2-K pump down studies at SNS

[摘要] The Spallation Neutron Source (SNS) linear accelerator (LINAC) consists of 81 superconducting radio frequency (SRF) cavities cooled to 2.1 K by a cryogenic refrigeration system. The 2-K cold box consists of four stages of cold compressors with liquid nitrogen cooled variable speed motors. Transitioning from 4.5-K operation to 2.1-K operation in the cryomodules involves pumping the cryomodules down from approximately 1 bar to 0.040 bar. This effort is conducted through the use of several sequences developed as a collaborative effort between Thomas Jefferson National Accelerator Facility (TJNAF) and SNS personnel during the original commissioning of the SNS cryogenic system. Over the last ten years, multiple lessons have been learned about VFD behavior, thermal stability, procedural development and refining the sequences. From 2012 to 2014, there were multiple pump down iterations that were not successful. Studies have been conducted to determine the cause of these unsuccessful iterations. The results of these studies including components replaced and aspects that have not yet been solved are presented in this paper. Future plans to refine the sequence and determine the cause of unsuccessful pump downs will also be presented.

[发布机构] Research Accelerator Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge; TN; 37831, United States^1;Engineering Division, Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News; VA; 23606, United States^2;FRIB Project, Michigan State University, 640 S. Shaw Lane, East Lansing; MI; 48824, United States^3

[效力级别] 物理学 [学科分类] 材料科学（综合）

[关键词] Accelerator facilities;Cold boxes;Cold compressors;Cryogenic refrigeration systems;Cryogenic system;Spallation neutron sources;Superconducting radio frequency;Variable speed