Retrieval of critical current distribution in small Josephson junctions

We have developed a method to retrieve or to estimate the spatial critical current distribution in a small Josephson junction from a critical current measurement in a magnetic field (the junction size is in reference to the Josephson length). The method is based on an iterative algorithm that uses fast Fourier transform and physical constraints to achieve the proper solution(s). We simulated some typical critical current distributions and the algorithm converged to a single solution. We applied the algorithm to measurements of the critical current of grain boundary junctions of an oxygen deficient YBa2Cu3O7−δ thin film. The convergence was always to one of a very few solutions very similar in nature.