Development of a dilution refrigerator for space applications

In order to study the fundamental properties of Universe, it is necessary to measure very small intensity signals in a wide range of frequencies. To capture such a signal, the detectors matrices are generally cooled down to temperature of the order of 100 mK. In order to reach those temperature levels, a dilution refrigerator dedicated to space application have been developed in Neel institute/CNRS. The cooling process relies on the dilution of 3He going from a concentrated phase to a 3He/4He dilute phase. For ground applications, the phase separation is made by gravity. During space missions, the phase separation is insured with capillary forces that replace gravity: the Closed Cycle Dilution Refrigerator (CCDR) overcome this limitation. A technological and know-how transfer is on-going between Neel institute/CNRS and CEA/DSBT.

The PhD thesis is organized on two axis. The main one consist in studying the physics in place in the phase separator that is a porous media which confine the mixture 3He/4He where the 4He is extracted through a fountain effect pump. For that, a dedicated experiment will be build to study the confinement and the 4He circulation. On the same time, the maturity of the CCDR shall be increased up to TRL 5 (Technology Readiness Level). The thesis will be in close collaboration with Neel institute.

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