Patent ID: 7505800

Claim:
A superconductive element containing Nb 3 Sn, in particular a multifilament wire, comprising at least one superconductive filament which is obtained by a solid state diffusion reaction from a preliminary filament structure, said preliminary filament structure containing an elongated hollow pipe having an inner surface and an outer surface, wherein said hollow pipe consists of Nb or an Nb alloy, in particular NbTa, wherein the outer surface is in close contact with a surrounding bronze matrix containing Cu and Sn, and wherein the inner surface is in close contact with an inner bronze matrix also containing Cu and Sn, characterized in that the inner bronze matrix of the preliminary filament structure encloses in its region an elongated core consisting of a metallic material, said metallic material of Ta or Ta alloy having at room temperature (=RT) a thermal expansion coefficient α core <17*10 −6 K −1 , preferably α core ≦8*10 −6 K −1 , said metallic material having at RT a field strength R p0.2 >300 Mpa, said metallic material having at RT an elongation at rupture A>20%, and wherein said metallic material of the core is chemically inert with respect to the material of the inner bronze matrix up to a reaction temperature T of the solid state diffusion reaction.