Development of a 1 to 5 W at 80 K stirling pulse tube cryocooler

Pulse tube cryocoolers have recently received considerable attention due to their advantages and reliability and to their reduced cold head vibrations compared with other regenerative cryocoolers ( e.g., GM and Stirling cryocoolers). The pulse tube cryocoolers used in this study are similar to Stirling cryocoolers but they do not require any moving displacer in the cold head. This is beneficial for mechanical simplicity, reliability, reduction of induced vibrations. Performance comparable to Stirling cryocoolers are achievable in terms of cooling power, cooling temperature and efficiency. To cool high-Tc superconductive devices, we have designed and tested a prototype of Stirling pulse tube cryocooler that has a cooling capacity of 1 to 5W at 80K and a dual-piston linear drive motor compressor. Presently for a compressor input power of 200W, this prototype has achieved a cooling capacity of a few watt at 80K. Measured test parameters include cooling loads, cooling temperature, input power, operating frequency and pressures. We evaluated two types phase shifter mechanisms, a double inlet type and an inertance tube type. To aid the design of cryocoolers, we developed a numerical analysis technique and validated it with the experimental results. This report presents experimental and numerical results for our pulse tube cryocooler design. To study the compatibility for SQUID applications, we also measured the magnetic noise of cryocooler operation with a fluxgate magnetometer outside the magnetically shield room.