Author: Hansen, B.J.
Paper Title Page
WEPML001 Passive Microphonics Mitigation during LCLS-II Cryomodule Testing at Fermilab 2668
  • J.P. Holzbauer, B.E. Chase, J. Einstein-Curtis, B.J. Hansen, E.R. Harms, J.A. Kaluzny, A.L. Klebaner, M.W. McGee, Y.O. Orlov, T.J. Peterson, Y.M. Pischalnikov, W. Schappert, R.P. Stanek, J. Theilacker, M.J. White, G. Wu
    Fermilab, Batavia, Illinois, 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.
The LCLS-II project calls for cryomodule production and testing at both Fermilab and JLab. Due to low beam loading and high cavity quality factor, the designed peak detuning specification is 10 Hz. Initial testing showed peak detuning up to 150 Hz with a complex and varying time-structure, showing both fast (1-2 second) and slow (1-2 hour) drifts in amplitude and spectrum. Extensive warm and cold testing showed Thermoacoustic Oscillations in the cryogenic valves were the primary source of the microphonics. This was mitigated by valve wipers and valve re-plumbing, resulting in a greatly improved cavity detuning environment. Additional modifications were made to the cavity mechanical supports and Fermilab test stand to improve detuning performance. These modifications and testing results will be presented.
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