Simulation of the collimation property of parabolically curved graded multilayer mirror

X-ray diffraction is an important method for investigating the structure of materials. The delivery of high intensity, monochromatic, and parallel X-ray to a sample is essential. The parabolically curved graded multilayer mirror can well collimate the divergent X-ray beam emitted from a source and enhance the beam flux, compared with the traditional slit system. To provide a guide on fabricating a W/Si graded multilayer collimator at 8 keV, the collimation property is simulated, including the collimation efficiency of the collimator, as well as the intensity uniformity and divergence of the collimated beam. In particular, the influences of errors on the collimation property are simulated and summarized. 1) The most influential slope error of the substrate, should be smaller than 0.005 deg to avoid deterioration of the uniformity and parallelism of the collimated beam. 2) The period thickness error of the graded multilayer should be smaller than 7 %. 3) The mirror-detector distance error should be smaller than 3 mm. 4) The grazing angle error should be smaller than 0.03 deg.