High Precision Measurements of Heat Capacity and Pressure Coefficient of Liquid He⁴

Abstract

An apparatus for measurements of the heat capacity and the pressure coefficient of liquid He⁴ under pressure is reported. A tunnel diode oscillator is used to measure the change of the pressure. The frequency resolution and the reproducibility of the oscillator for pressure measurements are found to be 1×10^-8 and 5×10^-4, respectively. The temperature resolution of the system is 4×10^-7K and the measurable range of pressure change is from 2×10^-6bar to 30bar.