Detection and Identification of Contraband in Air Caro Containers Using Neutron Based Techniques

This paper describes and discusses the combined system which was installed to allocate and identify contraband materials hidden in air cargo containers by fast neutron radiography and neutron elemental analysis techniques. A slit of fan beam of fast neutrons emitted from Pu-Be source was used. The fast neutron fluxes passed through different lines crossing the hidden object were detected by a neutron spectrometer applies stilbene scintillator and pulse shape method to discriminate agnist undesired pulses of gamma-rays. A two channel spectroscopy method was used to eleminate the effect of spectrum shift caused by the benign materials surrounding the hidden object. The recognetion of the allocated suspected object was performed by measuring the gamma-ray spectrum emitted from the suspected object by a gamma spectrometer with NaI(Tl) detector fixed at the middle point of the container and at a vertical plane to the incident beam. Tests were carried out using 2.5 kg of RDX explosive material hidden withen materials of pasta, onion and ceramic tiles. The results of fast neutron radiography are presented in the form of attenuation relation profiles and 2D constructed images. The measured spectra of emitted gammarays were used to determine the energy and intensity of gamma lines emitted from different elemental constituent of the suspected object. The analysis of the constructed images and gamma-ray spectra obtained for different tests indicated the reliability and capability of the installed combined system for inspection of small and medsize containers for illicit traficking.