High-efficiency logarithmic spiral monochromator for X-ray fluorescence

A spiral mosaic crystal monochromator system has been designed for high-efficiency collection of X-ray fluorescence. This is especially well suited for X-ray holography measurements, where a weak fluorescence signal must be separated from a strong background. Calculations show that pyrolytic graphite curved to a logarithmic spiral has a dramatically increased angular acceptance compared to standard graphite monochromator designs. The collection efficiency per unit area of graphite is improved by a factor of 200 compared to sagittal focusing geometries, while maintaining the intrinsic graphite energy resolution.