Radiometry at the electron storage rings BESSY I and BESSY II

The Physikalisch Technische Bundesanstalt (PTB), Germany's national metrology institute, has been operating a radiometry laboratory at the BESSY I 800 MeV electron storage ring since 1982 . BESSY I is used as a primary source standard of calculable spectral photon flux with relative uncertainties below 0.4 per cent in a broad spectral range from 1 eV to 15 keV. A cryogenic electrical-substitution radiometer is operated as a primary detector standard with a relative uncertainty of less than 0.2 per cent in the measurement of radiant power. Based on these primary standards, radiation sources, detectors and optical components are station. Currently, PTB is commissioning new experimental station in its radiometry laboratory at the third generation BESSY II 1.7 GeV electron storage ring to extend the spectral range to the hard X-ray range by using radiation from bending magnets and a superconducting wave length shifter and to improve radiometry by using undulator radiation. The current status of radiometry at BESSY I will be reviewed and the new radiometry programs outlined which have been planned for BESSY II. (author)