Emissivities of Metallic Surfaces at 76°K

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Abstract
Heat transport by radiation between surfaces at 300°K and 76°K was measured to evaluate the effective emissivities of a number of technical grade or commercially available metals with unknown metallurgical history. The surface with the lowest total hemispherical emissivity was an unbuffed silver-plated surface. It was found that the emissivity of surfaces was lowest when used without any mechanical working and that the ability to absorb radiant energy varied with the length of time the surface was kept cold, even at a pressure less than 10−6 mm Hg, indicating surface contamination by residual gases.