Simple design for dilution refrigerator with base temperature of 2.3 mK

A simple design is presented for a dilution refrigerator. Construction is not difficult. This refrigerator has been designed to allow measurements of the properties of small samples at low temperatures and to precool small nuclear demagnetization stages. The design consists of a concentric tube heat exchanger and several sintered silver discrete heat exchangers. The minimum base temperature was measured to be 2.3 mK.