If a plasma comes into contact with a material surface, it reacts in building up of a thin, non-neutral zone, the plasma boundry zone.
Here prevail strong electrical fields and spatial gradients, which shift the plasma into a pronounced nonequilibrium state
and induce appropriate transportation phenomena. With the technically particularly important high frequency plasmas in addition the
effect of the external modulation is taken into account. This has special influence in the boundry zone and prevents, as source of free energy, the
relaxation into the equilibrium.
The subject of subproject A8 is the experimental and theoretisshe investigation of non-equilibrium phenomena in the boundry zone, whereby
special attention is given to the case of the high frequency-modulated low pressure plasmas. The goal consists of the development
of a detailed physical understanding of the observed processes. From the beginning, kinetic conceptions are to be worked out, the
observable phenomena of the (spatial) transport and the heating are therefore seen as a special case of a more comprehensive phenomenon namely "Transport in
Due to their different mass and charge of the different species of plasma, they each require their own models, these are however closely bound
together by the strong reciprocal effect over the field as well as by the impacts with one another. In case of the the ions there is to be examined, how
the particles separate in wall proximity from the ambipolar transportation regime of the bulk and get inserted into the pronounced
kinetic regime of the layer, and which influence this process has on the details of the energy- and angle-distribution. On the other hand, in case of the
electrons the conception is, that especially transient fields force the deviation from the impulse equilibrium and thus create a transport.
Special attention rests therefore on the phenomenon of the smooth and stochastic heating. Finally also the dynamics of the neutral particles
in the boundry zone is to be examined. These are not directly affected by the electrical field, but are for themselves far from the state of
equilibrium: Sources of energetic neutrals are e.g. flexible and charge exchange impacts in the layer, or the neutralization and following
reflection of fast ions from the wall.
The project work is split up into experimental investigations, theoretical analysis coupled with application- and experiment-near modelling and
simulation. Due to the experiments a clear and complete insight into the dynamics of material plasmas is to be established on the basis of a parameter range as
broad as possible.Particularly selected mechanisms and/or regimes are to be understood in detail and so conceptual
clarification of the procedures is to be reached by the theoretical analysis.
The long-term goal of the project mainly consits of the development of a complete understanding of the procedures found in boundry layers of low pressure plasmas,
especially the clarification of transport processes and heating mechanisms in self-consistent fields. An experimentally and theoretically secured picture
of the phenomena is to be sketched and the connection between external parameters and decharging behavior to be understood. This is not only of fundamental
physical interest, but also of outstanding technological importance.