Parametric Optimization of the CEA TF Magnet Design of the EU DEMO Updated Configuration

In the framework the design activities conducted in EU for the future fusion demonstration reactor (DEMO), extensive analyses were led in the EUROfusion context, aiming at ultimately designing the DEMO magnets system. The DEMO tokamak configuration was updated in view of improving the operation merits versus the previous design defined in 2015. In the objective of properly addressing tokamaks general magnetic systems, CEA has adapted macroscopic design tools and associated methods to size magnets for pre-dimensionning or optimization purposes. Once pre-dimensioned using inputs from system-level analyses the magnet concepts undergo an evaluation process by detailed analyses (thermohydraulic and mechanical) highly accurate but strongly time consuming. To avoid repeating this sequence, we aimed in this paper at improving pre-dimensioning process reliability for the final benefit of the whole design workflow. The material exposed in this paper is the path to this improvement achieved through a sery of pre-dimensioning parametric cases applied on the DEMO TF system baseline newly issued in 2018 by EUROfusion. The optimization steps are described, showing which design TF system variables are chosen for optimization and what is their contribution to ultimately rend the design as efficient as possible with respect to given merits. In this aim, former detailed finite elements analyses, carried out on the previous DEMO configuration, are taken as reference to support the quantitative choices of the pre-dimensioning method improvement (criteria or input modifications). Furthermore, TF design is also explored on a new aspect: the possibility of including radial plates in the winding pack.