Comparison of AC Loss Reduction Methods Based on Striation of Ag-Stabilized REBCO Tapes

Alternating current (AC) losses in REBCO (RE – rare earth metal, B – barium, C – copper, O – oxygen) high-temperature superconductors, can be reduced by several orders of magnitudes by the tape striation. Various methods were investigated so far for the decrease of the superconductor's width-to-thickness ratio, and new methods (or novel combination of previously reported methods) are still developed. A reason for the latter efforts is to reduce the superconductor's degradation, which cannot be completely avoided, and it is inherent to each method. Unfortunately, the degradation also seems to depend on the architecture (i.e., on the thicknesses of layers, deposition techniques used, chemical composition, etc.) We thus compared the ac losses of REBCO tapes striated by a chemo-mechanical method, by photolithography, and by laser ablation approach. The ac loss measurements and transport properties of Ag-stabilized superconducting tapes from SuperPower are complemented by the analysis of their structure. All methods resulted in a substantial decrease in normalized ac loss (more than 9 times at 36 Hz for tape with 15 striations in compare with non-striated tape. The photolithography method exhibited the highest decrease of ac loss, but also led to a notable decline in the critical current.