3He constant-volume gas thermometry: Calculations for a temperature scale between 0.8 and 25 K

A discussion is presented on the possibilities of a³He gas thermometer for defining a temperature scale below 30 K, based on recent new measurements of the virial coefficient. The influence of all corrections of interest is given in comparison with⁴He gas thermometry and with⁴He and³He vapor pressure thermometry. It is shown that a³He gas thermometer can be operated down to temperatures <1 K, with an estimated inaccuracy of less than ±0.5 mK, thereby obviating the explicit need of the³He and⁴He vapor pressure scales below 5 K, and directly joining a possible scale based on the³He melting curve.