System for the Measurement of Spectral Emittance at High Temperature

Abstract

A system for measuring the emittance of refractory materials in vacuum for temperatures up to 3000C in the wavelength range of 0.4-5.0 has been developed and tested. In preferred operation, the specimen is machined to contain its own reference cavity. An optical nulling measurement system was developed in which the radiation from the sample and a reference lamp are focused alternately on the entrance aperture of a monochromator. Detailed error analysis and comparison with literature data for tungsten showed the system to be accurate to ± 0.02 for emittances above 0.50. Graphite, carbon foam, and aluminum oxide also were measured.