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Sumitomo Electric has been developing the silver-sheathed Bi2223 multi-filamentary wires since the discovery of Bi-based superconductors. DI-BSCCO is the high performance wires produced using the controlled-overpressure (CT-OP) sintering technique. The present commercial DI-BSCCO can provide the uniform high critical current, Ic, up to 180 A with length over 2000 m, and recently 200 A were succeeded to be obtained by the same kind of 1000 m length wires, resulting from the improvement and control of the microstructure in Bi2223 multi-filaments. The short trial wires of several meters have exhibited the highest Ic over 240 A at 77K in self-field (corresponding to 580 A per 1 cm-width). Besides, the optimization of carrier density after CT-OP led to further enhancement of Ic, reached 250 A. All the derivative products also have uniform critical current properties over entire length even after lamination with the reinforcing metals. The performances of DI-BSCCO can meet the growing needs for various application of high temperature superconductor like high in-field applications, such as magnets and motors. The recent progress in transport properties of commercial DI-BSCCO and R&D short trial wires is shown.

Distributions of critical current of damaged Bi2223 tape specimens bent by 0.6, 0.8 and 1.0% were investigated analytically with a modelling approach based on the correlation of damage evolution to distribution of critical current. It was revealed that the distribution of critical current is described by three parameter Weibull distribution function through the distribution of the tensile damage strain of Bi2223 filaments that determines the damage front in bent-composite tape. Also it was shown that the measured distribution of critical current values can be reproduced successfully by a Monte Carlo simulation using the distributions of tensile damage strain of filaments and original critical current.

The MgB₂ superconductor is a promising material for the coil conductors in the superconducting magnets. The anisotropy of the upper critical field of MgB₂ is one of the limiting factors to the critical current density especially in the high magnetic field. The correlation between the critical current density and the microstructure of the MgB₂ core part in the tape processed by the ex situ powder-in-tube method was investigated to obtain a clue for improving the critical current density values. The anisotropy in the field dependence of the critical current density was observed with respect to the angle between the applied magnetic field and the tape surface. Both the pole figure data in the x-ray diffraction analysis and the grain orientation map data in the electron back scattering pattern analysis indicated that the texture of the (001) plane occurred in the MgB₂ core part of the tape quantitatively. This result suggests that the critical current density can be enhanced through the control of the microstructure of the MgB₂ superconductor tapes.