Ion cyclotron emission on ASDEX upgrade

This works deals with the Ion Cyclotron Emission (ICE), a plasma instability that takes place both in astrophysical plasmas and in fusion energy facilities like Tokamaks and Stellarators, when a population of high energetic ions is present. These fast ions can interact with the waves which propagate in the background thermal plasma and excite instabilities in the Mega-Hertz range. This emission can be measured in a non-intrusive way with radio-frequency probes and provide information on the characteristics of the fast ions. The hope of a new diagnostic sparked many studies in the years 1992-2002 but, in spite of the theoretical and experimental progresses, no practical instrumentation was achieved. There are indeed two main difficulties: first, the ICE involves many different types of plasma phenomena: waves propagation, resonances, conversion and absorption in complex geometries, core and edge plasma modelling, fast ion creation and trajectories; all these aspects are entangled. Therefore, accurate data both in time and frequency domains and a theory that covers these physics fields are necessary to distinguish the impact of these different phenomena. Second, there are technical difficulties in measuring high-frequency signals with a sufficient Signal-to-Noise Ratio to discriminate it from the background noise. The purpose of this study is to address these issues with the use of the latest acquisition technologies and an improved ICE theory, which can relate in a new light the properties of the fast ions to the characteristics of the emission.