Components for the X-ray radiometry beamline at BESSY II.

Optical components for the X-ray radiometry beamline of the Physikalisch-Technische Bundesanstalt at BESSY II were investigated at BESSY I. Reflectometry measurements on different mirror coatings were used to calculate their capability to suppress higher-order radiation. An MgF(2) coating proved to be best suited for photon energies below 4 keV. The reflectance of silicon (111) monochromator crystals at low photon energies around 2 keV was homogeneous within +/-1%. In a test at a superconducting wavelength shifter the cooling system for the first crystal was shown to cope with the absorbed power of 14 W.