Current distributions in multi-filamentary HTS conductors

We have used scanning Hall probe microscopy to image in detail the current profile of two high-quality multi-filamentary Bi2223 tapes. In a tape with 37 twisted filaments, the derived current profile evolves smoothly across the width as the current is increased, whereas that of the untwisted 19-filament tape shows considerably more variation. In both cases, the central group of filaments carries most current at higher levels. The derived current distribution is well-described by the ellipsoidal solid conducting core model, rather than that of a thin flat conducting strip