Working Group 7.11
X-ray Radiometry

The working group X-ray radiometry operates the four-crystal monochromator beamline in the PTB laboratory at BESSY II to provide monochromatized synchrotron radiation in the photon energy range from 1.75 keV to 10 keV. For higher photon energies up to 120 keV, the BAMline, a wavelength-shifter beamline also located at BESSY II is used. A cryogenic electrical substitution radiometer serves as primary detector standard for detector calibration up to 60 keV, also for the calibration of semiconductor photodiodes as transfer detectors.

An UHV reflectometer is available for reflectometry. An important application of reflectometry is the layer thickness determination, focused on SiO₂ layers on Si in the thickness range from a few nm up to 1 µm, also on the surface of silicon spheres in connection with the redefinition of the unit kilogram.

Within the framework of scientific co-operations, detectors, filters and mirrors are characterized for future missions in astrophysics (ESA) and for plasma diagnostics (CEA). For the investigation of novel pore optics based on stacked silicon wafers, a dedicated beamline is being operated for ESA where a fixed-energy pencil beam is available.

Furthermore the energy-dependence of the biological effectiveness of X-rays is investigated and spectrally resolved measurements are performed on mammography and computer tomography units. A new main focus is the development of small-angle X-ray scattering for the traceable size determination of nanoparticles.