Monte Carlo ray-tracing code for RESTRAX

Abstract

The advent of powerful workstations and personal computers in the 1990s opened the way for widespread use of Monte Carlo (MC) methods in design and optimization of neutron scattering instruments. MC ray-tracing programs can be written for any instrument arrangement and allow for more realistic simulation of the instrument performance. The only practical limits are the computing speed and the accuracy of the physical models describing neutron transport through individual components, for example, diffraction from real crystals. Several MC ray-tracing simulation packages [1] have been developed in recent years in order to provide a tool for accurate assessment of the performance of instruments with new neutron-optical components, including focusing crystal arrays, supermirror guides, and polarizing benders. The existence of multiple software packages, sometimes considered as arising from a useless duplication of efforts, has its justification. On one hand, each program is optimized for a different mode of operation, resulting in a different trade-off between speed and flexibility. On the other hand, the comparison of independently obtained results allows one to minimize possible errors in the design of instruments.