Cryocoolers 11

Over the last two years we have witnessed a continuation in the breakthrough shift toward pulse tube cryocoolers for long-life, high-reliability cryocooler applications.One class of pulse tubes that has reached maturity is referred to as stirling type because they are based on the linear oxford stirling-cooler type compressor they generally provide cooling in the 30 to 100 k temperature range and operate at frequencies from 30 to 60 hz.The other type of pulse tube cooler making great advances is the so-called gifford-mcmahon type. Pulse tube coolers of this type use a g-m type compressor and lower frequency operation to achieve temperatures in the 2 to 10 k temperature range.Nearly a third of this proceedings covers these new developments in the pulse tube arena.Complementing the work on low-temperature pulse tubes is substantial continued progress on rare earth regenerator materials and gifford-mcmahon coolers.These technologies continue to make great progress in opening up the 2 4 K market.Also in the commercial sector, continued interest is being shown in the development of long-life, low-cost cryocoolers for the emerging high temperature superconductor electronics market, particularly the cellular telephone base-station market.At higher temperature levels, closed-cycle j-t or throttle-cycle refrigerators are taking advantage of mixed refrigerant gases, spearheaded in the former ussr, to achieve low-cost cr- cooler systems in the 65 80 K temperature range.

Over the last two years we have witnessed a continuation in the breakthrough shift toward pulse tube cryocoolers for long-life, high-reliability cryocooler applications.One class of