Burning of high Tc bridges

Magnetic flux distribution across a high-temperature superconductor strip is measured using magneto-optical imaging at 15 K. Both the current-carrying state and the remanent state after transport current are studied up to the currents 0.97Ic where Ic is the critical current. To avoid overheating of the sample current pulses with duration 50 ms were employed. The results are compared with predictions of the Bean model for the thin strip geometry. In the current-carrying state, reasonable agreement is found. However, there is a systematic deviation -the flux penetration is deeper than theoretically predicted. A much better agreement is achieved by accounting for flux creep as shown by our computer simulations. In the remanent state, the Bean model fails to explain the experimental results. The results for the currents I ≤ 0.7Ic can be understood within the framework of our flux creep simulations. However, after the currents I > 0.7Ic the total flux trapped in a strip is substantially less than predicted by the simulations. Furthermore, it decreases with increasing current. Excessive dissipation of power in the annihilation zone formed in the remanent state is believed to be the source of this unexpected behavior.

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“…This conclusion is confirmed by the fact that the bridge burn-out took place in its central part. 39 …”

Section: B Resultsmentioning

confidence: 99%

Magneto-optical study of magnetic-flux penetration into a current-carrying high-temperature-superconductor strip

et al. 1999

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“…Improvements to these magneto-optical techniques have revealed a wide class of instabilities, including magnetic macroturbulence 3,4 and a dendritic instability. 5 The instability of the magnetic flux and flux avalanches are observed both in anisotropic high temperature superconductor 4 and in an isotropic material like Nb. 5 Traditionally there are three possible scenarios in which the instabilities could arise.…”

Section: Introductionmentioning

confidence: 99%

Dynamics and thermal instability of magnetic flux in type-II superconductors

Shapiro

Rosenstein

et al. 2005

Phys. Rev. B

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In recent experiments, trapped magnetic flux is initially generated by abrupt laser heating of a strip of a type-II superconducting film subjected to a weak magnetic field. We study herein the nonequilibrium penetration of the flux into the Meissner state area. Effects of the heat dissipation and transport on the motion and stability of the interface between the magnetic flux and flux-free domains are considered. It is shown that the magnetic induction and the temperature have the form of a shock wave moving with constant velocity as large as that corresponding to the depairing current. In the vicinity of the front, superconductivity is suppressed by strong screening currents. The front velocity is determined by the Joule heat caused by the electric current in the normal domain at the flux front. The stability of the shock wave solution is investigated both analytically and numerically. For sufficiently small heat diffusion constant a finger shaped thermal instability is found.

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“…It may be caused, e.g., by a nonuniform chemical composition. 21 The kind of deviation shown in Fig. 4 can be explained by a suppressed j c near the strip edge.…”

Section: Discussionmentioning

confidence: 93%

Symmetry of the remanent-state flux distribution in superconducting thin strips: Probing the critical state

et al. 2001

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The critical-state in a thin strip of YBa 2 Cu 3 O 7Ϫ␦ is studied by magneto-optical imaging. The distribution of magnetic flux density is shown to have a specific symmetry in the remanent state after a large applied field. The symmetry was predicted ͓Phys. Rev. Lett. 82, 2947 ͑1999͔͒ for any j c (B), and is therefore suggested as a simple tool to verify the applicability of the critical-state model. At large temperatures we find deviations from this symmetry, which demonstrates a departure from the critical-state behavior. The observed deviations can be attributed to an explicit coordinate dependence of j c since both a surface barrier and flux creep would break the symmetry in a different way.

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Burning of high Tc bridges

Cited by 8 publications

References 8 publications

Magneto-optical study of magnetic-flux penetration into a current-carrying high-temperature-superconductor strip

Magneto-optical study of magnetic-flux penetration into a current-carrying high-temperature-superconductor strip

Dynamics and thermal instability of magnetic flux in type-II superconductors

Symmetry of the remanent-state flux distribution in superconducting thin strips: Probing the critical state

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