Microwave heating of overdense plasmas

Monday 11 March 2013, 10.15AM

Speaker(s): Alf Köhn, University of Stuttgart

Heating plasmas by means of radio frequency waves in the microwave range
has become a standard tool since its first usage in 1948. While the
heating in magnetized plasmas at the electron cyclotron resonance
frequency is well understood, heating of so-called overdense plasmas is
still a topic of ongoing research. In overdense plasmas the cutoff
frequency exceeds the electron cyclotron frequency and shields it
therefore from injected microwaves. The stellarator TJ-K located at the
university of Stuttgart allows to perform several discharge scenarios in
which different methods of overdense plasma heating can be investigated.
Accompanying to the experiments, a full-wave code has been developed which
allows to describe the various regimes observed based on a cold plasma
description. 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 presentations 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.

Location: Fusion Learning Studio, YPI

Simulation of an electro magnetic wave emitted from an antenna onto a curved plasma; plotted is the positive value of the wave electric field, iso-plasma-density surfaces are indicated by the yellow lines.