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Several Stirling-type pulse tube cryocoolers operating at liquid hydrogen temperatures for physical experiments have been designed, built and tested. For simplification and compactness, a single-stage configuration with a coaxial arrangement was employed. A multi-bypass configuration, together with a double-inlet and an inertance tube was adopted as the phase shifter, which resulted in the improved efficiencies. At present, typical cooling performance with a no-load temperature below 16 K and a cooling capacity over 1 W/30 K can be achieved with an input power less than 250 W. Some typical experimental results and considerations for achieving a better performance will be presented in this paper. [ABSTRACT FROM AUTHOR]

This paper analyzes the zero and first order pressure drop along the pulse tube system and presents a simple but elegant way of eliminating the third type of DC gas flow which increases the efficiency of a Stirling type PTC. Since the optimization of a PTC depends sensitively on the adjustment of the phase angle between the pressure and mass flow because of its influence on the suppression of the third type of DC gas flow, we have done a series of experiments on a Stirling type multi-bypass PTC in order to attain the lowest refrigeration temperature. After the multi-bypass PTC reaches its lowest temperature, we open the metering valve to the best degree which connects the back pressure chamber of the linear compressor to the reservoir. For this novel type of PTC, the lowest refrigeration temperature drops from 38.8 K to 25.9 K after opening the metering valve. This approach offers a promising way for a compact single stage Stirling type PTC to reach liquid hydrogen temperatures. [ABSTRACT FROM AUTHOR]