Phase Separation inHe3-He4Mixtures Observed With Slow Neutrons

Abstract

A method of studying phase separation in ${\mathrm{He}}^3$-${\mathrm{He}}^4$ mixtures is described in which thermal neutrons are used to determine the ${\mathrm{He}}^3$ number density in each phase. Results of measurements made over the temperature range 0.04-0.85°K are presented and compared with those obtained by other methods. Extrapolation of the measurements made below 0.15°K indicates that the limiting solubility of ${\mathrm{He}}^3$ in ${\mathrm{He}}^4$ at $T=0\mathrm{}$ °K is 6.84±0.06%. The second phase at low temperatures is found to be pure ${\mathrm{He}}^3$ within the 1% accuracy of the measurement.