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.