A portable He-3 cryostat for studies in astrophysics

The paper reviews the design, operation, and testing of a portable He-3 cryostat developed for astrophysical studies. The goal of the program was to develop an He-3 cryostat capable of cooling three bolometers to the 0.3-K temperature range for periods of more than six hours. A secondary goal was to evaluate the use of He-4 as the working fluid in a similar cryostat to provide cooling to infrared bolometers in the 0.8-K temperature range. It is planned to employ the He-3 cryostat for an infrared astronomy balloon flight. The cooler would be used with He-3 to achieve a 0.34-K bolometer temperature