Study On Two Patterns With Surface Discharge And A Honeycomb Pattern With Halo In Dielectric Barrier Discharge

Three novel plasma discharge patterns are obtained in dielectric barrier discharge?DBD?by using different glass frames.The spot-line white-eye hexagonal superlattice pattern is obtained and study in a round glass frame,the three-dimensional double bright-dark spot pattern is observed by using a special three-layers strip glass frame and the honeycomb hexagonal pattern with halo is observed by a square glass frame.The three patterns are studied by an intensified charge-coupled device?ICCD?camera,a lens photomultipliers?PMT?system,a high-speed video camera?HSVC?,and a spectrograph.Results show that in the spot-line white-eye hexagonal superlattice pattern and the three-dimensional double bright-dark spot pattern,the wall charges of the volume discharges?VDs?can induce surface discharge?SDs?,and the complex interactions between VDs and SDs play an indispensable role in the formation of the two patterns by changing the distribution of wall charges.In the honeycomb hexagonal pattern with halo,the halo discharges at the rising edge of voltage.The halo,rather than the honeycomb frame,discharges first on the rising edge of the voltage.The wall charges of hole dominate the discharge of the central spots at the falling edge of the voltage.However,the field of the wall charges of the honeycomb frame cannot reach the breakdown threshold at the falling edge of the voltage.The wall charge theory is used to explain the formation of these three plasma discharge patterns.The main research contents and results are as follows:Firstly,a novel pattern named spot-line white-eye hexagonal superlattice pattern is observed for the first time in DBD.The results show that the small spot-lines discharge at the first current pulse of the rising voltage,the halos discharge at the second current pulse of the rising edge.The small spots are VDs,and the lines are SDs induced by the small spots.The discharge time of small spots is incompletely simultaneous.The lines are direction-selective SDs.The number of wall charges transported by the line is different,so the small spots have poor simultaneity.The SDs can stretch to the neighboring small spots,and are extinguished in other directions because the neutralization of VDs?halo?and SDs?line?.Secondly,a continuous three-dimensional double bright-dark spot pattern with the symmetry of D_2h is obtained by introducing SDs with a specially designed device for the first time.Results show that the 3D pattern consists of bright bars,dark spots,the triangle halos and the halos around the dark spots.The dark spots and the halos around the dark spots are conventional VD.The bright bars are the novel VD and the triangle halos is the SDs of the bright bars.Different from the conventional VD,the novel VD bends through three gas gaps and discharges multiple times per half voltage cycle,which results from the complex interaction between VD and SD.The SDs induced by VDs transfer parts of wall charges to the corner of the thin gas gap,which results in the multiple discharges of the bright bars.The wall charges stored in the corner of the thin gas gap contribute to the bent VDs.By using this device,three surfaces of the sample inserted between electrodes are processed simultaneously,which greatly improves the plasma processing efficiency.Thirdly,the honeycomb hexagonal pattern with halo is obtained in DBD,it is found that the pattern has three structures.From the zero of the applied voltage,the micro-discharges sequence is halo structure,honeycomb frame structure and central sport structure.Although the honeycomb frame discharges after the halo at the rising edge of the applied voltage,the amount of charge transferred by the honeycomb frame is much smaller than that of the halo.the field of the wall charges of the honeycomb frame cannot reach the breakdown threshold at the falling edge of the voltage.After the discharge of the central spots at the falling edge,the residual wall charges of the halo are still more than that of the honeycomb frame.Therefore,the halo is still discharged first at the rising edge of the voltage.