Simulation on monochromators of double focusing perfect crystal and vertical focusing mosaic crystal

In order to satisfy both high flux and high resolution of residual stress neutron diffractometer, the monochromator was simulated using Monte Carlo simulation code SIMRES. A series of factors,including the diffraction geometries (symmetric diffraction, asymmetric diffraction and fully asymmetric diffraction), focusing conditions (vertical and horizontal focusing curvatures) and crystal types (perfect crystal and mosaic crystal), were considered in the simulation to study, taking the figure of merit (FoM) as a comparison measure, the influences of flux on resolution of the diffractometer. The results show that use of symmetric diffraction and perfect crystal double focusing could achieve the best performance. (authors)