Destabilization and characterization of Toroidicity-induced Alfvén Eigenmodes with Gysela

Nuclear fusion promises a clean, limitless energy source. This thesis focuses on magnetic confinement fusion in tokamaks, which use magnetic fields to contain hot plasma in a toroidal shape, creating a stable environment for fusion reactions. Deuterium and tritium (D-T) fusion is currently the most feasible, producing energy by forming a helium nucleus and a high-energy neutron. Effective confinement of alpha particles, produced in these reactions, is crucial for achieving ignition, a self-sustaining fusion process. External heating systems like neutral beam injection (NBI) and ion cyclotron resonance heating (ICRH) generate fast ions to maintain the high temperatures necessary for fusion. However, these ions can interact with plasma waves, such as Alfvén eigenmodes, causing instabilities that challenge plasma confinement. Alfvén waves are low-frequency oscillations in magnetized plasma, and their natural oscillation patterns (eigenmodes) are influenced by the tokamak's geometry and magnetic fields. Toroidicity-induced Alfvén Eigenmodes (TAEs), specific to the toroidal shape, can resonate with fast ions, leading to instabilities that affect plasma performance. The GYSELA code, an advanced simulation tool, models toroidal plasma dynamics and helps study plasma stability, confinement, and transport properties. GYSELA's simulations provide insights into high-temperature plasma physics, aiding the development of efficient fusion reactors. This research started by characterizing Alfvén eigenmodes in a cylindrical configuration to understand their fundamental properties. The study then advanced studying the TAE in a realistic toroidal setup. An electrostatic antenna that perturbs the plasma was implemented in GYSELA in order to examine the interaction between fast ions and TAEs. The antenna allows a controlled excitation and detailed analysis of how fast ions influence TAEs and impact plasma stability and confinement.