Determination of the current density distribution in Josephson tunnel junctions

The magnetic field dependence of the maximum Josephson current $I_m\left(H_y\right)$ in tunnel junctions is a function of the integral of the Josephson current density distribution in the direction of the magnetic field: $j_1\mathrm{}\left(x\right)=\int j_1(x,y) \mathrm{dy}$. It is shown that a determination of $j_1\mathrm{}\left(x\right)\mathrm{}$ from $I_m\mathrm{}\left(H\right)\mathrm{}$ is often ambiguous. Cases of different $j_1\mathrm{}\left(x\right)\mathrm{}$ with the same $I_m\mathrm{}\left(H\right)\mathrm{}$ are given. Experimental results of a study of the growth of microshorts in Josephson junctions are presented. Experimental configurations with which $j_1\mathrm{}\left(x\right)\mathrm{}$ can be determined are discussed.