Detector calibration at the PTB radiometry laboratory at BESSY

In the vacuum ultraviolet (VUV) and soft X-ray spectral ranges the radiometry laboratory of the Physikalisch-Technische Bundesanstalt (PTB) at the synchrotron radiation facility BESSY offers two different methods for the calibration of radiation detectors: ectron storage ring BESSY, in combination with suitable monochromators, reproducibly produces monochromatic radiation of tunable photon energy, high spectral purity (< 1% false light contribution), high spectral resolving power and high radiant power, which can be scaled down over twelve orders of magnitude. With this source of monochromatic radiation a cryogenic electrically substituted radiometer (ESR) is operated as a primary detector standard in the photon energy range from 3 to 1500 eV. The ESR is optimized for synchrotron radiation, capable of measuring radiant power in the order of some μW with an uncertainty below 0.2%. Sufficiently stable radiation detectors can be calibrated against the ESR with uncertainties well below 1%. Recent progress in this field will be demonstrated for the calibration of photodiodes. ectron storage ring BESSY is also used as a primary source standard, in the photon energy range from the infrared to the soft X-ray range. The spectral and spatial distribution of the broadband radiation emitted in the range from 1 to 15 keV is calculable from the known storage ring parameters with uncertainties from 0.04% to 0.35%. respectively. This allows the detection efficiency of energy-dispersive detectors such as solid-state detectors, charge coupled devices and others to be determined, provided the detector response function to monochromatic radiation is measured as well.