Superconducting and mechanical properties of internally steel reinforced Nb3Sn wires with Ta or (Ni+Zn) additions

The effects of internal steel reinforcement of Nb3Sn wires on the current carrying capacity are studied. A strong enhancement of the precompression is found with respect to unreinforced Nb3Sn wires: critical current density measurements as a function of the applied strain yielded εmvalues reaching up to ∼ 1%. The supercondcuting parameters are strongly affected: the upper critical field, Bc2*, is lowered from ∼20 to 16 T with respect to the unreinforced wire, while the ratio Jc/Jcmis very low, 0.37 at 10 T and 0.12 at 14 T. The effects of the enhanced precompression on Jcare found to be partly compensated by Ta or (Ni+Zn) additions to Nb3Sn.