Berlin 2005 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

P: Plasmaphysik

P 5: Niedertemperaturplasmen / Plasmatechnologie 2

P 5.1: Vortrag

Freitag, 4. März 2005, 14:45–15:00, HU 3038

Ionization fronts in a system with the high-ohmic electrode — •Shalva Amiranashvili, Svetlana Gurevich, and Hans-Georg Purwins — Institut für Angewandte Physik, Westfälische Wilhelms-Universität

Electrical breakdown and ionization fronts are considered in a sandwich-like discharge system consisting of two plane-parallel electrodes and a gaseous gap in between. The key system feature is a high-ohmic cathode opposed by an ordinary metal anode. Using two-scale expansion we demonstrate that in the low-current Townsend mode the discharge is governed by a two-component reaction-diffusion system. The latter quantities the system on the time scale that is much larger than the ion drift time. The breakdown appears as an instability of the uniform overvoltage state. A seed current fluctuation develops in a shock-like ionization front that propagates along the electrodes. The front is essentially nonlinear and spreads with the constant velocity, the latter is uniquely determined by system parameters and can be compared with experimental data. Depending on the cathode resistivity the front is either monotonic or oscillatory. Other breakdown features, such as current oscillations, are also traced.