Near-field linear sampling method for axisymmetric eddy current tomography

This paper is concerned with eddy-current (EC) nondestructive testing of conductive materials and focuses, in particular, on extending the well-known linear sampling method (LSM) to the case of EC equations. We first present the theoretical foundation of the LSM in the present context and in the case of point sources. We then explain how this method can be adapted to a realistic setting of EC probes. In the case of identifying the shape of external deposits from impedance measurements taken from inside of the tube (steam generator), we show how the method can be applied to measurements obtained from a sweeping set of coils. Numerical experiments suggest that good results can be achieved using only a few coils and even in the limiting case of backscattering data.