Design and testing of a high-temperature emissometer for porous and particulate dielectrics

A new, high-temperature (500–1500 °C) emissometer has been designed, assembled, and tested. The apparatus is unique in that it may be used to measure the emittance of media that are semitransparent and show substantial surface roughness, internal voidage, and/or chemical inhomogeneities throughout the emitting volume. Data reduction procedures are developed and an analysis of systematic error sources and experimental uncertainty is presented. The emittance of a high-purity alumina was measured at several temperatures in the wavelength range from 2 to 14 μm. Results are compared to published values.