Concentration dependence of the thermal boundary resistance between dilute3He−4He solutions and sintered silver powder

We have measured the3He concentration dependence of the thermal boundary resistanceRB between3He−4He dilute mixtures and submicron sintered silver between 10 and 150 mK. For concentrations greater than one percent, the results for the boundary resistance per inverse volume are insensitive to the concentration and have a magnitude similar to that predicted by the acoustic mismatch theory. For concentrations less than one percent, we observe an increase ofRB for decreasing concentrations.