Thermal Conductivity of Cryogenic Deuterium (LLE version)

Accurate values of the thermal conductivity and specific heat of deuterium are necessary to make high quality cryogenic laser fusion targets. Due to the difficulty of measuring these values at cryogenic temperatures, the “3ω” method is used. This involves passing an oscillating current through a platinum wire embedded in deuterium and measuring the third-harmonic voltage that results from the temperature dependence of the resistance. A two dimensional model has been built that calculates heat flow in both the axial and radial directions (i.e., along and perpendicular to the wire) including the frequency-dependent skin depth. The model has been fit to four sets of experimental data (the wire in a vacuum and in gaseous, liquid, and solid deuterium) by adjusting the parameters of thermal conductivity and specific heat. Generally, the model and data agree well. The model has enabled the thermal conductivity to be accurately determined at cryogenic temperatures for gaseous, liquid, and solid deuterium.