Hannover 2010 – scientific programme

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P: Fachverband Plasmaphysik

P 17: Low Temperature Plasmas II

P 17.2: Topical Talk

Thursday, March 11, 2010, 14:40–15:05, B 305

Simulation of a thin cathode discharge in argon at high pressures — •Sebastian Mohr, Beilei Du, Dirk Luggenhölscher, and Uwe Czarnetzki — Institut für Plasma- und Atomphysik, RUB

A thin cathode discharge consists of two electrodes separated by a dielectric layer with a thickness of ca. 100 µ m. While the anode can have essentially an arbitrary width, the cathode has to be thin in order to ensure a high current density (100 µ m in our case). The discharge burns in a hole of 200 µ m diameter that penetrates this sandwich. When such a device is operated with a DC supply voltage at pressures of several 100 hPa, it shows a self-pulsing behavior. Electrical measurements and CCD-images indicate, that this can be explained by the repeated ignition of a short-living arc discharge at the edge of the hole. Due to the high pressure and the related high collision frequencies, the afterglow of this discharge was expected to last several 10 ns. Instead, lifetimes of several 100 ns were observed. In order to identify the mechanisms responsible for this long-living afterglow, a kinetic model of the afterglow was developed. As a result, Penning-ionisation and superelastic collisions with metastables and excimers were found to play a crucial role in heating the electrons. Furthermore, the gas temperature has a significant influence on the lifetime of the afterglow.