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Discharge expansion in barrier discharge arrangements at low applied voltages

This study evaluates the spatial expansion of barrier discharges (BDs) in oxygen, carbon dioxide, synthetic air, and helium at atmospheric pressure. Despite being confined in narrow gas channels, the BD plasma only partially covers the available discharge area at low applied voltages as was experimentally observed. This is important for homogeneous surface treatment. The appearance of local discharge zones in the plasma development results in a variation of the capacitive behaviour of the equivalent electric circuit as a function of the applied voltage. This transient behaviour of the apparent dielectric capacitance is therefore investigated for various discharge areas and different gas compositions. Furthermore, a semi-empirical model describing the expansion behaviour is proposed and validated by means of the obtained experimental data. The results clearly show that a three times higher voltage excess is required for oxygen-containing gases compared with helium in order to develop full plasma expansion. For the discharge areas considered, the size of the available electrode plays a minor role in the plasma expansion process.