Effective transverse resistivity in superconducting tapes with variousfilament shapes and structures

Abstract

When a multi-filamentary superconductor is exposed to an alternatingexternal magnetic field, coupling-current loss is a significant part of themagnetization loss. The coupling-current loss at low magnetic-fieldfrequencies is determined by the effective transverse resistivity of the innerfilamentary region. The effective resistivity is calculated for various shapesand structures of the inner filaments. Bi-2223/Ag tapes typically havefilaments with a high aspect ratio, causing an anisotropic transverseresistivity. When there is no contact resistance between the filaments and thematrix material, the presence of the filaments decreases the effectiveresistivity. The decrease is greatest for overlapping filaments whose widesides are oriented parallel to the external magnetic field. Good insulatingbarriers result in a high contact resistance from the filaments to the matrix.Then the effective resistivity is greatly increased, especially for overlappingfilaments that are oriented perpendicularly to the magnetic field. The resultsare relevant for the calculation of the coupling-current loss in Bi-2223 tapeswith twisted filaments.