Fig. 4

Discharge characteristics change with distance between the electrodes in different discharges. a–d In dielectric barrier discharge (DBD) plasma (type 1), discharge current, time averaged number of discharge per cycle, effective value of current and mean power change (same characteristics as follows) when lifting the capillary with the copper wire electrode from the Kapton surface. In b, the symbol of ball means the median value and error bar indicates the range from 10% to 90% of the whole sampling data (similar as follows). e–h In microspark discharge (type 2), there is no dielectric film between the two electrodes. At the beginning of lifting the copper wire, there is a continuous discharge path between the two electrodes which results in no pulsed discharge current detected (g) but high effective value of current just like short circuit current (h). i–l Another type of microspark discharge (type 3) with a stainless-steel capillary tube. m–p Holding the height of 0.20 mm, capillary moving horizontally from the border of copper and Kapton towards left which leads to the obvious changes of discharge mode and status from microspark to DBD plasma. p The current and power are both much higher in spark zone than those in DBD zone, and they decline sharply in the coexist zone