APPARATUS FOR THE MEASUREMENT OF THE OPTICAL-CONSTANTS AND THERMAL RADIATIVE PROPERTIES OF PURE LIQUID-METALS FROM 0.4 TO 10 MU-M

Measurements of the optical constants and thermal radiative properties of high-temperature solid tungsten and molten aluminum have been made using a new instrument that includes two independent optical systems and surface control and, analysis capability. The two optical systems, one for measuring the complex index of refraction by ellipsometry, th e other for measuring the normal spectral emissivity by direct compari son to an integral blackbody cavity, operate over the wavelength range 0.4-10 mum with sample temperatures between 940 and 1630 K. The surfa ce science capabilities of the instrument permit the preparation of hi gh-purity samples of known composition in situ. The apparatus includes two 5-keV argon-ion sputter guns, an ultrahigh vacuum pumping system, and an Auger spectrometer. The two sputter guns allow surface cleanin g to occur while optical measurements are being made, or while Auger s pectroscopy is determining the surface composition of solid or liquid samples. The ellipsometric optical system uses a novel radiation sourc e (a carbon composite element), refractive optics (calcium fluoride), interference filters for spectral selection, and both calcite and wire grid polarizers to cover the extended wavelength range. The system fo r measuring the normal spectral emissivity uses reflective optics and an integral blackbody cavity that is located in the wall of the crucib le holding the liquid sample. The use of two measurement techniques gi ves independent determinations of the normal spectral emissivity and t hus allows reliable estimation of experimental errors.