New high-field Nb3Sn conductors prepared from Ta-Sn compound powder

New Nb3Sn conductors with excellent high-field performance have been fabricated using Ta-Sn ponder as a core material. The powder was easily synthesized by the melt diffusion reaction between Ta and Sn powders. The Ta-Sn powder was encased in a Nh or Nb-Ta alloy sheath to form a composite. The composite was fabricated into tape and wire specimens without intermediate annealing. The specimens were then reacted at 800-925 degrees C in vacuum. After the reaction a thick Nb3Sn layer, several tens of micrometers in thickness, is formed between the sheath and the core. No void is Termed in the core after the reaction. Ta is incorporated into the Nh,Sn layer from both the core and the Nb-Ta sheath The J(c) of the Nb3Sn layer reaches 5X10(4)A/cm(2) at 23T and 4.2K. The tape specimens show large critical current at WT due to the large thickness of the Nb3Sn layer. The optimum reaction temperature can be decreased by the small amount of Cu addition.