Observation and control of temperature instabilities in a four-valve pulse tube refrigerator Original Research Article

The use of a pulse tube cryocooler in an application requires temperature stability at the cold end. In our four-valve pulse tube refrigerator we have observed long-term temperature instabilities lasting some days and short-term instabilities lasting some hours or even minutes. Investigations have shown that the latter anomaly is caused by the dc-flow. The negative influence on the stability is due to an additional mass flow (dc-flow) to the cold end of the pulse tube, which results in a parasitic heat input. In this paper we present an actively controlled dc-flow suppression device, which uses a temperature gradient in the regenerator as a control parameter. This device enables us to eliminate the temperature instabilities.