Degradation of REBCO conductors caused by the screening current

A degradation phenomenon in RE-Ba-Cu-O (REBCO) coated conductors caused by the screening current was observed at 4.2 K. Even without transport current, delamination of the superconducting layer from the buffer layer occurred because of the cleavage force. The Lorentz force between an induced screening current and an external magnetic field is considered to generate the cleavage force. In this paper, we report the degradation of REBCO conductors due to the screening current and discuss the cleavage force using simple models. The degradation of the REBCO conductor was observed for inclination angles of 0°, 10°, 20°, 45°, 60° and 90°. We found serious degradation at 45°. In practical REBCO coils, especially feed through parts, degradation of the REBCO conductor by the cleavage force due to the induced screening current should be prevented.