Background analysis on a detector shield system for fast neutron scattering experiments

A detector shield system for fast neutron scattering experiments to be installed in the JAERI tandem accelerator building has been designed using three-dimensional Monte Carlo calculations. The energy range of incident neutrons taken in the design calculations is up to 40 MeV. It is required to construct the detector shield system which can shield these high energy background neutrons effectively to perform neutron scattering experiments with good S/N ratio. By performing design analysis in detail using contribution flux, the origins and the quantities of various background components to the detectors have been pursued, and the optimum shapes of the shadow bar and the collimator channel in the shield system have been obtained. (author)