In the context of this subproject following is planned: Basic studies at the heliconexperiment HE-L are to be accomplished,
which consists of a large volume helikonwave discharge in connection with a diffusion chamber. The following questions are treated:
At the heliconsource impactless, in particular stochastic processes of high frequency absorptions are to be examined.
They are based on nonlinear wave phenomena such as wave particle resonances (charge damping, particle trapping) or parametric
instabilities. Such processes in the long run lead to small-scale turbulences, which can be analyzed by microwave and
laser scattering diagnostics. The realizations are to flow into a self-consistent description of the helicon decharge.
Spectroscopic measurements of the neutralgases and the ion component are to give information on particle transport in the down-stream-range
of the helicon discharge and the particle inclusion in the diffusion chamber, in which transportation and volume processes compete with one
another. The ideal plasma characteristics in the chamber will be used in order to study the electron and ion dynamics, in particular the stochastic
electron heating in front of a highperformance-electrode.
A central point is the comparative investigation of the helicon discharges in the electropositive (argon) and electronegative
plasma (in oxygen or oxygen argon mixture). By the formation of negative ions at expense of the electrons, the electron dynamics in the electronegative
plasma can change drastically, which affects the HF power-in-coupling and the deposition in the heliconsource as well as
the diffusion behavior within the Down-Stream-range and in the diffusionchamber (with and without HF-electrode).
The research project pursues two major questions, which results from the division into two parts of the equipment: The heliconsource and the diffusion chamber:
- The planned investigations at the actual helicondischarge are to answer the still unresolved questions and to try to improve
the basic understanding of the latter.
- The down-stream-range of the helicondischarge is given by the transition to a large volume diffusion chamber. There, plasma transport
in electrpositive and electronegative plasmas with respect to volume processes is to be examined. The afterglowplasma in the
diffusion chamber is ideal a target plasma. At a there positioned high frequency electrode basic studies are to be accomplished, which are to give information
about the events in the pre-layer right before the Elekrtode.