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.