ENERGY-DISPERSIVE DIFFUSE-X-RAY SCATTERING TECHNIQUE .1. PRINCIPLES

Energy-dispersive diffuse X-ray scattering is a particularly appropriate technique for use with high-energy synchrotron-radiation sources. Its multiplex and geometric advantages are outlined and the comparatively simple principles behind the technique are detailed. The energy-dispersive scan spreads scattering in reciprocal space along radial lines, with equal-energy steps corresponding to equal-scattering-vector steps. In a typical experimental configuration, the resolution function of the apparatus is substantially lozenge shaped in reciprocal space: modest resolution is obtained along radial lines whereas good resolution can be obtained in transverse directions if the limiting geometrical factors are kept narrow. The factors influencing the conversion of the observed scan intensities to absolute units are discussed and methods given of minimizing the difficulties. Paper II of this series will discuss the application of these methods, notably to measurements of silicon.