Pulse tube refrigerator

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PROBLEM TO BE SOLVED : To shorten the length of a resonance tube for a heat driving type compressor to miniaturize and compact the same by a method wherein a mixed gas, in which helium and the other rare gas are mixed so that the acoustic velocity of the same becomes smaller than that of helium, is sealed into the resonance tube. SOLUTION : Upon operation, a mixed gas 27 of helium(He) and xenon(Xe) is sealed into a resonance tube. The molecular weight of the mixed gas 27 is increased by four times or more and the acoustic velocity of the same is reduced to the half or less, compared with conventional helium, whereby the length of the resonance tube 21 can be shortened to the half or less of a conventional resonance tube. Further, the Prandtl number of the mixed gas 27 is reduced to one by three (1/3) of helium whereby the thickness of temperature boundary layer of the mixed gas 27 is increased whereby the heat transfer characteristics of a stack 22 and the mixed gas 27 are improved. According to this method, the performance of heat driving type compressor 100 is improved and a miniaturized and compacted pulse pipe refrigerator can be obtained.