Calibration of energy-dispersive X-ray detectors at BESSY I and BESSY II

The un-dispersed synchrotron radiation from bending magnets at the primary standard source BESSY I has been used for many years for the calibration of energy-dispersive X-ray detectors. It has the advantage of continuously covering a broad spectral range from a few electron volts up to a few kilo-electron volts with lower uncertainty of the calculated spectral photon flux than any other source in that spectral range. With the recent establishment of BESSY Il as a primary source standard, the range of radiometry is further extended into the X-ray range up to about 50 keV. In this paper we present results on the calibration of a Si(Li) detector at BESSY I and Il. BESSY I was operated at a nominal electron energy of 800 MeV and BESSY II at 900 MeV and 1700 MeV. The comparison of the primary source standards BESSY I and II yielded perfect agreement. The relative uncertainty of the comparison of 0.007 is dominated by the measurement at B1. It is demonstrated that BESSY II operated at 1700 MeV electron energy is much more suitable for the calibration of energy-dispersive X-ray detectors. (authors)