A Closed Cycle Dilution Refrigerator For Space

Orateur : Ariel HAZIOT

The Planck mission sub-K cooler was the so called open cycle dilution refrigerator (OCDR) : incoming streams of liquid 3He and 4He mix in a Y-junction to produce cooling. S ince the isotopes mixture was ejected into space, the amount of helium stored on the satellite set the limit of the cooling power (0.1 μW at 100 mK) and the lifetime (30 months). Future space missions (X-IFU, PIXIE) require an order of magnitude more cooling power, lower temperatures and longer lifetime. We are developing a closed cycle dilution refrigerator (CCDR) with a lifetime around 5 years and a cooling power up to 1 μW at 50 mK or 3 μW at 100 mK. The CCDR design extends the one of the OCDR with an isotope separator (still) working at 1 K that allows to re-use the 3He and the 4He. Liquid 4He is extracted by a thermo-mechanical pump that uses the fountain effect of its superfluid phase, while almost pure vapor 3He is pumped thanks to the large difference in vapor pressure between 3He and 4He in the still conditions. The mixture in the still is confined in a porous material where capillarity forces replace gravity forces to form a liquid/vapor interface. The results of the prototypes will be presented as well as the perspective demonstration model integrating a structure more suitable for space missions.

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