Low loss and high current Nb3Sn conductors made by the internal-tin method

Upon reaction heat treatment of Nb₃Sn-type conductors, niobium filaments grow in size due to a volume expansion. In conductors made by the internal-tin method, the filaments are generally closer to each other than in the bronze-route conductors. This can lead to filament bridging after the reaction heat treatment. For magnet applications such as in fusion and high-energy physics where AC losses have to be limited, the authors have designed and fabricated conductors with sufficiently large filament separation. The conductors incorporate tantalum as a diffusion barrier. An outline is given of the manufacturing process, with details of significant design parameters. Required heat-treatment conditions are addressed. Critical-current performance and AC loss characteristics are presented and compared to those of other internal-tin processed conductors