Proof-of-principle Study of Explosive Detection Based on Nuclear Resonance Absorption

With the increasing of trade globalization, the amount of cargo container transportation between countries grows higher and higher. Handling the threat of explosive materials concealed in cargos is a prickly subject, since the conventional explosives are relatively easy to obtain and may cause massive harm to people and property. For this reason, a quick and accurate method of finding hidden explosives is a high priority in national security. Several methods have been used to detected explosives, such as Xray screening, neutron interrogation, etc. However, these explosives interrogation methods all have drawbacks that limit their effectiveness. Detection of explosives based on nuclear resonance absorption of gamma rays in 14N, which was proposed in 1991, is a promising method. Because most of the explosives have higher nitrogen density than other common materials, it can be exploited as a means of distinguishing them from a host of other commonly transported materials. It is known that the materials with largely concentrated nitrogen can resonantly absorb the γ-ray with the energy of 9.17 MeV. In this work, a proof-of-principle experiment on the 2×1.7 MV Tandem Accelerator at Beijing Normal University was performed. The 9.17 MeV γ-ray was produced by the 13C(p,γ)14N resonant reaction at the beam energy of 1.75 MeV. Different lengths of boxed melamine at the direction of 9.17 MeV γray emitted were used as absorbers to study the absorption effect of highly concentrated nitrogen materials. As a comparison, a graphite rod was also used in the experiment for the study of absorption effect of nonconcentrated nitrogen materials. It is verified that the longer of the melamine absorber, the more distinctive absorption effect are observed. A lower detection limit of 23 g/cm2 concentrated nitrogen was also obtained in the experiment. This work lays the foundations of the establishment of the detection method for explosive materials concealed in cargo containers.