Collapse of the critical state in superconducting niobium

TL;DR

This paper investigates sudden magnetic flux changes in niobium superconductors, revealing flux jumps and catastrophic collapses, analyzed through thermomagnetic instability mechanisms using visualization and measurements.

Contribution

It provides new insights into flux dynamics in niobium, highlighting the conditions leading to critical state collapse and thermomagnetic instability mechanisms.

Findings

Observation of flux jumps and catastrophic flux collapse in niobium

Identification of thermomagnetic instability as the cause

Visualization and measurements support the instability model

Abstract

Giant abrupt changes in the magnetic flux distribution in niobium foils were studied by using magneto-optical visualization, thermal and magnetic measurements. Uniform flux jumps and sometimes almost total catastrophic collapse of the critical state are reported. Results are discussed in terms of thermomagnetic instability mechanism with different development scenarios.