Development of a new method for the detection of illicit materials based on the Active Photon Interrogation Method and photo-neutron spectrometry

Abstract

The detection of illicit materials is a critical task in the field of homeland security, as international trade has contributed to the increase of smuggling activities. Nonintrusive on-site inspections are crucial in this context, but the current active interrogation methods have limitations. Neutron-induced reactions have been used, but the measurement of gamma spectra is complex due to background noise. Active photon interrogation methods have also been overlooked but they are currently limited to actinides detection using photo-fission reactions. This work presents a novel method for the detection of illicit materials based on active photon interrogation and photo-neutron spectrometry. This approach extends the application of active photon interrogation by including the detection of conventional explosives, narcotics, and chemical weapons based on the use photo-nuclear reactions to determine the content of light elements such as nitrogen, oxygen, and carbon. Monte-Carlo codes are the main tool used to simulate this process for the application need. However, because of the lack in the present literature of measured neutron spectra, the experimental validation of the simulations is not straight forward. At present, benchmarking the Monte-Carlo codes seems to be the sole option for testing their ability to accurately simulate photo-neutron production and spectra for the nuclear reactions of interest. Simultaneously, we designed a test bench based on a linear accelerator to generate photons, induce photonuclear reactions, and acquire photo-neutron spectra. This study on the fundamental aspects of photo-neutron production lays the groundwork for a promising new detection method for illicit materials.