An unconventional explosives detector

Almost all explosive materials and chemical weapons possess unique, distinguishing chemical characteristics and are frequently composed of these four elements: oxygen, nitrogen, hydrogen and carbon. For example, Trinitrotoluene more widely known as the TNT consist of seven carbon atoms (C7), five hydrogen atoms (H5), three nitrogen atoms (N3) and six oxygen atoms (O6). As reported by T. Kasperek (Czas Morza 1, 15/2001), explosive materials and various other hazardous compounds such sulphur mustard (i.e. mustard gas) were widely used during the World War II as the basis for the production of chemical weapons. He also highlights, that after the War, vast amount of the German arsenal, along with estimated number of tens of thousands of tons of chemical weapon agents were disposed of by sinking in the Baltic Sea e.g. the Little Belt and near the Bornholm and Gotland Deeps. Furthermore, these rusting metal barrels and shells pose a very severe and growing threat to all the sea and coastal Baltic wildlife and people living near or from the Baltic Sea are also exposed to this danger.

This distinctive chemical composition of compounds such as TNT or sulphur mustard makes their detection a perfect task for the novel, innovative methods of underwater detection using Neutron Activation Analysis (NAA) techniques. Neutron particles that together with protons compose atomic nucleus were first discovered in 1932 by James Chadwick at the Cavendish Laboratory in Cambridge. Neutron flux can be used to irradiate the atomic nuclei of a given substance. Interaction with the neutron excites the nucleus which emits gamma quanta, energy of which can be captured to conduct stoichiometric analysis of this chemical compound i.e. obtain its chemical composition.

Currently, a group of researchers at the Jagiellonian University in Kraków (SABAT Group) is working on designing a prototype of an underwater threat detector that utilize the NAA method. Such device can be used to detect submerged hazardous materials like, for instance, the chemical munition sunk in the Baltic Sea waters. To minimize both, the background interference and radiation effects on the environment, a novel, patented approach was introduced to the design (M.Silarski, P.Moskal, Patent application PL409388). The system uses additional guides (i.e. special stainless-steel tubes) attached to the neutron generator through which the neutron beams are transported almost to the object surface at the sea bottom. Another pipe is used to carry the gamma quanta emitted by the excited nuclei of the substance. Furthermore, the sophisticated Monte Carlo simulation software was developed to efficiently develop and test possible design variants.

About the Author

Sławomir TadejaSławomir Tadeja is currently pursuing a PhD degree in the Department of Engineering, University of Cambridge and Trinity Hall. He works on the novel approach to information visualisation within the Virtual Reality environment. Previously, he has graduated with Licencjat and Magister degrees in Computer Science from the Jagiellonian University in Kraków. During this time, he has been part of the SABAT Collaboration for underwater threat detection (UJ), worked at the European Space Agency (ESA/ESTEC), CERN, Microsoft (Dublin) and Institute of Nuclear Physics PAN (IFJ PAN). Apart from spending countless hours in front of his computer screen he is an avid reader of the Sci-Fi and fantasy literature.

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