Low cost Gifford-McMahon cryocooler development program

CTI-Cryogenics is under contract with ARPA/NRL to develop a low cost, long life cryocooler to meet the cryogenic cooling needs of emerging applications for high temperature superconductive (HTS) microwave components. The design for this application was targeted to produce a minimum of 15 watts of refrigeration at 50K. Early prototype testing of this low cost design has shown performance to be > 25 watts at 50K. The selection of a cryogenic cooling system for this HTS application started with a comprehensive study to evaluate both Stirling and Gifford-McMahon refrigerator design approaches. After completing a trade-off analysis that assessed and ranked refrigeration capacity, reliability, size, efficiency and price, the Gifford-McMahon (G-M) cycle was selected as the preferred design approach. The design and manufacture of the cold head component represented the greatest potential for reducing the cost of the cryocooling system. Early in the design process, the development team members focused their efforts primarily on the cost drivers and design approaches that would reduce the total number of refrigerator parts. This effort led to the elimination of the traditional drive motor and a complete redesign of the associated mechanical linkages and valving. The subsequent redesign reduced our standard refrigerator part count by approximately 40%. Material selection and construction methods, such as the use of ''near net shape'' fabrication techniques, were the keys to reducing the cost of the refrigerator parts. To substantiate that our cost goals were achieved, we solicited and received quotations on over 90% of the component parts. Analysis shows that, for large volume procurements, the price of a new cryogenic system can be reduced significantly from what is currently available.