Temperature Stability of Pulse Tube Refrigerators

Abstract

This chapter describes experimental results comparing four configurations in the two types of pulse tube refrigerators (the double inlet pulse tube refrigerators –DIPTR–and the single orifice pulse tube refrigerators –OPTR). In the DIPTR configuration, the cold end temperature is stable when orifice plates are used, but that is unstable when needle valves are used. The origin of this temperature instability is suggested that the gas flow circulating in the path which is composed of the bypass line, the regenerator and the pulse tube. This circulating flow is caused by the flow direction dependence of the valve impedance in the bypass line. When needle valves are used, the cold end temperature is stable in OPTR, but that is unstable in DIPTR. Thus, the impedance difference of the needle valve in the buffer inlet line does not disturb the gas flow in the refrigerator system. This is suggested to be the origin of temperature instability in long-term refrigerator operation.