Review and comparison of divertor configurations for High Magnetic Field Tokamak

One of the most promising fusion devices is the tokamak based on magnetic confinament of the plasma. However, effective magnetic confinement does not exempt the tokamak wall from receiving energy and particle fluxes. It is therefore necessary that these fluxes are compatible with the power handling capabilities and erosion lifetime of the components in contact with the plasma. The work presented here is dedicated to the study of the plasma at the edge, in the SOL, and in the divertor region, with the ultimate goal of contributing to the development and improvement of current and future devices, such as DTT (Diver- tor Tokamak Test facility) and ITER (International Thermonuclear Experimental Reactor). The first part of the Ph.D. was dedicated to studying the principles of edge and SOL physics, the Two-point model, which describes in first approxima- tion the physics of the SOL, the 2D fluid code SOLEDGE2D-EIRENE and the 3D turbulent code SOLEDGE3X. Subsequently, we focused on the analysis of the power exhaust and its impact on the edge plasma in different types of magnetic configuration, such as the conventional Single-Null (SN), the Negative Triangular- ity (NT) and the Super-X Divertor (SXD). One of the most promising among the advanced-tokamak scenarios is the Nega- tive Triangularity (NT) configuration, which achieves reactor-relevant conditions in the plasma core without, however, exhibiting the dangerous Edge Localised Modes (ELMs), instabilities that are present in the more commonly used Posi- tive Triangularity High-Confinement mode (PT H-Mode) configuration. To un- derstand the transport of energy and particles at the plasma edge of NT and to determine whether this configuration could be a viable alternative in terms of power exhaust, analytical and numerical studies have been conducted using TCV (Tokamak à configuration variable) experiments and the SOLEDGE2D-EIRENE code. Furthermore, studies in this field have been started using the turbulent code SOLEDGE3X. The detachment regime for future fusion reactors, thanks to the reduction of the particle and heat fluxes on the divertor targets, allows to have a decreasing in erosion and melting of the wall material. Among the optimal configurations to achieve these conditions there is the alternative SXD. This magnetic configuration is characterised by a larger radius of the outer strike point compared to the con- ventional PT, resulting in a decrease in parallel heat flux along the flux tube and therefore in a lower temperature at the divertor targets. To study its potential, we have used experiments on TCV and the SOLEDGE2D code. Magnetic confinement fusion devices must have both high confinement in the core to maximise fusion reactions and plasma conditions in the divertor that are com- patible with the limits of plasma-facing components. In the PT H-Mode config- uration, the density at its transport barrier (pedestal top, ne,ped) is an important indicator of confinement quality, while the density at the separatrix (ne,sep), which is the last flux surface between the core and the SOL, is a crucial factor in deter- mining the divertor regime. For this reason, several studies have been conducted on the relationship between ne,sep and ne,ped) using JET (Joint European Torus) experiments conducted in two possible divertor configurations known as Vertical- Vertical and Corner-Corner.