A complex pattern with hexagonal lattice and white-eye stripe in dielectric barrier discharge.

A novel type of white-eye pattern in a dielectric barrier discharge system has been investigated in this paper. It is a superposition of a hexagonal lattice and a white-eye stripe in appearance and evolves from a white-eye square grid state with the applied voltage increasing. Its spatio-temporal dynamics obtained by an intensified charge-coupled device shows that it consists of three transient rectangular sublattices. The spatiotemporally resolved evolutions of the molecular vibrational temperature and electron density of the pattern are measured by optical emission spectra. The evolution of surface charge distribution is given and its effect on the self-organized pattern formation is discussed.

[Study on Spectral Characteristics of Filaments in Three Layers Gas Gap in Dielectric Barrier Discharge].

By optical emission spectrum, we report on the first investigation on the spectral characteristics of filaments in three layers gas gap in dielectric barrier discharge, which filled with gas-mixture of argon and air. The filaments are generated in 1 mm gas gap, 4 mm gas gap and 2 mm gas gap, respectively. With previous single layers gas gap or double layers gas gap of the filaments are very different in terms of spectral characteristics. The emission spectra of the N2 second positive band (C(3)Π(u)→B(3)Π(g))are measured, from which the molecule vibrational temperature of the filaments which generated in different gas gap are calculated. Based on the relative intensity of the line at 391.4 nm and the N2 line at 394.1 nm, the electron average energy of the filaments which generated in different gas gap are investigated. Increasing the content of argon, the change of the molecule vibrational temperature and the electron average energy of the filaments are investigated. It is found the ascending order of the molecule vibrational temperature in the same argon content is: 2 mm gas gap, 1 mm gas gap and 4 mm gas gap. However the ascending order of the electron average energy in the same argon content is: 4 mm gas gap, 2 mm gas gap and 1 mm gas gap. The molecule vibrational temperature and the electron average energy of the filaments decrease with the argon content increasing.

[Study on the Plasma Parameters of the Spot-Halo Hexagon Pattern with Optical Emission Spectrum].

The spot-halo hexagon pattern consisted of the center spot and hexagon halo in dielectric barrier discharge is researched, which filled with gas-mixture of argon and air. The pictures taken from the experiment shows that there is an obvious difference on brightness between the center spot and hexagon halo. All of these phenomena suggest that the center spot and hexagon halo are probably in different plasma state. The plasma parameters of the center spot and hexagon halo in the spot-halo hexagon pattern as a function of gas pressure are studied in details by using optical emission spectra. The emission spectra of the N2 second positive band(C3Πu→B3Πg)are measured, from which the molecule vibrational temperature of the center spot and hexagon halo are calculated. Based on the relative intensity of the line at 391.4 nm and the N2 line at 394.1 nm, the change of the electron average energy of the center spot and hexagon halo as a function of gas pressure is investigated. The electron density is studied by using the broadening of the spectral line 696.5 nm. It is found that the main chart of the spot-halo hexagon pattern is the argon content from 60% to 75% and the pressure from 30 to 46 kPa. The molecule vibrational temperature and electron average energy of the hexagon halo are higher than those of the center spot at the same pressure. As the pressure gradually increased from 30 to 46 kPa, the molecule vibrational temperature and electron average energy of the center spot and hexagon halo are increased, too. The broadening of the spectral line of the hexagon halo is bigger than the center spot at the same pressure, which increases with the gas pressure increasing. It indicates that the electron density increases with gas pressure increasing. The different plasma state of the center spot and hexagon halo show that the different formations mechanism of them. It is found that there are volume discharges firstly and then comes surface discharges with e high speed camera.