Thermal and Electrical Conductivities of Electroplated Gold

Thermal conductivity of electroplated gold at cryogenic temperatures is an important parameter for predicting the thermal behavior of ignition hohlraums that will eventually be fielded on the National Ignition Facility. We have measured the ratios between the electrical conductivities at 4.2 K and room temperature for electroplated gold as a function of bath brightener concentration and plating current density. By using the Weidemann-Franz law we predict thermal conductivities of these samples. We find that even small amounts of bath brightener drastically reduce the conductivities, and that the conductivities have a strong dependence on plating current density.