Cooling power of dilution refrigerator

The cooling power (dQ/dt)sub(m) of a recirculating dilution refrigerator is (dQ/dt)sub(m)(Tsub(m))=(dn/dt)3[Hsub(l)(Tsub(m))-Hsub(C)(T0)], where (dn/dt)3 is the circulation rate of 3He, Hsub(l)(Tsub(m)) the enthalpy of the dilute solution at mixing temperature Tsub(m) (and at maximum concentration), and Hsub(C)(T0) the enthalpy of the concentrated solution (or mixture) at the outlet temperature of the heat exchanger, both enthalpies being calculated per mole of 3He. Hsub(C) is thus dependent on the 4He contamination in the circulation. The aim of this study is to find the maximum of (dQ/dt)sub(m), a basic and so far untreated problem in dilution refrigeration. (Auth.)