First operation of the XFEL linac with the 2 K cryogenic system

[摘要] The RF operation of the about 800 superconducting 1.3 GHz 9-cell cavities of the XFEL linac requires helium II bath cooling at 2 K, corresponding to a vapor pressure of 3100 Pa. After the first cool-down of the XFEL linac to 4 K in December, 27th2016 the operation of the 2 K cryogenic system was started in January, 2nd2017. The 2 K cryogenic system consist of a 4-stage set of cold compressors to compress helium vapor at a mass flow of up to 100 g/s from 2400 Pa to about 110 kPa and a full flow bypass with an arrangement of heat exchangers and control valves. This paper describes the XFEL refrigerating plant, especially the 2 K cryogenic system, the tuning of the cold compressor regulation to adapt to the XFEL linac static and dynamic heat loads and experience of about 6 months of operation.

[发布机构] Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany^1;Lindekryotechnik/Engie, Hamburg, Germany^2;Lindekryotechnik, Pfungen, Switzerland^3

[效力级别] 物理学 [学科分类] 材料科学（综合）

[关键词] Cold compressors;Control valves;Cryogenic system;Dynamic heat;Flow bypass;Helium II;Helium vapor;Mass flow