Current distribution and flow in magnetic fields for Ag-sheathed Bi2223 monocore tapes

Using a micro Hall-sensor, magnetic-field distributions are measured at 77 K on a surface of zero-field-cooled samples of Bi2223 monocore tapes, in magnetic fields B_ex up to 800 mT perpendicular to a tape surface. The one-dimensional magnetic profile along a width direction of a sample shows a marked concave due to shielding currents, which shape changes as B_ex increases. In low fields up to 10 mT, there is a sharp peak positioning at the tape center in the profile, while it disappears and converts to a broad concave with an increase of B_ex. From numerical calculations on magnetic fields, such a change in the profile is related to a change in current flow with B_ex. An increase in B_ex limits and narrows the region of current flow in the Ag-sheathed Bi2223 tapes, from the whole part of superconductor to the Ag/Bi2223 interface