Realization of the spectral irradiance scale in the air-ultraviolet using thermal radiators

Abstract

In a new facility, the use of thermal radiators such as FEL lamps and very-high-temperature black bodies as standards of spectral irradiance has been extended for the first time down to 200 nm, thus covering the whole air-ultraviolet range. This improvement is based on a significant increase of the throughput and signal-to-noise ratio of a spectroradiometer and on a large reduction in the effects from stray light within this new calibration facility. The reliability of this facility is demonstrated in a comparison between calibrations of spectral irradiance using a black body with different radiometric temperatures, and in a comparison of the calibration of an FEL lamp and a deuterium lamp with the existing scale. The uncertainties achieved are as low as or better than those of the standard facility in this spectral range.