Background and resolution functions in neutron time-of-flight spectrometers

In the context of the more complete characterisation of time-of-flight spectrometers based on pulsed white sources, neutron scattering effects in the source and detector areas are likely sources of resolution function asymmetry and background generation. A detailed Monte Carlo simulation has been made of the effects of source room return of scattered neutrons on pulsed and moderated white sources. It reveals significant resolution broadening effects only for compact sources (cyclotrons), but not for larger source enclosures (linacs). Source room return is unlikely to be a significant source of background for either cyclotrons or linac sources. The preliminary findings of a set of complementary calculations for scintillation detectors in practical shields are that both background generation and resolution broadening are likely to be significant following neutron scattering in this region. (Auth.)