Sensitive Helium Leak Detection in Cryogenic Vacuum Systems
Conventional leak detectors are not useful for cold leak detection of LHe cooled cryogenic vacuum systems since He is adsorbed onto the cold walls. Even though the He desorption leak detection system1 developed at the Continuous Electron Beam Accelerator Facility (CEBAF) is very sensitive, the cryogenic system needs to be warmed up to at least 10.5 K for leak detection purposes, and it still would be impossible to identify the location of the leak. Recently hot cathode extractor gauges have been found to be reliable, very useful and convenient for very low pressure measurement (10-14 torr) at LHe temperatures. This paper discusses the operation of extractor gauges at LHe temperatures and their in situ use for fast and convenient cold leak detection of cryogenic vacuum systems. Further, the location and identification of the leaks based on the principle of the pressure wave travel of He and time-of-flight measurements of the He signal are also discussed.
KeywordsCold Wall Leak Detection Niobium Oxide Cold Extractor Technical Surface
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