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TY - CONF AU - Holzbauer, J.P. AU - Chase, B.E. AU - Einstein-Curtis, J. AU - Hansen, B.J. AU - Harms, E.R. AU - Kaluzny, J.A. AU - Klebaner, A.L. AU - McGee, M.W. AU - Orlov, Y.O. AU - Peterson, T.J. AU - Pischalnikov, Y.M. AU - Schappert, W. AU - Stanek, R.P. AU - Theilacker, J. AU - White, M.J. AU - Wu, G. ED - Koscielniak, Shane ED - Satogata, Todd ED - Schaa, Volker RW ED - Thomson, Jana TI - Passive Microphonics Mitigation during LCLS-II Cryomodule Testing at Fermilab J2 - Proc. of IPAC2018, Vancouver, BC, Canada, April 29-May 4, 2018 C1 - Vancouver, BC, Canada T2 - International Particle Accelerator Conference T3 - 9 LA - english AB - 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. PB - JACoW Publishing CP - Geneva, Switzerland SP - 2668 EP - 2670 KW - cryomodule KW - cavity KW - cryogenics KW - controls KW - resonance DA - 2018/06 PY - 2018 SN - 978-3-95450-184-7 DO - 10.18429/JACoW-IPAC2018-WEPML001 UR - http://jacow.org/ipac2018/papers/wepml001.pdf ER -