Size of flux jumps in superconducting films

TL;DR

This paper investigates vortex avalanches in MgB2 superconducting films at 4K, revealing size distributions and field dependence, and proposes a thermal model incorporating nonlocal electrodynamics to explain the phenomena.

Contribution

It introduces a thermal adiabatic model accounting for nonlocal electrodynamics to explain flux jump sizes and their field dependence in thin superconducting films.

Findings

Avalanche sizes range from 50 to 50,000 vortices.

The size distribution peaks shift to larger sizes with increasing magnetic field.

The threshold field for avalanches is lower in thin films, matching model predictions.

Abstract

Magneto-optical imaging is used to visualize vortex avalanches in MgB2 films at 4K. Avalanches ranging from 50 to 50000 vortices were detected. The size distribution function has a clear peak whose position moves towards larger sizes as the applied field increases. This field dependence as well as variation of flux density profile during an avalanche are well described by a proposed model assuming a thermal origin of the avalanches. The model is based on the adiabatic approach and takes into account nonlocal electrodynamics in thin superconductors. The threshold field for thermal avalanches is predicted to be much smaller than that for thick superconductors, in agreement with the experiment.