Development of Ti-sheathed MgB$_{2}$ Superconducting Wires with Very High Current-carrying Capability

Ti-sheathed MgB$_{2}$ wires with very high magnetic critical current density ($J_{c})$ have been fabricated with the \textit{in situ} powder-in-tube method. The wires were characterized by magnetization, electrical resisitivity, x-ray diffraction and scanning electron microscopy measurements. At 5 K, the magnetic $J_{c}$ measured in magnetic fields of 2 Tesla (T) and 5T are about 4.1 $\times $ 10$^{5}$ A/cm$^{2}$ and 7.8 $\times $ 10$^{4}$ A/cm$^{2}$, respectively. The $J_{c}$ value at 20 K and 0.5 T is 3.6 $\times $ 10$^{5}$ A/cm$^{2}$. The superconducting volume fraction for the core material of the MgB$_{2 }$wires is about 71{\%}. These results show that the magnetic $J_{c}$ for the present Ti-sheathed MgB$_{2}$ wires is substantially higher (40{\%}-300{\%} higher) than the best magnetic $J_{c}$ results available for the Fe-sheathed MgB$_{2}$ wires made by similar processes. Because of such excellent $J_{c}$, it is anticipated that the Ti-sheathed MgB$_{2}$ wires developed by the present technique are very promising for future lightweight superconducting magnet applications.