Dendritic flux avalanches in a superconducting MgB2 tape

Abstract: MgB2 tapes with high critical current have a significant technological potential, but can experience operational breakdown due to thermomagnetic instability. Using magneto-optical imaging the spatial structure of the thermomagnetic avalanches has been resolved, and the reproducibility and thresholds for their appearance have been determined. By combining magneto-optical imaging with magnetic moment measurements, it is found that avalanches appear in a range between 1.7 mT and 2.5 T. Avalanches appearing at low fields are small intrusions at the tape's edge and non-detectable in measurements of magnetic moment. Larger avalanches have dendritic structures.