Titanium Doped ${\hbox {Nb}}_{3}{\hbox {Sn}}$ Superconductor Fabricated by the Internal Tin Tube (ITT) Approach

Multifilament Nb₃Sn superconductor has been produced by the internal tin tube (ITT) approach. The process employs tubular niobium filaments with cores consisting of tin or high tin alloy inside a copper sheath. The niobium annulus of each filament contained eight Nb-47Ti ldquoislands.rdquo During the subsequent reaction heat treatments the titanium was diffused out of these islands and throughout the niobium annulus resulting in a calculated titanium concentration of 1.5 wt%. The process holds the promise to minimize the amount of non-superconducting area in the conductor cross section and thereby maximize non-copper critical current density. Niobium tube fabrication, wire processing, filament quality, and microstructure are discussed, and superconducting properties are presented.