RETRIEVAL OF CRITICAL-CURRENT DISTRIBUTION IN SMALL JOSEPHSON-JUNCTIONS

We have developed a method to retrieve or to estimate the spatial crit ical current distribution in a small Josephson junction from a critica l current measurement in a magnetic field (the junction size is in ref erence to the Josephson length). The method is based on an iterative a lgorithm that uses fast Fourier transform and physical constraints to achieve the proper solution(s). We simulated some typical critical cur rent distributions and the algorithm converged to a single solution. W e applied the algorithm to measurements of the critical current of gra in boundary junctions of an oxygen deficient YBa2Cu3O7-delta thin film . The convergence was always to one of a very few solutions very simil ar in nature. (C) 1997 American Institute of Physics.