Study of flux entry and exit into Bi-2223 multifilamentary tapes

Using magneto-optic imaging, the flux entry and exit into a piece of Ag-sheathed multifilamentary tape are studied in an applied magnetic field. In low fields the shielding currents are seen to flow mostly in the outermost filaments. With increasing external magnetic field, the inner filaments also contribute to the current flow. In the remanent state, the flux is confined to the tape centre and is not pinned in each filament independently. The magneto-optic flux patterns obtained reveal that the filaments in the tape are coupled together, which enables the currents to flow around defects within the filaments.