Plasma confinement in non-axisymmetric closed magnetic configurations

This thesis contains a study of the MHD equilibrium and stability as well as classical diffusion in non-axisymmetric magnetic configurations of plasma confinement of interest to controlled thermonuclear reactions research. For a certain class of equilibria that has helicoidal symmetry in the vicinity of the magnetic axis we deduce the conditions in which this helicoidal symmetry can be considered as a very good approximation for a plasma ring when the ring is located around a closed non-planar curve with variable curvature and torsion. Equilibrium, classical diffusion, and localized perturbation criterion of stability are then studied for a plasma with a two variable helicoidal symmetry. These equilibria are in fact generalizations of axisymmetric configurations, and hence possess magnetic surfaces to a good approximation. The ideal MHD equilibrium for a toroidal plasma with non-circular cross section (elliptically or triangularly deformed) situated in a magnetic field with single non-planar magnetic axis, through which flows (in the forward and backward directions) longitudinal current with a flat profile, is solved. Special emphasis is given to a resonance case. The classical diffusion and localized perturbed criterion near the magnetic axis for such configurations are examined