Modified magnetoscan technique for assessing inhomogeneities in the current flow of coated conductors - Theory and experiment

摘要

The magnetoscan technique was recently introduced to investigate local inhomogeneities of large high T, superconductors without destroying them. Local currents are induced by a small permanent magnet moving slightly above the sample surface. The magnetic field of these currents, which depend on the local material properties, is measured by a Hall probe. We show that the technique can be successfully applied to coated conductors. Inhomogeneities and defects are easily detected by significant changes in the magnetoscan signal. To confirm our interpretation of the experiment, numerical simulations, based on Maxwell's equations, were carried out. We calculate the current flow and the magnetoscan signal for different experimental setups and critical current densities. Inhomogeneities were introduced by assuming a position dependent critical current density. Good agreement between experiment and theory is obtained. (c) 2007 Elsevier B.V. All rights reserved.