Transformation of the critical state in hard superconductors resulting from thermomagnetic avalanches

The results of experimental studies of magnetic flux dynamics in finite-size superconductors, obtained using integral and local measurements methods, are presented. Local methods were aimed at clarifying the role of the demagnetizing factor in the dynamic formation of a complex magnetic structure of...

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Bibliographic Details
Published in:Low temperature physics (Woodbury, N.Y.) N.Y.), 2016-04, Vol.42 (4), p.239-257
Main Authors: Chabanenko, V. V., Kuchuk, E. I., Rusakov, V. F., Abaloszewa, I., Nabiałek, A., Pérez-Rodríguez, F.
Format: Article
Language:English
Subjects:
Avalanches
Demagnetization
Dissipation factor
Magnetic flux
Magnetic induction
Magnetic shielding
Magnetic structure
Measurement methods
Optics
Propagation velocity
Superconductors
Temperature effects
Transformations
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Summary:The results of experimental studies of magnetic flux dynamics in finite-size superconductors, obtained using integral and local measurements methods, are presented. Local methods were aimed at clarifying the role of the demagnetizing factor in the dynamic formation of a complex magnetic structure of the critical state of hard superconductors. To understand the reasons for drastic transformation of the magnetic induction, we further analyzed the literature data on the visualization of flux dynamics in the presence of avalanches, obtained by magneto-optical methods. New features in the behavior of the magnetic flux during and after an avalanche were revealed and characterized: two stages in the formation of the magnetic induction distribution inside the avalanche region were established—homogeneous and heterogeneous filling with magnetic flux; the mechanism of inversion of the induction profile; velocity oscillations in the propagating magnetic flux front; transformation of the critical state band near the edge of the sample; and the role of the thermal effects and demagnetizing factor in the dissipative flux dynamics. The generalized information allowed us to present, within the framework of the Bean concept, a model of the transformation of the patterns of magnetic induction in the critical state and superconducting currents in a finite superconductor occurring as a result of flux avalanches in two different regimes—shielding and trapping of magnetic flux.
ISSN:1063-777X
1090-6517
DOI:10.1063/1.4947599