ABSTRACT
Heating plasmas by means of radio frequency waves in the microwave range has become a standard tool since its first usage in the late 1940s. While the heating in magnetized plasmas at the electron cyclotron resonance frequency is well understood, heating of so-called over-dense plasmas is still a topic of ongoing research. In these plasmas the electron cyclotron frequency is shielded by the cutoff frequency from the injected microwaves.
The stellarator TJ-K located at the University of Stuttgart allows to perform discharge scenarios in which different methods of over-dense plasma heating can be investigated. Accompanying to the experiments, a full-wave code based on a cold plasma description has been developed which allows to describe the various regimes observed. The code has also been used for optimizing electron Bernstein wave (EBW) heating scenarios. These waves are electrostatic waves that have no high density cutoff and are absorbed very well at the electron cyclotron resonance and its harmonics. In this presentation an overview of the experiments performed at TJ-K will be given as well as some insights into the generation process of EBWs obtained from the full-wave code.