Superconductor strip with transport current: Magneto-optical study of current distribution and its relaxation

TL;DR

This study uses magneto-optical imaging to analyze flux distribution and current relaxation in a YBaCuO superconductor strip under transport current, confirming qualitative agreement with Bean model predictions.

Contribution

It provides detailed experimental insights into flux dynamics and current redistribution in superconducting strips under realistic transport conditions.

Findings

Flux penetrates the strip during current pulses.

Local magnetic field can increase or decrease depending on position and current.

Current density tends to become more uniform over time.

Abstract

The dynamics of magnetic flux distributions across a YBaCuO strip carrying transport current is measured using magneto-optical imaging at 20 K. The current is applied in pulses of 40-5000 ms duration and magnitude close to the critical one, 5.5 A. During the pulse some extra flux usually penetrates the strip, so the local field increases in magnitude. When the strip is initially penetrated by flux, the local field either increases or decreases depending both on the spatial coordinate and the current magnitude. Meanwhile, the current density always tends to redistribute more uniformly. Despite the relaxation, all distributions remain qualitatively similar to the Bean model predictions.