The Investigation of the Effect of Niobium Artificial Doping with Titanium on Nb₃Sn Superconductors Properties

Abstract

The effect on titanium doping of Nb filaments, and thus on the properties of bronze processed multifilamentary Nb₃Sn wires and wires with internal tin sources with copper volume fraction up to 65 % has been analysed. Either titanium rods or rods of the Nb-50Ti alloy, inserted in the axial area of each filament, were used as a source of titanium. The influence of doping on the quantity, composition, structure and superconducting properties of intermetallic compound Nb₃Sn after heat treatments at 570–750°C with duration up to 350 h was investigated by means of electrical measurements, optical metallography and methods of microanalysis and X-ray analysis. It was shown that the non-copper critical current density of the doped wires attained 600 and 270 A/mm² in 12.5 and 16 T respectively for bronze processed wires and 800 and 300 A/mm² for wires with internal tin source. Upper critical field calculated in accordance with Kramer’s extrapolation was equal to 29–32 T.