4 Kelvin Cooling with Innovative Final Stage of Multistage Cryocooler

Proposed for development is a proof-of-concept prototype for the final stage of a multistage cryocooler. This final stage comprises a high frequency pulse tube cold head that cools from an intermediate temperature of 10?20 K down to below the critical temperature of helium (5.2 K) using an alternate approach compared to conventional technology. This approach offers unique advantages that have never before been explored and will allow us to achieve high thermodynamic efficiency with compact size, using ordinary helium as the working fluid. The first and second stages that will eventually pre-cool the third stage cold head can be either existing commercial Sunpower Stirling cryocoolers or pulse tube technology now under development. If the third stage cold head proves successful all the pieces will be in place for developing a compact, efficient and reliable cryocooler.