Superconducting Properties of Mg $_{2}$Cu-Doped MgB$_{2}$ Wires With Several Metal Sheath for Fusion Reactor Application

The advantages of MgB
₂
compound for a future fusion reactor application are not only high T
_c
(39 K) and low cost but also low activation material. MgB
₂
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 Mg
₂
Cu doped MgB
₂
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 Mg
₂
Cu 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/mm
²
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.