Pulse Tube Cryocoolers

Abstract

This paper presents a review of the pulse tube refrigerator from its inception in the mid-1960s up to the present. Various factors are discussed which brought it from a laboratory curiosity to the point where it is now the most efficient of all cryocoolers (cryogenic refrigerator) for temperatures between about 60 and 120 K, and it is reliable enough to be used on space missions. Efficiencies as high as 24% of Carnot at 80 K and temperatures as low as 2 K have been achieved in pulse tube refrigerators. The operating principles for the different types of pulse tube and thermoacoustic refrigerators are described. Pulse tube refrigerators operate with oscillating pressures and mass flows and have no moving parts in the cold end. For large industrial systems the mechanical compressor can be replaced with one of two types of thermoacoustic drivers to yield a refrigerator with no moving parts. Recent advances in understanding and reducing losses in various components are described that have led to the improved efficiencies. A brief description is also given of other types of cryocoolers to aid in a comparison of the pulse tube cryocooler with other types of cryocoolers. The major problems associated with cryocoolers are listed, and it is shown that pulse tube refrigerators have begun to overcome many of these problems. As a result, they are now being used or considered for many different applications. Some of these applications as well as example pulse tube refrigerators are described.