Monte Carlo modelling of a neutron-induced gamma-ray sensor for landmine or explosive detection

Monte Carlo simulations were carried out to model a thermal neutron-induced gamma-ray sensor for anti-personnel-landmine (APM) or explosive detection. This is done by employing the thermal neutron prompt gamma activation (TNPGA) technique. The neutron capture reaction on nitrogen N-14(n,gamma)N-15 is analyzed to detect the subsequent characteristic 10.8 MeV gamma rays. This is done by modelling a suitable geometry consisting of a point Cf-252 source placed inside a sphere of lead (Pb) which is contained in a cylinder of high density polyethylene (HDPE), together with a NaI (Tl) detector. The sensor geometry was optimized and the optimal configuration was selected to scan a plastic APM buried (2-10) cm. The Monte Carlo results obtained in terms of variations of the signal-to-background ratio, indicated the feasibility of employing N-14(n,gamma)N-15 neutron capture reaction for landmine detection and the suitability of the proposed sensor for airport explosives as well.