Ti and Ta additions to Nb3Sn by the powder in tube process

Nb₃Sn superconductors made by the powder-in-tube process have demonstrated the ability to meet the needs of high energy physics applications with good strain tolerance, high non-Cu critical current density (J_c), and good filament quality. The process starts by filling a Nb tube with NbSn₂ powder. This assembly is compacted and re-stacked in a Cu matrix to form a multifilamentary billet. At final size the composite wire is then heat treated to form the Nb₃Sn layer from the Nb tube wall with the powder core serving as the Sn source. Heat treatment conditions are limited to prevent full reaction of the Nb tube and possible Sn contamination of the Cu stabilizer. In this work, composite tubes were made out of fine grain Nb, NbTa, and NbTi alloy sheets. Additions serve to improve high field performance. An outer layer of Ta was added to serve as diffusion barrier to allow full reaction of the Nb tube wall and thus increase non-Cu J_c