Author: Palczewski, A.D.
Paper Title Page
TUXC02
The LCLS-II-HE R&D Program: New Insights into Improving the Performance of Nitrogen-Doped SRF Cavities  
 
  • D. Gonnella, S. Aderhold, J.T. Maniscalco, M.C. Ross
    SLAC, Menlo Park, California, USA
  • D. Bafia, M. Checchin, A. Grassellino, S. Posen
    Fermilab, Batavia, Illinois, USA
  • A.D. Palczewski, C.E. Reece
    JLab, Newport News, Virginia, USA
 
  Funding: US DOE and the LCLS-II-HE Project
Nitrogen doping has now been demonstrated to produce SRF cavities of unprecedented Q0 values when manufactured in an industrial setting. LCLS-II has shown over 300 cavities with an average Q0 of more than 3·1010 at 16 MV/m and represents an overwhelming success of the doping protocol. LCLS-II-HE will add an additional 23 superconducting cryomodules to the LCLS-II linac, requiring cavities to operate at similar levels of high Q0 but at 21 MV/m instead of 16 MV/m. Nitrogen-doped cavities have been historically plagued by lower quench fields than other cavity preparation methods. Therefore, an R&D effort was launched to improve upon the quench fields of doped cavities while maintaining the high Q0. Here we present results on single-cells and 9-cells from new doping recipe pursuits, transfer of these new recipes to cavity vendors, and results on vendor-produced 9-cell cavities. This program has led to the discovery of the importance of the cold electropolish for producing higher quench fields. Finally, we will show results from the first cryomodule produced with these new cavities operating at HE gradients.
 
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