Operation of a dilution refrigerator in a micromode

Two design versions of a 3He-in-4He dilution refrigerator with 3He pumping out through its condensation on a cold wall are described: a classical refrigerator with a heat exchanger and a refrigerator with a collector that allows for operation in a quasi-single mode. The refrigerator operated stably in both cases when a power of &le30 μW was fed to the still, i.e., at a circulation rate of 3He of a few micromoles per second. In this case, the mixing chamber was cooled down to a temperature below 0.05 K.