Deconvolution of 2D transport currents from the local magnetic field distribution above flat superconducting samples

Measurements of the magnetic field distribution (magnetic images) above flat superconducting samples provide information on the pattern of current flow within the material. While several deconvolution procedures to calculate the current flow have been proposed, we show here that they do not always give accurate results in situations where the current flow extends to regions that are outside of the magnetic image window, as with transport currents in a conductor. We describe two new procedures which overcome the problem. The most accurate (and most direct) approach is to incorporate magnetic images at different heights above the sample. The second method relates to the more conventional case using only one field image at a finite height above a thin sample (but of finite thickness). The results compare favourably to existing approaches.