A three-stage helium sorption refrigerator for cooling of infrared detectors to 280 mK Original Research Article

We review some of the applications of submillimetre instruments for astronomy and Earth atmospheric sciences where helium sorption refrigerators have been used. We describe a three-stage helium refrigerator which uses a 4He–3He double-stage refrigerator to precool and intercept the parasitic heatload on a final 3He single-stage refrigerator. This multi-stage configuration permits operation of the refrigerator system without externally pumping on a 4He bath. This results in simpler integration with the instrument and allows scientific observations to be more easily made. We have achieved a base temperature of 234 mK for a hold time of 20.4 h. The heat lift at 280 mK is 15 μW.