Diamonds for X-ray optical applications at 3^rd and 4 ^th generation X-ray sources

There is currently interest in low strain HPHT diamond due to its expected application as various types of X-ray optical elements at Synchrotrons, where the X-ray intensity is becoming progressively too severe for the existing materials. The diamond crystals need to be synthesised with unprecedented lattice quality. In recent measurements at the ID19 beamline of European Synchrotron Radiation Facility (ESRF), the strain sensitivity of the (quantitative) X-ray plane wave monochromatic topography was increased to the level of 10^-8 using the double crystal technique with successively higher order reflections and correspondingly higher energy X-rays. At this level the strain fields of certain defects have a clearly visible macroscopic extent. In particular, both compressive and tensile strain fields of sparse single dislocations are well observed, as are long range strain fields due to isolated surface scratches. The surface processing of diamond for low roughness and good near surface crystal quality is a priority. A study of the progress towards this goal using the X-ray techniques of reflectivity, Grazing Incidence small angle X-ray Scattering (GISAXS) and Grazing Incidence X-ray Diffraction (GID) has been undertaken. The ability of diamond X-ray optical elements to process X-ray beams while preserving the coherence properties of the beam is essential to establish, and measurements of this via the Talbot effect have been carried out. This contribution will detail some of the latest results and comment on future prospects.