Development of the Long-Lifetime Solid Nitrogen Dewar for NICMOS
The NICMOS dewar design was driven by requirements for long cryogen lifetime and minimal detector contamination. Several unique design features were implemented to meet the long-lifetime requirement, and are discussed. These include thermoelectric cooling, a single cryogen fill/vent line, and unique electrical cabling. Because the dewar annulus vacuum is not opened to space after launch, component outgassing was carefully evaluated during dewar integration. A series of tests was performed to evaluate the contributions of all non-metallic materials. Development of the outgassing rate specification and comparison to the measured rate at the end of dewar vacuum acquisition is presented. The methods used for long-term vacuum maintenance following pumpout, and long-term performance results are presented. The no-vent LN2 fill technique and the fill efficiency achieved using this process are described.
KeywordsHubble Space Telescope Thermoelectric Cool Thermal Shield Cryogenic Engineer Outgassing Rate
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