Impact of filamentary architecture on AC loss in coated conductor tapes

Abstract

Abstract

Abstract The tapes based on high-temperature superconducting ceramic REBCO compounds, commonly known as coated conductors (CC), are a promising solution for future magnetic systems in particle accelerators, nuclear fusion reactors, and electrical machines. Nevertheless, under dynamic operation, the dissipation known as AC loss represents a critical factor setting the limit of their applicability. Game changer is the introduction of the filamentized coated conductor (FCC), in which the superconducting layer is striated into parallel strips called filaments. Proportional to the number of filaments, this measure suppresses the hysteresis loss caused by supercurrents circulating exclusively inside the superconductor. However, there are good reasons to provide a metallic connection between the filaments, with the adverse effect of introducing 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 to 2 mm) and in the dimensions of metallic layer filling the gaps between filaments structure, was investigated. We found that the analytical formulas for computing both main AC loss components (hysteresis and coupling) provide relevant predictions aligned with experimental findings. Such approach simplifies parametric studies of loss dependence on tape architecture, necessary for rigorous understanding of the AC loss issue. It is illustrated here by presenting the correlations between selected parameters (filament width, transverse resistivity) and the AC loss behaviour observed in experiments.