Dendritic flux avalanches in superconducting Nb3Sn films

TL;DR

This study visualizes dendritic flux avalanches in Nb3Sn superconducting films at low temperatures, revealing complex behaviors and interactions with defects that influence flux penetration and magnetization.

Contribution

It provides the first detailed visualization and analysis of dendritic flux avalanches in Nb3Sn films, highlighting their interactions with linear defects.

Findings

Dendritic flux avalanches occur below 8 K in Nb3Sn films.

Avalanches interact with defects, altering their propagation.

Magnetization curves show small, random jumps due to avalanches.

Abstract

The penetration of magnetic flux into a thin superconducting film of Nb3Sn with critical temperature 17.8K and critical current density 6MA/cm^2 was visualized using magneto-optical imaging. Below 8 K an avalanche-like flux penetration in form of big and branching dendritic structures was observed in response to increasing perpendicular applied field. When a growing dendritic branch meets a linear defect in the film, several scenarios were observed: the branch can turn and propagate along the defect, continue propagation right through it, or "tunnel" along a flux-filled defect and continue growth from its other end. The avalanches manifest themselves in numerous small and random jumps found in the magnetization curve.