Electrically driven 4He-circulating dilution refrigerator for cooling aboard spacecraft Original Research Article

So far, 3He–4He dilution refrigerators in terrestrial laboratories are the most effective way for obtaining steady low temperatures down to ∼10 mK. Gravity plays a key role as a force that separates the heavier 3He-dilute (d) phase and the lighter 3He-concentrated (c) phase into two distinct bulks with a well-defined horizontal flat interface. An equivalent for gravity must be found if 3He–4He dilution refrigerators are planned for operating in space. We give a concrete technical design of 4He-circulating dilution refrigerator (4He-DR) for the use in a microgravity environment. This is done on the basis of a detailed consideration of the various features of 3He–4He liquid mixtures.