Thermal diffusion ratio of a³He/⁴He mixture near its λ transition: The onset of heat flush

Abstract

We present experimental data on the thermal diffusion ratioK _T for a 15 molar % mixture near its λ transition obtained from measurements of the convection velocity of a mixture contained in a vertical column. The physical nature of the normal modes of heat and mass transfer near the transition is discussed. One possibility that arises from this discussion is that the temperature dependence ofk _T may be such that$k_{T_\lambda } - k_T \sim D^{--{\text{1/2}}}$, where$k_{T_\lambda }$ is the value ofk _T at the transition andD is the mass diffusion coefficient. There is limited support for this conjecture by the data over a restricted temperature range.