Abstract

A transient calorimetric method of measuring the total hemispherical emittance of transparent materials in the temperature range 75°K to 312°K is described. Measured emittance values with an estimated accuracy of ±5% are presented for various thicknesses of NaCl and fused quartz. The emittance of NaCl decreased from 0.67 at 75°K to 0.34 at 312°K. The emittance of quartz was approximately constant at 0.73 over the same temperature range. Increasing the thickness of NaCl resulted in slight increases in emittance; no thickness effect was observed in the quartz. Total normal emissivity values calculated for NaCl from optical constants were not appreciably different from the measured total hemispherical emittances.

© 1967 Optical Society of America

Total Hemispherical Emittance of Irtran 2, 4, and 6 at Low Temperatures

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