New detector calibration facility for the wavelength range 35–400 nm based on an electrical substitution radiometer

In the radiometry laboratory of the Physikalisch-Technische Bundesanstalt at the Berlin electron storage ring BESSY a new instrumentation has been set up for the calibration of transfer detectors in the wavelength range from 35 to 400 nm with an aspired uncertainty of <1%. The spectral responsivity of a detector is determined by comparison with the known responsivity of an electrical substitution radiometer operated at liquid helium temperature as the primary detector standard. A first calibration of silicon photodiodes was performed in the spectral range above 250 nm. The spectral responsivity determined with 3% uncertainty was found to agree with previous calibrations conducted with lasers as sources.