Monte Carlo Simulation Of Active Neutron Interrogation System Developed For Detection Of Illicit Materials.

Nowadays, the current threat of international terrorism is set to a severe level, demanding worldwide enhanced security. Radioactive materials that could be fashioned into a radiation dispersal device typically emit gamma rays, while fissile materials such as uranium and plutonium emit both neutrons and gamma rays via spontaneous or induced fission. Therefore, the detection and identification of hazardous materials has become increasingly important. We present the results of GEANT4 Monte Carlo simulation of an active neutron interrogation system based on highly segmented neutron/gamma-ray detector and pulsed neutron generator. This system is capable of detecting and imaging radioactive and special nuclear materials, explosives and drugs. The segmented scintillation detector works as a scatter camera, allowing selection of a gamma ray events that undergo multiple interaction in detector blocks for radioactive source localization. The detector consist of blocks made of plastic scintillator which provide scattering and blocks of CsI, used as an absorber, used as an absorber, which has to be efficient to detect the characteristic gamma radiation for the identification. Because of this imaging capability background events can be significantly rejected, decreasing the number of events required for high confidence detection and thereby greatly improving its sensitivity. A scatter imager for the detection of shielded radioactive materials has been conceptualized, simulated, and refined to maximize sensitivity while minimizing cost.