Status and recent trends in cryocooler research.

The five types of cryocoolers used to provide cryogenic temperatures for various applications are the Joule-Thomson, Brayton, Stirling, Gifford-McMahon, and pulse tube cryocoolers. Many advances in all types have occurred in the past twenty years that have allowed all of them to be used for a wide variety of applications. The current status of these cryocoolers as they are used in commercial, military, or space applications is reviewed. In the past five years, new research on these cryocoolers offers the potential to significantly improve them and make them suitable for even more applications. The general trend of this new cryocooler research is also presented.