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arXiv · 2511.22397

Thermally-controlled flux avalanche dynamics in bulk NbTi superconductor

Irina Abaloszewa·Viktor V. Chabanenko·Aleksander Abaloszew
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Abstract

We report the first direct visualization of flux avalanche propagation dynamics in bulk superconducting NbTi, tracking individual events and measuring their velocities using high-speed magneto-optical imaging. Unlike thin films with electromagnetic avalanches at km/s speeds, we observe velocities of 15--25 m/s, which are orders of magnitude slower. Analysis of characteristic timescales reveals that these avalanches are governed by local heating and limited heat dissipation through the adhesive layer, establishing a fundamentally different, thermally limited propagation regime. The threshold field for avalanche nucleation decreases with temperature, contrary to the increasing trend in thin films with efficient cooling - a behavior consistent with slow heat removal and thermal runaway in our system. All observed avalanches exhibit universal normalized velocity-distance scaling despite varying morphologies, confirming the robustness of thermal control. These findings reveal that bulk superconductors with poor thermal coupling operate in a previously uncharacterized avalanche regime, with direct implications for flux stability and quench protection in NbTi-based magnets, as well as a broader understanding of thermomagnetic instabilities in technological superconductors.

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Irina Abaloszewa, Viktor V. Chabanenko, Aleksander Abaloszew. 2025-11-27. Thermally-controlled flux avalanche dynamics in bulk NbTi superconductor. https://doi.org/10.1103/lq5f-lvh7

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