A SURF beamline for synchrotron source-based absolute radiometry

A new source-based radiometry beamline was recently constructed at the Synchrotron Ultraviolet Radiation Facility (SURF III). The goal of this beamline is to establish a national source standard with a wide spectral range from the far ultraviolet to the infrared by using the calculability of SURF III. The new beamline is a straight-through white-light beamline with few, if any, optical components involved in delivering the radiation to the user end-station for applications such as source and irradiance intercomparisons. Due to the low tunable operating electron energy of SURF III (from 380 MeV to less than 100 MeV), the beamline is uniquely suited to work in the ultraviolet to infrared spectral range. In this paper we discuss the design of the beamline and present first results on the vertical angular distribution of the radiation determined with filtered radiometers in the ultraviolet, visible and near-infrared spectral ranges.