Screening current effect on the stress and strain distribution in REBCO high-field magnets: experimental verification and numerical analysis

The shielding (or screening current) effect in high-Tc coated conductors has a strong influence on its stress/strain distribution in a coil winding, especially during high-field operations. To demonstrate this phenomenon, a special experimental setup was designed. With an LTS background magnet and a small HTS insert coil, we were able to carry out direct observations on the hoop strains of a 10 mm wide REBCO sample. Measured data was compared with numerical solutions obtained from models based on T-A formulation and elastic models, showing good agreement. An analytical expression was proposed to estimate the maximum radial Lorentz force considering the screening current effect. Using the developed numerical models, we further studied two methods that are utilized for reducing the screening-current-induced magnetic field, i.e. use of multi-filamentary conductors and current sweep reversal approach.