Electro-Mechanical Characteristics of REBCO Tapes Over a Wide Temperature Using Pulsed Current

The electro-mechanical properties of REBCO tapes with Cu stabilizing layer were evaluated over a wide temperature range from 30 to 77 K under self-field conditions using the pulsed current method. This approach enabled stable critical current measurements in the kiloampere range while effectively suppressing Joule heating, thereby allowing the simultaneous acquisition of the relationships among tensile strain, critical current, and stress. The results showed that the irreversible strain,ϵirr, defined by a 2% degradation in the critical current, remained nearly constant at approximately 0.4% throughout the temperature range of 30-77 K, indicating negligible temperature dependence. Moreover, sinceϵirrwas smaller than the yield strain,ϵy, it was clarified that electrical degradation occurred prior to the onset of plastic deformation in the metallic substrate. The effective Young's modulus,E0.3%, determined from the slope in the initial elastic region (0-0.3%), increased with decreasing temperature, exhibiting a parabolic temperature dependence. These results indicate that while the elastic properties of REBCO tapes are sensitive to temperature, their electro-mechanical limit, represented byϵirr, is essentially temperature-independent. The findings suggest that the value ofϵirrobtained at 77 K can be directly applied as a design parameter for high-field REBCO magnets operating at lower temperatures (30-50 K). This study contributes to improving the mechanical reliability and establishing precise design criteria for REBCO-based high-field superconducting magnets.