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

Abstract

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" 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 Je = 30'000 A/cm2. The superconducting volume fraction of the conductor is 18 % which results in a critical current density in the superconductor of Jc = 170'000 A/cm2. 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 Ic(77K) = 60 A and critical current densities up to are realised.

Intrinsic limits ofJcin composite metallic/Bi(Pb)-2223 multifilamentary tapes with twisted filaments

“…For large γ k (long twist pitches) θ k,max take lesser values, but changes progressively across the tape, while for small γ k the variation of θ k is concentrated at the edges of the manifold. These results qualitatively follow the experimental findings on tapes with twisted filaments [2,5,6,15] when the metallic cladding sheaths are removed.…”

“…Multifilamentary tapes sheathed with silver and silver alloys and filaments with long twist pitches, have shown self-field J c (77 K) values comparable to the results on tapes with untwisted filaments [5,6,10,11], similar dimensional uniformity and the same superconducting filling factor.…”

“…Diminishing the filaments thickness down to 10 µm would give minimum hysteresis losses without dramatic decreases of J c . Increasing the effective resistivity between filaments by using Ag-Mg, Ag-Au and Ag-Pd alloys [3][4][5][6][7] or inserting isolating barrier layers [8,9] would decrease the eddy current and the coupling current losses. By application of filament twisting, the coupling current losses may be further decreased, but shorter twist pitches, t p , are limited by increasing damage of the filaments [3] and intrinsic geometric reductions.…”

Numerical analysis of AC loss in high T/sub c/ twisted tape carrying AC transport current in external AC magnetic field. Effect of twisting on loss reduction

“…superconducting power transmission lines. Recently, the twisted high Tc multifilamentary composite tapes have been fabricated, which is expected to reduce losses in those apparatuses [ 11, [2].…”

26 T 35 mm all-GdBa2Cu3O7–xmulti-width no-insulation superconducting magnet

“…7 (REBCO, RE=rare Earth) [1][2][3][4][5]. REBCO tapes are one of the viable HTS options for high-field (>23 T) magnets, mainly owing to their strong mechanical properties and large in-field current-carrying capacities [6][7][8][9][10][11][12][13][14][15].…”