M. Zehetmayer, M. Eisterer, H. W. Weber:
"Simulation of the current dynamics in a supercondutcor induced by a small permanent magnet: application to the magnetoscan technique";
Superconductor Science and Technology,
The magnetoscan is a rather new technique for investigating local inhomogeneities of large bulk high-Tc superconductors. Local (shielding) currents, which are induced by a small permanent magnet slightly above the sample surface, generate a magnetic field that is recorded by a Hall probe. We report on a theoretical analysis of such a three-dimensional system using numerical simulations to calculate the current dynamics during a magnetoscan.
The magnetoscan signal is analysed for different experimental setups and different critical current densities of the superconductor. We show that the shape of small defects (~1 mm in size) is almost exactly displayed, even if the radius of the permanent magnet is much larger than the defect size. The critical current density of larger inhomogeneities can be directly determined at the sample surface, if all details of the experimental setup are known. Different aspects of how to improve the experimental resolution are discussed.
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