Investigation of transient dynamic behaviors of striations in direct current discharges

Summary form only given. In this study, the spatial temporal characteristics of striations of a dc discharge during the ignition phase of the discharge are investigated. A high speed intensified charge- coupled-device (ICCD) camera is employed to take the dynamic images of optical emissions from the striations of the discharge. Voltage and current probes are also used for measuring the temporal characteristics of voltage and discharge current. The plasma ignition interval can then be divided into three periods to describe physical mechanisms responsible for the dynamic behaviors in each period. Plasma discharges using several different gases, such as Ar, Xe and Ne, were also examined and the spatial and temporal variations were compared. A model to explain the formation mechanism of striations in DC discharge is then proposed. The model correlates strongly to the striation formation mechanism in DBDs, e. g., discharge begins at anode side. Then, the main discharge moves toward cathode due to cathode sheath contraction and wall charge accumulation at anode region during the same time. Secondary electrons emitted from cathode surface inject into anode side and gain energy to occur inelastic collision then striations appear. Detailed experimental results, as well as the proposed formation mechanisms of the striations will be presented.