-electron-laser

4514

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

With the FLASH2020+ upgrade, one of the beamlines of the free-electron laser FLASH at DESY will be based on the Echo-Enabled Harmonic Generation (EEHG) seeding scheme and provide high-repetition-rate, coherent radiation down to 4 nm. To reach this wavelength, it is necessary to imprint intricate structures on the longitudinal phase space of the electron bunch at a very high harmonic of the seed laser wavelength, making the scheme potentially vulnerable to beam instabilities. Part of the beamline is a strong chicane, which is necessary to create the dispersion required by EEHG. Resulting effects such as Coherent Synchrotron Radiation (CSR) can be very detrimental for the bunching process and have to be taken into account already in the design of the beamline to ensure optimum FEL performance. We investigate and propose possible mitigation solutions to such instabilities in the FLASH2020+ parameter range.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXA06

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

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FRXB07

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

emittance, FEL, gun, operation

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 ※ 14 August 2021

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FRXC03

Modern Ultra-Fast Detectors for Online Beam Diagnostics

detector, electron, experiment, FPGA

4540

M.M. Patil, E. Bründermann, M. Caselle, A. Ebersoldt, S. Funkner, B. Kehrer, A.-S. Müller, M.J. Nasse, G. Niehues, J.L. Steinmann, W. Wang, M. Weber, C. Widmann
KIT, Karlsruhe, Germany

Funding: This work is supported by the BMBF project 05K19VKD STARTRAC and DFG-funded Doctoral School ’Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology’
Synchrotron light sources operate with bunch repetition rates in the MHz regime. The longitudinal and transverse beam dynamics of these electron bunches can be investigated and characterized by experiments employing linear array detectors. To improve the performance of modern beam diagnostics and overcome the limitations of commercially available detectors, we have at KIT developed KALYPSO, a detector system operating with an unprecedented frame rate of up to 12 MHz. To facilitate the integration in different experiments, a modular architecture has been utilized. Different semiconductor microstrip sensors based on Si, InGaAs, PbS, and PbSe can be connected to the custom-designed low noise front-end ASIC to optimize the quantum efficiency at different photon energies, ranging from near-UV, visible, and up to near-IR. The front-end electronics are integrated within a heterogeneous DAQ consisting of FPGAs and GPUs, which allows the implementation of real-time data processing. This detector is currently installed at KARA, European XFEL, FLASH, Soleil, DELTA. In this contribution, we present the detector architecture, the performance results, and the ongoing technical developments.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXC03

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paper received ※ 19 May 2021 paper accepted ※ 22 July 2021 issue date ※ 01 September 2021

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FRXC04

Time-Resolved H⁻ Beam Emittance Measurement at the SNS Linac Using a Laser Comb

emittance, neutron, diagnostics, beam-diagnostic

4545

Y. Liu, A.V. Aleksandrov, C.D. Long
ORNL, Oak Ridge, Tennessee, USA

Funding: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE).
We proposed and demonstrated a novel technique to measure time-resolved transverse emittances of the hydrogen ion (H⁻) beam in a 1-GeV high-power accelerator. The measurement is performed in a non-intrusive manner by using laser comb - laser pulses with controllable multi-layer temporal structure generated from a fiber-based master laser oscillator and diode-pumped solid-state laser amplifiers. The technique has been applied to the transverse emittance measurement of 1-GeV H⁻ beam at the Spallation Neutron Source (SNS) high energy beam transport (HEBT). More than 20 time-resolved emittances have been simultaneously measured within a macro-pulse, a single mini-pulse, or a single bunch of the 1.4-MW neutron production H⁻ beam from one measurement.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXC04

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paper received ※ 18 May 2021 paper accepted ※ 08 July 2021 issue date ※ 20 August 2021

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