A novel approach to make fine filament superconductors

Multifilamentary superconductors with 2.5 to 6 micron sized NbTi filaments are required for most of the High Energy Physics accelerator magnets. Present manufacturing technology employs a single stack method for conductors with up to 10,000 filaments and a double stack method for larger numbers of filaments. A unique new approach has been developed at IGC Advanced Superconductors, Inc., to fabricate fine filament conductors containing up to ∼50,000 filaments. The method offers important technological and economic advantages even for the manufacture of conductors with less than 10,000 filaments. The feasibility of the new approach has been successfully demonstrated on small scale pilot billets. Large scale billets are currently being developed. Three 309 mm diameter billets with 7,251; 22,313; and 38,663 filaments respectively, have been fabricated to strand and cable. The details of the new approach along with its advantages will be presented in this paper. Metallurgical aspects of the NbTi filaments, namely, diffusion barrier integrity, geometric uniformity in addition to the superconducting properties of the strand are reported. Relevant comparisons are made with conductor fabricated using conventional methods