Investigation into a suitable scintillator and coded-aperture material for a mixed-field radiation imaging system

Monte-Carlo modelling (MCNPX) methods have been employed to conduct an investigation into a suitable scintillator and coded-aperture material for a scintillator based mixed-field radiation imaging system. Single stilbene crystal, pure and Li-6-loaded plastic scintillators were simulated and their neutron/gamma detection performance compared when exposed to the spontaneous fission spectrum produced by Cf-252. The most suitable candidate was then incorporated into a scintillator based mixed-field coded-aperture imaging system. Coded-aperture models made of three W and Cd-113 compositions were tested in different neutron/gamma environments with a square W collimator modelled around the aperture. Each simulation involved recording the interactions of neutron events in organic solid scintillator, whose neutron/gamma detection performance was assessed prior to the coded-aperture material investigation. Three coded-aperture material compositions have been tested with the simulated Cf-252 spontaneous fission as well as (AmBe)-Am-241 neutron sources. Results generally claim very good detection sensitivity and spatial resolution for the radioactive sources located in the centre of the aperture.