Density, Coefficient of Thermal Expansion, and Entropy of Compression of Liquid Helium-3 under Pressure below 1.2°K

Abstract

The method of dielectric-constant measurement has been used to determine the density of liquid ${\mathrm{He}}^3$ under pressure between 0.07 and 1.2°K. It consists of measuring the resonant frequency of a tunnel-diode oscillator, the $\mathrm{LC}$ tank circuit of which includes a capacitor filled with the liquid ${\mathrm{He}}^3$. The tunnel-diode oscillator is kept at low temperature and is described and analyzed in detail. A description is given of the system necessary to keep the pressure of the ${\mathrm{He}}^3$ constant. From the density measurements, the coefficient of thermal expansion and the entropy of compression are derived. The results are compared with earlier work. They are found to be thermodynamically consistent with the data obtained by other methods.