Correlation Between Resistances of Face-to-Face Soldered Joints and Interface Resistance Between Layers in Superconducting Tapes

It is known from the literature that the resistance of soldered joints between two high-temperature superconducting (HTS) tapes is different not only for different tape producers, but also within the same producer for different tape batches. The resistance of joint can be considered consisting of several contributions: Resistances of solder and stabilizing layers covering superconducting layers, and interface resistances between solder and metals and between metal and superconducting layer within the tape. If the same solder is used, and metals are similar for the same manufacturer, different interface resistances between metallic layers and the superconducting layer within the tape can be a reason for the observed scattering in joints resistances. The interface resistance is difficult to measure directly. It can be indirectly evaluated from the measurement of the current transfer length (CTL) from a metal layer into the HTS layer within a superconducting tape. In this paper, we report on a systematic study on CTL and interface resistance between the HTS layer and stabilizing layers for selected commercial rare earth-barium-copper-oxide (R EBCO) tapes, and resistance of face-to-face joints made from the same tapes, in order to find a correlation between the evaluated interface resistance and the resistance of the corresponding lap joints.