Inspections for contraband in a shipping container using fast neutrons and the associated alpha particle technique: Proof of principle Davorin Sudac * , Sasha Blagus, Vladivoj Valkovic Rudjer Boskovic Institute, P.O. Box 180, 10002 Zagreb, Croatia Available online 24 August 2005 Abstract Gamma rays produced by scattering of 14 MeV neutrons with detection of associated alpha particles were used for determination of object location in a shipping container. It is shown that is possible to locate an objectÕs position inside the container and, in some cases, also obtain some compositional information (at least carbon and oxygen in TNT). The movement of the peak in the time spectrum corresponds to the change of the object location in the container. Carbon was successfully identified together with its position in the container, even behind 5.1 cm thick iron slabs which is impossible to be seen by an industrial 300 keV X-ray radiographic system. Also, 7.5 kg of TNT was successfully iden- tified inside containers filled with soil. Ó 2005 Elsevier B.V. All rights reserved. PACS: 25.40.Fq; 29.40.M; 82.80.Ej Keywords: The associated alpha particle method; Gamma spectroscopy; Container inspections; Fast neutrons 1. Introduction The fight against terrorism is one of the most important issues in todayÕs international commu- nity. Acts of terrorism are associated with the illi- cit trafficking of explosives, narcotics, chemical weapons, hazardous chemicals, radioactive materi- als or humans. Old control measures slow down the traffic flow and they are time consuming and inefficient. Neutron-based inspection technologies have some powerful advantages over other tech- nologies [1]. Contraband objects possess elemental signatures that distinguish them from benign materials. Explosives are well characterized by their C/O and N/O ratios. In contrast to [2] where the (d,T) reaction was used with a 30 ls pulsed 0168-583X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.07.135 * Corresponding author. Tel.: +385 1 4561 161/1531; fax: +385 1 4680 239. E-mail address: dsudac@rudjer.irb.hr (D. Sudac). Nuclear Instruments and Methods in Physics Research B 241 (2005) 798–803 www.elsevier.com/locate/nimb