Optimization of a bent perfect Si(111) monochromator at a small take-off angle for use in a stress instrument

Abstract

The reflectivity and resolution properties of focusing cylindrically bent perfect crystal Si(111) monochromators of different diffraction geometries were tested with the aim of evaluating their possible use in a stress instrument with an unusually small take-off angle (2θM≃ 30°). The experiments showed that an Si crystal with reflecting planes (111) in the symmetric diffraction geometry provides a maximum figure of merit for accuracy in the peak position that is comparable to that achieved previously from an optimized Si(220) monochromator at 2θM≃ 55°.