Degradation and reenhancement of the peak critical current in superconducting lead

Certain samples of the type discussed in a previous article have been shown to exhibit greatly broadened I-R transitions. Although the axial asymmetry of the sample appears to induce the broadening, the transition can be made to approach that of a right circular cylinder of lead by certain surface treatments or by flux trapping. A simple qualitative model is outlined to correlate these phenomena.