Setup for calorimetric measurements at temperatures below 1 K

A compact, top-loading 3 He evaporation refrigerator is built for doing heat-capacity studies on various samples at temperatures below 1 K. It uses adsorption pumping and utilizes a portable helium Dewar of the STG-40 type as the cryostat. A calorimetric cell is built which permits investigation of the heat capacity of samples with masses of less than one gram. The lowest measurement temperature is 0.32 K. The dependence of the temperature of the 3 He evaporation chamber on the power delivered to it is established. The refrigerator can operate continuously for two hours at a heat load of 50 μW.