Instrumental line shapes in neutron powder diffraction with focusing monochromators

The optics of neutron powder diffractometers with bent-crystal monochromators is considered with respect to the computation of instrumental line shapes, accounting for second-order aberrations. A procedure of Monte Carlo simulation of instrumental line shapes has been developed. An analytical approximation of these shapes is described. Computational results for the case of the MURR diffractometer with position-sensitive detection and a focusing silicon monochromator are presented.