A Non-Equal Gap Distance Dielectric Barrier Discharge: Between A Wedge-Shaped And A Plane-Shaped Electrode

For all volume dielectric barrier discharges (DBDs) reported, including both planar configuration volume DBDs and cylindrical or coaxial volume DBDs, the gap distance between the two electrodes is always a constant. In this paper, a non-equal gap distance DBD between a wedge electrode and a plane-shaped electrode is reported. It is found that the plasma can self-organize into a striped shape, which makes it possible to achieve a homogeneous plasma treatment effect by scanning the plasma over the surface. The high-speed photographs show that the discharge first occurs at the center of the wedge-shaped electrode where the gap distance is smallest, and it jumps to the next position with a relatively larger gap distance after a certain delay time. This is because of the build up of the reverse voltage due to the deposit of charges at the locations where discharge is ignited. Detailed analysis shows that the width of the equivalent charge deposit region is larger than that of the bright plasma stripe. According to the intensity ratio of N-2 (+) (391.4 nm) and N-2 (394.3 nm), the reduced electric field strength is evaluated to be in the range of 250-370 Td. It decreases with the increase in the gap distance. In addition, plasma of another type of non-equal gap distance DBD with a conical shape and a plane-shaped electrode is explored, and it is found that the plasma can also self-organize into concentric rings.