Thermal Boundary Resistance between Solids and Helium below 1°K

Abstract

Results are reported from measurements of the thermal boundary resistance between liquid ${\mathrm{He}}^{3}$ and copper or epoxy resin, and between solid ${\mathrm{He}}^{3}$ or liquid ${\mathrm{He}}^{4}$ and copper. Measurements were made in the range 0.05 to 0.9\ifmmode^\circ\else\textdegree\fi{}K and at pressures up to 395 psi. No quantitative agreement has been found with theory. Above 0.11\ifmmode^\circ\else\textdegree\fi{}K, the thermal boundary resistance of liquid ${\mathrm{He}}^{3}$ and liquid ${\mathrm{He}}^{4}$ both have a temperature dependence stronger than ${T}^{\ensuremath{-}3}$. Below 0.11\ifmmode^\circ\else\textdegree\fi{}K the thermal boundary resistance of ${\mathrm{He}}^{3}$ varies as ${T}^{\ensuremath{-}3}$ over the full pressure range in the liquid. In the case of ${\mathrm{He}}^{4}$ at low pressure, however, the stronger temperature dependence continues to the lowest temperature measured (0.075\ifmmode^\circ\else\textdegree\fi{}K). It is not clear whether the qualitative difference in the behavior of liquid ${\mathrm{He}}^{3}$ and liquid ${\mathrm{He}}^{4}$ is associated with zero sound in liquid ${\mathrm{He}}^{3}$.