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TY - CONF AU - Geng, R.L. AU - Huang, S.C. ED - Schaa, Volker RW ED - Pei, Guoxi ED - Chin, Yong Ho ED - Fu, Shinian ED - Zhao, Ning TI - Magnetic Flux Generated by Thermal Current in CEBAF 5-Cell Cavity System J2 - Proc. of LINAC2018, Beijing, China, 16-21 September 2018 CY - Beijing, China T2 - Linear Accelerator Conference T3 - 29 LA - english AB - The unloaded quality factor Q0 of many 5-cell CEBAF cavities were lowered by a factor of ~2 from their vertical qualification testing to their beam operation in CEBAF tunnel. Causes of this Q0 degradation were studied previously, including a more recent one addressing static fluxes arising from magnetic components near a 5-cell cavity. This paper reports on a preliminary study of the dynamic fluxes generated by a thermal current. Such a thermal current arises from the Seebeck effect and flows in closed loops formed by a niobium cavity and its surrounding tuner rods and liquid helium vessel that are made of stainless-steel. The behaviors of magnetic fluxes in response to various thermal profiles on a 5-cell CEBAF cavity with integrated tuner rods were studied in a JLAB VTA dewar. An outcome of this study is a proposed cool-down procedure for eliminating the thermal current generated magnetic fluxes around 5-cell cavities placed in CEBAF tunnels. This procedure may be useful to improve cavity Q0 in a cost-effective manner, which in turn saves cryogenic expenditures for sustaining CEBAF operation. PB - JACoW Publishing CP - Geneva, Switzerland SP - 273 EP - 276 KW - cavity KW - cryomodule KW - niobium KW - experiment KW - operation DA - 2019/01 PY - 2019 SN - 2226-0366 SN - 978-3-95450-194-6 DO - DOI: 10.18429/JACoW-LINAC2018-MOPO130 UR - http://jacow.org/linac2018/papers/mopo130.pdf ER -