Evaluation of the Emissivity of a Cavity Source by Reflection Measurements

Abstract

The emissivity epsilon(c) of cylindrical cavities with different bases (flat, perpendicular to the axis; flat, inclined to the axis; conical) is derived from measurements of the cavity reflectance rho(c). A general formula for the calculation of rho(c) = 1 - epsilon(c) is given, which holds for high values of the ratio length L of the cylinder to radius R of the cylinder. For a flat base perpendicular to the axis only the value of the reflectance rho(o) of the wall material is needed; in both other cases one must refer to the measurements.