Spectral emissivity and optical properties at λ = 632.8 nm for liquid uranium and zirconium at high temperatures

The spectral emissivities, refractive indices, and extinction coefficients of pure liquid uranium and zirconium were measured vs. temperature by He--Ne laser polarimetry at a wavelength of 632.8 nm. The experiments were conducted under containerless conditions using electromagnetic levitation and heating supplemented by CO sub 2 laser beam heating. Clean liquid metal surfaces were achieved by heating the specimens to high temperatures at which oxides evaporated and nitrides decomposed. Results were obtained for liquid U and Zr in the temperature ranges 2000-2800K and 2000- 2600K, respectively, and included data for liquid Zr undercooled by 125K. The spectral emissivity of Zr was equal to 0.345 and was independent of temperature. The spectral emissivity of U increased with temperature from 0.272 at 2000K to 0.294 at 2800K. The melting temperature of Zr was determined from its emissivity and apparent melting temperature to be 2125 plus/minus 11K, in good agreement with values in the literature.