Impact of filamentary architecture on AC loss in coated conductor tapes

Abstract Tapes made from high-temperature superconducting ceramic REBCO compounds, commonly known as coated conductors (CC), offer a promising solution for future magnetic systems in particle accelerators, nuclear fusion reactors, and electrical machines. Nevertheless, under dynamic operations, dissipation known as AC loss represents a critical factor restricting their applicability. The introduction of the filamentized CC (FCC), wherein the superconducting layer is striated into parallel strips called filaments, has emerged as a game changer. Proportional to the number of filaments, this measure suppresses the hysteresis loss caused by supercurrents circulating exclusively inside the superconductor. However, providing a metallic connection between the filaments is necessary despite the introduction of a new loss mechanism called the coupling loss. In our AC loss study, a series of FCC prepared by the two-level-undercut–profile-substrate (2LUPS) process, differing in the filament width (0.25–2 mm) and in the dimensions of metallic layer filling the gaps between the filaments structure, was investigated. We found that the analytical formulas for computing both primary AC loss components (hysteresis and coupling) yield relevant predictions aligned with experimental findings. Such an approach simplifies parametric studies of loss dependence on tape architecture, which is crucial for the rigorous understanding of the AC loss issue. This phenomenon is illustrated here by presenting the correlations between selected parameters (filament width, transverse resistivity) and the AC loss behavior observed in experiments.