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

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.