Discharge Characteristics Of A Cold-Atmospheric-Plasma Jet Array Generated With Single-Electrode Configuration

As one of the immediate areas of research focus, cold atmospheric pressure plasma jets (CAPJ) is a rapidly developing technology of non-thermal atmospheric pressure plasma sources.This kind of discharge technology ejects plasma from the nozzle or aperture of the discharge region by virtue of the air flow and electric field, achieving the separation of their generation from their application regions and transporting the high reactive chemical species produced in generation region to the application region. The desirable properties of these chemical species, including high chemical reaction activity, easy to react with material surface, have made them considerably promising for a number of important applications in traditional areas and the emerging areas of biomedical.At this stage, the CAPJ technology mainly develops into two directions:miniaturization and large scale plasma jets. By means of the expansion of the scale of plasma source or using a large amount of cold plasma jets running in parallel (plasma jet array) to form large scale uniform plasma, which is mainly used for material surface treatment.CAPJ array source is by grouping many small CAP jets together to form an array of plasma jets. Our work aims to develop a two dimensional (2-D) CAP jet array with single-capillary electrode configuration as the fundamental plasma jet to form large scale uniform plasma. Before this work, we studied the discharge characteristics of the single-electrode plasma jet source to find the appropriate discharge parameters. The2-D CAP jet array considered in this study consists of seven identical quartz tubes, each of which housed a single-capillary electrode configuration. The seven identical quartz tubes are structured in a honeycomb arrangement in which one central quartz tube is surrounded by six quartz tubes placed at the six points of an equilateral hexagon. By means of detailed electrical, spectroscopic, and imaging diagnoses, we studied the discharge characteristics of the plasma jet array.Good uniformity is shown by the CAP jet array both in time and space in terms of optical emission intensities of four characteristic spectral lines, i.e., N2at337nm, N2+at391.4nm, He at706.5nm, and O at844.5nm. Besides, the rotational and vibrational temperatures of the CAP jet array are found to be in the range of300-310K and2100-2200K, respectively. Furthermore, we also study the jets discharge evolution process and jet-to-jet interactions via two series of ICCD images which are taken at the side and end views. It demonstrates that spatial uniformity is followed by abundant dynamics, for instance, a slight repulsion at surrounding jet heads, especially for small gas flow rate of He. According to the photoionization-based plasma-bullet model, the bullet head is assumed to consist of numerous positive ions. Thus, individual jet shape would be affected by the Coulomb repulsion with the other six jets, mainly at the jet head.