Pulse Tube refrigerator-an alternative Cryocooler for low temperature applications down to 2.5K

A two-stage Pulse Tube Cryocooler (PTC) is developed with a no-load temperature of 2.5K in the second stage and 67K in the first stage at an operating frequency of 1.6Hz. The system gives a cooling power of 250 mW at 5K in the second stage. Several PTCs have been experimentally studied by varying the dimensions of the pulse tubes and the regenerators, as well as the regenerator materials to arrive at the best configuration. Studies conducted with several configurations indicate that the Pulse Tube dimensions are more critical compared to those of regenerator to achieve low temperatures. Also the system performance improved with the proper design of cold end heat exchangers with minimum flow impedance. These results along with cooling power characteristics of the cryocooler are discussed in this paper.