Cryogenic thermal emittance measurements on small-diameter stainless steel tubing

[摘要] The Mid Infrared Instrument aboard the James Webb Space Telescope includes a mechanical cryocooler which cools its detectors to their 6 K operating temperature. The refrigerant flows through several meters of ∼2 mm diameter 304L stainless steel tubing, with some sections gold plated, and some not, which are exposed to their environment. An issue of water freezing onto the tube surfaces is mitigated by running a warm gas through the lines to sublimate the frozen water. To model the effect of this process on nearby instruments, an accurate measure of the tube emittance is needed. Previously we reported the absorptance of the gold plated stainless steel tubing as a function of source temperature (i.e. its environment). In this work the thermal emittance of the uncoated tubing is measured as a function of its temperature between 100 and 280 K. These values lead to an accurate prediction of the minimum length of time required to thermally recycle the system. We report the technique and present the results.

[发布机构] NASA Goddard Space Flight Center, Greenbelt; MD; 20771, United States^1

[效力级别] 物理学 [学科分类] 材料科学（综合）

[关键词] 304L stainless steel;Accurate prediction;James Webb space telescope;Mid infra-red instruments;Operating temperature;Source temperature;Stainless steel tubing;Thermal emittance