Author: Mitchell, A.L.A.
Paper Title Page
MOPTEV014 New Improved Horizontal Electropolishing System for SRF Cavities 237
 
  • C.E. Reece, S. Castagnola, P. Denny, A.L.A. Mitchell
    JLab, Newport News, Virginia, USA
 
  Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OThR23177.
The best performance of niobium SRF accelerating cavities is obtained with surfaces smoothed with electropolishing chemical finishing. Jefferson Lab has recently specified, procured, installed, and commissioned a new versatile production electropolishing (EP) tool. Experience with EP research and operations at JLab as well as vendor interactions and experience guided development of the system specification. Detailed design and fabrication was awarded by contract to Semiconductor Process Equipment Corporation (SPEC). The delivered system was integrated into the JLab chemroom infrastructure and commissioned in 2020. The new EP tool provides much improved heat exchange from the circulating H2SO4/HF electrolyte and also the cavity via variable temperature external cooling water flow, resulting in quite uniform cavity wall temperature control and thus improved removal uniformity. With the JLab infrastructure, stabilized process temperature as low as 5 C is available. We describe the system and illustrate operational modes in this contribution.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPTEV014  
About • Received ※ 21 June 2021 — Revised ※ 08 July 2021 — Accepted ※ 19 August 2021 — Issue date ※ 31 March 2022
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MOPCAV001 Cavity Production and Testing of the First C75 Cryomodule for CEBAF 250
 
  • G. Ciovati, G. Cheng, E. Daly, G.K. Davis, M.A. Drury, J.F. Fischer, D. Forehand, K. Macha, F. Marhauser, E.A. McEwen, A.L.A. Mitchell, A.V. Reilly, R.A. Rimmer, S. Wang
    JLab, Newport News, Virginia, USA
 
  Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
The CEBAF cryomodule rework program was updated over the last few years to increase the energy gain of refurbished cryomodules to 75 MeV. The concept recycles the waveguide end-groups from original CEBAF cavities fabricated in the 1990s and replaces the five elliptical cells in each with a new optimized cell shape fabricated from large-grain, ingot Nb material. Eight cavities were fabricated at Research Instruments, Germany, and two cavities were built at Jefferson Lab. Each cavity was processed by electropolishing and tested at 2.07 K. The best eight cavities were assembled into ’cavity pairs’ and re-tested at 2.07 K, before assembly into the cryomodule. All but one cavity in the cryomodule were within 10% of the target accelerating gradient of 19 MV/m with a quality factor of 8·109. The performance limitations were field emission and multipacting.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV001  
About • Received ※ 17 June 2021 — Accepted ※ 21 February 2022 — Issue date; ※ 10 April 2022  
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MOPCAV005 Status of SNS Proton Power Upgrade SRF Cavities Production Qualification 265
 
  • P. Dhakal, E. Daly, G.K. Davis, J.F. Fischer, D. Forehand, N.A. Huque, A.L.A. Mitchell, P.D. Owen
    JLab, Newport News, Virginia, USA
  • M.P. Howell, S.-H. Kim, J.D. Mammosser
    ORNL, Oak Ridge, Tennessee, USA
 
  The Proton Power Upgrade project at Oak Ridge National Lab’s Spallation Neutron Source (SNS PPU) currently being constructed will double the proton beam power from 1.4 to 2.8 MW by adding 7 additional cryomodules, each contains four six-cell high beta (\beta = 0.81) superconducting radio frequency cavities. The cavities were built by Research Instruments, Germany, with all the cavity processing done at the vendor site, including electropolishing as the final active chemistry step. All 28 cavities needed for 7 cryomodules were delivered to Jefferson Lab, ready to be tested. The cryogenic RF qualifications and helium vessel welding were done at Jefferson Lab. The performance largely exceed the requirements, and greatly exceeded the performance of the original SNS cavity production series. Here, we present the summary of RF test on production cavities to this date.
This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
 
poster icon Poster MOPCAV005 [1.061 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV005  
About • Received ※ 19 June 2021 — Revised ※ 10 July 2021 — Accepted ※ 12 March 2022 — Issue date ※ 06 April 2022
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