Measurements of the Thermal Radiative Properties of Liquid Uranium

Measurements of the thermal radiative properties of liquid uranium have been made using an instrument with two optical systems, one for measuring the complex index of refraction by ellipsometry, the other for measuring the normal spectral emissivity by direct comparison to an integral blackbody cavity. The measurements cover the wavelength range 0.4–10 μm with sample temperatures between 1410 and 1630 K. Two 5-KeV ion sputter guns and an Auger spectrometer produce and verify, in situ, atomically pure sample surfaces. Good agreement between the two methods is observed for the normal spectral emissivity, which varies with wavelength in a manner typical of transition metals. The two components of the complex index of refraction—the index of refraction and the extinction coefficient—increase with wavelength, from ~3 at 0.4 μm to ~20 at 9.5 μm. Both components of polarized reflectivity are shown for visible to infrared wavelengths.