Explosive detection system using pulsed 14 MeV neutron source

The main elements present in the explosives are hydrogen (H), nitrogen (N), oxygen (O) and carbon (C). The elemental density ratios (C/O, N/O, H/N, etc.) of explosives are different from the other substances. The explosives are characterized by low H and C concentration and high N and O concentration. The elemental composition of explosive materials can be found by measuring the γ-rays produced due to the activation of explosive material by 14 MeV neutrons. A pulsed fast neutron system is used for the identification of H, N and O. Ammonium nitrate sample has been irradiated by pulsed 14 MeV neutrons of 108 neutrons/pulse and the pulse width less than a microsecond. The material has been irradiated with 5–7 neutron pulse in order to increase the γ-ray count. The resulting γ-ray spectrum due to the activation of ammonium nitrate is recorded and presented in this work. The γ-ray spectrum has been recorded using 3″ × 3″ Bismuth Germanium Orthosilicate (BGO) and fast digitizer with sampling rate of 2 GS/s. The signal is transferred through fiber optic cable to the personal computer for further processing and analyzing. Pulse-height spectrum is constructed through a dedicate MATLAB routine in which the number of energy bins can be kept as per requirement.