SRF2023 - List of Authors (Kim, S.H.)

Paper	Title	Page
FRTUT02	RF Coupler
	S.H. Kim FRIB, East Lansing, Michigan, USA
	This lecture will learn how to supply RF power into the cavity in order to accelerate the beam, and how to design and fabricate the device. Lessons learned in the past will be included, and important guidelines established for the design will be included.
	Slides FRTUT02 [8.894 MB]
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MOIAA01	FRIB Transition to User Operations, Power Ramp Up, and Upgrade Perspectives	1
	J. Wei, H. Ao, B. Arend, S. Beher, G. Bollen, N.K. Bultman, F. Casagrande, W. Chang, Y. Choi, S. Cogan, C. Compton, M. Cortesi, J.C. Curtin, K.D. Davidson, X.J. Du, K. Elliott, B. Ewert, A. Facco, A. Fila, K. Fukushima, V. Ganni, A. Ganshyn, T.N. Ginter, T. Glasmacher, J.-W. Guo, Y. Hao, W. Hartung, N.M. Hasan, M. Hausmann, K. Holland, H.-C. Hseuh, M. Ikegami, D.D. Jager, S. Jones, N. Joseph, T. Kanemura, S.H. Kim, C. Knowles, T. Konomi, B.R. Kortum, E. Kwan, T. Lange, M. Larmann, T.L. Larter, K. Laturkar, R.E. Laxdal, J. LeTourneau, Z. Li, S.M. Lidia, G. Machicoane, C. Magsig, P.E. Manwiller, F. Marti, T. Maruta, E.S. Metzgar, S.J. Miller, Y. Momozaki, D.G. Morris, M. Mugerian, I.N. Nesterenko, C. Nguyen, P.N. Ostroumov, M.S. Patil, A.S. Plastun, L. Popielarski, M. Portillo, J. Priller, X. Rao, M.A. Reaume, K. Saito, B.M. Sherrill, M.K. Smith, J. Song, M. Steiner, A. Stolz, O. Tarasov, B.P. Tousignant, R. Walker, X. Wang, J.D. Wenstrom, G. West, K. Witgen, M. Wright, T. Xu, Y. Yamazaki, T. Zhang, Q. Zhao, S. Zhao FRIB, East Lansing, Michigan, USA K. Hosoyama KEK, Ibaraki, Japan P. Hurh Fermilab, Batavia, Illinois, USA M.P. Kelly, Y. Momozaki ANL, Lemont, Illinois, USA R.E. Laxdal TRIUMF, Vancouver, Canada S.O. Prestemon LBNL, Berkeley, California, USA M. Wiseman JLab, Newport News, Virginia, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661. After project completion on scope, on cost, and ahead of schedule, the Facility for Rare Isotope Beams began operations for scientific users in May of 2022. During the first 12 months of user operations, the FRIB accelerator complex delivered 5250 beam hours, including 1528 hours to nine science experiments conducted with primary beams of 36Ar, 48Ca, 70Zn, 82Se, 124Xe, and 198Pt at beam energies >200 MeV/u; 2724 hours for beam developments, studies, and tuning; and 998 hours to industrial users and non-scientific programs using the FRIB Single Event Effect (FSEE) beam line. The ramp-up to a beam power of 400 kW is planned over a six-year period; 1 kW was delivered for initial user runs from in 2022, and 5 kW was delivered as of February 2023. Upgrade plans include doubling the primary-beam energy to 400 MeV/nucleon for enhanced discovery potential (¿FRIB 400¿). This talk reports on FRIB status and progress since SRF2021, emphasizing lessons learned during the transition from beam commissioning to machine operations, challenges and resolutions for the power ramp-up, progress with accelerator improvements, and R&D for the energy upgrade.
	Slides MOIAA01 [7.037 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOIAA01
About •	Received ※ 20 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 03 July 2023 — Issue date ※ 19 July 2023
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MOPMB026	Development of Transformative Cavity Processing - Superiority of Electropolishing on High Gradient Performance over Buffered Chemical Polishing at Low Frequency (322 MHz)	145
	K. Saito, C. Compton, K. Elliott, W. Hartung, S.H. Kim, T.K. Konomi, E.S. Metzgar, S.J. Miller, L. Popielarski, A.T. Taylor, T. Xu FRIB, East Lansing, Michigan, USA
	Funding: The work is supported by DOE Awards DE-SC0022994. A DOE grant R&D titled ¿Development of Transformative Preparation Technology to Push up High Q/G Performance of FRIB Spare HWR Cryomodule Cavities¿ is ongoing at FRIB. This R&D is for 2 years since September 2022. This project proposes four objectives: 1) Superiority on high gradient performance of electropolishing (EP) over buffered chemical polishing at low frequency (322 MHz), 2) High Qo performance by the local magnetic shield, 3) Development of HFQS-free BCP and, 4) Wet N-doping method. This paper will report the result of first object, and a local magnetic shield design and simulation to reduce the residual magnetic field < 0.1 mG in the vertical test Dewar, for the object 2.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB026
About •	Received ※ 14 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 08 July 2023
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MOPMB067	Design of a Cathode Insertion and Transfer System for LCLS-II-HE SRF Gun	267
	R. Xiang, A. Arnold, S. Gatzmaga, A. Hoffmann, P. Murcek, R. Steinbrück, J. Teichert HZDR, Dresden, Germany C. Adolphsen, J. Smedley SLAC, Menlo Park, California, USA W. Hartung, S.H. Kim, T.K. Konomi, S.J. Miller, L. Popielarski, K. Saito, T. Xu FRIB, East Lansing, Michigan, USA M.P. Kelly, T.B. Petersen ANL, Lemont, Illinois, USA J.W. Lewellen LANL, Los Alamos, New Mexico, USA
	Funding: Work supported by cooperation project between MSU and HZDR RC113062 from the U.S. Department of Energy Office of Science under Cooperative Agreement DE-AC02-76SF00515. Superconducting radio frequency photo injectors (SRF gun) offer advantages for operating in continuous wave (CW) mode and generating high-brightness and high-current beams. A new SRF gun is designed as a low emittance photo injector for LCLS-II-HE and a prototype gun is currently being developed under collaboration between SLAC, FRIB, HZDR and ANL. The aim is to demonstrate stable CW operation at a cathode gradient of 30 MV/m. One of the crucial component for successful SRF gun operation is the photocathode system. The new SRF gun will adopt the HZDR-type cathode, which includes a cathode holder fixture (cathode stalk) developed by FRIB and a sophisticated cathode exchange system designed by HZDR. This innovative cathode insertion system ensures accurate, particle-free and warm cathode exchanges. A novel alignment process targets the cathode to the stalk axis without touching cathode plug itself. To commission the prototype gun, metallic cathodes will be used. A specifically designed vacuum system ensures vacuum pressure of 10^-9 mbar for transport of a single cathode from the cleanroom to the gun. Thus maintaining cathode quality.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB067
About •	Received ※ 18 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023
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MOPMB084	FRIB Driver Linac Integration to Support Operations and Protect SRF Cryomodules	316
	H. Ao, K. Elliott, D.D. Jager, S.H. Kim, L. Popielarski FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661. The driver linac for the Facility for Rare Isotope Beams (FRIB) at Michigan State University includes 324 superconducting radio-frequency (SRF) cavities, and the SRF particle-free beamline spans approximately 300 meters. Protecting the beamlines against contamination is critical to FRIB operations, and thus, various administrative and engineered controls have been put in place to protect the SRF cryomodules. These controls include local vacuum interlocks for cryomodule isolation, accelerator-wide interlocks, and software controls to safeguard the cryomodules and beamlines. Meanwhile, efforts are being made to provide training and develop programs with the goal of preventing critical failures during maintenance. This paper discusses the measures and approaches used for both system integration to support operations and SRF beamline protection.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB084
About •	Received ※ 14 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023
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TUPTB040	Mechanical Design and Analysis of SRF Gun Cavity Using ASME BPVC Section Viii, Division-2, Design by Analysis Requirement	501
	M.S. Patil, C. Compton, S.H. Kim, S.J. Miller, T. Xu FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the Department of Energy Contract DE-AC02- 76SF00515 A prototype SRF gun is currently being designed at FRIB, MSU for the Low Emittance Injector of the Linac Coherent Light Source high energy upgrade at SLAC. This employs a 185.7 MHz superconducting quarter-wave resonator (QWR). The mechanical design of this cavity has been optimized for performance and to comply with ASME Section VIII, Div 2, Design by analysis requirements. This paper presents the various design by analysis procedures and how they have been adopted for the SRF gun cavity design.
	Poster TUPTB040 [1.235 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB040
About •	Received ※ 15 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023
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TUPTB063	Fabrication Efforts Toward a Superconducting Rf Photo-Infector Quarter-Wave Cavity for Use in Low Emittance Injector Applications	568
	C. Compton NSCL, East Lansing, Michigan, USA K. Elliott, W. Hartung, J.D. Hulbert, S.H. Kim, T. Konomi, S.J. Miller, M.S. Patil, J.T. Popielarski, L. Popielarski, K. Saito, K. Witgen, T. Xu FRIB, East Lansing, Michigan, USA M. Kedzie, M.P. Kelly, T.B. Petersen ANL, Lemont, Illinois, USA J.W. Lewellen, J. Smedley SLAC, Menlo Park, California, USA
	Funding: * Work supported by the Department of Energy Contract DE-AC02- 76SF00515 The Facility for Rare Isotope Beams (FRIB), in collaboration with Argonne National Laboratory (ANL) and Helmholtz-Zentrum Dresden-Rossendorf (HDZR), is working on the design and fabrication of a photo-injector cryomodule; suitable for operation as part of accelerator systems at SLAC National Accelerator Laboratory. Project scope requires the fabrication of two 185.7 MHz superconducting, quarter-wave resonators (QWR) based, injector cavities. Cavity fabrication will be completed at FRIB with contracted vendors supporting subcomponent fabrication and electron-beam welding. Fabrication will use poly-crystalline and large grain RRR niobium materials. The current status of cavity fabrication will be presented including material procurement, prototype forming, and electron-beam welding development.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB063
About •	Received ※ 17 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 21 August 2023 — Issue date ※ 21 August 2023
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TUPTB069	Design and Tests of a Cathode Stalk for the LCLS-II-HE Low Emittance Injector SRF Gun	589
	T.K. Konomi, W. Hartung, S.H. Kim, S.J. Miller, D.G. Morris, K. Saito, A.T. Taylor, T. Xu, Z.Y. Yin FRIB, East Lansing, Michigan, USA C. Adolphsen, J. Smedley, L. Xiao SLAC, Menlo Park, California, USA S. Gatzmaga, P. Murcek, R. Xiang HZDR, Dresden, Germany M.P. Kelly, T.B. Petersen ANL, Lemont, Illinois, USA J.W. Lewellen LANL, Los Alamos, New Mexico, USA
	A SRF gun can operate CW with a high gradient and ultra-low vacuum for high-quantum efficiency, low MTE photocathodes, useful features for delivery of high-brightness, high-repetition-rate beams. For these reasons, an SRF gun based photoinjector was chosen for a proposed Low Emittance Injector addition to the LCLS-II-HE facility, which will operate CW with bunch rates up to 1 MHz. For this injector, a prototype 185.7 MHz QWR gun is being developed in a collaborative effort among FRIB, HZDR, ANL and SLAC, with the goal of achieving a photocathode gradient of at least 30 MV/m. The photocathode is held by a coaxial fixture (cathode stalk) for thermal isolation from the cavity body. The system must allow for precise alignment of the photocathode, particle-free photocathode exchange, cryogenic (55-70 K) or warm (273-300 K) photocathode operating temperatures, and DC biasing to inhibit multipacting. A prototype cathode stalk has been built and bench tests are underway to validate the design. Measurements include RF power dissipation, DC bias hold-off, multipacting suppression and heat transfer effectiveness. This paper describes the cathode stalk design and the test results.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB069
About •	Received ※ 03 July 2023 — Revised ※ 27 July 2023 — Accepted ※ 19 August 2023 — Issue date ※ 20 August 2023
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WEPWB113	Evaluation of Photo-Cathode Port Multipacting in the SRF Photo-Injector Cryomodule for the LCLS-II High-Energy Upgrade	859
SUSPB032	use link to see paper's listing under its alternate paper code
	Z.Y. Yin, W. Hartung, S.H. Kim, T. Konomi, T. Xu FRIB, East Lansing, Michigan, USA
	The high-energy upgrade of the Linac Coherent Light Source (LCLS-II-HE) will increase the photon energy and brightness. A low-emittance injector (LEI) was proposed to increase the photon flux for high X-ray energies. FRIB, HZDR, Argonne, and SLAC are developing a 185.7 MHz superconducting radio-frequency photo-injector (SRF-PI) cryomodule for the LEI. The photo-cathode system requirements are challenging, as cathodes must be maintained at the desired temperature, precisely aligned, and operated without multipacting (MP); to avoid field emission, cathode exchange must be particulate-free. A support stalk has been designed to hold the cathode in position under these requirements. A DC bias is used to inhibit MP. We simulated MP for various surface conditions and bias levels. An RF/DC test was developed to evaluate the cathode stalk performance as a subsystem and to identify and correct issues before assembly into the full cryomodule. The RF/DC test makes use of a resonant coaxial line to generate an RF magnetic field similar to that of the cathode-in-SRF-PI-cavity case. High-power test results will be presented and compared to the MP simulations. * Work supported by the Department of Energy Contract DE-AC02-76SF00515
	Poster WEPWB113 [1.410 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB113
About •	Received ※ 20 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 26 July 2023
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WEPWB127	Investigation of Coupler Breakdown Thresholds for Plasma Processing of FRIB Quarter-Wave Resonators with Fundamental and Higher-Order Modes	893
SUSPB035	use link to see paper's listing under its alternate paper code
	P.R. Tutt, W. Hartung, S.H. Kim, T. Xu FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics and used resources of the Facility for Rare Isotope Beams (FRIB) under Award Number DE-SC0000661. FRIB is developing plasma processing techniques for in-situ recovery of cavity performance in linac cryomodules during long-term user operation. While plasma processing has been shown to be effective for high-frequency (0.8 - 1.5 GHz) elliptical cavities, one of the challenges for FRIB is to avoid plasma breakdown in the fundamental input coupler (FPC), which has relatively weak coupling strength (Q_ext ranging from 2E6 to 1E7). FRIB cavities are not equipped with higher-order-mode (HOM) couplers; however, in preliminary tests, we found that HOMs are suitable for plasma processing of FRIB Quarter-Wave Resonators (QWRs) driven via the FPC. In this study, we investigated plasma breakdown thresholds in the fundamental and the first 2 HOMs for the FRIB β = 0.085 QWRs. Electric field distributions in the FPC region and cavity region were calculated for the room-temperature case using CST Microwave Studio’s frequency domain solver (FDS). Simulation results will be presented, with comparison of breakdown thresholds inferred from the RF modeling to the experimental results.
	Poster WEPWB127 [5.068 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB127
About •	Received ※ 19 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 11 August 2023
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WEPWB128	Experimental Study of Mechanical Dampers for the FRIB β=0.041 Quarter-Wave Resonators	898
SUSPB036	use link to see paper's listing under its alternate paper code
	J. Brown, W. Chang, W. Hartung, S.H. Kim, T. Xu FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the US Department of Energy, Office of Science, High Energy Physics under Cooperative Agreement award numbers DE-SC0018362 and DE-SC0000661 and Michigan State University. The ’pendulum’ mechanical mode of quarter-wave resonators (QWR) often causes an issue with microphonics and/or ponderomotive instability unless otherwise the inner conductors are properly stiffened and/or damped. FRIB QWRs are equipped with a Legnaro-style frictional damper installed inside of the inner conductor such that it counteracts the oscillations of the inner conductor. In cryomodule tests and linac operation, we observed that the damping efficiency is different for a few β=0.041 QWRs. This study aimed to experimentally characterize the damping efficacy as a function of damper mass and surface roughness. We present damping measurements at room temperature and at two different masses and surface roughness as well as discuss future studies for damper re-optimization based on this follow-on study.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB128
About •	Received ※ 20 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 04 August 2023
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THIXA01	Investigation of Plasma Processing for Coaxial Resonators	960
	W. Hartung, W. Chang, K. Elliott, S.H. Kim, T. Konomi, K. Saito, P.R. Tutt, T. Xu FRIB, East Lansing, Michigan, USA
	Plasma processing has been investigated by several facilities as a method to mitigate degradation of SRF cavity performance. It provides an alternative to removal and disassembly of cryomodules for refurbishment of each cavity via repeat etching and rinsing. Promising results have been obtained by several groups. Studies of plasma processing for quarter-wave resonators (QWRs) and half-wave resonators (HWRs) were undertaken at FRIB, where a total of 324 such resonators are presently in operation. Plasma ignition and optimization measurements were done with room-temperature-matched input couplers. Plasma cleaning tests were done on several QWRs using the fundamental power coupler (FPC) to drive the plasma. We investigated the usefulness of higher-order modes (HOMs) to drive the plasma. HOMs allow for less mismatch at the FPC and hence lower field in the coupler relative to the cavity. Before-and-after cold tests showed a significant reduction in field emission X-rays with judicious application of plasma processing.
	Slides THIXA01 [2.060 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIXA01
About •	Received ※ 01 September 2023 — Accepted ※ 02 September 2023 — Issue date ※ 02 September 2023
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FRIBA01	SRF R&D for FRIB Linac Energy Upgrade with High-performance Medium-beta Elliptical Cavity CW Cryomodules
	S.H. Kim, W. Chang, K. Elliott, W. Hartung, K.E. McGee, E.S. Metzgar, P.N. Ostroumov, L. Popielarski, J. Rathke, T. Xu, S. Zhao FRIB, East Lansing, Michigan, USA D.J. Bice, C. Contreras-Martinez, G.V. Eremeev, Y.M. Pischalnikov Fermilab, Batavia, Illinois, USA B.M. Guilfoyle, M.P. Kelly, T. Reid ANL, Lemont, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy under Award Number DE-SC0000661. Further support provided by the US Department of Energy under Cooperative Agreement award number DE-SC0018362. Michigan State University is pursuing SRF R&D for FRIB400 upgrade, doubling the FRIB linac beam energy (400 MeV/u for the heaviest uranium beam) using ßopt=0.65 644 MHz 5-cell elliptical cavities. We have achieved unprecedented Q₀ in this cavity class, Q₀ = 3.5·10¹⁰ at E_acc of 17.5 MV/m in a nitrogen-doped bare niobium cavity in collaboration with FNAL and ANL. The next missions are achieving such high Q₀ in jacketed cavities and in cryomodules, achieving field-emission free performance at Epeak of 40 MV/m with reproducibility, developing a compact two-window high-power fundamental power coupler (15 kW CW), and achieving stable resonance control of cavities integrated with tuners in cryomodules. In this talk, we will present progress of the SRF R&D and discuss future plan.
	Slides FRIBA01 [2.513 MB]
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FRIBA05	Automation of FRIB SRF Cavities and SC Solenoids Turn-on/off	999
	W. Chang, Y. Choi, X.J. Du, W. Hartung, S.H. Kim, T. Konomi, S.R. Kunjir, H. Nguyen, K. Saito, T. Xu, S. Zhao FRIB, East Lansing, Michigan, USA A. Facco INFN/LNL, Legnaro (PD), Italy
	The superconducting driver Linac for the Facility for Rare Isotope Beams (FRIB) is a heavy ion accelerator that accelerate ions to 200 MeV per nucleon. The Linac has 46 cryomodules that contain 324 superconducting radio frequency (SRF) cavities and 69 superconducting (SC) solenoid packages. For operation of all cryomodules with high efficiency and reliability, automation for SRF cavity and SC solenoid fast turn-on/off is essentially. Based on cryomodule commissioning results and expert experience, all manual cavity and solenoid turn-on/off procedures and steps have been replaced by automatic programs for FRIB linac operation. This allows the operators to turn the systems on and off without expert-level training. Automation reduces the risk of human error, speeds up beam recovery after user access to experimental areas, and increases beam availability. The cavity turn-on procedure makes sure that the cavity can operate at low field with expected read backs, ramps up the field, and makes sure that the RF amplitude and phase are stable. The design, implementation, and operating experience with automation will be presented.
	Slides FRIBA05 [3.503 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-FRIBA05
About •	Received ※ 29 June 2023 — Revised ※ 16 August 2023 — Accepted ※ 21 August 2023 — Issue date ※ 21 August 2023
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FRIBA07	Status of the SLAC/MSU SRF Gun Development Project	1003
	S.J. Miller, Y. Al-Mahmoud, W. Chang, Y. Choi, C. Compton, X.J. Du, K. Elliott, W. Hartung, J.D. Hulbert, S.H. Kim, T. Konomi, D.G. Morris, M.S. Patil, L. Popielarski, K. Saito, A. Taylor, B.P. Tousignant, J. Wei, J.D. Wenstrom, K. Witgen, T. Xu FRIB, East Lansing, Michigan, USA C. Adolphsen, R. Coy, F. Ji, M.J. Murphy, J. Smedley, L. Xiao SLAC, Menlo Park, California, USA A. Arnold, S. Gatzmaga, P. Murcek, J. Teichert, R. Xiang HZDR, Dresden, Germany M.P. Kelly, T.B. Petersen, P. Piot ANL, Lemont, Illinois, USA J.W. Lewellen LANL, Los Alamos, New Mexico, USA
	Funding: Work supported by the Department of Energy under Contract DE-AC02-76SF00515 The Linac Coherent Light Source II High Energy (LCLS-II-HE) Project at SLAC includes the construction of a low-emittance injector (LEI) and a superconducting quarter-wave resonator (QWR) at 185.7 MHz. Several alternatives to a superconducting radio frequency (SRF) QWR gun were considered for the LEI, including nor-mal-conducting RF guns evolved from the LCLS-II gun design. Compared to normal-conducting designs, the combination of an intrinsically outstanding vacuum environment (for cathode lifetime), and the potential for a larger ultimate performance envelope, led to the deci-sion to pursue development of the QWR-SRF gun. A prototype gun is currently being designed and fabricated at the Facility for Rare Isotope Beams (FRIB) at Michi-gan State University (MSU). This paper presents perfor-mance goals for the new gun design, an overview of the prototype development effort, status, and future plans including fabrication.
	Slides FRIBA07 [9.655 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-FRIBA07
About •	Received ※ 15 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 11 July 2023
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Paper

Title

Page

FRTUT02

RF Coupler

S.H. Kim
FRIB, East Lansing, Michigan, USA

This lecture will learn how to supply RF power into the cavity in order to accelerate the beam, and how to design and fabricate the device. Lessons learned in the past will be included, and important guidelines established for the design will be included.

Slides FRTUT02 [8.894 MB]

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MOIAA01

FRIB Transition to User Operations, Power Ramp Up, and Upgrade Perspectives

1

J. Wei, H. Ao, B. Arend, S. Beher, G. Bollen, N.K. Bultman, F. Casagrande, W. Chang, Y. Choi, S. Cogan, C. Compton, M. Cortesi, J.C. Curtin, K.D. Davidson, X.J. Du, K. Elliott, B. Ewert, A. Facco, A. Fila, K. Fukushima, V. Ganni, A. Ganshyn, T.N. Ginter, T. Glasmacher, J.-W. Guo, Y. Hao, W. Hartung, N.M. Hasan, M. Hausmann, K. Holland, H.-C. Hseuh, M. Ikegami, D.D. Jager, S. Jones, N. Joseph, T. Kanemura, S.H. Kim, C. Knowles, T. Konomi, B.R. Kortum, E. Kwan, T. Lange, M. Larmann, T.L. Larter, K. Laturkar, R.E. Laxdal, J. LeTourneau, Z. Li, S.M. Lidia, G. Machicoane, C. Magsig, P.E. Manwiller, F. Marti, T. Maruta, E.S. Metzgar, S.J. Miller, Y. Momozaki, D.G. Morris, M. Mugerian, I.N. Nesterenko, C. Nguyen, P.N. Ostroumov, M.S. Patil, A.S. Plastun, L. Popielarski, M. Portillo, J. Priller, X. Rao, M.A. Reaume, K. Saito, B.M. Sherrill, M.K. Smith, J. Song, M. Steiner, A. Stolz, O. Tarasov, B.P. Tousignant, R. Walker, X. Wang, J.D. Wenstrom, G. West, K. Witgen, M. Wright, T. Xu, Y. Yamazaki, T. Zhang, Q. Zhao, S. Zhao
FRIB, East Lansing, Michigan, USA
K. Hosoyama
KEK, Ibaraki, Japan
P. Hurh
Fermilab, Batavia, Illinois, USA
M.P. Kelly, Y. Momozaki
ANL, Lemont, Illinois, USA
R.E. Laxdal
TRIUMF, Vancouver, Canada
S.O. Prestemon
LBNL, Berkeley, California, USA
M. Wiseman
JLab, Newport News, Virginia, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
After project completion on scope, on cost, and ahead of schedule, the Facility for Rare Isotope Beams began operations for scientific users in May of 2022. During the first 12 months of user operations, the FRIB accelerator complex delivered 5250 beam hours, including 1528 hours to nine science experiments conducted with primary beams of 36Ar, 48Ca, 70Zn, 82Se, 124Xe, and 198Pt at beam energies >200 MeV/u; 2724 hours for beam developments, studies, and tuning; and 998 hours to industrial users and non-scientific programs using the FRIB Single Event Effect (FSEE) beam line. The ramp-up to a beam power of 400 kW is planned over a six-year period; 1 kW was delivered for initial user runs from in 2022, and 5 kW was delivered as of February 2023. Upgrade plans include doubling the primary-beam energy to 400 MeV/nucleon for enhanced discovery potential (¿FRIB 400¿). This talk reports on FRIB status and progress since SRF2021, emphasizing lessons learned during the transition from beam commissioning to machine operations, challenges and resolutions for the power ramp-up, progress with accelerator improvements, and R&D for the energy upgrade.

Slides MOIAA01 [7.037 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOIAA01

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Received ※ 20 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 03 July 2023 — Issue date ※ 19 July 2023

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MOPMB026

Development of Transformative Cavity Processing - Superiority of Electropolishing on High Gradient Performance over Buffered Chemical Polishing at Low Frequency (322 MHz)

145

K. Saito, C. Compton, K. Elliott, W. Hartung, S.H. Kim, T.K. Konomi, E.S. Metzgar, S.J. Miller, L. Popielarski, A.T. Taylor, T. Xu
FRIB, East Lansing, Michigan, USA

Funding: The work is supported by DOE Awards DE-SC0022994.
A DOE grant R&D titled ¿Development of Transformative Preparation Technology to Push up High Q/G Performance of FRIB Spare HWR Cryomodule Cavities¿ is ongoing at FRIB. This R&D is for 2 years since September 2022. This project proposes four objectives: 1) Superiority on high gradient performance of electropolishing (EP) over buffered chemical polishing at low frequency (322 MHz), 2) High Qo performance by the local magnetic shield, 3) Development of HFQS-free BCP and, 4) Wet N-doping method. This paper will report the result of first object, and a local magnetic shield design and simulation to reduce the residual magnetic field < 0.1 mG in the vertical test Dewar, for the object 2.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB026

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Received ※ 14 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 08 July 2023

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MOPMB067

Design of a Cathode Insertion and Transfer System for LCLS-II-HE SRF Gun

267

R. Xiang, A. Arnold, S. Gatzmaga, A. Hoffmann, P. Murcek, R. Steinbrück, J. Teichert
HZDR, Dresden, Germany
C. Adolphsen, J. Smedley
SLAC, Menlo Park, California, USA
W. Hartung, S.H. Kim, T.K. Konomi, S.J. Miller, L. Popielarski, K. Saito, T. Xu
FRIB, East Lansing, Michigan, USA
M.P. Kelly, T.B. Petersen
ANL, Lemont, Illinois, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by cooperation project between MSU and HZDR RC113062 from the U.S. Department of Energy Office of Science under Cooperative Agreement DE-AC02-76SF00515.
Superconducting radio frequency photo injectors (SRF gun) offer advantages for operating in continuous wave (CW) mode and generating high-brightness and high-current beams. A new SRF gun is designed as a low emittance photo injector for LCLS-II-HE and a prototype gun is currently being developed under collaboration between SLAC, FRIB, HZDR and ANL. The aim is to demonstrate stable CW operation at a cathode gradient of 30 MV/m. One of the crucial component for successful SRF gun operation is the photocathode system. The new SRF gun will adopt the HZDR-type cathode, which includes a cathode holder fixture (cathode stalk) developed by FRIB and a sophisticated cathode exchange system designed by HZDR. This innovative cathode insertion system ensures accurate, particle-free and warm cathode exchanges. A novel alignment process targets the cathode to the stalk axis without touching cathode plug itself. To commission the prototype gun, metallic cathodes will be used. A specifically designed vacuum system ensures vacuum pressure of 10^-9 mbar for transport of a single cathode from the cleanroom to the gun. Thus maintaining cathode quality.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB067

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Received ※ 18 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023

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MOPMB084

FRIB Driver Linac Integration to Support Operations and Protect SRF Cryomodules

316

H. Ao, K. Elliott, D.D. Jager, S.H. Kim, L. Popielarski
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
The driver linac for the Facility for Rare Isotope Beams (FRIB) at Michigan State University includes 324 superconducting radio-frequency (SRF) cavities, and the SRF particle-free beamline spans approximately 300 meters. Protecting the beamlines against contamination is critical to FRIB operations, and thus, various administrative and engineered controls have been put in place to protect the SRF cryomodules. These controls include local vacuum interlocks for cryomodule isolation, accelerator-wide interlocks, and software controls to safeguard the cryomodules and beamlines. Meanwhile, efforts are being made to provide training and develop programs with the goal of preventing critical failures during maintenance. This paper discusses the measures and approaches used for both system integration to support operations and SRF beamline protection.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB084

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Received ※ 14 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023

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TUPTB040

Mechanical Design and Analysis of SRF Gun Cavity Using ASME BPVC Section Viii, Division-2, Design by Analysis Requirement

501

M.S. Patil, C. Compton, S.H. Kim, S.J. Miller, T. Xu
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the Department of Energy Contract DE-AC02- 76SF00515
A prototype SRF gun is currently being designed at FRIB, MSU for the Low Emittance Injector of the Linac Coherent Light Source high energy upgrade at SLAC. This employs a 185.7 MHz superconducting quarter-wave resonator (QWR). The mechanical design of this cavity has been optimized for performance and to comply with ASME Section VIII, Div 2, Design by analysis requirements. This paper presents the various design by analysis procedures and how they have been adopted for the SRF gun cavity design.

Poster TUPTB040 [1.235 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB040

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Received ※ 15 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023

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TUPTB063

Fabrication Efforts Toward a Superconducting Rf Photo-Infector Quarter-Wave Cavity for Use in Low Emittance Injector Applications

568

C. Compton
NSCL, East Lansing, Michigan, USA
K. Elliott, W. Hartung, J.D. Hulbert, S.H. Kim, T. Konomi, S.J. Miller, M.S. Patil, J.T. Popielarski, L. Popielarski, K. Saito, K. Witgen, T. Xu
FRIB, East Lansing, Michigan, USA
M. Kedzie, M.P. Kelly, T.B. Petersen
ANL, Lemont, Illinois, USA
J.W. Lewellen, J. Smedley
SLAC, Menlo Park, California, USA

Funding: * Work supported by the Department of Energy Contract DE-AC02- 76SF00515
The Facility for Rare Isotope Beams (FRIB), in collaboration with Argonne National Laboratory (ANL) and Helmholtz-Zentrum Dresden-Rossendorf (HDZR), is working on the design and fabrication of a photo-injector cryomodule; suitable for operation as part of accelerator systems at SLAC National Accelerator Laboratory. Project scope requires the fabrication of two 185.7 MHz superconducting, quarter-wave resonators (QWR) based, injector cavities. Cavity fabrication will be completed at FRIB with contracted vendors supporting subcomponent fabrication and electron-beam welding. Fabrication will use poly-crystalline and large grain RRR niobium materials. The current status of cavity fabrication will be presented including material procurement, prototype forming, and electron-beam welding development.

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB063

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Received ※ 17 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 21 August 2023 — Issue date ※ 21 August 2023

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TUPTB069

Design and Tests of a Cathode Stalk for the LCLS-II-HE Low Emittance Injector SRF Gun

589

T.K. Konomi, W. Hartung, S.H. Kim, S.J. Miller, D.G. Morris, K. Saito, A.T. Taylor, T. Xu, Z.Y. Yin
FRIB, East Lansing, Michigan, USA
C. Adolphsen, J. Smedley, L. Xiao
SLAC, Menlo Park, California, USA
S. Gatzmaga, P. Murcek, R. Xiang
HZDR, Dresden, Germany
M.P. Kelly, T.B. Petersen
ANL, Lemont, Illinois, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA

A SRF gun can operate CW with a high gradient and ultra-low vacuum for high-quantum efficiency, low MTE photocathodes, useful features for delivery of high-brightness, high-repetition-rate beams. For these reasons, an SRF gun based photoinjector was chosen for a proposed Low Emittance Injector addition to the LCLS-II-HE facility, which will operate CW with bunch rates up to 1 MHz. For this injector, a prototype 185.7 MHz QWR gun is being developed in a collaborative effort among FRIB, HZDR, ANL and SLAC, with the goal of achieving a photocathode gradient of at least 30 MV/m. The photocathode is held by a coaxial fixture (cathode stalk) for thermal isolation from the cavity body. The system must allow for precise alignment of the photocathode, particle-free photocathode exchange, cryogenic (55-70 K) or warm (273-300 K) photocathode operating temperatures, and DC biasing to inhibit multipacting. A prototype cathode stalk has been built and bench tests are underway to validate the design. Measurements include RF power dissipation, DC bias hold-off, multipacting suppression and heat transfer effectiveness. This paper describes the cathode stalk design and the test results.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB069

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Received ※ 03 July 2023 — Revised ※ 27 July 2023 — Accepted ※ 19 August 2023 — Issue date ※ 20 August 2023

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WEPWB113

Evaluation of Photo-Cathode Port Multipacting in the SRF Photo-Injector Cryomodule for the LCLS-II High-Energy Upgrade

859

SUSPB032

use link to see paper's listing under its alternate paper code

Z.Y. Yin, W. Hartung, S.H. Kim, T. Konomi, T. Xu
FRIB, East Lansing, Michigan, USA

The high-energy upgrade of the Linac Coherent Light Source (LCLS-II-HE) will increase the photon energy and brightness. A low-emittance injector (LEI) was proposed to increase the photon flux for high X-ray energies. FRIB, HZDR, Argonne, and SLAC are developing a 185.7 MHz superconducting radio-frequency photo-injector (SRF-PI) cryomodule for the LEI. The photo-cathode system requirements are challenging, as cathodes must be maintained at the desired temperature, precisely aligned, and operated without multipacting (MP); to avoid field emission, cathode exchange must be particulate-free. A support stalk has been designed to hold the cathode in position under these requirements. A DC bias is used to inhibit MP. We simulated MP for various surface conditions and bias levels. An RF/DC test was developed to evaluate the cathode stalk performance as a subsystem and to identify and correct issues before assembly into the full cryomodule. The RF/DC test makes use of a resonant coaxial line to generate an RF magnetic field similar to that of the cathode-in-SRF-PI-cavity case. High-power test results will be presented and compared to the MP simulations.
* Work supported by the Department of Energy Contract DE-AC02-76SF00515

Poster WEPWB113 [1.410 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB113

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Received ※ 20 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 26 July 2023

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WEPWB127

Investigation of Coupler Breakdown Thresholds for Plasma Processing of FRIB Quarter-Wave Resonators with Fundamental and Higher-Order Modes

893

SUSPB035

use link to see paper's listing under its alternate paper code

P.R. Tutt, W. Hartung, S.H. Kim, T. Xu
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics and used resources of the Facility for Rare Isotope Beams (FRIB) under Award Number DE-SC0000661.
FRIB is developing plasma processing techniques for in-situ recovery of cavity performance in linac cryomodules during long-term user operation. While plasma processing has been shown to be effective for high-frequency (0.8 - 1.5 GHz) elliptical cavities, one of the challenges for FRIB is to avoid plasma breakdown in the fundamental input coupler (FPC), which has relatively weak coupling strength (Q_ext ranging from 2E6 to 1E7). FRIB cavities are not equipped with higher-order-mode (HOM) couplers; however, in preliminary tests, we found that HOMs are suitable for plasma processing of FRIB Quarter-Wave Resonators (QWRs) driven via the FPC. In this study, we investigated plasma breakdown thresholds in the fundamental and the first 2 HOMs for the FRIB β = 0.085 QWRs. Electric field distributions in the FPC region and cavity region were calculated for the room-temperature case using CST Microwave Studio’s frequency domain solver (FDS). Simulation results will be presented, with comparison of breakdown thresholds inferred from the RF modeling to the experimental results.

Poster WEPWB127 [5.068 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB127

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Received ※ 19 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 11 August 2023

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WEPWB128

Experimental Study of Mechanical Dampers for the FRIB β=0.041 Quarter-Wave Resonators

898

SUSPB036

use link to see paper's listing under its alternate paper code

J. Brown, W. Chang, W. Hartung, S.H. Kim, T. Xu
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the US Department of Energy, Office of Science, High Energy Physics under Cooperative Agreement award numbers DE-SC0018362 and DE-SC0000661 and Michigan State University.
The ’pendulum’ mechanical mode of quarter-wave resonators (QWR) often causes an issue with microphonics and/or ponderomotive instability unless otherwise the inner conductors are properly stiffened and/or damped. FRIB QWRs are equipped with a Legnaro-style frictional damper installed inside of the inner conductor such that it counteracts the oscillations of the inner conductor. In cryomodule tests and linac operation, we observed that the damping efficiency is different for a few β=0.041 QWRs. This study aimed to experimentally characterize the damping efficacy as a function of damper mass and surface roughness. We present damping measurements at room temperature and at two different masses and surface roughness as well as discuss future studies for damper re-optimization based on this follow-on study.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB128

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Received ※ 20 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 04 August 2023

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THIXA01

Investigation of Plasma Processing for Coaxial Resonators

960

W. Hartung, W. Chang, K. Elliott, S.H. Kim, T. Konomi, K. Saito, P.R. Tutt, T. Xu
FRIB, East Lansing, Michigan, USA

Plasma processing has been investigated by several facilities as a method to mitigate degradation of SRF cavity performance. It provides an alternative to removal and disassembly of cryomodules for refurbishment of each cavity via repeat etching and rinsing. Promising results have been obtained by several groups. Studies of plasma processing for quarter-wave resonators (QWRs) and half-wave resonators (HWRs) were undertaken at FRIB, where a total of 324 such resonators are presently in operation. Plasma ignition and optimization measurements were done with room-temperature-matched input couplers. Plasma cleaning tests were done on several QWRs using the fundamental power coupler (FPC) to drive the plasma. We investigated the usefulness of higher-order modes (HOMs) to drive the plasma. HOMs allow for less mismatch at the FPC and hence lower field in the coupler relative to the cavity. Before-and-after cold tests showed a significant reduction in field emission X-rays with judicious application of plasma processing.

Slides THIXA01 [2.060 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIXA01

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Received ※ 01 September 2023 — Accepted ※ 02 September 2023 — Issue date ※ 02 September 2023

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FRIBA01

SRF R&D for FRIB Linac Energy Upgrade with High-performance Medium-beta Elliptical Cavity CW Cryomodules

S.H. Kim, W. Chang, K. Elliott, W. Hartung, K.E. McGee, E.S. Metzgar, P.N. Ostroumov, L. Popielarski, J. Rathke, T. Xu, S. Zhao
FRIB, East Lansing, Michigan, USA
D.J. Bice, C. Contreras-Martinez, G.V. Eremeev, Y.M. Pischalnikov
Fermilab, Batavia, Illinois, USA
B.M. Guilfoyle, M.P. Kelly, T. Reid
ANL, Lemont, Illinois, USA

Funding: Work supported by the U.S. Department of Energy under Award Number DE-SC0000661. Further support provided by the US Department of Energy under Cooperative Agreement award number DE-SC0018362.
Michigan State University is pursuing SRF R&D for FRIB400 upgrade, doubling the FRIB linac beam energy (400 MeV/u for the heaviest uranium beam) using ßopt=0.65 644 MHz 5-cell elliptical cavities. We have achieved unprecedented Q₀ in this cavity class, Q₀ = 3.5·10¹⁰ at E_acc of 17.5 MV/m in a nitrogen-doped bare niobium cavity in collaboration with FNAL and ANL. The next missions are achieving such high Q₀ in jacketed cavities and in cryomodules, achieving field-emission free performance at Epeak of 40 MV/m with reproducibility, developing a compact two-window high-power fundamental power coupler (15 kW CW), and achieving stable resonance control of cavities integrated with tuners in cryomodules. In this talk, we will present progress of the SRF R&D and discuss future plan.

Slides FRIBA01 [2.513 MB]

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FRIBA05

Automation of FRIB SRF Cavities and SC Solenoids Turn-on/off

999

W. Chang, Y. Choi, X.J. Du, W. Hartung, S.H. Kim, T. Konomi, S.R. Kunjir, H. Nguyen, K. Saito, T. Xu, S. Zhao
FRIB, East Lansing, Michigan, USA
A. Facco
INFN/LNL, Legnaro (PD), Italy

The superconducting driver Linac for the Facility for Rare Isotope Beams (FRIB) is a heavy ion accelerator that accelerate ions to 200 MeV per nucleon. The Linac has 46 cryomodules that contain 324 superconducting radio frequency (SRF) cavities and 69 superconducting (SC) solenoid packages. For operation of all cryomodules with high efficiency and reliability, automation for SRF cavity and SC solenoid fast turn-on/off is essentially. Based on cryomodule commissioning results and expert experience, all manual cavity and solenoid turn-on/off procedures and steps have been replaced by automatic programs for FRIB linac operation. This allows the operators to turn the systems on and off without expert-level training. Automation reduces the risk of human error, speeds up beam recovery after user access to experimental areas, and increases beam availability. The cavity turn-on procedure makes sure that the cavity can operate at low field with expected read backs, ramps up the field, and makes sure that the RF amplitude and phase are stable. The design, implementation, and operating experience with automation will be presented.

Slides FRIBA05 [3.503 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-FRIBA05

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Received ※ 29 June 2023 — Revised ※ 16 August 2023 — Accepted ※ 21 August 2023 — Issue date ※ 21 August 2023

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FRIBA07

Status of the SLAC/MSU SRF Gun Development Project

1003

S.J. Miller, Y. Al-Mahmoud, W. Chang, Y. Choi, C. Compton, X.J. Du, K. Elliott, W. Hartung, J.D. Hulbert, S.H. Kim, T. Konomi, D.G. Morris, M.S. Patil, L. Popielarski, K. Saito, A. Taylor, B.P. Tousignant, J. Wei, J.D. Wenstrom, K. Witgen, T. Xu
FRIB, East Lansing, Michigan, USA
C. Adolphsen, R. Coy, F. Ji, M.J. Murphy, J. Smedley, L. Xiao
SLAC, Menlo Park, California, USA
A. Arnold, S. Gatzmaga, P. Murcek, J. Teichert, R. Xiang
HZDR, Dresden, Germany
M.P. Kelly, T.B. Petersen, P. Piot
ANL, Lemont, Illinois, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the Department of Energy under Contract DE-AC02-76SF00515
The Linac Coherent Light Source II High Energy (LCLS-II-HE) Project at SLAC includes the construction of a low-emittance injector (LEI) and a superconducting quarter-wave resonator (QWR) at 185.7 MHz. Several alternatives to a superconducting radio frequency (SRF) QWR gun were considered for the LEI, including nor-mal-conducting RF guns evolved from the LCLS-II gun design. Compared to normal-conducting designs, the combination of an intrinsically outstanding vacuum environment (for cathode lifetime), and the potential for a larger ultimate performance envelope, led to the deci-sion to pursue development of the QWR-SRF gun. A prototype gun is currently being designed and fabricated at the Facility for Rare Isotope Beams (FRIB) at Michi-gan State University (MSU). This paper presents perfor-mance goals for the new gun design, an overview of the prototype development effort, status, and future plans including fabrication.

Slides FRIBA07 [9.655 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-FRIBA07

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Received ※ 15 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 11 July 2023

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