Author: Aderhold, S.
Paper Title Page
MOPMB063 Multipacting Processing in Cryomodules for LCLS-II and LCLS-II-HE 259
 
  • A.T. Cravatta, T.T. Arkan, D. Bafia, J.A. Kaluzny, S. Posen
    Fermilab, Batavia, Illinois, USA
  • S. Aderhold, M. Checchin, D. Gonnella, J. Hogan, J.T. Maniscalco, J. Nelson, R.D. Porter, L.M. Zacarias
    SLAC, Menlo Park, California, USA
  • M.A. Drury, H. Vennekate
    JLab, Newport News, VA, 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.
Multipacting (MP) is a phenomenon which can affect stability in particle accelerators and limit performance in superconducting radio frequency cavities. In the TESLA shaped, 1.3 GHz, 9-cell cavities used in the LCLS-II (L2) and LCLS-II-HE (HE) projects, the MP-band (~17-24 MV/m) lies within the required accelerating gradients. For HE, the operating gradient of 20.8 MV/m lies well within the MP-band and cryomodule testing has confirmed that this is an issue. As such, MP processing for the HE cryomodule test program will be discussed. Early results on MP processing in cryomodules installed in the L2 linac will also be presented, demonstrating that the methods used in cryomodule acceptance testing are also successful at conditioning MP in the accelerator and that this processing is preserved in the mid-term.
 
poster icon Poster MOPMB063 [1.066 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB063  
About • Received ※ 25 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 30 June 2023
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MOPMB072 LCLS-II-HE Cavity Qualification Testing 279
 
  • J.T. Maniscalco, S. Aderhold, M. Checchin, D. Gonnella, J. Hogan, R.D. Porter
    SLAC, Menlo Park, California, USA
  • T.T. Arkan, D. Bafia, A.T. Cravatta, J.A. Kaluzny, S. Posen
    Fermilab, Batavia, Illinois, USA
  • M.E. Bevins, A.J. Grabowski, C.E. Reece, H. Vennekate
    JLab, Newport News, VA, USA
 
  Acceptance testing of the LCLS-II-HE production cavities is approximately 65% complete. In this report, we present details of the test results, including summaries of the quench fields, intrinsic quality factors, and experience with field emission. We also offer an outlook on the remaining tests to be performed.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB072  
About • Received ※ 20 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 03 July 2023 — Issue date ※ 07 July 2023
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MOPMB081 Microphonics in the LCLS-II Superconducting Linac 302
 
  • R.D. Porter, S. Aderhold, L.E. Alsberg, D. Gonnella, J. Nelson, N.R. Neveu, L.M. Zacarias
    SLAC, Menlo Park, California, USA
  • A.T. Cravatta, J.P. Holzbauer, S. Posen
    Fermilab, Batavia, Illinois, USA
  • M.A. Drury, M.D. McCaughan, C.M. Wilson
    JLab, Newport News, Virginia, USA
  • G. Gaitan, N.A. Stilin
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: Work supported by the LCLS-II project
The LCLS-II project has installed a new superconducting linac at SLAC that consists of 35 1.3 GHz cryomodules and 2 3.9 GHz cryomodules. The linac will provide a 4 GeV electron beam for generating soft and hard X-ray pulses. Cavity detuning induced by microphonics was a significant design challenge for the LCLS-II cryomodules. Cryomodules were produced that were within the detuning specification (10 Hz for 1.3 GHz cryomodules) on test stands. Here we present first measurements of the microphonics in the installed LCLS-II superconducting linac. Overall, the microphonics in the linac are manageable with 94% of cavities coming within the detune specification. Only two cavities are gradient limited due to microphonics. We identify a leaking cool down valve as the source of microphonics limiting those two cavities.
 
poster icon Poster MOPMB081 [1.284 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB081  
About • Received ※ 18 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 30 June 2023 — Issue date ※ 01 July 2023
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MOPMB089 Installation of LCLS-II Cryomodules 324
 
  • D.A. White, S. Aderhold, R. Coy, D. Gonnella
    SLAC, Menlo Park, California, USA
 
  Funding: U.S. Department of Energy
The Linac Coherent Light Source II (LCLS-II) super-conducting accelerator is fully installed and operational. Cryomodules were designed and manufactured by Fermi National Accelerator Laboratory (FNAL) and Thomas Jefferson National Laboratory (JLab) during 2017-2020. From November 2018 through March 2021, SLAC Na-tional Accelerator Laboratory installed 37 Cryomodules. Full system cooldown was completed in March 2022. Installation processes were optimized at SLAC for best quality, especially during particle-free and UHV assem-bly. These processes and successful Cavity and Cry-omodule manufacturing resulted in installed gradient exceeding design requirements by more than 20%. No statistical variation in field emission onsets or magni-tudes were observed between manufacturing and site testing. This paper summarizes SLAC experience during installation, and relevant testing results.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB089  
About • Received ※ 20 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 15 July 2023
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MOPMB090 Measuring Q₀ in LCLS-II Cryomodules Using Helium Liquid Level 327
 
  • L.M. Zacarias, S. Aderhold, D. Gonnella, J.T. Maniscalco, J. Nelson, R.D. Porter
    SLAC, Menlo Park, California, USA
  • A.T. Cravatta, J.P. Holzbauer, S. Posen
    Fermilab, Batavia, Illinois, USA
  • M.A. Drury, M.D. McCaughan, C.M. Wilson
    JLab, Newport News, Virginia, USA
 
  The nitrogen-doped cavities used in the Linac Coherent Light Source II (LCLS-II) cryomodules have shown an unprecedented high Q₀ in vertical and cryomodule testing compared with cavities prepared with standard methods. While demonstration of high Q₀ in the test stand has been achieved, maintaining that performance in the linac is critical to the success of LCLS-II and future accelerator projects. The LCLS-II cryomodules required a novel method of measuring Q₀, due to hardware incompatibilities with existing procedures. Initially developed at Jefferson Lab during cryomodule acceptance testing before being used in the tunnel at SLAC, we use helium liquid level data to estimate the heat generated by cavities. We first establish the relationship between the rate of helium evaporation from known heat loads using electric heaters, and then use that relationship to determine heat from an RF load. Here we present the full procedure along with the development process, lessons learned, and reproducibility while demonstrating for the first time that world record Q₀ can be maintained within the real accelerator environment.  
poster icon Poster MOPMB090 [1.867 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB090  
About • Received ※ 20 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 30 June 2023 — Issue date ※ 13 July 2023
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WEPWB120 Flux Expulsion Testing for LCLS-II-HE Cavity Production 876
 
  • J.T. Maniscalco, S. Aderhold, M. Checchin, D. Gonnella, R.D. Porter
    SLAC, Menlo Park, California, USA
  • T.T. Arkan, D. Bafia, J.A. Kaluzny, S. Posen
    Fermilab, Batavia, Illinois, USA
  • M.E. Bevins, A.J. Grabowski, J. Hogan, C.E. Reece, D. Savransky, H. Vennekate
    JLab, Newport News, VA, USA
 
  Nitrogen-doped niobium SRF cavities are sensitive to trapped magnetic flux, which decreases the cavity intrinsic Q₀. Prior experimental results have shown that heat treatments to 900°C and higher can result in stronger flux expulsion during cooldown; the precise temperature required tends to vary by vendor lot/ingot of the niobium material used in the cavity cells. For LCLS-II-HE, to ensure sufficient flux expulsion in all cavities, we built and tested single-cell cavities to determine this required temperature for each vendor lot of niobium material to be used in cavity cells. In this report, we present the results of the single-cell flux expulsion testing and the Q₀ of the nine-cell cavities built using the characterized vendor lots. We discuss mixing material from different vendor lots, examine the lessons learned, and finally present an outlook on possible refinements to the single-cell technique.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB120  
About • Received ※ 15 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 03 July 2023 — Issue date ※ 13 July 2023
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