Dilution refrigerator for space use
朱 紹偉 （同済大）
Abstract:Some space missions need a refrigeration temperature below 50mK. The magnetic refrigerator is very complex, open cycle dilution refrigerator life time depends on the storage of He3 and He4 in space. Close cycle dilution refrigerator could be a good choice because it is very simple. How to separate He3 and He4 in space is a problem because ordinary still cannot make a clear phase boundary of liquid He4 and gas He3 near zero gravity. Another problem is no He3 rich phase and He3 dilution phase in the mixing chamber near zero gravity. A still filled with porous material along the inner wall and keeping the center empty is introduced. The porous material traps super He4, the empty center is filled with He3 gas, and heats up to a little higher temperature, so that the liquid/gas phase boundary is made. A chamber which is separated by porous material plugs into rich space and dilution space replaces the ordinary mixing chamber. When He3 flows from rich space to dilution space through the porous material, it penetrates to He4 which is trapped on the surface of the porous material, and mixes well after passing the porous material to dilution space. Here, the rich space may be filled with mixing of He4 He3 drops or almost He3. The porous material has the functions of mixing and fin for transferring cooling power. Then traditional dilution cycle could be used in space.