On-chip cooling for detectors in space applications

Miniature Joule-Thomson (JT) coolers can be used for cooling small optical detectors. Both, cooler and detector can be integrated on a single chip by means of micro-electromechanical systems technology. For future space missions, the European Space Agency is interested in on-chip detector cooling for the temperature range 70 K - 250 K. Within this temperature range the working fluid in a JT cold stage is optimized. Only pure working fluids are taken into account. The optimum working fluid is selected on basis of the coefficient of performance of the cold stage. In addition, a figure of merit of the heat exchange in the counterflow heat exchanger (CFHX) is evaluated. The results of this optimization are discussed. In order to simulate the performance of a miniature JT cold stage, a static model of the CFHX is built in the software program ESATAN. The results of the simulations are compared with experimental data and also discussed.