US Patent 7368021 Critical current density in Nb

Critical current densities of internal tin wire to the range of 3000 A/mm2 at temperature of 4.2 K and in magnetic field 12 T are achieved by controlling the following parameters in a distributed barrier subelement design: wt % Sn in bronze; atomic Nb:Sn; local area ratio; reactable barrier; barrier thickness relative to the filament thickness; additions of a dopant such as Ti or Ta to the Nb3Sn; and the design for restacking and wire reduction to control the maximum filament diameter at the subsequent heat reaction stage.