Sagittal focusing of synchrotron radiation diffracted on the walls of a longitudinal hole drilled into a single-crystal monochromator

A very simple method of sagittal focusing of X-ray synchrotron radiation is presented. A special ray-tracing program which utilizes the diffraction-re fraction effect is developed. It is demonstrated both by ray-tracing simula tions and by an experiment whereby a reasonably good sagittal concentration of 8 keV synchrotron radiation may be achieved by diffraction on the walls of a cylindrical hole drilled into an Si crystal. The holes were drilled p arallel to the (111) planes and their diameter, 1 mm, was chosen so that th e focusing distance fits the geometrical arrangement of beamline BM5 at the ESRF. Two such crystals have been used in a dispersive and non-dispersive arrangement. The better result was achieved using the dispersive arrangemen t. The intensity at the centre of the focus is increased by five times with respect to unfocused radiation. Excellent agreement exists between the ray -tracing simulations and experimental results.