Monte-Carlo simulation of a neutron Brillouin scattering spectrometer

A Monte-Carlo simulation was done to optimise the setup of a new type of time-of-flight spectrometer, a thermal neutron Brillouin scattering (NBS) spectrometer. After collimation of the incident white neutron beam five incident energies between 20 and 138 meV can be obtained from four different monochromator crystal faces. The monochromatic beam is split into nine pencil-like separate beams to improve the Q-resolution of the NBS-spectrometer. Including the time resolution of the Fermi chopper (after a background chopper) an energy resolution for elastic scattering between 2% and 7% and a momentum transfer resolution of 1.3–2.0% are obtained.