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تسجيل مستخدم جديدThe Bean model of the critical state in a magnetically shielded superconductor filament
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We study the magnetization of a cylindrical type-II superconductor filament covered by a coaxial soft-magnet sheath and exposed to an applied transverse magnetic field. Examining penetration of magnetic flux into the superconductor core of the filament on the basis of the Bean model of the critical state, we find that the presence of a non-hysteretic magnetic sheath can strongly enhance the field of full penetration of magnetic flux. The average magnetization of the superconductor/magnet heterostructure under consideration and hysteresis AC losses in the core of the filament are calculated as well.
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The distribution of the transport current in a superconducting filament aligned parallel to the flat surface of a semi-infinite bulk magnet is studied theoretically. An integral equation governing the current distribution in the Meissner state of the
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nterface as well as on the relative permeability of the involved magnetic constituent. The modification of the barrier by the presence of the magnet can be significant, as demonstrated for a cylindrical superconducting filament covered with a coaxial magnetic sheath. Using typical values of the relative permeability, the critical field of first penetration of magnetic flux is predicted to be strongly enhanced, whereas the variation of the average critical current density with the external field is strongly depressed, in accord with the observations of recent experiments.
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