Influence of Ta and Ti Doping on the High Field Performance of (Nb,Ta,Ti)(3)Sn Multifilamentary Wires based on Osprey Bronze with High Tin Content

Ta and Ti are the most widely used additions for technical Nb3Sn multifilamentary superconductors. These elements are known to influence grain growth, grain morphology and chemical composition in the A15 layer, hence the current carrying properties of the wires over a wide magnetic field range. So far only few studies tried to compare systematically Ta and Ti doped and undoped Nb3Sn wires in the frame of the same work, down to a nanometric scale. We present an investigation on several multifilamentary (Nb,Ta,Ti)3Sn bronze route wires, fabricated at a laboratory scale, with various amounts of additives. The wires consist of fine filaments embedded in a Cu-Sn or Cu-Sn-Ti Osprey bronze with > 15 wt.% Sn and an external Cu stabilization. Microstructural observations are compared with the results of Jc and n values measured up to 21 T at 4.2 and 2.2 K, and for longitudinal strains up to 0.5%. Non-Cu Jc values up to 300 Amm-2 and n values up to 50 at 17 T and 4.2 K show clearly that wires with Ti addition to the bronze have a better performance with respect to wires with Ti additions to the filaments.