Structure of the current-induced intermediate state in type I superconductors

Several models have been proposed for the intermediate state which occurs when superconductivity is destroyed in type I wires by a current. Experimental testing of these models has, so far, only been possible through measurements of the resistance and the intermediate state core radius during the transition. We describe an experiment in which a wire specimen is placed along the axis of solenoid whose inductance is monitored as a steadily increasing direct current destroys superconductivity in the wire. The change in inductance of the solenoid is a function of the intermediate state structure, and the experimental results are compared with theoretical values obtained on the basis of the various models. Our results appear to favour the model presented by Baird and Mukherjee in 1971.