Author: Davis, G.K.
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TUP034 Microphonics Testing of LCLS II Cryomodules at Jefferson Lab 493
  • T. Powers, N.C. Brock, G.K. Davis
    JLab, Newport News, Virginia, USA
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Jefferson Lab is partnering with Fermilab to build the 36 cryomodules for the LCLS II accelerator that will be installed at SLAC. The cavities have design loaded-Q of 4×107, which means that it has a control bandwidth of 16 Hz. The JLab prototype cryomodule was instrumented with a series of seven accelerometers, and impulse hammer response measurements were made while the cryomodule was being built and after it was installed in the JLab cryomodule test facility. This was done so that we could understand the shapes of the modes of the structure. These results were compared to impulse hammer testing from the outside of the cryomodule and to individual cavity frequency shifts when the cryomodule was cold. The prototype cryomodule had excessive microphonics of 150 Hz peak due to a thermos-acoustic oscillation. Design modifications were implemented and subsequently the cryomodules had microphonics on the order of 10 to 20 Hz. Results of the modal analysis as well as the background microphonics observed when operated under various cryogenic conditions and with different modifications will be presented.
DOI • reference for this paper ※  
About • paper received ※ 21 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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FRCAA3 Industrial Cavity Production: Lessons Learned to Push the Boundaries of Nitrogen-Doping 1199
  • D. Gonnella, S. Aderhold, A. Burrill, M.C. Ross
    SLAC, Menlo Park, California, USA
  • E. Daly, G.K. Davis, F. Marhauser, A.D. Palczewski, K.M. Wilson
    JLab, Newport News, Virginia, USA
  • A. Grassellino, C.J. Grimm, T.N. Khabiboulline, O.S. Melnychuk, S. Posen, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
  Funding: Work supported by US DOE Contract DE-AC02-76SF00515.
Nitrogen doping has been proven now in several labs to enhance Q0 values of 1.3 GHz cavities in the gradient domain favored by CW operation. The choice of doping for the LCLS-II project has given the community a wealth of statistics and experience on the challenge of transferring the doping technology to industry. Overall, industry-produced nitrogen-doped cavities have shown excellent performance, however some technical issues have arisen. This talk focuses on lessons learned from the production of over 300 nitrogen-doped cavities for LCLS-II and how issues were mitigated to further improve performance. Finally, I will discuss pushing the boundaries of nitrogen-doping further by exploring different doping regimes in order to maintain excellent Q0 performance, while reaching higher quench fields.
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DOI • reference for this paper ※  
About • paper received ※ 02 July 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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