Focusing properties of curved x-ray diffractors

Calculations are described and results are given for the focusing properties of six curved x-ray diffractors for Bragg angles ranging from 15° to 75°. The geometries considered include cylindrical, spherical, and toroidal cases. The type of slit necessary to eliminate stray radiation in applications of doubly curved diffractors to scanning monochromators is discussed. Three of the most efficient diffractors are compared with respect to the solid angle for collection of x rays and the possible spectral resolution. A diffractor with spherically curved planes and toroidally curved surface is shown to be superior to the Johansson geometry and the spherically curved plate.