Resistive REBCO-Coated Conductor Butt-Joints Based on an Ultrasonic Welding Method

The development of low-resistance coated conductor (CC) joints is important in viewpoint of applications using power cables, coils, and magnets. In particular, a stable and reliable CC tape joint applicable to practical electrical devices should be developed. In this study, CC tape butt-joints with low joint resistance in terms of transport were fabricated by direct bonding at the interface of the Cu-Cu stabilizers in overlapped GdBCO CC tapes. Both ultrasonic welding and hybrid welding processes, which have been attempted recently to achieve low joint resistance in lap-joint CC tapes, were used. The joint quality of butt-joint CC tapes fabricated by various joining methods was evaluated and compared to that in lap-joints. The variation of joint resistance with joint length was also evaluated. The electromechanical properties of butt-joints were examined using the double-bending test. The minimum bending diameter for the retained critical current and joint resistance degradation was determined for CC butt-joints.