Instabilities in Capacitively Coupled Radio-Frequency Discharges

Instabilities in an asymmetric capacitively coupled radio-frequency discharge are observed at pressures above 100 Pa if a circular quartz glass tube is inserted into the discharge parallel to the powered electrode. The instabilities are observed with a charge-coupled-device camera as localized plasma balls. The number of these so-called plasmoids increases with increasing pressure. At different pressures, different modes are observed.