Development of twisted Bi-2212 and Bi-2223 powder in tube conductors for ac applications

Within Alcatel Alsthom Group, Alcatel Cable and Alcatel Alsthom Recherche Center have undertaken a HTc research program, with support from EDF : the aim was to develop conductors suitable for ac applications, where major market opportunities are expected, For ac applications at 50 Hz low ac loss conductors with a resistive matrix material and a twist length of the superconducting filaments of less than 10 mm are required. Bi-2223 and Bi-2212 conductors are fabricated up to lengths of 200 m of 64 filaments tape by the patented rectangular Alcatel Alsthom route, Recently Bi-2212 conductors for 20 K applications have been tested at liquid helium temperatures, Different Bi-2212 conductors with a twist length of 7 to 9 mm, with a silver-alloy matrix and a cross section of 0,5 mm x 3 mm have been realised, In such conductors transport currents of 400-500 A have been measured at 4 K in self fields with a very good reproducibility, The engineering current density in the wire has reached the threshold value of J(e) = 30'000 A/cm(2), The superconducting volume fraction of the conductor is 18% which results in a critical current density in the superconductor of J(c) = 170'000 A/cm(2), At liquid nitrogen temperature transport currents of 18 A are carried in this conductor, For this temperature range the development of a Bi-2223 conductor is under progress, For instance, different untwisted conductors with transport currents up to I-c(77K) = 60 A and critical current densities up to are realised.