Development of internal-tin processed Nb3Sn superconducting wires

The development of high performance Nb3Sn wires with an internal-tin route was reviewed. The internal-tin wires have excellent productivity and low production cost because the drawing process does not require intermediate annealing. This process has the advantage of producing several types of wires with wide superconducting properties for practical applications. We have been producing wires with high critical current density (Jc) and low hysteresis loss for fusion applications such as the ITER and KSTAR. We have also developed internal-tin wires with Jc>1600 A/mm2 at 12 T, 4.2 K for general high field magnets. Recently, we have been developing a new wire configuration for next generation high energy accelerators in collaboration with the KEK High Energy Accelerator Research Organization. The wire, called a distributed-tin (DT) wire, has an original structure in which the multi-Nd filament modules and Sn rods are uniformly distributed in a Cu matrix. The values of Jc of the DT wire are 2120 A/mm2 at 12 T, 4.2 K, which was obtained by increasing the Nb and Sn fractions of the wires, and 207 A/mm2 at 20 T, 4.2 K, because of the improvements in Bc2 and Tc. It is anticipated that the DT wires will be applied to not only next generation accelerators, but also high resolution NMRs. (author)