Effects of a nonuniform current distribution on the kinetic inductance of a thin superconducting film

Kinetic inductance measurements were used to probe the current uniformity in thin amorphous Bi0.97 Tl0.03 films. Measurements were made on films having widths of 0.5 and 0.2 mm with thick thicknesses ranging from 300 to 2000 Å condensed on both quartz plates and Nb shield planes. The results for films without shield planes are compared to predictions based on approximate expressions for the current density in a thin film. The Nb shield plane appears to produce considerable smoothing of the current distribution. Measurements of the kinetic inductance of films on such a shield plane appear to provide a good method for the determination of the penetration depth in a-Bi.