Description
The stellarator offers key advantages over the tokamak as a magnetic fusion reactor concept, including intrinsic steady-state operation capability and immunity to current-driven instabilities and disruptions. Unlike in tokamaks, good confinement is not guaranteed in a generic stellarator but requires a careful design of the three-dimensional magnetic field, usually known as stellarator optimization. Owing to its inherent advantages, together with progress in theory and computational optimization, the stellarator has emerged as a solid contender for fusion reactors [1].
In this talk, CIEMAT-QI4X [2] is presented, a new four-field-period quasi-isodynamic configuration featuring low neoclassical and electrostatic turbulent transport, good fast-ion confinement across a wide β range, and a small bootstrap current. CIEMAT-QI4X has been obtained by building on the optimization strategy and sophisticating the methods employed in [3] to achieve high-quality nested flux surfaces in the confinement region and a robust island structure at the edge compatible with an island divertor. A set of filamentary coils wil be presented that generate the configuration with enough accuracy to preserve the aforementioned physics properties. In terms of physics performance, CIEMAT-QI4X establishes as a strong candidate for stellarator
fusion reactor designs.
[1] Global Fusion Industry Report 2025. The Fusion Industry Association. 2025.
[2] Sánchez E. et al. Nuclear Fusion 2026 (submitted).
[3] Sánchez E. et al. 2023 Nucl. Fusion 63 066037.