Design, manufacturing, and testing of a Nb3Sn coil employing Ti alloy as structural material

Describes the design, manufacturing, and testing results of a Nb₃Sn superconducting coil in which TiAlV alloys were used instead of stainless steel to reduce the magnetization contribution caused by the heat treatment for the A-15 Nb₃Sn phase formation that affects the magnetic field homogeneity. Prior to the coil manufacturing several structural materials were studied and evaluated in terms of their mechanical and magnetic properties in as-worked, welded, and heat-treated conditions. The manufacturing process employed the wind-and-react technique followed by vacuum-pressure impregnation (VPI) at 1 MPa atm. The critical steps of the manufacturing process, besides the heat treatment and impregnation, are the wire splicing and joint manufacturing in which copper posts supported by Si₃N₄ ceramic were used. The coil was tested with and without a background NbTi coil and the results have shown performance exceeding the design quench current confirming the successful coil construction.