X-ray detector calibration in the PTB radiometry laboratory at the electron storage ring BESSY II

The Physikalisch-Technische Bundesanstalt (PTB) currently operates a laboratory for radiometry from the VUV to the hard X-ray spectral range at the 1.7 GeV electron storage ring BESSY II. Detector calibration, performed by the PTB at BESSY I up to photon energies of about 1.5 keV, can now be extended up to 10.5 keV based on an electrical substitution radiometer as a primary detector standard and on the use of monochromatized bending magnet and undulator radiation of high spectral purity. This energetic range will be further extended up to 50 keV by using radiation from a 7 T wavelength shifter. Moreover, BESSY II is a primary source standard offering calculable bending magnet radiation. The PTB uses these primary standards for the absolute calibration of detectors with relative uncertainties below 1%. Up until now, photodiodes, energy-dispersive semiconductor detectors and also superconducting tunnel junctions have been characterized for photon energies up to 10.5 keV.