MHD stability analysis of the SMall Aspect Ratio Tokamak (SMART)

Abstract

At the University of Seville, a significant leap forward is being pursued in the race towards achieving viable fusion energy. In this pursuit, the construction of the SMall Aspect Ratio Tokamak (SMART), a spherical tokamak, is currently underway. Having good confinement is essential for the proper function of a tokamak. Different operation regimes have been proposed. The advanced tokamak regime seems to be the more promising for nuclear fusion plants. The high pressures in this regime give rise to pressure driven instabilities that deteriorate the confinement and limit the operational space. A good understanding of the instabilities is key to operate the tokamak. The objective of this master thesis is to ascertain the influence of an ideal wall on the plasma stability. To accomplish this, CHEASE and MARS-F codes have been employed. The simulations are centered on the ideal magnetohydrodynamic (MHD) scenario, neglecting plasma rotation and kinetic effects, as well as plasma resistivity and viscosity. The aim of this simplified approach is to isolate and comprehend the fundamental impacts of the wall on plasma stability. MHD instabilites in the advanced tokamak regime for low-n modes (n = 1, ..., 6), and the effects of the wall at varying distances, were studied. Taking advantage of SMART’s capability to operate at different triangularities, a study to determine the most favorable triangularity for achieving good confinement has been conducted. The highest positive triangularities have shown better MHD stability.