Visualization of coupling current paths in striated YBCO-coated conductors at frequenciesup to 400 Hz

Abstract

The magnetic flux density component perpendicular to the broad tape face was mapped byminiature Hall probes in the vicinity of a striated YBCO-coated tape at frequencies ofexternal magnetic field from 21 to 400 Hz, applied perpendicularly to the tapesurface. For reasons of modelling the coupling current behaviour in tapes with aconductive substrate, we amplified the coupling current–amplitude by soldering25 µm thick copper foil on the top of the filaments. The aim of this procedure was to decrease thetransverse resistivity of the tape. The longitudinal components of the total currents flowingin the tape were calculated by an inverse method from the field map corresponding to thezero phase of the applied field. The diffusion lengths, characterizing the flux penetrationinto the tape, were determined for the respective frequencies. The experimentallydetermined diffusion length is in good accordance with theoretical models. While at 21 Hzboth weak coupling currents and distinctive hysteretic currents of individual filaments areobserved, at 400 Hz the coupling currents are predominant in this YBCO tape.