Identification of materials hidden inside a sea-going cargo container filled with an organic cargo by using the tagged neutron inspection system

A tagged neutron inspection system was used to search for the presence of explosives hidden inside a sea-going cargo container. Several measurements were done with paper, semtex1a and flour samples placed inside a container filled with an organic cargo made of wooden plates. The results of time-of-flight and gamma-ray spectra measurements obtained with a 14 MeV tagged neutron beam have shown that the investigated materials could be well distinguished in a triangle plot with the following coordinates: the number of counts in the carbon peak, the number of counts in the oxygen peak and the number of counts in the transmitted neutron peak. The signature from the semtex1a explosive could be distinguished from the paper and flour signatures in the organic cargo by using the transmission detectors. Some knowledge about the organic matrix type and density is required, otherwise a high rate of false alarm could be expected. According to the present measurements it seems that the system will work in the organic matrix if its density is ⩽0.25 g/cm3.