Sub-Kelvin Sorption Coolers for Space Application

Abstract

The European Space Agency's FIRST satellite will be a multi-userobservatory looking at the universe in the infrared and submillimeterwavelength range from 80 to 670 mum. It accommodates three instruments,all of which have detectors or mixers operating in the range 0.3 K - 2K. A large superfluid helium (He II) dewar provides a cold heat sink ataround 1.8 K, with the last cooling stage, down to 0.3 K, effectedinside the instruments using a recyclable He-3 sorption cooler developedat CEA-SBT.Although these hardware developments are expected to begin in fall 2000,CEA-SBT, in collaboration with CSL, was awarded in September 1998 an ESATechnological Research Program (TRP) contract whose objective is todesign, manufacture, test and qualify for space an engineering model ofa sorption cooler. In this framework, two prototype coolers, one He-3and one He-4, have been designed and fabricated. To benefit the futuredevelopment of the FIRST coolers, the He-3 prototype was sized accordingto the main specifications of the SPIRE instrument. These two prototypeshave been assembled, and the test plan, which shall lead to thequalification of the coolers, is currently being performed, Preliminaryresults are presented.In parallel with these projects and prior to the detailed design of theengineering models, a laboratory sorption cooler prototype which can berun with He-3 or He-4 was developed to further study specific aspectsand answer various questions. For instance, convective effects thatcould severely impact the performance during ground test operation, andsuperfluid film behavior were both investigated. In addition, variousmeasurements were performed on the titanium alloy Ta6V and Kevlar 29.These results are presented as well.