An underwater system for explosive detection

Abstract

Once the presence of the anomaly on the bottom of the shallow coastal sea water is confirmed it is necessary to establish if it contains explosive charge. This could be performed by using neutron sensor installed within an underwater vessel - surveyor. When positioned above the object, or to its side, the system inspects the object for the presence of the explosive by using neutrons from the sealed tube d+t neutron generator. In order to evaluate various components and geometries a test basin containing sea water and sand was constructed. Components of the neutron sensor were placed inside a waterproof stainless steel box which could be moved up and down inside the basin. Measurements were performed by neutron generators with and without detection of associated alpha particles. Low energy resolution gamma detectors (BGO and NaI) were used. The sensor using neutron generator with detection of associated alpha particles was found to have a superior performance since the detection of alpha particles defines the neutron beam which helps the reduction of the background. The most common military explosives are characterized by H, C, N, O concentration values. Whole spectrum signature could be used for the identification of the materials investigated.