Reduction of coupling current losses by internal resistive barrier structures in multifilamentary Bi(2223) tapes in external magnetic fields

摘要

The AC losses in multifilamentary Bi(2223) tapes in external magnetic fields are dominated by the hysteresis losses in the superconducting filaments and by coupling current losses in the normal conducting matrix. In the last years great effort has been made in the development of low loss barrier tapes with internal interfilamentary resistive barriers, which reduce the coupling currents. The recent improvements of these conductors are presented. 37-filamentary tapes with a reduced barrier thickness, enhanced superconductor content as well as overall critical current densities were developed. Different barrier materials were used to study the effect of different barrier hardnesses on the deformation, barrier homogeneity, matrix resistivity and critical current density. The tapes were twisted with a twist length down to l_p = 5 mm. The parameters of filament twist and the AC losses of the tapes were investigated and are discussed in comparison to former conductors to find an optimum conductor design.