Prototype fabrication of ultrafine filament NbTi conductors for the SSC

Production quantities of multifilamentary NbTi/Cu composite wire have been fabricated for SSC dipole magnet development. These composites contained 10,000 to 37,000 filaments having a diameter of 5.0 to 2.7 micrometers at final wire size. The large number of filaments in these composites has been achieved by employing a double extrusion process. The critical current density (Jc) has been optimized for the final wires as well as for samples taken from the first stage extrusion. Jc ranged from 2300 to 3400 A/mm
²
at 5 tesla depending on filament size and process history. The Jc results obtained in this investigation along with resistive transition parameter "n" are reported.