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An Explanation for Observed Flux Creep in Opposite Direction to Lorentz Force in Partially-Magnetized Bulk Superconductors

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Ainslie, Mark Douglas 
Weinstein, Roy 
Sawh, Ravi-Persad 

Abstract

Sawh et al. recently reported experimental results that showed, in the case of a partially-magnetized bulk superconductor, magnetized using zero-field-cooling, that flux creep resulted in a reduced field measured at the center of the top surface of the bulk. The authors reported that this may suggest magnetic flux vortices, in this case, move against the Lorentz force, contravening commonly-accepted theory. In this paper, we report the results of numerical simulations explaining the observed measurements, and show that the vortices do indeed move with the Lorentz force, but that geometric effects from the finite geometry of the bulk and the form of the resulting induced supercurrent flowing within the bulk play a key role in this observed phenomenon. As a result, the relaxation of the magnetic flux can result in a measured magnetic field above the bulk superconductor that could be perceived as magnetic flux moving against the Lorentz force, when applying a simple Bean model (infinite slab) analysis to the problem.

Description

Keywords

Bulk high-temperature superconductors, finite element method, numerical simulation, trapped field magnets, Lorentz force

Journal Title

IEEE Transactions on Applied Superconductivity

Conference Name

Journal ISSN

1051-8223
1558-2515

Volume Title

29

Publisher

Institute of Electrical and Electronics Engineers
Sponsorship
Engineering and Physical Sciences Research Council (EP/P020313/1)