Seiji Yasuhara

Properties of Ag-Sheathed Bi-Pb-Sr-Ca-Cu-O Superconducting Tapes Prepared by the Intermediate Pressing Process

The influence of an intermediate pressing process on the superconducting properties of Ag-sheathed Bi-Pb-Sr-Ca-Cu-O superconducting tapes has been investigated. The critical current density (Jc) was improved by the effect of the uniaxial pressing and by a sintering process after the initial sintering. The maximum transport Jc at 77.3 K under zero magnetic field was indicated as 2.36×104 A/cm2, and that at 4.2 K under zero magnetic field was indicated as 1.5×105 A/cm2. The magnetic field dependence on the Jc at 4.2 K was summarized as follows: 5×104 A/cm2 (I⊥H, C-axis⊥H, 10 T) and 3×104 A/cm2 (I⊥H, C-axis//H, 10 T).

Superconducting Properties of Bi-2212 Multifilamentary Round Wires With Double Layered Core Filaments

Multifilamentary Ag-sheathed Bi-2212 round-shaped wires with double layered core-filaments and AgCu alloy sheathed Bi-2212 round wires were fabricated by the powder in tube technique. Composites consisting of Ag outer sheath and the filaments with number of 7, 37 and 61 and a composite of AgCu alloy outer sheath having 37 and 61 filaments were drawn into wires of 1mm in diameter. The wires were heat treated by a conventional partial-melting process. High oxide core ratio of ∼50% to wire-cross-sectional area could realize high overall critical current densities (Jc) of 280A/mm2 at 4.2K, 10T in Ag sheathed wires with 61-filaments and Jc of 310A/mm2 in AgCu alloy sheathed wires with 37-filaments.

Bi-2212 Ag-Sheathed Round Cross Section Wires

Bi-2212 Ag-sheathed round cross sectional wires which are suited as winding materials for realizing high homogeneity superconducting magnets have been successfully fabricated by the powder-in-tube technique. High overall critical current density, Jc, up to 2.8x104 A/cm4 at 4.2 K, 10 T was achieved in the multifilamentary wire consisting of 37 double tubed core filaments. Highly deformed Bi-2212 microstructures which were formed along a small curvature Ag sheath surfaces of the core filaments were observed, which might be responsible for the high Jc properties. Effects of wire bending before the heat treatment on the Jc property have been examined with respect to a solenoid winding. It was confirmed that the decrease in Ic in a 40 mm bore solenoid compared with that of short sample is estimated to remain less than about 15%.