Superconducting Properties of Mg 2Cu-Doped MgB2 Wires With Several Metal Sheath for Fusion Reactor Application

The advantages of MgB₂ compound for a future fusion reactor application are not only high T_c (39 K) and low cost but also low activation material. MgB₂ compound is non Nb-based superconductor and its decay time of induced radioactivity may be about 10 years and significantly shorter than Nb-based superconductors. In this paper, we fabricated the Mg₂Cu doped MgB₂ wires using several metal sheath materials to improve J_c property. The selection of metal sheath materials is also important to apply for fusion reactor. Pure Fe, Ta and Cu have faster decay time of induced radioactivity compared the other metals. T_c values of all Mg₂Cu doped samples were higher than those of non-doping samples, and T_c values were improved with increasing amount of Cu doping. And the maximum core-J_c value was estimated to be 100 A/mm² over at 4.2 K under 8 T for 3 at% Cu doping sample. The comparisons of superconducting property between different metal sheath materials are discussed.