Identification of object composition with magnetic inductive tomography

The inductive response of an object to an oscillating magnetic field reveals information about its electrical conductivity and magnetic permeability. Here, we introduce a technique that uses measurements of the angular, frequency, and spatial dependence of the inductive signal to determine the object composition. Identification is performed by referencing an object's inductive response to that of materials with mutually exclusive properties such as copper (high electrical conductivity and negligible magnetic permeability) and ferrite (negligible electrical conductivity and high magnetic permeability). The technique uses a sensor with anisotropic sensitivity to discriminate between the different characters of the eddy current and magnetization driven object responses. Experimental validation of the method is performed using magnetic induction tomography measurement with a radio-frequency atomic magnetometer. Possible applications of the technique in security screening devices are discussed.