Synchrotron-radiation-based cryogenic radiometry in the X-ray range

Abstract

The Physikalisch-Technische Bundesanstalt (PTB) has installed an X-ray radiometry beamline at the new electron storage ring BESSY II. The synchrotron radiation is monochromatized by a four-crystal monochromator in the photon-energy range from 1.75 keV to 10 keV. The known radiant power, determined with a cryogenic electrical-substitution radiometer (ESR) as primary detector standard, is used for the calibration of detectors such as semiconductor photodiodes. Relative uncertainties of spectral responsivity well below 1 % have been achieved.