Titolo della tesi: Equilibrium Properties of a Magnetically Confined Plasma and Beam-Plasma Instability
In this thesis, we deal with different topics of plasma physics, with its core findings relevant for the operation of tokamak devices. The topics belong to two main lines of research: axisymmetric equilibrium configurations, and fast particle dynamics.
In the context of equilibrium configurations, we extend the traditional theory of ideal static plasma equilibria to include bulk plasma rotation in the toroidal direction, in order to investigate the impact of plasma motion on the most relevant equilibrium properties. Separately, we also study the diffusive (slowly evolving) regime of equilibrium configurations when subject to electrical resistivity, describing the equilibrium relaxation and discussing its implications.
Concerning fast particle dynamics, we investigate the theory of the beam-plasma instability, revising some of the traditional assumptions made in its treatment. We also show how two additional effects can be included in the system dynamics through its N-body formulation, namely the backreaction of the medium, inducing a suppression of the mode saturation levels, and separately the effect of particle collisions, inducing a progressive resonance detuning.
Lastly, a cross-fertilization investigation is presented, in which we link the theoretical procedures of the beam-plasma scenario and the study of gravitational waves beyond General Relativity, namely in the Horndeski framework. In this context, we prove the existence of an analogous instability phenomenon between the scalar mode of such gravitational waves and a background gravitational plasma.