Variation of Q with energy in mosaic analyzers for inelastic x-ray measurements

Abstract

Curved mosaic graphite analyzers have been used for many years for inelastic scattering measurements with both conventional x-ray sources as well as synchrotron sources (1). The trend in recent years has been to use spherically bent perfect crystal analyzers to collect large solid angles with high energy resolution. Although, these spherical analyzers achieve excellent energy resolution, the large solid angle limits the Q resolution. For cylindrically bent mosaic graphite, it is possible to obtain good energy and Q resolution simultaneously, while maintaining a large solid angle by collecting a range of energies dispersed along a linear position detector. However, if the mosaic spread of the crystal is less than the acceptance angle subtended in the scattering plane, the energy spectrum from a mosaic analyzer as collected in a linear detector will have Q varying with energy. The resolution and the variation in Q with energy along a linear detector are discussed in relation to inelastic x-ray scattering measurements.