Design and Testing of an Improved Cryopump for the Confined Helium Experiment
A cryopump flown on the space shuttle for the Lambda Point Experiment1 (LPE) was improved and redesigned for use in the Confined Helium Experiment (CHeX). The successful Lambda Point Experiment (LPE) flew on the space shuttle in October 1992. The Confined Helium Experiment (CHeX) will launch in October 1997. CHeX uses high resolution thermometers2 to measure the heat capacity of liquid helium when confined within finely spaced parallel disks. To eliminate heat flow between the calorimeter and the cryogenic bath, a cryopump is used to reduce the pressure in the experimental probe. The LPE cryopump trapped activated charcoal behind a nuclepore filter. The new cryopump uses activated charcoal glued to copper plates to eliminate the nuclepore filter. Vibration tests verified that the cryopump does not generate charcoal dust contamination. Early performance tests indicated that the probe vacuum is significantly lower with the new pump, and that the pressure falls more rapidly than with the previous design. Recent tests with the CHeX experimental probe show a significant reduction in the heat leak between the calorimeter and the cryogenic bath.
KeywordsActivate Charcoal Vibration Test Bottom Flange Heat Leak Charcoal Particle
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