Mechanical and superconducting properties of 6-filament MgB2 wires reinforced by Cu, Cu-Nb and NbTi

► Strengthening abilities of Cu, Cu-Nb, and NbTi reinforced MgB2 wires were investigated. ► Cu-Nb was suitable as reinforcing core. ► Cu-Nb reinforced MgB2 wires with unit length over 1 km were manufactured. ► Demo-solenoid is in construction using the Cu-Nb reinforced long wires.