Microsecond Laser Polarimetry for Emissivity Measurements on Liquid Metals at High Temperatures—Application to Tantalum

The aim of this work was to determine accurate and reliable thermophysical properties of liquid tantalum from melting up to temperatures of 5000 K. Temperature measurements on pulse-heated liquid metal samples reported by different authors have always been performed under the assumption of a constant emissivity over the whole liquid range because of the lack of data for liquid metals. The uncertainty in temperature measurement is reduced in this work by the direct measurement of emissivity during the experiments. The emissivity measurements are performed by linking a laser polarimetry technique with the established method for performing high speed measurements on liquid tantalum samples at high temperatures during microsecond pulse-heating experiments. A set of improved thermophysical properties for liquid tantalum, such as temperature dependences of normal spectral emissivity at 684.5 nm, heat capacity, enthalpy, electrical resistivity, thermal diffusivity, and thermal conductivity, was obtained.