Abstract
Various local probes have been applied to understanding current flow through superconducting films, which are often surprisingly inhomogeneous. Here, we show that magnetic imaging allows quantitative reconstruction of both current density and electric field resolved in time and space in a film carrying subcritical ac current. Current reconstruction entails inversion of the Biot-Savart law, while electric fields are reconstructed using Faraday’s law. We describe the corresponding numerical procedures, largely adapting existing work to the case of a strip carrying ac current, but including other methods of obtaining the complete electric field from the inductive portion determined by Faraday’s law. We also delineate the physical requirements behind the mathematical transformations. We then apply the procedures to images of a strip of carrying an ac current at . Our scanning Hall probe microscope produces a time series of magnetic images of the strip with spatial resolution and time resolution. Combining the reconstructed and , we obtain a complete characterization including local critical current density, curves, and power losses. This analysis has a range of applications from fundamental studies of vortex dynamics to practical coated conductor development.
1 More- Received 27 November 2006
DOI:https://doi.org/10.1103/PhysRevB.75.144503
©2007 American Physical Society