Simulating Neutron Diffraction from Deformed Mosaic Crystals in McStas

Monochromator and analyzer systems that rely on bent single crystals are in use throughout the neutron scattering community. An adequate component for the simulation of such crystals was missing in the widely used neutron simulation software package McStas. The newly developed component Monochromator_bent, which fills this gap, is introduced. It can serve as a model for crystal monochromators and analyzers of various kinds, including the bent perfect crystals, mosaic crystals, and crystals combining mosaicity with bending. The performance of the component is tested at several configurations and compared with the results of another simulation program, SIMRES. Validation is carried out using analytical calculations and the McStas NCrystal_sample component for the case of unbent crystals. Excellent agreement in all tests and good performance in terms of computing speed has been found. The component has been included in the present distribution of McStas 3.5.