A mixed-gas miniature Joule-Thomson cooling system

A mixed-gas Joule-Thomson cm cooling system is investigated in which a micromachined JT cold stage of 60 x 10 x 0.7 mm(3) is combined with a linear compressor. The cooling system is operated between 1.3 bar and 9.4 bar with a ternary gas mixture of 39 mol% methane, 20 mol% ethane and 41 mol% isobutane. It cools down to below 130 K, and at a cold-tip temperature of 150 K, a cooling power of 46 mW is obtained at a mass-flow rate of 1.35 mg s(-1). The background losses are experimentally determined to be 20 mW and are in good agreement with the calculated value of 21 mW. The linear compressor can be used to drive 19 of these miniature JT cold stages in parallel, e.g. for cooling optical detectors in future space missions. In this mode, the compressor pressure ratio is slightly less, resulting in a net cooling power of 23 mW per miniature JT cold stage. (C) 2013 Elsevier Ltd. All rights reserved.