Development of internal-tin diffusion multifilamentary Nb3Sn conductors including hydrostatic extrusion

Progress is reported on the development of internal-tin-diffusion processed multifilamentary Nb₃Sn wires containing (19 approximately 55) by (132 approximately 588) Nb filaments with diameters between 1 and 5 mu m. A fabrication process comprising the co-reduction of copper, niobium, tin, and the tantalum barrier to the final size by using cold hydrostatic extrusion has been established. During the whole deformation process, the workability of the wire was reported to be excellent. The present wires exhibit a homogeneous distribution of Sn cores and Nb filaments through the whole cross-section area. Data on critical current, critical temperature, and critical magnetic field are presented for different reaction conditions. At 10 T, a magnetization current density of 1.49*10⁵A/cm² was measured for the non-copper cross section. The present results are compared to data in the literature.