Thermal conductivity of argon at high pressures and high temperatures

Knowledge of the thermal conductivity of Ar under conditions of high pressures and temperatures (P-T) is important for model calculations of heat transfer in the laser heated diamond anvil cell (DAC) as it is commonly used as a pressure transmitting medium and for thermal insulation. We used a modified transient heating technique utilizing microsecond laser pulses in a symmetric DAC to determine the P-T dependent thermal conductivity of solid Ar up to 50 GPa and 2500 K. The temperature dependent thermal conductivity of Ar was obtained by fitting the results of finite element calculations to the experimentally determined time dependent temperature of a thin Ir foil surrounded by Ar. Our data for the thermal conductivity of Ar are larger than that theoretically calculated using the Green-Kubo formalism, but they agree well with those based on kinetic theory. These results are important for ongoing studies of the thermal transport properties of minerals at pressures and temperatures native to the mantle and core.