Compacted Ag powder at very low temperatures: acoustic and magnetic properties and their influence on the thermal coupling to liquid 3He

Abstract The temperature range of about 10–20 mK marks the crossover from the acoustic to a predominantly magnetic coupling between liquid 3He and Ag sinter heat exchangers. In order to provide new information on the possible mechanisms of energy transfer at this solid/liquid interface at very low temperatures, we have performed measurements of the acoustic and magnetic properties of compacted Ag powders at 0.1⩽T⩽100 mK using the vibrating reed technique and AC susceptibility, respectively. We will also show preliminary data of measurements of the thermal boundary resistance RK between liquid 3He and an Ag sinter at 0.8⩽T⩽1.4 mK.