Final Report - Strategic Environmental Research and Development ...

AbstractThis research project concerns the fundamental physics of the electromagnetic response ofmunitions items and metallic clutter and its application to procedures for the classification ofunknown buried objects using electromagnetic induction (EMI) data. The EMI response for acompact steel object exhibits an early algebraic regime wherein the response transitions from t -1/2to t -3/2 decay, followed by a late regime characterized by an exponential decay of the response.The early, algebraic regime is associated with eddy currents confined near the surface of theobject (magnetic surface modes), and its progress is described by the classical mathematics ofdiffusion. At late times the eddy currents have diffused throughout the object and the responsedecays exponentially.An extensive database of EMI responses for munitions and clutter items was assembled for thisproject. The database has been used to explore the significance of the two regimes forclassification. Our basic conclusion is that a decay time interval of about 0.1 ms to 3 ms isadequate for classification. This range lies within the magnetic surface mode regime for mosttargets of interest.This report includes detailed descriptions of the EMI signature database, parameterization of theEMI signatures and their interpretation in terms of magnetic surface modes and exponentiallydecaying body modes.