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

Abstract

MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , which has a critical temperature T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> of 39 K, is a candidate for the practical application of liquid-helium-free magnetic resonance imaging systems. Since the discovery of MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , the performance of MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> wires. Our group has been developing high-performance IMD wires. In this study, a joint connecting two IMD-processed MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-13</sup> Ω was obtained by measuring the current decay at the joint.