Flux avalanches in Nb superconducting shifted strip arrays

TL;DR

This study investigates flux avalanches in shifted three-dimensional Nb superconducting strip arrays using magneto-optical imaging, revealing new avalanche behaviors related to layer overlap and superconductor thickness.

Contribution

It introduces the observation of flux avalanches in shifted Nb superconducting strip arrays and analyzes their origins considering flux penetration models.

Findings

Flux avalanches occur with large layer overlap.

Linear avalanches are observed when superconductor thickness exceeds penetration depth.

Avalanche behavior depends on array geometry and superconductor properties.

Abstract

Flux penetrations into three-dimensional Nb superconducting strip arrays, where two layers of strip arrays are stacked by shifting a half period, are studied using a magneto-optical imaging method. Flux avalanches are observed when the overlap between the top and bottom layers is large even if the width of each strip is well below the threshold value. In addition, anomalous linear avalanches perpendicular to the strip are observed in the shifted strip array when the overlap is very large and the thickness of the superconductor is greater than the penetration depth. We discuss possible origins for the flux avalanches, including linear ones, by considering flux penetration calculated by the Campbell method assuming the Bean model.