Superconducting Joints Made With Internal-Magnesium-Diffusion-Processed MgB2 Wires

MgB
₂
, which has a critical temperature T
_c
of 39 K, is a candidate for the practical application of liquid-helium-free magnetic resonance imaging systems. Since the discovery of MgB
₂
, the performance of MgB
₂
wires and the technology required to manufacture long-length conductors have been significantly improved. Wires processed by internal magnesium diffusion (IMD) show high performance in comparison with powder-in-tube-processed MgB
₂
wires. Our group has been developing high-performance IMD wires. In this study, a joint connecting two IMD-processed MgB
₂
wires was fabricated. The maximum critical current in the connected wires was 1/3 lower than that in a normal IMD-processed wire at each considered magnetic field strength. However, the critical current of the joint at 3 T was equal to that of a normal IMD-processed wire at 10 T, suggesting that this joint would be effective at magnetic fields of around 3 T. Furthermore, a joint resistance of 10
^-13
Ω was obtained by measuring the current decay at the joint.