Combined Axial Pressure and Screening Current Induced Stress Test on REBCO Pancake Coils

Abstract

Screening current induced stress (SCIS) causes conical deformation in REBCO pancake coils. In an actual ultra-high field magnet, a REBCO pancake coil is subjected to axial pressure from upper pancake coils, in addition to SCIS. This axial pressure likely enhances the conical deformation and hoop strain. In this study, we developed a test scheme, referred to as the combined axial pressure and tape tilting (CATT) test, to investigate the degree of strain enhancement caused by axial pressure. As a result of the test, a 50% increase of hoop strain was observed at an axial load of 180 kN, leading to yielding of the REBCO tapes. Buckling deformation due to compressive hoop strain was also observed during the charging test with current in negative direction under a background field.