Speaker
Description
Fusion magnets experience sharp dB/dt excursions, especially during plasma breakdown and current ramp-up. Calculating the instantaneous power dissipation is therefore essential for quantifying, through thermal-hydraulic simulations, the local heat load that must be handled. Toward this purpose, we have developed a modelling framework, combining analytical formulations with finite-element tools, to quantify hysteresis losses in REBCO tapes and coupling/eddy-current losses in advanced cable concepts such as sector-assembled cables (SECAS), twisted-stacked-tape conductors (TSTC), and highly-flexible-REBCO-conductors (HFRC). The approach builds on established analytical foundations, such as Brandt/Halse/Bean-type models for magnetization loss and Laplace-based formulations for coupling losses, and captures the interplay between superconducting and metallic dissipation mechanisms through field- and geometry-dependent descriptions of magnetization, effective transverse resistivity and coupling time constants.
Applied to EU-DEMO operating scenarios, the models show that magnetization losses dominate at high fields, while coupling losses become relevant during fast transients where the relaxation time τ governs the shielding of rapid dB/dt variations. These results indicate two key design directions for HTS fusion cables: (i) striated REBCO tapes to mitigate hysteresis, and (ii) sectorized conductors with increased effective transverse resistivity to enhance τ and suppress inter-stack coupling currents. The study also shows that sound analytical models can efficiently complement FEM simulations, providing fast and physically transparent estimations for the design of next-generation HTS fusion magnets.