Longitudinal Uniformity of Commercial Bi2223 Tapes Characterized by Scanning Hall-Probe Microscopy

We investigated remanent field distributions for commercial Bi2223 tapes with length of 1 m and high critical current I_c of 150 A (77 K, self-field) developed by Sumitomo Electric Industries (SEI) Ltd., by scanning Hall-probe microscopy (SHM) with an active area of 50μm × 50μm. All tapes are prepared by powder-in-tube process and sintered by controlled-over pressure (CT-OP) processing at final sintering stage. A bare tape and a 3-ply reinforced one with stainless tape laminations were used for measurements. The distribution of remanent field B_rz in perpendicular to broader face of a magnetized tape was measured using SHM, at a fixed distance of 0.5 mm away from a tape surface. Although absolute B_rz values in a reinforced tape were 10% lower than bare one, the shape of B_rz profile along a lateral direction of a tape was hardly affected by reinforcement and uniformly distributed along a length of each tape. Moreover, we cut away 15 cm piece sample from each tape and measured B_rz profile before and after double-sided bending with a bending diameter of 30 mm. The results indicated that degradation in both intensity and longitudinal uniformity of B_rz for a reinforced tape is much smaller than for a bare one.