Simple cryostat for measuring rf susceptibility from 4.2 to 300 K

Abstract

We describe a cryostat for measuring the rf (100 kHz) susceptibility of insulators in the temperature range from 300 to 4.2 K. The sample is connected by a tube to room temperature and is moved in and out of the coil of a tunnel diode oscillator located at a constant low temperature. The change in frequency of the oscillator is measured with a digital frequency counter. The oscillator is stable to ±2 Hz over periods of several hours. The counter resolution and the attainable filling factor limit the resolution χ/δχ to about 2×104. The susceptibility of anhydrous NiCl2 powder was measured to evaluate the apparatus and determine the filling factor.