A high-temperature blackbody radiation source.

A high -temperature blackbody radiation source, consisting of an electrically heated graphite tube with a small centrally located hole through one wall, was developed for use as a secondary standard in the calibration of radiometric and spectrometrlc instruments. The spectral emlssivity of this source, at 0.65 M» was calculated by the DeVos method, for which graphite emissivities and temperature gradients were measured in situ with an optical pyrometer. The values of source emlssivity ranged from 09981 t 0.0004 at 1000C to 0.9997 i 0.0002 at 2000C.