Time Resolved Magneto-Optical Imaging in High Frequency AC Currents of YBa₂Cu₃O_7-&[delta]Thin Films

Abstract

We present a time-resolved magneto-optical (MO) imaging study of high-temperature superconductor (HTS) in high-frequency alternating current (AC) regime. The evolution of the magnetic flux density distribution in YBa 2 Cu 3 O 7-δ (YBCO) thin film samples is studied in small steps of the phase of the applied AC current. The flux distribution at 10 K exhibits instabilities including flux jumps and flux creep. A quantitative analysis of the data allows us to obtain the current density evolution. The current profile changes considerably with the phase differently from the prediction of the critical state model. These observations can be explained by the higher self-field at the sample edge and the effects of flux creep.

AC Current Driven Flux Dynamics in YBCO Coated Conductors

“…The values of J c can vary from 60 to 193 A/cm-width along the tape length at alternating intervals. TRMO imaging studies on YBCO thin film samples showed a symmetric phase evolution of the magnetic flux [7,9]. Several pieces 10 mm long were cut along the tape transversal direction.…”