Gifford-McMahon/Joule-Thomson cryocooler with high-flow-conductance counterflow heat exchanger for use in resistance thermometer calibration

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  • Takeshi Shimazaki
    National Institute of Advanced Industrial Science and Technology (AIST) National Metrology Institute of Japan (NMIJ), , Tsukuba Central 3, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan
  • Keishi Toyoda
    National Institute of Advanced Industrial Science and Technology (AIST) National Metrology Institute of Japan (NMIJ), , Tsukuba Central 3, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan
  • Osamu Tamura
    National Institute of Advanced Industrial Science and Technology (AIST) National Metrology Institute of Japan (NMIJ), , Tsukuba Central 3, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan

Description

<jats:p>A cryocooler that consists of a two-stage Gifford-McMahon (GM) mechanical refrigerator and a Joule-Thomson (JT) expansion circuit is developed for use in resistance thermometer calibration. The cryocooler is designed to attain a lower temperature rather than to produce a higher cooling power. A simple but high-performance counterflow heat exchanger is developed for the cryocooler. The heat exchanger has a high flow conductance while maintaining a high heat exchange efficiency. It is an improved type of counterflow heat exchanger composed of a spiral capillary and a thin-wall straight outer tube. The developed cryocooler uses a single counterflow heat exchanger not like a conventional GM/JT cryocooler, which usually has two or three counterflow heat exchangers. He4 is used as the working fluid for the JT expansion circuit. The pot where the condensed He4 collects after the JT expansion can reach 1.3K in the continuous operation mode and 1.0K in the single-cycle operation mode. The cooling power of the cryocooler is 580μW at 1.34K with a molar flow rate of 300μmol∕s. Temperature control of the pot was demonstrated from 1.4to12K using two control methods. One method involves controlling the evacuation speed in the JT circuit and the other involves controlling the heat input from a heater to the pot. The temperature of the pot is controlled within the order of magnitude of 2mK from peak to peak with either method.</jats:p>

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