Technical Paper
Development Status of a 2.5 K - 4 K Closed Cycle Cooler Suitable for Space Use
1994-06-01
941280
Temperatures below 2.5 K have been reached in a continuously operating closed cycle cooler that has been engineered for space applications. This cooler is a modification of a 4 K development model cryocooler that consists of a two-stage Stirling cycle precooler with a closed cycle Joule-Thomson (JT) stage. The Stirling cycle precooler and the compressors for the JT system incorporate all the long life features of the Oxford/RAL single stage coolers which are now in orbit and operating successfully. The precooler now incorporates larger pistons and a slightly modified regenerator; this has led to a lower precooler temperature and increased JT cooling power. A new heat exchanger between the lower and upper stages of the precooler has reduced the heat load on the precooler. 4He is used in the JT system for temperatures around 4 K and 3He is used below 3 K. Different JT expansion orifices are used to optimise the cooler at 4 K and 2.5 K.
