Cross-field demagnetization of stacks of tapes: 3D modelling and measurements
29 Nov 2019
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Kapolka Milan
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Pardo Enric
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Grilli Francesco
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Baskys Algirdas
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Climente-Alarcon Vicente
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Dadhich Anang
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Glowacki Bartek A.
Stacks of superconducting tapes can trap much higher magnetic fields than
conventional magnets. This makes them very promising for motors and generators...However, ripple magnetic fields in these machines present a cross-field
component that demagnetizes the stacks. At present, there is no quantitative
agreement between measurements and modeling of cross-field demagnetization,
mainly due to the need of a 3D model that takes the end effects and real
micron-thick superconducting layer into account. This article presents 3D
modeling and measurements of cross-field demagnetization in stacks of up to 5
tapes and initial magnetization modeling of stacks of up to 15 tapes. 3D
modeling of the cross-field demagnetization explicitly shows that the critical
current density, $J_c$, in the direction perpendicular to the tape surface does
not play a role in cross-field demagnetization. When taking the measured
anisotropic magnetic field dependence of $J_c$ into account, 3D calculations
agree with measurements with less than 4 % deviation, while the error of 2D
modeling is much higher. Then, our 3D numerical methods can realistically
predict cross-field demagnetization. Due to the force-free configuration of
part of the current density, J, in the stack, better agreement with experiments
will probably require measuring the Jc anisotropy for the whole solid angle
range, including $J$ parallel to the magnetic field.(read more)