NAPAC2022 - List of Keywords (cryomodule)

Paper	Title	Other Keywords	Page
MOYE5	In Situ Plasma Processing of Superconducting Cavities at JLab	cavity, plasma, HOM, radiation	22
	T. Powers, N.C. Brock, T.D. Ganey JLab, Newport News, Virginia, USA
	Jefferson Lab has an ongoing R&D program in plasma processing which is close to going into production processing in the CEBAF accelerator. Plasma processing is a common technique for removing hydrocarbons from surfaces, which increases the work function and reduces the secondary emission coefficient. Unlike helium processing which relies on ion bombardment of the field emitters, plasma processing uses free oxygen produced in the plasma to break down the hydrocarbons on the surface of the cavity. The initial focus of the effort was processing C100 cavities by injecting RF power into the HOM coupler ports. Results from processing cryomodule in the cryomodule test bunker as well as vertical test results will be presented. We plan to start processing cryomodules in the CEBAF tunnel within the next year. The goal will be to improve the operational gradients and the energy margin of the linacs. This work will describe the systems and methods used at JLAB for processing cavities using an argon oxygen gas mixture. Before and after plasma processing results will also be presented.
	Slides MOYE5 [2.679 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOYE5
About •	Received ※ 01 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 01 October 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA12	Commissioning of HOM Detectors in the First Cryomodule of the LCLS-II Linac	HOM, cavity, MMI, alignment	69
	J.A. Diaz Cruz UNM-ECE, Albuquerque, USA B.T. Jacobson, N.R. Neveu, J.P. Sikora SLAC, Menlo Park, California, USA
	Long-range wakefields (LRWs) may cause emittance dilution effects. LWRs are especially unwanted at facilities with low emittance beams like the LCLS-II at SLAC. Dipolar higher-order modes (HOMs) are a set of LRWs that are excited by off-axis beams. Two 4-channel HOM detectors were built to measure the beam-induced HOM signals for TESLA-type superconducting RF (SRF) cavities; they were tested at the Fermilab Accelerator Science and Technology (FAST) facility and are now installed at SLAC. The HOM detectors were designed to investigate LRW effects on the beam and to help with beam alignment. This paper presents preliminary results of HOM measurements at the first cryomodule (CM01) of the LCLS-II linac and describes the relevant hardware and setup of the experiment.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA12
About •	Received ※ 09 August 2022 — Accepted ※ 20 August 2022 — Issue date ※ 31 August 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA23	Tests of the Extended Range SRF Cavity Tuners for the LCLS-II HE Project	cavity, operation, SRF, vacuum	100
	C. Contreras-Martinez, T.T. Arkan, A.T. Cravatta, B.D. Hartsell, J.A. Kaluzny, T.N. Khabiboulline, Y.M. Pischalnikov, S. Posen, G.V. Romanov, J.C. Yun Fermilab, Batavia, Illinois, USA
	The LCLS-II HE superconducting linac will produce multi-energy beams by supporting multiple undulator lines simultaneously. This could be achieved by using the cavity SRF tuner in the off-frequency detune mode. This off-frequency operation method was tested in the verification cryomodule (vCM) and CM 1 at Fermilab at 2 K. In both cases, the tuners achieved a frequency shift of -565±80 kHz. This study will discuss cavity frequency during each step as it is being assembled in the cryomodule string and finally when it is being tested at 2 K. Tracking the cavity frequency helped enable the tuners to reach this large frequency shift. The specific procedures of tuner setting during assembly will be presented.
	Poster MOPA23 [0.654 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA23
About •	Received ※ 03 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 19 August 2022 — Issue date ※ 31 August 2022
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MOPA24	LCLS-II and HE Cryomodule Microphonics at CMTF at Fermilab	cavity, cryogenics, SRF, niobium	103
	C. Contreras-Martinez, B.E. Chase, A.T. Cravatta, J.A. Einstein-Curtis, E.R. Harms, J.P. Holzbauer, J.N. Makara, S. Posen, R. Wang Fermilab, Batavia, Illinois, USA L.R. Doolittle LBNL, Berkeley, California, USA
	Microphonics causes the cavity to detune. This study discusses the microphonics of 16 cryomodules, 14 for LCLS-II and 2 for LCLS-II HE tested at CMTF. The peak detuning, as well as the RMS detuning for each cryomodule, will be discussed. For each cryomodule, the data was taken with enough soaking time to prevent any thermalization effects which can show up in the detuning. Each data capture taken was 30 minutes or longer and sampled at 1 kHz.
	Poster MOPA24 [1.428 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA24
About •	Received ※ 03 August 2022 — Revised ※ 10 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 20 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA83	Automation of Superconducting Cavity and Superconducting Magnet Operation for FRIB	cavity, operation, linac, solenoid	239
	W. Chang, Y. Choi, X.-J. Du, W. Hartung, S.H. Kim, T. Konomi, S.R. Kunjir, H. Nguyen, J.T. Popielarski, K. Saito, T. Xu, S. Zhao FRIB, East Lansing, Michigan, USA
	The superconducting (SC) 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 SC cavities and 69 SC solenoid packages. For linac operation with high availability and high reliability, automation is essential for such tasks as fast device turn-on/off, fast recovery from trips, and real-time monitoring of operational performance. We have implemented several automation algorithms, including one-button turn-on/off of SC cavities and SC magnets; automated degaussing of SC solenoids; mitigation of field emission-induced multipacting during recovery from cavity trips; and real-time monitoring of the cavity field level calibration. The design, development, and operating experience with automation will be presented.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA83
About •	Received ※ 02 August 2022 — Revised ※ 03 August 2022 — Accepted ※ 06 August 2022 — Issue date ※ 26 August 2022
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MOPA84	Superconducting Cavity Commissioning for the FRIB Linac	cavity, MMI, controls, linac	242
	W. Chang, W. Hartung, S.H. Kim, T. Konomi, S.R. Kunjir, J.T. Popielarski, K. Saito, T. Xu, S. Zhao FRIB, East Lansing, Michigan, USA
	The superconducting driver linac for the Facility for Rare Isotope Beams (FRIB) is a heavy ion accelerator that has 46 cryomodules with 324 superconducting (SC) cavities that accelerate ions to 200 MeV per nucleon. Linac commissioning was done in multiple phases, in parallel with technical installation. Ion beam have now been accelerated to the design energy through the full linac; rare isotopes were first produced in December 2021; and the first user experiment was completed in May 2022. All cryomodules were successfully commissioned. Cryomodule commissioning included establishing the desired cavity fields, measuring field emission X-rays, optimizing the tuner control loops, measuring the cavity dynamic heat load, and confirming the low-level RF control (amplitude and phase stability). Results on cryomodule commissioning and cryomodule performance will be presented.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA84
About •	Received ※ 13 July 2022 — Revised ※ 02 August 2022 — Accepted ※ 13 August 2022 — Issue date ※ 05 September 2022
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MOPA86	Conditioning of Low-Field Multipacting Barriers in Superconducting Quarter-Wave Resonators	cavity, coupling, multipactoring, electron	249
	S.H. Kim, W. Chang, W. Hartung, J.T. Popielarski, T. Xu FRIB, East Lansing, Michigan, USA
	Funding: This is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University. Multipacting (MP) barriers are typically observed at very low RF amplitude, at a field 2 to 3 orders of magnitude below the operating gradient, in low-frequency (<~100 MHz), quarter-wave resonators (QWRs). Such barriers may be troublesome, as RF conditioning with a fundamental power coupler (FPC) of typical coupling strength (external Q = 10⁶ to 10⁷) is generally difficult. For the FRIB \beta = 0.085 QWRs (80.5 MHz), the low barrier is observed at an accelerating gradient (E_acc) of ~10 kV/m; the operating E_acc is 5.6 MV/m. Theoretical and simulation studies suggested that the conditioning is difficult due to the relatively low RF power dissipated into multipacting rather than being a problem of the low barrier being stronger than other barriers. We developed a single-stub coaxial FPC matching element for external adjustment of the external Q by one order of magnitude. The matching element provided a significant reduction in the time to condition the low barrier. We will present theoretical and simulation studies of the low MP barrier and experimental results on MP conditioning with the single-stub FPC matching element.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA86
About •	Received ※ 03 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 21 August 2022
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MOPA91	Plasma Processing of Superconducting Quarter-Wave Resonators Using a Higher-Order Mode	plasma, cavity, SRF, HOM	267
	W. Hartung, W. Chang, K. Elliott, S.H. Kim, T. Konomi, J.T. Popielarski, K. Saito, T. Xu FRIB, East Lansing, Michigan, USA
	The Facility for Rare Isotope Beams (FRIB) is a superconducting ion linac with acceleration provided by 104 quarter-wave resonators (QWRs) and 220 half-wave resonators (HWRs); FRIB user operations began in May 2022. Plasma cleaning is being developed as a method to mitigate possible future degradation of QWR or HWR performance: in-situ plasma cleaning represents an alternative to removal and disassembly of cryomodules for refurbishment of each cavity via repeat etching and rinsing. Initial measurements were done on a QWR and an HWR with room-temperature-matched input couplers to drive the plasma via the fundamental mode. Subsequent plasma cleaning tests were done on two additional FRIB QWRs using the fundamental power coupler (FPC) to drive the plasma. When using the FPC, a higher-order mode (HOM) at 5 times the accelerating mode frequency was used to drive the plasma. Use of the HOM allowed for less mismatch at the FPC and hence lower field in the coupler relative to the cavity. A neon-oxygen gas mixture was used for plasma generation. Before and after cold tests showed a significant reduction in field emission X-rays after plasma cleaning. Results will be presented.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA91
About •	Received ※ 12 August 2022 — Revised ※ 16 August 2022 — Accepted ※ 25 August 2022 — Issue date ※ 16 September 2022
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WEYE2	Upgrade of the FRIB ReAccelerator	experiment, cavity, MMI, ion-source	572
	A.C.C. Villari, B. Arend, G. Bollen, D.B. Crisp, K.D. Davidson, K. Fukushima, A.I. Henriques, K. Holland, S.H. Kim, A. Lapierre, Y. Liu, T. Maruta, D.G. Morris, S. Nash, P.N. Ostroumov, A.S. Plastun, J. Priller, S. Schwarz, B.M. Sherrill, M. Steiner, C. Sumithrarachchi, R. Walker, T. Zhang, Q. Zhao FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the NSF under grant PHY15-65546 and DOE-SC under award number DE-SC0000661 The reaccelerator facility at FRIB was upgraded to provide new science opportunities. The upgrade included a new ion source to produce stable and long livied rare isotopes in a batch mode, a new room-temperature rebuncher, a new β = 0.085 quarter-wave-resonator cryomodule to increase the beam energy from 3 MeV/u to 6 MeV/u for ions with a charge-to-mass ratio of 1/4, and a new experimental vault with beamlines.
	Slides WEYE2 [4.220 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEYE2
About •	Received ※ 13 July 2022 — Revised ※ 01 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 10 August 2022
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WEPA03	Status of the SLAC/MSU SRF Gun Development Project	cathode, gun, cavity, SRF	623
	J.W. Lewellen, C. Adolphsen, R. Coy, L. Ge, F. Ji, M.J. Murphy, L. Xiao SLAC, Menlo Park, California, USA A. Arnold, S. Gatzmaga, P. Murcek, R. Xiang HZDR, Dresden, Germany Y. Choi, C. Compton, X.-J. Du, D.B. Greene, W. Hartung, S.H. Kim, T. Konomi, S.J. Miller, D.G. Morris, M.S. Patil, J.T. Popielarski, L. Popielarski, K. Saito, T. Xu FRIB, East Lansing, Michigan, USA M.P. Kelly, T.B. Petersen ANL, Lemont, Illinois, USA
	Funding: US Department of Energy. The LCLS-II-HE project at SLAC is intended to increase the photon energy reach of the LCLS-II FEL to at least 20 keV. In addition to upgrading the undulator system, and increasing the electron beam energy to 8 GeV, the project will also construct a low-emittance injector (LEI) in a new tunnel. To achieve the LEI emittance goals, a low-MTE photocathode will be required, as will on-cathode electric fields up to 50% higher than those achievable in the current LCLS-II photoinjector. The beam source for the LEI will be based around a superconducting quarterwave cavity resonant at 185.7 MHz. A prototype gun is currently being designed and fabricated at the Facility for Rare Isotope Beams (FRIB) at Michigan State University. This paper presents the performance goals for the new gun design, an overview of the prototype development effort, current status, and future plans including fabrication of a "production" gun for the LEI.
	Poster WEPA03 [4.510 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA03
About •	Received ※ 21 July 2022 — Revised ※ 28 July 2022 — Accepted ※ 08 August 2022 — Issue date ※ 11 August 2022
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WEPA12	Operational Experience of the New Booster Cryomodule at the Upgraded Injector Test Facility	cavity, booster, simulation, experiment	640
	M.W. Bruker, R. Bachimanchi, J.M. Grames, M.D. McCaughan, J. Musson, P.D. Owen, T.E. Plawski, M. Poelker, T. Powers, H. Wang, Y.W. Wang JLab, Newport News, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. Since the early 1990s, the injector of the CEBAF accelerator at Jefferson Lab has relied on a normal-conducting RF graded-beta capture section to boost the kinetic energy of the electron beam from 100 / 130 keV to 600 keV for subsequent acceleration using a cryomodule housing two superconducting 5-cell cavities similar to those used throughout the accelerator. To simplify the injector design and improve the beam quality, the normal-conducting RF capture section and the cryomodule will be replaced with a new single booster cryomodule employing a superconducting, β = 0.6, 2-cell-cavity capture section and a single, β = 0.97, 7-cell cavity. The Upgraded Injector Test Facility at Jefferson Lab is currently hosting the new cryomodule to evaluate its performance with beam before installation at CEBAF. While demonstrating satisfactory performance of the booster and good agreement with simulations, our beam test results also speak to limitations of accelerator operations in a noisy, thermally unregulated environment.
	Poster WEPA12 [3.726 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA12
About •	Received ※ 03 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 06 September 2022
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WEPA19	HE Production Update at JLab - Introducing an Enhanced Nitrogen Purge for Clean String Assembly	cavity, controls, vacuum, hardware	659
	P.D. Owen JLab, Newport News, Virginia, USA
	A major limitation to cryomodule performance is field emission caused by particulates within the superconducting cavities. To reduce contamination of the inner surfaces during assembly in a cleanroom, the whole string can be connected to a purge system, which maintains a constant overpressure of dry, clean nitrogen gas. Following successes of similar systems at XFEL and Fermilab, Jefferson Lab followed this example for the production of LCLS-II HE cryomodules. Implementing this system required new procedures, infrastructure, and hardware, as well as significant testing of the system before production began. This paper will summarize the implemented controls and procedures, including lessons learned from Fermilab, as well as the results of mock-up tests. Based on the latter, the system was used to assemble the first article string in April 2022, and was also used during a rework required due to issues with cold FPC ceramics two months later. The benefits of using a purge system with regards to procedure, time savings, and added flexibility for potential rework have already proven to provide a significant improvement for the production of LCLS-II-HE cryomodules at Jefferson Lab.
	Poster WEPA19 [1.538 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA19
About •	Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 21 August 2022
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WEPA29	Real-Time Cavity Fault Prediction in CEBAF Using Deep Learning	cavity, network, SRF, experiment	687
	M. Rahman, K.M. Iftekharuddin ODU, Norfolk, Virginia, USA A. Carpenter, T.S. McGuckin, C. Tennant, L.S. Vidyaratne JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Data-driven prediction of future faults is a major research area for many industrial applications. In this work, we present a new procedure of real-time fault prediction for superconducting radio-frequency (SRF) cavities at the Continuous Electron Beam Accelerator Facility (CEBAF) using deep learning. CEBAF has been afflicted by frequent downtime caused by SRF cavity faults. We perform fault prediction using pre-fault RF signals from C100-type cryomodules. Using the pre-fault signal information, the new algorithm predicts the type of cavity fault before the actual onset. The early prediction may enable potential mitigation strategies to prevent the fault. In our work, we apply a two-stage fault prediction pipeline. In the first stage, a model distinguishes between faulty and normal signals using a U-Net deep learning architecture. In the second stage of the network, signals flagged as faulty by the first model are classified into one of seven fault types based on learned signatures in the data. Initial results show that our model can successfully predict most fault types 200 ms before onset. We will discuss reasons for poor model performance on specific fault types.
	Poster WEPA29 [1.339 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA29
About •	Received ※ 02 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 17 August 2022
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THZD6	An 8 GeV Linac as the Booster Replacement in the Fermilab Power Upgrade	linac, injection, cavity, SRF	897
	D.V. Neuffer, S.A. Belomestnykh, M. Checchin, D.E. Johnson, S. Posen, E. Pozdeyev, V.S. Pronskikh, A. Saini, N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: Work supported by the Fermi National Accelerator Laboratory, managed and operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. Increasing the Main Injector (MI) beam power above ~1.2 MW requires replacement of the 8-GeV Booster by a higher intensity alternative. In the Project X era, rapid-cycling synchrotron (RCS) and linac solutions were considered for this purpose. In this paper, we consider the linac version that produces 8 GeV H⁻ beam for injection into the Recycler Ring (RR) or Main Injector (MI). The linac takes ~1-GeV beam from the PIP-II Linac and accelerates it to ~2 GeV in a 650-MHz SRF linac, followed by a 8-GeV pulsed linac using 1300 MHz cryomodules. The linac components incorporate recent improvements in SRF technology. Research needed to implement the high power SRF Linac is described.
	Slides THZD6 [4.078 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THZD6
About •	Received ※ 03 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 04 October 2022
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Paper

Title

Other Keywords

Page

MOYE5

In Situ Plasma Processing of Superconducting Cavities at JLab

cavity, plasma, HOM, radiation

22

T. Powers, N.C. Brock, T.D. Ganey
JLab, Newport News, Virginia, USA

Jefferson Lab has an ongoing R&D program in plasma processing which is close to going into production processing in the CEBAF accelerator. Plasma processing is a common technique for removing hydrocarbons from surfaces, which increases the work function and reduces the secondary emission coefficient. Unlike helium processing which relies on ion bombardment of the field emitters, plasma processing uses free oxygen produced in the plasma to break down the hydrocarbons on the surface of the cavity. The initial focus of the effort was processing C100 cavities by injecting RF power into the HOM coupler ports. Results from processing cryomodule in the cryomodule test bunker as well as vertical test results will be presented. We plan to start processing cryomodules in the CEBAF tunnel within the next year. The goal will be to improve the operational gradients and the energy margin of the linacs. This work will describe the systems and methods used at JLAB for processing cavities using an argon oxygen gas mixture. Before and after plasma processing results will also be presented.

Slides MOYE5 [2.679 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOYE5

About •

Received ※ 01 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 01 October 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA12

Commissioning of HOM Detectors in the First Cryomodule of the LCLS-II Linac

HOM, cavity, MMI, alignment

69

J.A. Diaz Cruz
UNM-ECE, Albuquerque, USA
B.T. Jacobson, N.R. Neveu, J.P. Sikora
SLAC, Menlo Park, California, USA

Long-range wakefields (LRWs) may cause emittance dilution effects. LWRs are especially unwanted at facilities with low emittance beams like the LCLS-II at SLAC. Dipolar higher-order modes (HOMs) are a set of LRWs that are excited by off-axis beams. Two 4-channel HOM detectors were built to measure the beam-induced HOM signals for TESLA-type superconducting RF (SRF) cavities; they were tested at the Fermilab Accelerator Science and Technology (FAST) facility and are now installed at SLAC. The HOM detectors were designed to investigate LRW effects on the beam and to help with beam alignment. This paper presents preliminary results of HOM measurements at the first cryomodule (CM01) of the LCLS-II linac and describes the relevant hardware and setup of the experiment.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA12

About •

Received ※ 09 August 2022 — Accepted ※ 20 August 2022 — Issue date ※ 31 August 2022

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA23

Tests of the Extended Range SRF Cavity Tuners for the LCLS-II HE Project

cavity, operation, SRF, vacuum

100

C. Contreras-Martinez, T.T. Arkan, A.T. Cravatta, B.D. Hartsell, J.A. Kaluzny, T.N. Khabiboulline, Y.M. Pischalnikov, S. Posen, G.V. Romanov, J.C. Yun
Fermilab, Batavia, Illinois, USA

The LCLS-II HE superconducting linac will produce multi-energy beams by supporting multiple undulator lines simultaneously. This could be achieved by using the cavity SRF tuner in the off-frequency detune mode. This off-frequency operation method was tested in the verification cryomodule (vCM) and CM 1 at Fermilab at 2 K. In both cases, the tuners achieved a frequency shift of -565±80 kHz. This study will discuss cavity frequency during each step as it is being assembled in the cryomodule string and finally when it is being tested at 2 K. Tracking the cavity frequency helped enable the tuners to reach this large frequency shift. The specific procedures of tuner setting during assembly will be presented.

Poster MOPA23 [0.654 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA23

About •

Received ※ 03 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 19 August 2022 — Issue date ※ 31 August 2022

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA24

LCLS-II and HE Cryomodule Microphonics at CMTF at Fermilab

cavity, cryogenics, SRF, niobium

103

C. Contreras-Martinez, B.E. Chase, A.T. Cravatta, J.A. Einstein-Curtis, E.R. Harms, J.P. Holzbauer, J.N. Makara, S. Posen, R. Wang
Fermilab, Batavia, Illinois, USA
L.R. Doolittle
LBNL, Berkeley, California, USA

Microphonics causes the cavity to detune. This study discusses the microphonics of 16 cryomodules, 14 for LCLS-II and 2 for LCLS-II HE tested at CMTF. The peak detuning, as well as the RMS detuning for each cryomodule, will be discussed. For each cryomodule, the data was taken with enough soaking time to prevent any thermalization effects which can show up in the detuning. Each data capture taken was 30 minutes or longer and sampled at 1 kHz.

Poster MOPA24 [1.428 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA24

About •

Received ※ 03 August 2022 — Revised ※ 10 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 20 September 2022

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA83

Automation of Superconducting Cavity and Superconducting Magnet Operation for FRIB

cavity, operation, linac, solenoid

239

W. Chang, Y. Choi, X.-J. Du, W. Hartung, S.H. Kim, T. Konomi, S.R. Kunjir, H. Nguyen, J.T. Popielarski, K. Saito, T. Xu, S. Zhao
FRIB, East Lansing, Michigan, USA

The superconducting (SC) 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 SC cavities and 69 SC solenoid packages. For linac operation with high availability and high reliability, automation is essential for such tasks as fast device turn-on/off, fast recovery from trips, and real-time monitoring of operational performance. We have implemented several automation algorithms, including one-button turn-on/off of SC cavities and SC magnets; automated degaussing of SC solenoids; mitigation of field emission-induced multipacting during recovery from cavity trips; and real-time monitoring of the cavity field level calibration. The design, development, and operating experience with automation will be presented.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA83

About •

Received ※ 02 August 2022 — Revised ※ 03 August 2022 — Accepted ※ 06 August 2022 — Issue date ※ 26 August 2022

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MOPA84

Superconducting Cavity Commissioning for the FRIB Linac

cavity, MMI, controls, linac

242

W. Chang, W. Hartung, S.H. Kim, T. Konomi, S.R. Kunjir, J.T. Popielarski, K. Saito, T. Xu, S. Zhao
FRIB, East Lansing, Michigan, USA

The superconducting driver linac for the Facility for Rare Isotope Beams (FRIB) is a heavy ion accelerator that has 46 cryomodules with 324 superconducting (SC) cavities that accelerate ions to 200 MeV per nucleon. Linac commissioning was done in multiple phases, in parallel with technical installation. Ion beam have now been accelerated to the design energy through the full linac; rare isotopes were first produced in December 2021; and the first user experiment was completed in May 2022. All cryomodules were successfully commissioned. Cryomodule commissioning included establishing the desired cavity fields, measuring field emission X-rays, optimizing the tuner control loops, measuring the cavity dynamic heat load, and confirming the low-level RF control (amplitude and phase stability). Results on cryomodule commissioning and cryomodule performance will be presented.

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA84

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Received ※ 13 July 2022 — Revised ※ 02 August 2022 — Accepted ※ 13 August 2022 — Issue date ※ 05 September 2022

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MOPA86

Conditioning of Low-Field Multipacting Barriers in Superconducting Quarter-Wave Resonators

cavity, coupling, multipactoring, electron

249

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

Funding: This is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University.
Multipacting (MP) barriers are typically observed at very low RF amplitude, at a field 2 to 3 orders of magnitude below the operating gradient, in low-frequency (<~100 MHz), quarter-wave resonators (QWRs). Such barriers may be troublesome, as RF conditioning with a fundamental power coupler (FPC) of typical coupling strength (external Q = 10⁶ to 10⁷) is generally difficult. For the FRIB \beta = 0.085 QWRs (80.5 MHz), the low barrier is observed at an accelerating gradient (E_acc) of ~10 kV/m; the operating E_acc is 5.6 MV/m. Theoretical and simulation studies suggested that the conditioning is difficult due to the relatively low RF power dissipated into multipacting rather than being a problem of the low barrier being stronger than other barriers. We developed a single-stub coaxial FPC matching element for external adjustment of the external Q by one order of magnitude. The matching element provided a significant reduction in the time to condition the low barrier. We will present theoretical and simulation studies of the low MP barrier and experimental results on MP conditioning with the single-stub FPC matching element.

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA86

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Received ※ 03 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 21 August 2022

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MOPA91

Plasma Processing of Superconducting Quarter-Wave Resonators Using a Higher-Order Mode

plasma, cavity, SRF, HOM

267

W. Hartung, W. Chang, K. Elliott, S.H. Kim, T. Konomi, J.T. Popielarski, K. Saito, T. Xu
FRIB, East Lansing, Michigan, USA

The Facility for Rare Isotope Beams (FRIB) is a superconducting ion linac with acceleration provided by 104 quarter-wave resonators (QWRs) and 220 half-wave resonators (HWRs); FRIB user operations began in May 2022. Plasma cleaning is being developed as a method to mitigate possible future degradation of QWR or HWR performance: in-situ plasma cleaning represents an alternative to removal and disassembly of cryomodules for refurbishment of each cavity via repeat etching and rinsing. Initial measurements were done on a QWR and an HWR with room-temperature-matched input couplers to drive the plasma via the fundamental mode. Subsequent plasma cleaning tests were done on two additional FRIB QWRs using the fundamental power coupler (FPC) to drive the plasma. When using the FPC, a higher-order mode (HOM) at 5 times the accelerating mode frequency was used to drive the plasma. Use of the HOM allowed for less mismatch at the FPC and hence lower field in the coupler relative to the cavity. A neon-oxygen gas mixture was used for plasma generation. Before and after cold tests showed a significant reduction in field emission X-rays after plasma cleaning. Results will be presented.

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA91

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Received ※ 12 August 2022 — Revised ※ 16 August 2022 — Accepted ※ 25 August 2022 — Issue date ※ 16 September 2022

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WEYE2

Upgrade of the FRIB ReAccelerator

experiment, cavity, MMI, ion-source

572

A.C.C. Villari, B. Arend, G. Bollen, D.B. Crisp, K.D. Davidson, K. Fukushima, A.I. Henriques, K. Holland, S.H. Kim, A. Lapierre, Y. Liu, T. Maruta, D.G. Morris, S. Nash, P.N. Ostroumov, A.S. Plastun, J. Priller, S. Schwarz, B.M. Sherrill, M. Steiner, C. Sumithrarachchi, R. Walker, T. Zhang, Q. Zhao
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the NSF under grant PHY15-65546 and DOE-SC under award number DE-SC0000661
The reaccelerator facility at FRIB was upgraded to provide new science opportunities. The upgrade included a new ion source to produce stable and long livied rare isotopes in a batch mode, a new room-temperature rebuncher, a new β = 0.085 quarter-wave-resonator cryomodule to increase the beam energy from 3 MeV/u to 6 MeV/u for ions with a charge-to-mass ratio of 1/4, and a new experimental vault with beamlines.

Slides WEYE2 [4.220 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEYE2

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Received ※ 13 July 2022 — Revised ※ 01 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 10 August 2022

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WEPA03

Status of the SLAC/MSU SRF Gun Development Project

cathode, gun, cavity, SRF

623

J.W. Lewellen, C. Adolphsen, R. Coy, L. Ge, F. Ji, M.J. Murphy, L. Xiao
SLAC, Menlo Park, California, USA
A. Arnold, S. Gatzmaga, P. Murcek, R. Xiang
HZDR, Dresden, Germany
Y. Choi, C. Compton, X.-J. Du, D.B. Greene, W. Hartung, S.H. Kim, T. Konomi, S.J. Miller, D.G. Morris, M.S. Patil, J.T. Popielarski, L. Popielarski, K. Saito, T. Xu
FRIB, East Lansing, Michigan, USA
M.P. Kelly, T.B. Petersen
ANL, Lemont, Illinois, USA

Funding: US Department of Energy.
The LCLS-II-HE project at SLAC is intended to increase the photon energy reach of the LCLS-II FEL to at least 20 keV. In addition to upgrading the undulator system, and increasing the electron beam energy to 8 GeV, the project will also construct a low-emittance injector (LEI) in a new tunnel. To achieve the LEI emittance goals, a low-MTE photocathode will be required, as will on-cathode electric fields up to 50% higher than those achievable in the current LCLS-II photoinjector. The beam source for the LEI will be based around a superconducting quarterwave cavity resonant at 185.7 MHz. A prototype gun is currently being designed and fabricated at the Facility for Rare Isotope Beams (FRIB) at Michigan State University. This paper presents the performance goals for the new gun design, an overview of the prototype development effort, current status, and future plans including fabrication of a "production" gun for the LEI.

Poster WEPA03 [4.510 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA03

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Received ※ 21 July 2022 — Revised ※ 28 July 2022 — Accepted ※ 08 August 2022 — Issue date ※ 11 August 2022

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WEPA12

Operational Experience of the New Booster Cryomodule at the Upgraded Injector Test Facility

cavity, booster, simulation, experiment

640

M.W. Bruker, R. Bachimanchi, J.M. Grames, M.D. McCaughan, J. Musson, P.D. Owen, T.E. Plawski, M. Poelker, T. Powers, H. Wang, Y.W. Wang
JLab, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Since the early 1990s, the injector of the CEBAF accelerator at Jefferson Lab has relied on a normal-conducting RF graded-beta capture section to boost the kinetic energy of the electron beam from 100 / 130 keV to 600 keV for subsequent acceleration using a cryomodule housing two superconducting 5-cell cavities similar to those used throughout the accelerator. To simplify the injector design and improve the beam quality, the normal-conducting RF capture section and the cryomodule will be replaced with a new single booster cryomodule employing a superconducting, β = 0.6, 2-cell-cavity capture section and a single, β = 0.97, 7-cell cavity. The Upgraded Injector Test Facility at Jefferson Lab is currently hosting the new cryomodule to evaluate its performance with beam before installation at CEBAF. While demonstrating satisfactory performance of the booster and good agreement with simulations, our beam test results also speak to limitations of accelerator operations in a noisy, thermally unregulated environment.

Poster WEPA12 [3.726 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA12

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Received ※ 03 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 06 September 2022

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WEPA19

HE Production Update at JLab - Introducing an Enhanced Nitrogen Purge for Clean String Assembly

cavity, controls, vacuum, hardware

659

P.D. Owen
JLab, Newport News, Virginia, USA

A major limitation to cryomodule performance is field emission caused by particulates within the superconducting cavities. To reduce contamination of the inner surfaces during assembly in a cleanroom, the whole string can be connected to a purge system, which maintains a constant overpressure of dry, clean nitrogen gas. Following successes of similar systems at XFEL and Fermilab, Jefferson Lab followed this example for the production of LCLS-II HE cryomodules. Implementing this system required new procedures, infrastructure, and hardware, as well as significant testing of the system before production began. This paper will summarize the implemented controls and procedures, including lessons learned from Fermilab, as well as the results of mock-up tests. Based on the latter, the system was used to assemble the first article string in April 2022, and was also used during a rework required due to issues with cold FPC ceramics two months later. The benefits of using a purge system with regards to procedure, time savings, and added flexibility for potential rework have already proven to provide a significant improvement for the production of LCLS-II-HE cryomodules at Jefferson Lab.

Poster WEPA19 [1.538 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA19

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Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 21 August 2022

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WEPA29

Real-Time Cavity Fault Prediction in CEBAF Using Deep Learning

cavity, network, SRF, experiment

687

M. Rahman, K.M. Iftekharuddin
ODU, Norfolk, Virginia, USA
A. Carpenter, T.S. McGuckin, C. Tennant, L.S. Vidyaratne
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Data-driven prediction of future faults is a major research area for many industrial applications. In this work, we present a new procedure of real-time fault prediction for superconducting radio-frequency (SRF) cavities at the Continuous Electron Beam Accelerator Facility (CEBAF) using deep learning. CEBAF has been afflicted by frequent downtime caused by SRF cavity faults. We perform fault prediction using pre-fault RF signals from C100-type cryomodules. Using the pre-fault signal information, the new algorithm predicts the type of cavity fault before the actual onset. The early prediction may enable potential mitigation strategies to prevent the fault. In our work, we apply a two-stage fault prediction pipeline. In the first stage, a model distinguishes between faulty and normal signals using a U-Net deep learning architecture. In the second stage of the network, signals flagged as faulty by the first model are classified into one of seven fault types based on learned signatures in the data. Initial results show that our model can successfully predict most fault types 200 ms before onset. We will discuss reasons for poor model performance on specific fault types.

Poster WEPA29 [1.339 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA29

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Received ※ 02 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 17 August 2022

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THZD6

An 8 GeV Linac as the Booster Replacement in the Fermilab Power Upgrade

linac, injection, cavity, SRF

897

D.V. Neuffer, S.A. Belomestnykh, M. Checchin, D.E. Johnson, S. Posen, E. Pozdeyev, V.S. Pronskikh, A. Saini, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: Work supported by the Fermi National Accelerator Laboratory, managed and operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
Increasing the Main Injector (MI) beam power above ~1.2 MW requires replacement of the 8-GeV Booster by a higher intensity alternative. In the Project X era, rapid-cycling synchrotron (RCS) and linac solutions were considered for this purpose. In this paper, we consider the linac version that produces 8 GeV H⁻ beam for injection into the Recycler Ring (RR) or Main Injector (MI). The linac takes ~1-GeV beam from the PIP-II Linac and accelerates it to ~2 GeV in a 650-MHz SRF linac, followed by a 8-GeV pulsed linac using 1300 MHz cryomodules. The linac components incorporate recent improvements in SRF technology. Research needed to implement the high power SRF Linac is described.

Slides THZD6 [4.078 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THZD6

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Received ※ 03 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 04 October 2022

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