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TY - CONF AU - Pischalnikov, Y.M. AU - Arkan, T.T. AU - Cheban, S. AU - Holzbauer, J.P. AU - Kaluzny, J.A. AU - Orlov, Y.O. AU - Yun, J.C. ED - Koscielniak, Shane ED - Satogata, Todd ED - Schaa, Volker RW ED - Thomson, Jana TI - Modified Slow Tuner Design for Cavity 1 Inside LCLS II Cryomodules 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 - Initial LCLS-II cryomodule testing at Fermilab showed microphonics on the furthest upstream cavity (number 1) at least factor 2 larger than on the rest of the cavities. Testing indicated that this was a difference in the mechanical support of cavity 1, not a local acoustic source. Further investigation pointed to the upstream beam-pipe of the cavity 1. The upstream cavity flange has a solid spool piece connection to the beamline gate valve unlike the other cavities, which all connect through bellows. The gate valve's weight is supported by sliding system (free in z-axis) connected to large diameter Helium gas return pipe. The tuner design was modified to transform interface between cavity#1 and gate valve. Arms of the tuner for cavity 1 were extended and became the support structure for gate valve, eliminating the connection to the helium return pipe. Modification of the tuner design and results in microphonics mitigations will be presented. PB - JACoW Publishing CP - Geneva, Switzerland SP - 2684 EP - 2686 KW - cavity KW - cryomodule KW - interface KW - SRF KW - simulation DA - 2018/06 PY - 2018 SN - 978-3-95450-184-7 DO - 10.18429/JACoW-IPAC2018-WEPML006 UR - http://jacow.org/ipac2018/papers/wepml006.pdf ER -