NAPAC2019 - List of Keywords (SRF)

Paper	Title	Other Keywords	Page
MOYBB3	Progress in Nb₃Sn SRF Cavities at Cornell University	cavity, accelerating-gradient, site, superconductivity	37
	R.D. Porter, H. Hu, M. Liepe, N.A. Stilin, Z. Sun, M.J. Tao Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Niobium-3 Tin (NbSn) is the most promising alternative material for next-generation SRF cavities. The material can obtain high quality factors (> 10¹⁰) at 4.2 K and could theoretically support ~ 96 MV/m operation of a TESLA elliptical style cavity. Current Nb₃Sn cavities made at Cornell University achieve high quality factors but are limited to about 17 MV/m in CW operation due to the presence of a surface defect. Here we examine recent results on studying the quench mechanism and propose that surface roughness is a major limiter for accelerating gradients. Furthermore, we discuss recent work on reducing the surface roughness including chemical polishing, modification of material growth, and tin electroplating.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB3
About •	paper received ※ 02 September 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019
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MOYBB4	Large-Scale Dewar Testing of FRIB Production Cavities: Statistical Analysis	cavity, multipactoring, linac, cryomodule	41
	C. Zhang, W. Chang, W. Hartung, S.H. Kim, J.T. Popielarski, K. Saito, J.F. Schwartz, T. Xu FRIB, East Lansing, Michigan, USA
	The Facility for Rare Isotope Beams (FRIB) requires a driver linac with 324 superconducting cavities to deliver ion beams at 200 MeV per nucleon. About 1/3 of the cavities are quarter-wave resonators (QWRs, 805. MHz); the rest are half-wave resonators (HWRs, 322 MHz). FRIB cavity production is nearly complete, with more than 90% of the required cavities certified for installation into cryomodules (as of May 2019). We have accumulated a large data set on performance of production QWRs and HWRs during Dewar certificating testing of jacketed cavities. In this paper, we will report on the data analysis, including statistics on the BCS resistance, residual resistance, energy gap, and Q-slope. Additionally, we will discuss performance limitations and conditioning (multipacting, field emission).
	Slides MOYBB4 [1.200 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB4
About •	paper received ※ 01 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019
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MOZBA1	LCLS-II SC Linac: Challenges and Status	cavity, cryomodule, linac, FEL	51
	M.C. Ross SLAC, Menlo Park, California, USA
	Funding: ∗ This work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 The Linac Coherent Light Source II (LCLS-II) project requires the assembly, test, and installation of 37 cry-omodules (CM) in order to deliver a 4 GeV CW electron beam to the FEL undulators for production of both hard and soft X-ray pulses at a repetition rate of up to 1 MHz. All of the cryomodules will operation in continuous wave mode, with 35 operating at 1.3 GHz for acceleration and 2 operating at 3.9 GHz to linearize the longitudinal beam profile. The assembly and testing of the 1.3 GHz cry-omodules is nearing completion and the 3.9 GHz cry-omodules work is entering to assembly and testing phase. Roughly 60% of the cryomodules have been shipped to SLAC for installation in the accelerator enclosure. The status and challenges of these efforts will be reported in this paper.
	Slides MOZBA1 [80.533 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA1
About •	paper received ※ 02 September 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019
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MOPLS06	Mu*STAR: An Accelerator-Driven Subcritical Modular Reactor	target, site, neutron, operation	163
	R.P. Johnson, R.J. Abrams, M.A. Cummings, T.J. Roberts Muons, Inc, Illinois, USA
	We present a conceptual design for a new modular, accelerator-driven subcritical reactor based on a molten salt. MuSTAR is a reactor, that without re-design, can burn a variety of nuclear fuels, with the beam tuned to that fuel. We will discuss the elements of this system: the accelerator, the reactor, the spallation target, and the fractional distillation to separate volatile fission products. Our GAIN project with ORNL is successfully completed, with a design of the Fuel Processing Plant that will convert spent nuclear fuel into the molten-salt fuel for MuSTAR.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLS06
About •	paper received ※ 01 September 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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MOPLO17	Large-Scale Dewar Testing of FRIB Production Cavities: Results	cavity, cryomodule, MMI, linac	270
	W. Hartung, W. Chang, S.H. Kim, D. Norton, J.T. Popielarski, K. Saito, J.F. Schwartz, T. Xu, C. Zhang FRIB, East Lansing, Michigan, USA
	The Facility for Rare Isotope Beams (FRIB), under construction at Michigan State University (MSU), includes a superconducting driver linac to deliver ion beams at 200 MeV per nucleon. The driver linac requires 10⁴ quarter-wave resonators (QWRs, β = 0.041 and 0.085) and 220 half-wave resonators (HWRs, β = 0.29 and 0.54). The jacketed resonators are Dewar tested at MSU before installation into cryomodules. The cryomodules for β = 0.041, 0.085, and 0.29 have been completed and certified; 89% of the β = 0.54 HWRs have been certified (as of May 2019). The Dewar certification tests have provided valuable information on the performance of production QWRs and HWRs at 4.3 K and 2 K and on performance limits. Results will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO17
About •	paper received ※ 08 November 2019 paper accepted ※ 26 November 2019 issue date ※ 08 October 2019
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MOPLO19	Test Results of PIP2IT MEBT Vacuum Protection System	vacuum, cavity, cryomodule, MEBT	278
	A.Z. Chen, R. Andrews, C.M. Baffes, D.D. Lambert, L.R. Prost, A.V. Shemyakin, T.J. Zuchnik Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics The central part of PIP-II program of upgrades proposed for the Fermilab injection complex is an 800 MeV, 2 mA, CW-compatible SRF linac. Acceleration in superconducting cavities begins from a low energy of 2.1 MeV, so that the first cryomodule, Half Wave Resonator (HWR) borders the warm Medium Beam Transport (MEBT) line. To minimize the amount of gas that may enter the SRF linac in a case if a vacuum failure occurs in the warm front end, a vacuum protection system is envisioned to be used in the PIP-II MEBT. It features a fast closing valve with two sensors and a differential pumping insert. The system prototype is installed in the PIP-II Injector Test (PIP2IT) accelerator and recently is successfully tested in several modes modelling the vacuum failures. The report presents the design of the vacuum protection system and results of its tests.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO19
About •	paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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TUYBA4	Optimization of an SRF Gun Design for UEM Applications	gun, laser, cavity, electron	305
	A. Liu, P.V. Avrakhov Euclid TechLabs, LLC, Solon, Ohio, USA C. Jing, R.A. Kostin Euclid Beamlabs LLC, Bolingbrook, USA
	Funding: DOE contract DE-SC0018621 Benefiting from the rapid progress on RF photocathode gun technologies in the past two decades, the development of MeV-range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation, which may lead to breakthroughs in fundamental science and applied technologies . Euclid is designing an SRF cavity as the UEM electron gun. As implementing a solenoid for emittance compensation in the gun is limited by the superconductivity performance and available space, the geometry of the first 0.3 cell of the cavity is optimized for transverse focusing and emittance reduction. : T. Chase, et al, "Ultrafast electron diffraction from non- equilibrium phonons in femtosecond laser heated Au films." Applied Physics Letters, 2016
	Slides TUYBA4 [7.583 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBA4
About •	paper received ※ 30 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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TUPLH17	Design Study of Low-Level RF Control System for CW Superconducting Electron Linear Accelerator in KAERI	controls, LLRF, linac, cavity	512
	S.H. Lee, J.Y. Lee Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea P. Buaphad, I.G. Jeong, Y.J. Joo, H.R. Lee University of Science and Technology of Korea (UST), Daejeon, Republic of Korea M.-H. Chun, I.H. Yu PAL, Pohang, Republic of Korea Y. Kim KAERI, Jeongeup-si, Republic of Korea
	Korea Atomic Energy Research Institute (KAERI) has been operating a 20 MeV superconducting RF linear accelerator (SRF LINAC) to conduct research on atom/nuclear reaction using neutron Time-Of-Flight (nTOF). It can accelerate electron beams up to 20 MeV with 1 kW continuous wave (CW) operation mode. Unfortunately, this machine has been aged over 15 years that brings about considerably difficulty in normal operation due to the performance degradation of sub-systems. To improve the operation condition of 20 MeV SRF LINAC, we has been carrying out an upgrade project with replacement and repair of old sub-systems from 2018. This paper describes a design study of Low-Level RF (LLRF) feedback system to raise the stability and acceleration efficiency of the electric field generated in the superconducting RF cavity structure in 20 MeV SRF LINAC.
	Poster TUPLH17 [0.644 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH17
About •	paper received ※ 30 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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TUPLH24	Performance of CeC PoP Accelerator	electron, FEL, gun, hadron	526
	I. Pinayev, Z. Altinbas, J.C. Brutus, A.J. Curcio, A. Di Lieto, T. Hayes, R.L. Hulsart, P. Inacker, Y.C. Jing, V. Litvinenko, J. Ma, G.J. Mahler, M. Mapes, K. Mernick, K. Mihara, T.A. Miller, M.G. Minty, G. Narayan, I. Petrushina, F. Severino, K. Shih, Z. Sorrell, J.E. Tuozzolo, E. Wang, G. Wang, A. Zaltsman BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Coherent electron cooling experiment is aimed for demonstration of the proof-of-principle demonstration of reduction energy spread of a single hadron bunch circulating in RHIC. The electron beam should have the required parameters and its orbit and energy should be matched to the hadron beam. In this paper we present the achieved electron beam parameters including emittance, energy spread, and other critical indicators. The operational issues as well as future plans are also discussed.
	Poster TUPLH24 [11.180 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH24
About •	paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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WEPLM21	High-Quality Resonators for Quantum Information Systems	cavity, controls, cryogenics, photon	690
	S.V. Kuzikov IAP/RAS, Nizhny Novgorod, Russia S.P. Antipov, P.V. Avrakhov, E. Gomez Euclid TechLabs, LLC, Solon, Ohio, USA
	We analyze ultra-high-quality factor resonators for quantum computer architectures. As qubit operation requires external DC fields, we started our study with a conventional closed copper cavity which naturally allows external magnetic field. In order to increase quality factor and to keep DC magnetic field control at a level less than critical field, an open SRF resonator promises much higher quality. The next step resonator is a photonic band gap (PBG) resonator. This resonator allows easy external either magnetic or electric field control. It consists of a periodic 3D set of sapphire rods assembled between two superconducting plates. The PBG resonator exploits unique properties of the crystalline sapphire. Tangent delta for sapphire in X-band is reported at 10^-9 ’ 10-10 at 4 K. That is why, the Q-factor of the sapphire PBG resonator can be expected as high as 10 billions at mK temperatures which provides long relaxation times (dephasing etc.). The established PBG design implies obtaining a large Purcell factor, i.e. large ratio of quality to mode volume which is important parameter to establish strong interaction of a qubit with the cavity mode rather than RF noise.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM21
About •	paper received ※ 27 August 2019 paper accepted ※ 01 September 2019 issue date ※ 08 October 2019
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WEPLM47	Analysis of High Field Q-Slope (HFQS) Causes and Development of New Chemical Polishing Acid	cavity, experiment, superconductivity, niobium	699
	D. Luo, E.S. Metzgar, L. Popielarski, K. Saito, S.M. Shanab, G.V. Simpson FRIB, East Lansing, Michigan, USA T. Nakajima, I. Nasu, J. Taguchi Nomura Plating Co, Ltd., Osaka, Japan
	Funding: U.S. National Science Foundation under Grant PHY-1565546. In our previous studies of High Field Q-slope (HFQS) we have concluded that nitrogen contamination from the nitric acid is the main cause of the degradation of the Q in buffered chemical polished cavities. Our conclusion is made based on previously unresolved phenomena which are found from huge amount of published cavity test data, include fine grain, large grain and single crystal cavities treated with EP and BCP. According to this analysis, we have started developing new nitrogen-free chemical polishing acid. Hydrogen peroxide with HF mixture was reported able to react with Nb, and there’s no extra element contamination in it, so we replace the conventional BCP with this mixture to start our study. In this paper, some Nb coupon sample results with new acid will be reported. We complete the first step of developing the new acid and we got the Nb finish roughness no worse than conventional BCP.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM47
About •	paper received ※ 13 September 2019 paper accepted ※ 04 December 2019 issue date ※ 08 October 2019
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WEPLM52	Recent Developments of Nb₃Sn at Jefferson Lab for SRF Accelerator Application	cavity, accelerating-gradient, cryomodule, factory	713
	U. Pudasaini, M.J. Kelley The College of William and Mary, Williamsburg, Virginia, USA G.V. Eremeev, M.J. Kelley, C.E. Reece JLab, Newport News, Virginia, USA
	Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics. The desire to reduce the construction and operating costs of future SRF accelerators motivates the search for alternative, higher-performing materials. Nb₃Sn (Tc ~ 18.3 K and Hsh ~ 425 mT) is the front runner. However, tests of early Nb₃Sn-coated cavities encountered strong Q-slopes limiting the performance. Learnings from studies of coated materials related to cavity performance prompted significant changes to the coating process. It is now possible to routinely produce slope-free single-cell cavities having Q₀ ≥ 2×10¹⁰ at 4 K and > 4×10¹⁰ at 2 K up to the accelerating gradient in excess of 15 MV/m at its best. Obtaining similar results in five-cell cavities is a current goal to test them under an accelerator environment. This contribution discusses recent developments at Jefferson Lab.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM52
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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WEPLM60	Fast Sn-Ion Transport on Nb Surface for Generating NbxSn Thin Films and XPS Depth Profiling	interface, electron, cavity, radio-frequency	727
	Z. Sun, M. Liepe, J.T. Maniscalco, T.E. Oseroff, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA X. Deng University of Virginia, Charlottesville, Virginia, USA D. Zhang Cornell University, Ithaca, New York, USA
	Funding: U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams In this work, we propose and demonstrate a fast and facile approach for NbxSn thin film deposition through the ion exchange reaction. By simply dipping a tin precursor on the Nb substrate surface, a ~600 nm thin film is generated due to the electronegativity differ-ence between Sn and Nb. Through X-ray photoelec-tron spectroscopy (XPS) depth profiling, the composi-tional information as a function of film thickness was obtained. Results showed a Sn layer on the film sur-face, Sn-rich and Nb-rich NbxSn layers as the majority of the film, and a ~60 nm Nb₃Sn layer at the film/substrate interface. Quantitative analysis con-firmed stoichiometric Nb/Sn ratio for the Nb₃Sn layer. This deposition method is demonstrated to be an alter-native choice for Nb₃Sn film growth.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM60
About •	paper received ※ 05 September 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019
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WEPLM63	Development of a Secondary Sn Source for Nb₃Sn Coating of Half-Wave Coaxial Resonator	cavity, niobium, MMI, superconductivity	735
	J.K. Tiskumara, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA G.V. Eremeev JLab, Newport News, Virginia, USA U. Pudasaini The College of William and Mary, Williamsburg, Virginia, USA
	Superconducting thin films have the potential of reducing the cost of particle accelerators. Among the potential materials, Nb₃Sn has a higher critical temperature and higher critical field compared to niobium. Sn vapor diffusion method is the preferred technique to coat niobium cavities. Although there are several thin-film-coated basic cavity models that are tested at their specific frequencies, the Half-wave resonator could provide us data across frequencies of interest for particle accelerators. With its advanced geometry, increased area, increased number of ports and hard to reach areas, the half-wave resonator needs a different coating approach, in particular, a development of a secondary Sn source. We are commissioning a secondary Sn source in the coating system and expand the current coating system at JLab to coat complex cavity models.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM63
About •	paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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WEPLM64	High Dynamic Voltage Range Studies of Piezoelectric Multilayer Actuators at Low Temperatures	linac, cavity, operation, vacuum	739
	C. Contreras-Martinez FRIB, East Lansing, Michigan, USA Y.M. Pischalnikov, J.C. Yun Fermilab, Batavia, Illinois, USA
	Piezo actuators are used for resonance control in superconducting linacs. In high accelerating gradients linacs, such as those operated in a pulsed mode, the piezos require a large operating voltage. This is due to the Lorentz forced detuning which causes a large frequency shift and is compensated with an active piezo-tuning system. In this high dynamic voltage range the piezo is expected to warm up drastically due to it being in an insulated vacuum. This study characterizes the dielectric properties (capacitance, dielectric losses), the piezo stroke (from geophone), and thermal properties such as heating. Results obtained in the temperature range of 20K to 300K will be presented and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM64
About •	paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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WEPLM73	Bunker Testing of FRIB Cryomodules	cavity, cryomodule, solenoid, dipole	765
	W. Chang, S. Caton, A. Ganshyn, W. Hartung, S.H. Kim, B. Laumer, H. Maniar, J.T. Popielarski, K. Saito, M. Xu, T. Xu, C. Zhang, S. Zhao FRIB, East Lansing, Michigan, USA
	The FRIB superconducting driver Linac requires 10⁴ quarter-wave resonators (QWRs, β = 0.041, 0.085), 220 half-wave resonators (HWRs, β = 0.29, 0.53), and 74 superconducting solenoid packages. Resonators and solenoids are assembled into cryomodules; 4 accelerating and 2 matching cryomodule types are required. Each cryomodule undergoes cryogenic and RF testing in a bunker prior to installation in the tunnel. The cryomodule test verifies operation of the cavities, couplers, tuners, solenoid packages, magnetic shield, and thermal shield at 4.3 K and 2 K. All of the required cryomodules for β = 0.041, 0.085, and 0.29 have been tested and certified. As of May 2019, five of the β = 0.53 cryomodules have been certified; the remaining modules are being assembled or are in the queue for testing. Cryomodule test results will be presented, including cavity performance (accelerating gradient, field emission X-rays, multipacting conditioning); solenoid package operation (current, current-lead cooling flow rate); and cryomodule heat load (static and dynamic).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM73
About •	paper received ※ 06 September 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019
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WEPLH09	FRIB Driver Linac Integration to be ready for Phased Beam Commissioning	MMI, cryomodule, cavity, linac	823
	H. Ao, S. Beher, N.K. Bultman, F. Casagrande, C. Compton, J.C. Curtin, K.D. Davidson, K. Elliott, V. Ganni, A. Ganshyn, P.E. Gibson, I. Grender, W. Hartung, L. Hodges, K. Holland, A. Hussain, M. Ikegami, S. Jones, P. Knudsen, S.M. Lidia, G. Machicoane, S.J. Miller, D.G. Morris, P.N. Ostroumov, J.T. Popielarski, L. Popielarski, J. Priller, T. Russo, K. Saito, S. Stanley, D.R. Victory, X. Wang, J. Wei, M. Xu, T. Xu, Y. Yamazaki, S. Zhao FRIB, East Lansing, Michigan, USA A. Facco INFN/LNL, Legnaro (PD), Italy R.E. Laxdal TRIUMF, Vancouver, Canada
	Funding: Work supported by the U.S. Department of Energy (DOE) Office of Science under Cooperative Agreement DE-SC0000661 The driver linac for Facility for Rare Isotope Beams (FRIB) will accelerate all stable ion beams from proton to uranium beyond 200 MeV/u with beam powers up to 400 kW. The linac now consists of 10⁴ superconducting quarter-wave resonators (QWR), which is the world largest number of low-beta SRF cavities operating at an accelerator facility. The first 3 QWR cryomodules (CM) (β = 0.041) were successfully integrated with cryogenics and other support systems for the 2nd Accelerator Readiness Review (ARR). The 3rd ARR scope that includes 11 QWR CM (β=0.085) and 1 QWR matching CM (β=0.085) was commissioned on schedule by January 2019, and then we met the Key Performance Parameters (KPP), accelerating Ar and Kr > 16 MeV/u at this stage, in a week upon the ARR authorization. We examine a variety of key factors to the successful commissioning, such as component testing prior to system integration, assessment steps of system/device readiness, and phased commissioning. This paper also reports on the integration process of the β=0.085 CMs including the test results, and the current progress on β=0.29 and 0.53 CMs in preparation for the upcoming 4th ARR.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH09
About •	paper received ※ 02 September 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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Paper

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Other Keywords

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MOYBB3

Progress in Nb₃Sn SRF Cavities at Cornell University

cavity, accelerating-gradient, site, superconductivity

37

R.D. Porter, H. Hu, M. Liepe, N.A. Stilin, Z. Sun, M.J. Tao
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Niobium-3 Tin (NbSn) is the most promising alternative material for next-generation SRF cavities. The material can obtain high quality factors (> 10¹⁰) at 4.2 K and could theoretically support ~ 96 MV/m operation of a TESLA elliptical style cavity. Current Nb₃Sn cavities made at Cornell University achieve high quality factors but are limited to about 17 MV/m in CW operation due to the presence of a surface defect. Here we examine recent results on studying the quench mechanism and propose that surface roughness is a major limiter for accelerating gradients. Furthermore, we discuss recent work on reducing the surface roughness including chemical polishing, modification of material growth, and tin electroplating.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB3

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paper received ※ 02 September 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019

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MOYBB4

Large-Scale Dewar Testing of FRIB Production Cavities: Statistical Analysis

cavity, multipactoring, linac, cryomodule

41

C. Zhang, W. Chang, W. Hartung, S.H. Kim, J.T. Popielarski, K. Saito, J.F. Schwartz, T. Xu
FRIB, East Lansing, Michigan, USA

The Facility for Rare Isotope Beams (FRIB) requires a driver linac with 324 superconducting cavities to deliver ion beams at 200 MeV per nucleon. About 1/3 of the cavities are quarter-wave resonators (QWRs, 805. MHz); the rest are half-wave resonators (HWRs, 322 MHz). FRIB cavity production is nearly complete, with more than 90% of the required cavities certified for installation into cryomodules (as of May 2019). We have accumulated a large data set on performance of production QWRs and HWRs during Dewar certificating testing of jacketed cavities. In this paper, we will report on the data analysis, including statistics on the BCS resistance, residual resistance, energy gap, and Q-slope. Additionally, we will discuss performance limitations and conditioning (multipacting, field emission).

Slides MOYBB4 [1.200 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB4

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paper received ※ 01 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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MOZBA1

LCLS-II SC Linac: Challenges and Status

cavity, cryomodule, linac, FEL

51

M.C. Ross
SLAC, Menlo Park, California, USA

Funding: ∗ This work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515
The Linac Coherent Light Source II (LCLS-II) project requires the assembly, test, and installation of 37 cry-omodules (CM) in order to deliver a 4 GeV CW electron beam to the FEL undulators for production of both hard and soft X-ray pulses at a repetition rate of up to 1 MHz. All of the cryomodules will operation in continuous wave mode, with 35 operating at 1.3 GHz for acceleration and 2 operating at 3.9 GHz to linearize the longitudinal beam profile. The assembly and testing of the 1.3 GHz cry-omodules is nearing completion and the 3.9 GHz cry-omodules work is entering to assembly and testing phase. Roughly 60% of the cryomodules have been shipped to SLAC for installation in the accelerator enclosure. The status and challenges of these efforts will be reported in this paper.

Slides MOZBA1 [80.533 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA1

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paper received ※ 02 September 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019

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MOPLS06

Mu*STAR: An Accelerator-Driven Subcritical Modular Reactor

target, site, neutron, operation

163

R.P. Johnson, R.J. Abrams, M.A. Cummings, T.J. Roberts
Muons, Inc, Illinois, USA

We present a conceptual design for a new modular, accelerator-driven subcritical reactor based on a molten salt. Mu*STAR is a reactor, that without re-design, can burn a variety of nuclear fuels, with the beam tuned to that fuel. We will discuss the elements of this system: the accelerator, the reactor, the spallation target, and the fractional distillation to separate volatile fission products. Our GAIN project with ORNL is successfully completed, with a design of the Fuel Processing Plant that will convert spent nuclear fuel into the molten-salt fuel for Mu*STAR.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLS06

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paper received ※ 01 September 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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MOPLO17

Large-Scale Dewar Testing of FRIB Production Cavities: Results

cavity, cryomodule, MMI, linac

270

W. Hartung, W. Chang, S.H. Kim, D. Norton, J.T. Popielarski, K. Saito, J.F. Schwartz, T. Xu, C. Zhang
FRIB, East Lansing, Michigan, USA

The Facility for Rare Isotope Beams (FRIB), under construction at Michigan State University (MSU), includes a superconducting driver linac to deliver ion beams at 200 MeV per nucleon. The driver linac requires 10⁴ quarter-wave resonators (QWRs, β = 0.041 and 0.085) and 220 half-wave resonators (HWRs, β = 0.29 and 0.54). The jacketed resonators are Dewar tested at MSU before installation into cryomodules. The cryomodules for β = 0.041, 0.085, and 0.29 have been completed and certified; 89% of the β = 0.54 HWRs have been certified (as of May 2019). The Dewar certification tests have provided valuable information on the performance of production QWRs and HWRs at 4.3 K and 2 K and on performance limits. Results will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO17

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paper received ※ 08 November 2019 paper accepted ※ 26 November 2019 issue date ※ 08 October 2019

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MOPLO19

Test Results of PIP2IT MEBT Vacuum Protection System

vacuum, cavity, cryomodule, MEBT

278

A.Z. Chen, R. Andrews, C.M. Baffes, D.D. Lambert, L.R. Prost, A.V. Shemyakin, T.J. Zuchnik
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics
The central part of PIP-II program of upgrades proposed for the Fermilab injection complex is an 800 MeV, 2 mA, CW-compatible SRF linac. Acceleration in superconducting cavities begins from a low energy of 2.1 MeV, so that the first cryomodule, Half Wave Resonator (HWR) borders the warm Medium Beam Transport (MEBT) line. To minimize the amount of gas that may enter the SRF linac in a case if a vacuum failure occurs in the warm front end, a vacuum protection system is envisioned to be used in the PIP-II MEBT. It features a fast closing valve with two sensors and a differential pumping insert. The system prototype is installed in the PIP-II Injector Test (PIP2IT) accelerator and recently is successfully tested in several modes modelling the vacuum failures. The report presents the design of the vacuum protection system and results of its tests.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO19

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paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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TUYBA4

Optimization of an SRF Gun Design for UEM Applications

gun, laser, cavity, electron

305

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

Funding: DOE contract DE-SC0018621
Benefiting from the rapid progress on RF photocathode gun technologies in the past two decades, the development of MeV-range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation, which may lead to breakthroughs in fundamental science and applied technologies *. Euclid is designing an SRF cavity as the UEM electron gun. As implementing a solenoid for emittance compensation in the gun is limited by the superconductivity performance and available space, the geometry of the first 0.3 cell of the cavity is optimized for transverse focusing and emittance reduction.
*: T. Chase, et al, "Ultrafast electron diffraction from non- equilibrium phonons in femtosecond laser heated Au films." Applied Physics Letters, 2016

Slides TUYBA4 [7.583 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBA4

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paper received ※ 30 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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TUPLH17

Design Study of Low-Level RF Control System for CW Superconducting Electron Linear Accelerator in KAERI

controls, LLRF, linac, cavity

512

S.H. Lee, J.Y. Lee
Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea
P. Buaphad, I.G. Jeong, Y.J. Joo, H.R. Lee
University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
M.-H. Chun, I.H. Yu
PAL, Pohang, Republic of Korea
Y. Kim
KAERI, Jeongeup-si, Republic of Korea

Korea Atomic Energy Research Institute (KAERI) has been operating a 20 MeV superconducting RF linear accelerator (SRF LINAC) to conduct research on atom/nuclear reaction using neutron Time-Of-Flight (nTOF). It can accelerate electron beams up to 20 MeV with 1 kW continuous wave (CW) operation mode. Unfortunately, this machine has been aged over 15 years that brings about considerably difficulty in normal operation due to the performance degradation of sub-systems. To improve the operation condition of 20 MeV SRF LINAC, we has been carrying out an upgrade project with replacement and repair of old sub-systems from 2018. This paper describes a design study of Low-Level RF (LLRF) feedback system to raise the stability and acceleration efficiency of the electric field generated in the superconducting RF cavity structure in 20 MeV SRF LINAC.

Poster TUPLH17 [0.644 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH17

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paper received ※ 30 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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TUPLH24

Performance of CeC PoP Accelerator

electron, FEL, gun, hadron

526

I. Pinayev, Z. Altinbas, J.C. Brutus, A.J. Curcio, A. Di Lieto, T. Hayes, R.L. Hulsart, P. Inacker, Y.C. Jing, V. Litvinenko, J. Ma, G.J. Mahler, M. Mapes, K. Mernick, K. Mihara, T.A. Miller, M.G. Minty, G. Narayan, I. Petrushina, F. Severino, K. Shih, Z. Sorrell, J.E. Tuozzolo, E. Wang, G. Wang, A. Zaltsman
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Coherent electron cooling experiment is aimed for demonstration of the proof-of-principle demonstration of reduction energy spread of a single hadron bunch circulating in RHIC. The electron beam should have the required parameters and its orbit and energy should be matched to the hadron beam. In this paper we present the achieved electron beam parameters including emittance, energy spread, and other critical indicators. The operational issues as well as future plans are also discussed.

Poster TUPLH24 [11.180 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH24

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paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLM21

High-Quality Resonators for Quantum Information Systems

cavity, controls, cryogenics, photon

690

S.V. Kuzikov
IAP/RAS, Nizhny Novgorod, Russia
S.P. Antipov, P.V. Avrakhov, E. Gomez
Euclid TechLabs, LLC, Solon, Ohio, USA

We analyze ultra-high-quality factor resonators for quantum computer architectures. As qubit operation requires external DC fields, we started our study with a conventional closed copper cavity which naturally allows external magnetic field. In order to increase quality factor and to keep DC magnetic field control at a level less than critical field, an open SRF resonator promises much higher quality. The next step resonator is a photonic band gap (PBG) resonator. This resonator allows easy external either magnetic or electric field control. It consists of a periodic 3D set of sapphire rods assembled between two superconducting plates. The PBG resonator exploits unique properties of the crystalline sapphire. Tangent delta for sapphire in X-band is reported at 10^-9 ’ 10-10 at 4 K. That is why, the Q-factor of the sapphire PBG resonator can be expected as high as 10 billions at mK temperatures which provides long relaxation times (dephasing etc.). The established PBG design implies obtaining a large Purcell factor, i.e. large ratio of quality to mode volume which is important parameter to establish strong interaction of a qubit with the cavity mode rather than RF noise.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM21

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paper received ※ 27 August 2019 paper accepted ※ 01 September 2019 issue date ※ 08 October 2019

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WEPLM47

Analysis of High Field Q-Slope (HFQS) Causes and Development of New Chemical Polishing Acid

cavity, experiment, superconductivity, niobium

699

D. Luo, E.S. Metzgar, L. Popielarski, K. Saito, S.M. Shanab, G.V. Simpson
FRIB, East Lansing, Michigan, USA
T. Nakajima, I. Nasu, J. Taguchi
Nomura Plating Co, Ltd., Osaka, Japan

Funding: U.S. National Science Foundation under Grant PHY-1565546.
In our previous studies of High Field Q-slope (HFQS) we have concluded that nitrogen contamination from the nitric acid is the main cause of the degradation of the Q in buffered chemical polished cavities. Our conclusion is made based on previously unresolved phenomena which are found from huge amount of published cavity test data, include fine grain, large grain and single crystal cavities treated with EP and BCP. According to this analysis, we have started developing new nitrogen-free chemical polishing acid. Hydrogen peroxide with HF mixture was reported able to react with Nb, and there’s no extra element contamination in it, so we replace the conventional BCP with this mixture to start our study. In this paper, some Nb coupon sample results with new acid will be reported. We complete the first step of developing the new acid and we got the Nb finish roughness no worse than conventional BCP.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM47

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paper received ※ 13 September 2019 paper accepted ※ 04 December 2019 issue date ※ 08 October 2019

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WEPLM52

Recent Developments of Nb₃Sn at Jefferson Lab for SRF Accelerator Application

cavity, accelerating-gradient, cryomodule, factory

713

U. Pudasaini, M.J. Kelley
The College of William and Mary, Williamsburg, Virginia, USA
G.V. Eremeev, M.J. Kelley, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics.
The desire to reduce the construction and operating costs of future SRF accelerators motivates the search for alternative, higher-performing materials. Nb₃Sn (Tc ~ 18.3 K and Hsh ~ 425 mT) is the front runner. However, tests of early Nb₃Sn-coated cavities encountered strong Q-slopes limiting the performance. Learnings from studies of coated materials related to cavity performance prompted significant changes to the coating process. It is now possible to routinely produce slope-free single-cell cavities having Q₀ ≥ 2×10¹⁰ at 4 K and > 4×10¹⁰ at 2 K up to the accelerating gradient in excess of 15 MV/m at its best. Obtaining similar results in five-cell cavities is a current goal to test them under an accelerator environment. This contribution discusses recent developments at Jefferson Lab.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM52

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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WEPLM60

Fast Sn-Ion Transport on Nb Surface for Generating NbxSn Thin Films and XPS Depth Profiling

interface, electron, cavity, radio-frequency

727

Z. Sun, M. Liepe, J.T. Maniscalco, T.E. Oseroff, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
X. Deng
University of Virginia, Charlottesville, Virginia, USA
D. Zhang
Cornell University, Ithaca, New York, USA

Funding: U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams
In this work, we propose and demonstrate a fast and facile approach for NbxSn thin film deposition through the ion exchange reaction. By simply dipping a tin precursor on the Nb substrate surface, a ~600 nm thin film is generated due to the electronegativity differ-ence between Sn and Nb. Through X-ray photoelec-tron spectroscopy (XPS) depth profiling, the composi-tional information as a function of film thickness was obtained. Results showed a Sn layer on the film sur-face, Sn-rich and Nb-rich NbxSn layers as the majority of the film, and a ~60 nm Nb₃Sn layer at the film/substrate interface. Quantitative analysis con-firmed stoichiometric Nb/Sn ratio for the Nb₃Sn layer. This deposition method is demonstrated to be an alter-native choice for Nb₃Sn film growth.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM60

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paper received ※ 05 September 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019

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WEPLM63

Development of a Secondary Sn Source for Nb₃Sn Coating of Half-Wave Coaxial Resonator

cavity, niobium, MMI, superconductivity

735

J.K. Tiskumara, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
G.V. Eremeev
JLab, Newport News, Virginia, USA
U. Pudasaini
The College of William and Mary, Williamsburg, Virginia, USA

Superconducting thin films have the potential of reducing the cost of particle accelerators. Among the potential materials, Nb₃Sn has a higher critical temperature and higher critical field compared to niobium. Sn vapor diffusion method is the preferred technique to coat niobium cavities. Although there are several thin-film-coated basic cavity models that are tested at their specific frequencies, the Half-wave resonator could provide us data across frequencies of interest for particle accelerators. With its advanced geometry, increased area, increased number of ports and hard to reach areas, the half-wave resonator needs a different coating approach, in particular, a development of a secondary Sn source. We are commissioning a secondary Sn source in the coating system and expand the current coating system at JLab to coat complex cavity models.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM63

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paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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WEPLM64

High Dynamic Voltage Range Studies of Piezoelectric Multilayer Actuators at Low Temperatures

linac, cavity, operation, vacuum

739

C. Contreras-Martinez
FRIB, East Lansing, Michigan, USA
Y.M. Pischalnikov, J.C. Yun
Fermilab, Batavia, Illinois, USA

Piezo actuators are used for resonance control in superconducting linacs. In high accelerating gradients linacs, such as those operated in a pulsed mode, the piezos require a large operating voltage. This is due to the Lorentz forced detuning which causes a large frequency shift and is compensated with an active piezo-tuning system. In this high dynamic voltage range the piezo is expected to warm up drastically due to it being in an insulated vacuum. This study characterizes the dielectric properties (capacitance, dielectric losses), the piezo stroke (from geophone), and thermal properties such as heating. Results obtained in the temperature range of 20K to 300K will be presented and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM64

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paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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WEPLM73

Bunker Testing of FRIB Cryomodules

cavity, cryomodule, solenoid, dipole

765

W. Chang, S. Caton, A. Ganshyn, W. Hartung, S.H. Kim, B. Laumer, H. Maniar, J.T. Popielarski, K. Saito, M. Xu, T. Xu, C. Zhang, S. Zhao
FRIB, East Lansing, Michigan, USA

The FRIB superconducting driver Linac requires 10⁴ quarter-wave resonators (QWRs, β = 0.041, 0.085), 220 half-wave resonators (HWRs, β = 0.29, 0.53), and 74 superconducting solenoid packages. Resonators and solenoids are assembled into cryomodules; 4 accelerating and 2 matching cryomodule types are required. Each cryomodule undergoes cryogenic and RF testing in a bunker prior to installation in the tunnel. The cryomodule test verifies operation of the cavities, couplers, tuners, solenoid packages, magnetic shield, and thermal shield at 4.3 K and 2 K. All of the required cryomodules for β = 0.041, 0.085, and 0.29 have been tested and certified. As of May 2019, five of the β = 0.53 cryomodules have been certified; the remaining modules are being assembled or are in the queue for testing. Cryomodule test results will be presented, including cavity performance (accelerating gradient, field emission X-rays, multipacting conditioning); solenoid package operation (current, current-lead cooling flow rate); and cryomodule heat load (static and dynamic).

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM73

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paper received ※ 06 September 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019

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WEPLH09

FRIB Driver Linac Integration to be ready for Phased Beam Commissioning

MMI, cryomodule, cavity, linac

823

H. Ao, S. Beher, N.K. Bultman, F. Casagrande, C. Compton, J.C. Curtin, K.D. Davidson, K. Elliott, V. Ganni, A. Ganshyn, P.E. Gibson, I. Grender, W. Hartung, L. Hodges, K. Holland, A. Hussain, M. Ikegami, S. Jones, P. Knudsen, S.M. Lidia, G. Machicoane, S.J. Miller, D.G. Morris, P.N. Ostroumov, J.T. Popielarski, L. Popielarski, J. Priller, T. Russo, K. Saito, S. Stanley, D.R. Victory, X. Wang, J. Wei, M. Xu, T. Xu, Y. Yamazaki, S. Zhao
FRIB, East Lansing, Michigan, USA
A. Facco
INFN/LNL, Legnaro (PD), Italy
R.E. Laxdal
TRIUMF, Vancouver, Canada

Funding: Work supported by the U.S. Department of Energy (DOE) Office of Science under Cooperative Agreement DE-SC0000661
The driver linac for Facility for Rare Isotope Beams (FRIB) will accelerate all stable ion beams from proton to uranium beyond 200 MeV/u with beam powers up to 400 kW. The linac now consists of 10⁴ superconducting quarter-wave resonators (QWR), which is the world largest number of low-beta SRF cavities operating at an accelerator facility. The first 3 QWR cryomodules (CM) (β = 0.041) were successfully integrated with cryogenics and other support systems for the 2nd Accelerator Readiness Review (ARR). The 3rd ARR scope that includes 11 QWR CM (β=0.085) and 1 QWR matching CM (β=0.085) was commissioned on schedule by January 2019, and then we met the Key Performance Parameters (KPP), accelerating Ar and Kr > 16 MeV/u at this stage, in a week upon the ARR authorization. We examine a variety of key factors to the successful commissioning, such as component testing prior to system integration, assessment steps of system/device readiness, and phased commissioning. This paper also reports on the integration process of the β=0.085 CMs including the test results, and the current progress on β=0.29 and 0.53 CMs in preparation for the upcoming 4th ARR.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH09

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paper received ※ 02 September 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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