High-efficiency logarithmic spiral monochromator for X-ray fluorescence

A spiral mosaic crystal monochromator system has been designed for high-eff iciency collection of X-ray fluorescence. This is especially well suited fo r X-ray holography measurements, where a weak fluorescence signal must be s eparated from a strong background. Calculations show that pyrolytic graphit e curved to a logarithmic spiral has a dramatically increased angular accep tance compared to standard graphite monochromator designs. The collection e fficiency per unit area of graphite is improved by a factor of 200 compared to sagittal focusing geometries, while maintaining the intrinsic graphite energy resolution. (C) 2000 Elsevier Science B.V. All rights reserved.