La réponse à un échelon de champ d'un supraconducteur de type II: un moyen simple de tester l'ancrage des vortex en volume The magnetic-field step response of a type II superconductor as a simple test of the vortex bulk pinning

Abstract

A slab in parallel field is submitted to a step-like magnetic-field excitation, of amplitude 1-10 G, in the same direction as the applied field. The slab has been rolled or spark cut, without special care, from a conventional superconductor ingot (lead-indium alloy) and its critical currents have standard values. The transitory electrical field induced on a face of the slab has been measured. Thus, we obtain information about the magnetic flux penetrating and vortices entering the sample through this face. The only observed deviation from the ideal response is that magnetic-field diffusion is limited by surface screening, associated with a superficial critical current density. Otherwise, the vortex array inside the slab responds exactly as if bulk pinning were ineffective.