Design of internal-tin Nb3Sn current switch strand and strand for accelerator magnets

Different areas of internal-tin Nb3Sn strands application have been analyze d. It was shown that internal-tin strands could be most promising for use i n persistent current switches and for high field, enhanced current magnet s ystems. Appropriate Nb3Sn internal-tin strands have been designed, fabricat ed and tested. The design of Nb3Sn strand for current switch consists of hi gh resistance Cu-Sn-Ni matrix and Nb3Sn filaments. It was shown that Nb3Sn switch strand 0.9 mm in dia has a current capacity of 1 kA at 4.2 K, 1 T an d resistance above 8 mu Omega*cm at 20 K. For the magnets of next generatio n accelerators Nb3Sn internal-tin strand with enhanced current capacity has been designed. Critical current density of that strand was above 2000 A/mm (2) at 4.2 K, 12 T,0.1 mu V/cm.