Evaluation of Magnetic Field Dependence of the Interface Resistivity in REBCO Tape

As a result of REBCO tape having a multi-layered structure, electrical resistance of REBCO/Ag and Ag/Cu interfaces (interface resistance) is one of the major factors of joint resistance for tape-to-tape lap joints. Since the interface resistance widely varies depending on the manufacturers and the spool batches of the tapes, detailed study of the interface resistance is important for tape-to-tape joint technology. In our previous study, the contact-probing current transfer length (CTL) method was proposed as a nondestructive method to evaluate the interface resistivity. In this paper, the authors evaluated the magnetic field and temperature dependences of the interface resistivity of REBCO tapes in the range of 10 to 70 K and 0 to 15 T. First, a numerical simulation was conducted to obtain the calibration curves which show the relationship between the CTL and the interface resistivity. Then, the CTL was experimentally measured at each temperature and magnetic field. The interface resistivity was derived by comparing the calibration curves and the experimentally measured CTLs. As a result, the interface resistivity decreased with increasing magnetic field below 40 K. On the other hand, it changed to become constant or increase over 50 K. Furthermore, the interface resistivity decreased with an increase in temperature at self-field. These behaviors are different from those of the resistance for metals, therefore, REBCO's properties near the interface may have a huge influence on the whole interface resistivity.