Computations on the spatial neutron moderation in target and moderator schemes for spallation sources

By a fully spatial Monte Carlo computation on the neutron moderation in a whole system consisting of target(s), moderator and reflector for a spallation source, the trajectories of slowing down neutrons in some newly proposed schemes are calculated and the configuration effects on the neutron moderation are visualized. The computations also enable us to predict the characteristics of the spectra obtained by the schemes. The calculation is based on a simple model of isotropic neutron scattering in the centre of mass system, however, the results on the trajectories and the spectrum in a whole system will be an intuitive help for us to design a new moderator scheme intending to obtain an intense thermal neutron flux with a spallation source.