Controlling instabilities in tokamak plasmas through modeling and experiments

The dream of obtaining a green source of energy, reproducing the fusion process occurring in nature inside the stars, has been pursued for many years by the scientific community. Although significant results have been achieved, unstable phenomena are one of the main concerns in future fusion plasma reactors, such as ITER, that is the largest experimental tokamak under construction. Edge localized modes and runaway electrons are two of the most relevant problems in tokamak dynamics. The aim of this thesis is to design and test new techniques to identify and control instabilities affecting plasma performance. Different approaches have been investigated, ranging from practical experiments using electrical analogue to synchrotron images processing and simulations. The first part of the thesis focuses on the design of an electrical analogue of the plasma behavioural model, exploiting a qualitative low dimensional model of plasma instabilities. The central part of the thesis regards runaway electrons detection and simulations. An automatic platform for the runaway electron pitch angle estimation is implemented. Progressively, the synchrotron images are analysed using a diagnostic simulation, based on a simplified theoretical model. In the last part of the work, a comparative study of remote recovery algorithms of audio signal paves the way for new applications in the nuclear fusion diagnostics field. Generally, results confirm the theoretical hypothesis and experimental data, giving a contribution in the path to make the nuclear fusion process self-sustainable.