Preparation of Nb3Sn-NbTi Hybrid Superconducting Joint by Resistive Welding Technique

Abstract:

In high magnetic field magnets, especially those with high stability requirements, superconducting joints with ultra-low resistances play an important role in magnet fabrication. The Nb₃Sn and NbTi joints were fabricated by the resistive welding technique. The Nb₃Sn joint was fabricated by sintering the Nb-Sn precursors after mechanical alloying. Then the Nb₃Sn bulk in the Nb₃Sn joint was welded to the NbTi conductor. The microstructure and grain sizes of Nb₃Sn bulk after long periods of time at high temperature were investigated. After welding, the joint was analyzed using X-ray nano-CT technology to display the connecting status and the defects between the Nb₃Sn and NbTi conductor without destroying the joint. The electrical characteristics of the joints were measured under background fields through the field decay method. Results show that compared with the ones prepared by the commonly used solid matrix replacement technique, the prepared joint exhibits better magnetic field resistance and lower resistance at 1.5 T background field.