Thermal conductivity of condensed D-T andT2

The thermal conductivity of condensed ${\mathrm{T}}_2$ and D-T has been measured by conventional techniques. Measurements for solid ${\mathrm{T}}_2$ and D-T (${\mathrm{D}}_2$-DT-${\mathrm{T}}_2$) from the triple points to 3 K are presented, along with measurements in the liquid phases from the triple points to 25 K. The sample geometry was that of a thin disk, a single heater being used to produce a temperature difference between the faces of the disk. The steady-state thermal conductivity of the solid increases from 0.15 W/m K at 3 K to between 0.5 and 0.7 W/m K at 8 to 10 K before dropping to 0.3 W/m K at the triple points. Two ${\mathrm{T}}_2$ samples had large thermal conductivities (≊1.2 W/m K) at 9 K, probably caused by accidentally good sample packing. The liquid thermal conductivity increases from 0.3 W/m K at the triple points to between 2 and 6 W/m K at 25 K, with convection of the liquid being probable. The effect of shrinkage upon freezing is considered, and an unexplained time-dependent behavior, seen in both ${\mathrm{T}}_2$ and D-T, is described. The considerable importance of the solid thermal conductivity to nuclear spin polarization of D-T is discussed in detail. The need for a triton spin-lattice-relaxation time greater than 100 s is made evident by the need to remove the heat due to tritium decay and that from microwave pumping of the electron spins.