A CCPR international comparison of spectral radiance measurements in the air-ultraviolet

An international comparison of the spectral radiance scales of the National Physical Laboratory (NPL), the National Institute of Standards and Technology (NIST) and the Physikalisch-Technische Bundesanstalt (PTB) was carried out in 1993 and 1994, under the auspices of the Comite Consultatif de Photometrie et Radiometrie (CCPR) of the Comite International des Poids et Mesures (CIPM). The comparison covered the spectral range 200 nm to 350 nm. The transfer standards were deuterium discharge lamps, with examples of the lamps used at each of the participating laboratories included in the comparison to aid in the identification of systematic errors and to gather information on their relative performance. The scales of the laboratories agreed within the combined uncertainties. However, the combined uncertainties were high (an expanded uncertainty with a coverage factor of k = 2 of up to 8 %), and further work is required to reduce the uncertainties associated with the spectral radiance scales of each laboratory. Little difference was observed in the performance of the three different transfer standard sources used.