Developments of 1-4 K Class Space Mechanical Coolers for New Generation Satellite Missions in JAXA

Abstract

Mechanical coolers are a key enabling technology to utilize low temperature scientific instruments for the new generation of space science missions, such as the new X-ray astronomical satellite Astro-H, and the new infrared astronomical satellite SPICA. In particular, 1-4 K class mechanical coolers are required as a precooler for the low temperature detector’s cooling system and to cool a space telescope with a very low radiation background. In JAXA, two-stage Stirling coolers (2ST) for 20 K and a 4He Joule-Thomson (J-T) cooler for 4.5 K have been successfully developed and operated in space, e.g. Akari (Astro-F) and the Japanese Experiment Module/SMILES. Based on this heritage, the 2ST coolers and the 4He J-T coolers have been modified and upgraded to achieve high reliability, more cooling power, lower mechanical vibration, and longer life time. In performance tests of upgraded prototypes of the mechanical coolers, the required cooling power of each cooler has been obtained. The engineering model of the 4 K class cooler, consisting of two 2ST coolers and a 4He J-T cooler for the Astro-H payload will be fabricated, and undergo performance tests, including the level of vibration and cooling behavior at the expected heat load in Astro-H. In this paper, the R&D status and performance test results of the 2ST coolers and the 4He J-T coolers are reported. We also report on the development of 3He J-T cooler for the SPICA detectors.