The last two years have witnessed an explosion in interest in pulse tube cryocoolers follow ing the achievement by TRW of high efficiency long-life pulse tube cryocoolers based on the flexure-bearing Stirling-cooler compressors from Oxford University, and have seen the initiation of development of long-life, low-cost cryocoolers for the emerging high temperature supercon ductor electronics market. Hydrogen sorptioncryocoolers achieved their first operation in Space this year, and closed-cycle helium Joule-Thomson cryocoolers continue to make progress in promising long-life space applications in the 4 K temperature range. On the commercial front, Gifford-McMahoncryocoolers with rare earth regenerators are making greatprogress inopening up the 4 K market, and new closed-cycle J-T or throttle-cycle refrigerators are taking advantage of mixed refrigerant gases to achieve low-cost cryocooler systems in the 65 - 80K temperature range. Tactical Stirling cryocoolers, now commonplace in thedefense industry, continue to find application in a number ofcost-constrained commercial applications and space missions, but are shrinking in numbers as the defense industry goes through a period ofconsolidation. Building on the expanding stable of available cryocoolers, numerous new applications are being enabled; many ofthese involve infrared imaging systems, and high-temperature supercon ductors in the medical and communications fields. Application experiments, designed to ex plore, troubleshootand resolve product integration issues, continue tooccur onan ever widening front, particularly in the fields of infrared imaging and spectroscopy, gamma-ray spectroscopy, and high-temperature superconductor applications."
