A new generation of split, closed-cycle, cryogenic coolers for infrared systems

Abstract

Unfortunately, for user and manufacturer both, the closed-cycle cryogenic cooler to date has deserved its reputation as the “weak-link” in i.r. systems. When the cooler requires service at intervals of a few hundred hours at best, the quality of the system it serves is unfairly diminished. This paper addresses technological advances in the art of Stirling-cycle coolers which will increasingly cause that image of military cryocoolers to change for the better. A family of split-cycle coolers designed for long MTBF and in the final stages of development is the focus of the discussion. Their technological evolution, from multi-year-MTBF satellite system Stirling coolers developed in the U.S., and the UA 7011 cooler (the first all-linear, military, production cooler) developed in Holland, is explained. Three new machines are discussed. Both 1 4 and l W (nominal capacity) at 80 K linear-resonant, free-displacer Stirling coolers designed for a minimum of 2500 hours MTBF are examined. The third machine is an advanced 1 4 W at 80 K Stirling cooler incorporating the same component improvements in its free-displacer while utilizing a crankshaft-driven compressor. All three are designed to be compatible with standard U.S. 60 element and 120 180 element detector/Dewars. The technologies of linear-resonant compressors and free-displacer expanders as embodied in these machines is discussed in sufficient detail that the reasons for their superior performance will be clear.