Investigations on the afterglow of a thin cathode discharge in argon at atmospheric pressure

A thin cathode discharge consists of two electrodes separated by a dielectric layer with a thickness of ca 100 µm. The shape of the anode can be chosen arbitrarily, while the thickness of the cathode is also about 100 µm. Through this ‘sandwich’, a hole with a diameter of 200 µm is drilled. When such a device is operated at pressures of several hundred hectopascals, it shows a self-pulsing behaviour in which high electron densities of several 1016 cm−3 are reached. Electrical measurements showed that this can be explained by the repeated ignition of a short-living spark discharge. Due to the high pressure and the related high collision frequencies, the afterglow of this discharge was expected to last several tens of nanoseconds. Instead, lifetimes of several hundred nanoseconds 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 ionization, superelastic collisions with both atoms in excited states and excimers were found to play a crucial role in the production and heating of electrons.