One Step Internal Tin Nb3Sn Superconductor Fabrication.

The object of this research is to demonstrate the feasibility of producing a Nb3Sn superconductor in a single extrusion process with a large number of filaments with internal tin. The technique chosen uses .010 diameter Nb and tin plated Cu wires formed into a solenoid. The solenoid is covered with tin plated copper foil and isostatically compacted to a pressure of 17,000 psi. The solenoid is slit along its length. This results in a ribbon about 40 inches long by about 5 inches wide, with the Nb wires running across the 5 inch width. The ribbon is then rolled up Jelly Roll around a 0.5 inch diameter Ta covered copper rod to produce a composite of about 1.5 inches in diameter by 5 inches long. The composite geometry is now a cylindrical bundle of 0.010 inch diameter Nb wire separated from each other by tin plated copper. Each Nb wire is aligned with the axis of cylinder. The cylinder is slid into a Ta lines copper extrusion can which is evacuated and sealed. The can is extruded at a low temperature and drawn to final wire size without intermediate annealing. The advantage of the process is that it is an internal tin process with the tin uniformly distributed through the matrix. The Nb is in a relatively soft state having been fully annealed at 0.020 inch diameter. Only one extrusion is required since the bundling technique allows a large number of wires to be precisely aligned and spaced in the matrix.