ジェリーロール法による高磁界(Nb,Ta)₃Sn超伝導線材の研究

抄録

Tightly shrunk Sn-Ta ingots with excellent workability were prepared by the reaction at 750∼800°C from the mixed powder of Sn and Ta containing a few wt% of Cu. Then Jelly Roll processed wires were fabricated starting from Sn-Ta/Nb composites, in which thick (Nb,Ta)₃Sn layers were produced after the heat treatment. A few at% Ti substitution for Sn+Ta composision produces denser Sn-Ta ingots and decreases the necessary Ta concentration from 25∼30 at% to 20 at%, which is favorable for the materials cost reduction. The wires with a few at% Ti substitution in the Sn-Ta sheet show a non-Cu J_c of 150 A/mm² at 22 T and 4.2 K after the reaction at 725∼750°C. The Ti substitution appreciably enhances the formation rate of (Nb,Ta)₃Sn layers and increases their areal fraction resulting the increase of non-Cu J_c of the wire.