Highly-sensitive investigation of a helium leak in a cryogenic valve

Abstract

We report the results and techniques developed to find a small helium leak in a valve developed for use at cryogenic temperatures. The leak was found during testing of NASA's XRISM/Resolve Instrument after it was integrated into the Flight Dewar that would later be installed onto the spacecraft. This leak was determined to be on the order of ▪. Initial testing in the Dewar showed the leak disappeared when the valve was cooled below ▪. The rate and temperature behavior was verified by testing the valve in a controlled environment within a range of temperatures that span from room temperature to below the superfluid transition of helium-4. The techniques employed to minimize the detection of helium external to the measurement as well as the analysis necessary to tease the weak signal from the leak in the presence of a small helium background signal will be discussed.