A mechanical cooler for the spectrometer experiment on board the integral spacecraft

Abstract

The International Gamma Ray Astrophysics Laboratory (INTEGRAL) is an ESA satellite to be used for gamma ray astronomy. The detector of the gamma ray spectrometer is kept to its nominal temperature of 85 K by means of a mechanical cryocooler system. The cryocooler system, developed by MMS Bristol, consists of four 50–80 K Stirling cycle coolers, controlled by two drive electronics units, coupled such that cooling performances are guaranteed after one failure. The four displacers have a common interface, via a beryllium rod, to the instrument detector. In nominal operations the heat lift capability provided at the cryocooler interface will exceed 2000 mW at 80 K. The purpose of this paper is to present the cryocooler design and to review the main thermal, mechanical and accommodation aspects relevant to its installation and operation on the instrument and spacecraft. A brief description of the detector cryostat is also given. The measured performances of the cryocooler in the various modes of operation will be summarised and a brief survey of the model philosophy and qualification test program will be presented.