SPACE-BORNE HE-3 REFRIGERATOR

A space-compatible 3He refrigerator is being developed for cooling the bolometric detectors of the Far Infrared Photometer (FIRP) in the Infrared Telescope in Space (IRTS). The refrigerator is self-contained and compact, and can be recycled in zero gravity with low power dissipation (≤ 20 mW). A laboratory prototype that contains 2 STP dm3 of 3He has been successfully cycled upside-down, i.e. against gravity, thus proving the feasibility of the cycle in zero gravity. Sintered copper confines the 3He to the evaporator during the low temperature phase. Temperatures as low as 280 mK have been achieved with this configuration. Other types of porous material which have lower mass density are currently under investigation. A flight model has been designed which contains 18 STP dm3 and will provide two weeks of continuous cooling at 300 mK when operated on a 2 K cold stage. The long hold time and the low power dissipation of the refrigerator are made possible by using gas heat switches to make and break thermal contact with the adsorption pump and with the evaporator, and by using tensioned Kevlar cord to provide rigid support with excellent thermal isolation. © 1990.