Superconducting properties of internal-tin Nb/sub 3/Sn wire with enhanced current capacity

The possibilities for further enhancement of critical current density in internal tin Nb/sub 3/Sn strands have been investigated. An appropriate modified design of internal-tin composite wire has been developed and samples of the wire have been fabricated and analyzed. It was shown that non-copper critical current density J/sub c/ attained 2000 A/mm/sup 2/ (at 12 T, 4.2 K, 0.1 /spl mu/V/cm) and the hysteresis losses were equal to 770 mJ/cm/sup 3/ (for magnetic field varying in the range of /spl plusmn/3 T). The variations of the critical current density and hysteresis losses were investigated as a function of the wire diameter. The Nb/sub 3/Sn layer microstructure has been investigated and the relationships between the microstructure parameters and superconducting properties have been discussed. The measurements of critical current were carried out at the temperatures from 4.2 K up to T/sub c/ and the results obtained are given.