29 April 2008 Underwater UXO detection and discrimination: understanding EMI scattering phenomena in a conducting environment
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There are approximately one million acres of underwater lands at Department of Defense (DOD) and Department of Energy (DOE) sites that are highly contaminated with unexploded ordnance (UXO) and land mines. The detection and disposal of Underwater Military Munitions are more expensive than excavating the same targets on land. Electromagnetic induction (EMI) sensing has emerged as one of the most promising technologies for underwater detection. In order to explore the full potential of various EMI sensing technologies for underwater detection and discrimination, to achieve a high (~100%) probability of detection, and to distinguish UXO from non-UXO items accurately and reliably, first the underlying physics of EM scattering phenomena in underwater environments needs to be investigated in great detail. This can be achieved by using an accurate 3D numerical code, such as the combined method of auxiliary sources and thin skin depth approximation (MAS/TSA), the pseudospectral time-domain technique, finite element methods or other approaches. This paper utilizes the combined MAS/TSA, originally developed for detection and discrimination of highly conducting and permeable metallic objects placed in an environment with zero or negligible conductivity. Here, first the theoretical basis of the MAS/TSA is presented for metallic objects placed in an electrically conductive environment. Then numerical experiments are conducted for homogeneous targets of canonical (spheroidal) shapes subject to frequency- or time-domain illumination. The results illustrate coupling effects between the object and its surrounding conductive medium, particularly at high frequencies (early times for time-domain sensors), and the way this coupling depends on the distance between the sensor and the object's center.
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Fridon Shubitidze, Fridon Shubitidze, Benjamin Barrowes, Benjamin Barrowes, Irma Shamatava, Irma Shamatava, Juan Pablo Fernández, Juan Pablo Fernández, Kevin O'Neill, Kevin O'Neill, } "Underwater UXO detection and discrimination: understanding EMI scattering phenomena in a conducting environment", Proc. SPIE 6953, Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XIII, 69530M (29 April 2008); doi: 10.1117/12.777876; https://doi.org/10.1117/12.777876

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