Neutron Ray-Tracing Simulations of a New Supermirror Guide for the Osiris Spectrometer

A new supermirror guide has been proposed to replace the current neutron guide of the indirect time-of-flight near-backscattering spectrometer OSIRIS at the ISIS facility. Here we present an extensive Monte Carlo simulation study for the design and optimisation of a new guide system. Among the several guide geometry assessed, a curved guide with elliptical defocusing and focusing sections is shown to perform best. The estimated gain in intensity is a factor of 5-6 at the sample position with a homogeneous distribution of the divergence. The elliptic geometry results in a smaller beam spot and smaller samples will particularly benefit from this upgrade. The proposed guide replacement will ensure that the OSIRIS spectrometer will remain competitive in the years to come.