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A double stage Stirling cryocooler for long life space borne operation is under development at CEA/SBT. The cooler has been designed to provide simultaneously cooling capacities of 1 Watt at 50 K and 5 Watts at 190 K, with maximum efficiency. An original technology using hydrodynamic gas bearings and clearance seals for contactless operation has been developed and successfully assessed. A twin piston pressure oscillator and a two stage cold expander both using hydrodynamic gas bearings and clearance seals have been designed and fabricated. The performance of the oscillator have been reported elsewhere and are summarised in this paper. The cold finger uses a linear motor and a magnetic spring is inserted between both bearings for resonant operation. Linear motor performance, magnetic spring stiffness and resonant frequency experiments have been carried out. Preliminary pneumatic and thermal tests of the overall system are in progress.

Interest in the pulse tube comes from its potential for high reliability and low level of induced vibration. A numerical model has been developed to provide a tool for practical design. It has been successfully validated against the experimental results obtained with a single stage double inlet pulse tube which has achieved a temperature of 28 K at a frequency of a few Hz. Further developments have demonstrated the capability of operating a pulse tube at higher frequencies in association with a Stirling pressure oscillator. Current projects include coaxial geometry for miniature pulse tubes with linear resonant pressure oscillators. A 4 K multistaged pulse tube is also in development.