EMC3-EIRENE simulations of the ASDEX-Upgrade tokamak in support of experiments with a toroidally localised liquid Sn module

Nuclear fusion is the fundamental nuclear reaction that powers stars, and it is currently being considered as a potential method for energy production. Harnessing nuclear fusion poses a global challenge due to the difficulty of replicating the ideal conditions for these reactions on Earth. These conditions are partially reproduced inside machines called Tokamaks through the use of a localized magnetic system, where the fusion fuel (plasma heated to approximately 100 million degrees Kelvin) is magnetically confined. The power production levels achieved in the confined area, combined with the limited surface area of the Plasma Facing Components (PFCs), make managing the thermal load on the wall very challenging, threatening the integrity of the materials used. This phenomenon is referred to as the power exhaust problem and is one of the fundamental challenges in designing a future fusion reactor. The primary component for the power exhaust problem is the divertor, a solid-state component commonly located at the bottom of the plasma chamber. It is specifically designed to handle the flow of particles and thermal energy ejected from the confined plasma and to maintain the structure's integrity, as well as managing impurities generated by the interactions between incoming particles and PFCs. The complexity of this system necessitates plasma simulations, a powerful tool not only useful in the absence of diagnostics but also for interpreting experimental results, as well as for conducting predictive optimization for the experiments aimed at future applications. This thesis, in particular, focuses on simulating the behavior of plasma in pure deuterium within the ASDEX Upgrade (AUG) experimental reactor, aiming to establish a foundation for future studies incorporating impurities. For this goal, the 3D modeling system EMC3-EIRENE was utilized, integrating EMC3 (fluid model) for describing plasma transport and EIRENE (kinetic model) for describing neutral transport processes, providing enhanced localized phenomena representation, with an accurate 3D description of charge and neutral particles behaviour. To structure the simulation, it was necessary to supplement experimental data obtained from the IPP database (Max Planck Institute for Plasma Physics, Garching, Germany), responsible for the data collection of experiments conducted by AUG, with data from similar case study simulations. The thesis was thus conceived as a foundational study for future 3D simulations that will include impurities, especially in case studies where alternative divertor configurations are proposed. A potential application for this study is the simulation of a scenario in which a self-healing liquid metal divertor (LMD) module is localized in a well-defined toroidal position of the ASDEX machine. This concept is driven by the anticipated need to manage increased thermal loads in upcoming reactors like EU-DEMO. The interaction between the plasma and the surface of this model generates a protective cloud of evaporated particles above the divertor, aiding in the dissipation of transmitted power through radiation emission. Such a configuration would result in an asymmetric characterization of the system, making 3D EMC3-EIRENE modeling the most suitable approach for representing localized phenomena. The results of the pure deuterium simulation coincide with the theoretical expectations, with lower plasma density and temperature near the divertor compared to the central region.