An Evaluation of an High Temperature Blackbody As a Working Standard of Spectral Radiance

Abstract

For those interested in measuring the spectral radiance of high-intensity arcs, especially in the ultraviolet region, the 3000 degrees C blackbody has several advantages over the conventional tungsten ribbon filament standard of spectral radiance. At a wavelength of 250 nm, it is between two and three orders of magnitude more intense and could have 30% to 40% less uncertainty in its spectral radiance. Moreover, by using the blackbody, measurements could be extended to wavelengths shorter than 250 nm. On the other hand, the intensity advantage of the blackbody can be nearly eliminated by operating and calibrating a tungsten standard-type lamp well over its rated current. Tests have shown that the stability of these lamps operated at 45 A and 50 A is suitable for calibration purposes.