New spectral radiance scale from 220 nm to 2500 nm

Abstract

The Physikalisch-Technische Bundesanstalt (PTB) has developed a spectral comparator facility for accurate spectral radiance measurements. As a primary standard source, a high-temperature black body (HTBB) is operated in the temperature range 1500 K to 3200 K. The black-body temperature is determined by two methods: monochromatic radiation thermometry relative to the freezing point of gold; and absolute radiometry with filter radiometers calibrated against a cryogenic radiometer. For these purposes, the HTBB is operated in radiance and irradiance modes at the same time. This paper presents an uncertainty analysis of the new spectral radiance scale embodied by gas-filled tungsten strip lamps from 220 nm to 2500 nm. Such lamps are currently used as transfer standards for the Consultative Committee for Photometry and Radiometry (CCPR) comparison of spectral radiance (CCPR-S1).