Patterns In Dielectric Barrier Discharge Research Articles

Formation mechanism of bright and dark concentric-ring pattern in dielectric barrier discharge

Abstract In this work, a bright and dark concentric-ring pattern is reported in the dielectric barrier discharge for the first time. The spatiotemporal dynamics of the bright and dark concentric-ring pattern is investigated by an intensified charge-coupled device and photomultiplier tubes. The results indicate that the bright and dark concentric-ring pattern is composed of three concentric-ring sub-lattices. They are bright concentric-ring structures, dark concentric-ring structures and wider concentric-ring structures, respectively. The bright concentric-ring structures and dark concentric-ring structures are alternately distributed. The bright concentric-ring structures are located at the centre of the wider concentric-ring structures. The formation of the wider concentric-ring structures is first formed from the outer edge and gradually develops to the centre. The essence of all three concentric-ring structures is the individual discharge filaments. The optical emission spectra of different sub-lattices are acquired and analyzed. It is found that the plasma parameters of the three concentric-ring sub-lattices are different. Finally, the formation mechanism of the bright and dark concentric-ring pattern is discussed.

Three-dimensional pattern in dielectric barrier discharge with modulated gas gap

We report a three-dimensional pattern with self-organization in three spatial dimensions in dielectric barrier discharge (DBD) by designing a novel device with modulated gas gap. The distribution of electric field by solving the Poisson equation in the x-y plane varies along the z-axis, and three kinds of gas gaps with different thicknesses have different electric fields. The spatiotemporal dynamics of the pattern is obtained by photomultiplier tubes and intensified charge-coupled device. For estimating the plasma parameters, the emission optical spectra are detected by a spectrograph. In three gas gaps, there are five substructures with different morphologies and plasma states in which two structures discharge at the falling edge of the applied voltage. The variation along the z-axis demonstrates that a three-dimensional pattern is truly obtained. It exhibits some novel phenomena that should advance plasma physics in DBD and pattern dynamics as follows. At the falling edge discharge, the discharge moment of a substructure is dependent upon the polarity of the electrode where the gas gap is close. The variation trend of the molecular vibration temperatures is opposite to that of the electron density whether at the rising or the falling edge of the applied voltage for five substructures. The difference between spatial distribution of the substructure and that of the corresponding electric field indicates the effects of the wall charges. Overall, the formation of the pattern includes the resonance of multiple waves by exciting two pre-set wave vectors at different positions of the z-axis and the self-organization effect caused by the wall charge.

Erratum: “The interaction between volume discharges and surface discharges in spot-line white-eye hexagonal superlattice pattern in dielectric barrier discharge” [Phys. Plasmas 26, 023507 (2019)

Erratum: “The interaction between volume discharges and surface discharges in spot-line white-eye hexagonal superlattice pattern in dielectric barrier discharge” [Phys. Plasmas <b>26</b>, 023507 (2019)

Striped superlattice pattern in dielectric barrier discharge

We report on the striped superlattice pattern in dielectric barrier discharge for the first time. The spatiotemporal structure of the striped superlattice pattern is investigated by a high-speed framing camera. The result shows that the striped superlattice pattern consists of three different transient sub-lattices which are striped-dots, stripes, and small-dots surrounding a striped-dot, respectively. Images of a single frame indicate that the stripes which look like they are diffused are actually made up of individual filaments. The optical emission spectra of different sub-lattices are collected and investigated; it is found that plasma parameters of the three different transient sub-lattices are different. The formation mechanism of the striped superlattice pattern is discussed. And a tunable plasma photonic crystal with one and two-dimensions structures which has the dynamic controllability based on the striped superlattice pattern is present.

Spatio-temporal dynamics and formation mechanism of the square super-lattice pattern with saturn-like white-eye in dielectric barrier discharge

We report a square superlattice pattern with two types of white-eyes in dielectric barrier discharge, one of which has an obvious black area around the center spot and is named “saturnlike white-eye.” By using an intensified charge-coupled device, it is found that the pattern has five spatiotemporal sublattices, which should be the most complex pattern in dielectric barrier discharge to date. The results measured by the spectrograph and photomultiplier tubes show that the center spots of two types of white-eyes approximately have the same plasma parameters, while the current intensity of the center spot of saturnlike white-eye is about 1/3 of that of ordinary white-eye. Based on the above results, it can be estimated that the velocity of electrons in discharge of the center spot of saturnlike white-eye is much slower than that of ordinary white-eye, resulting in exhaustion of wall charges at the falling edge of voltage (d∣Uapp∣∕dt &amp;lt; 0) and occurrence of discharge at the next rising edge of voltage (d∣Uapp∣∕dt &amp;gt; 0). It inhibits discharge around the center spot and then the black area is formed. The differences of formation processes between two types of white-eyes are discussed. We believe that the research will contribute to advancement of pattern dynamics in dielectric barrier discharge.

Formation of kagome-white-eye-honeycomb hexagonal superlattice pattern in dielectric barrier discharge.

A kagome-white-eye-honeycomb hexagonal superlattice pattern is observed in dielectric barrier discharge and studied by two photomultipliers, an intensified charge-coupled device, and a spectrograph. It consists of four sublattices, which are kagome structure, halos of white-eye hexagon, honeycomb frame, and central spots hexagon. As an unconventional symmetry sublattice, the kagome structure results in amazing sublattice discharge order. Based on the consideration that any discharge is related to all previous discharges, a mapping matrix which governs self-organization of the pattern is proposed. These results will promote the development of the pattern dynamics.

Influence of vibration on spatiotemporal structure of the pattern in dielectric barrier discharge

The influence of vibration on the spatiotemporal structure of the pattern in dielectric barrier discharge is studied for the first time. The spatiotemporal structure of the pattern investigated by an intensified charge-coupled device shows that it is an interleaving of three sublattices, whose discharge sequence is small rods–halos–large spots in each half-cycle of the applied voltage. The result of the photomultiplier indicates that the small rods are composed of moving filaments. The moving mode of the moving filaments is determined to be antisymmetric stretching vibration by analyzing a series of consecutive images taken by a high-speed video camera. The antisymmetric stretching vibration affects the distribution of wall charges and leads to the halos. Furthermore, large spots are discharged only at the centers of the squares consisting of vibrating filaments. The vibration mechanism of the vibrating filaments is dependent on the electric field of wall charges.

The interaction between volume discharges and surface discharges in spot-line white-eye hexagonal superlattice pattern in dielectric barrier discharge

We report on the interaction between surface discharges (SDs) and volume discharges (VDs) in the spot-line white-eye hexagonal superlattice pattern in dielectric barrier discharge using an intensified charge-coupled device camera, a high-speed video camera, and a spectrograph. The small spot-lines and halos discharge in the first pulse and the second pulse at the rising edge of the voltage, respectively. The central spots discharge at the falling edge of voltage. The small spots are VDs whose discharge time is incompletely simultaneous. The lines are direction-selective SDs induced by small spots. It is found that the above phenomena result from the interaction between SDs and VDs. The incompletely simultaneous discharge of the small spots is due to the different quantities of wall charges transported by the SDs induced by small spots. The directional selectivity of the SDs results from that the SDs are extinguished when they are close to halos due to the neutralization of the wall charge of halos (VDs) and the wall charge of SDs, while they can stretch to other small spots.

Study on moving filaments in honeycomb pattern in dielectric barrier discharge

We report on the study of moving filaments in a honeycomb pattern in a dielectric barrier discharge system using photomultipliers, a high-speed video camera, and a spectrometer. The honeycomb pattern bifurcates from the hexagonal super-lattice pattern with increasing voltage. It is found that the honeycomb framework is composed of filaments with irregular reciprocating motion, which indicates that the honeycomb framework results from statistical self-organization. The spatiotemporal dynamics show that the pattern consists of three different sub-lattices. The plasma parameters (molecular vibrational temperature and electron density) of the pattern, determined from the optical emission spectra, show that different sub-lattices are in different plasma states. Based on these measurements, the mechanism of the movement of filaments is analyzed briefly.

Formation of a complex luminous pattern in dielectric barrier discharge investigated by an intensified-charge coupled device

A complex luminous pattern showing square superlattice pattern (SSP) appearance on the edge and dot-line square superlattice pattern (DLSSP) appearance in the middle, which is called coexistence of SSP and DLSSP (CSSP), is observed in a dielectric barrier discharge (DBD) system. The spatio-temporal structure of CSSP obtained by using an intensified-charge coupled device (ICCD) indicates that CSSP is an interleaving of three kinds of square subpatterns in one half voltage, which is similar to that of SSP and DLSSP. Based on the activation-inhibition mechanism of surface charges, the influence of surface charges of prior discharge to the pattern formation is discussed by comparing the discharge characteristics of CSSP with those of SSP and DLSSP. The amount of surface charges corresponding to the prior discharges for SSP, DLSSP and CSSP is calculated respectively by using the time integration of the total current pulse to verify the above theoretical explanation.

Comparing investigation of pattern formation in glow and streamer DBD

In this paper, we investigate the behaviors of patterns in dielectric barrier discharge (DBD) in glow and streamer regimes under different operating conditions (driving frequency and voltage) and external electric/magnetic field to explore the similarity and difference of pattern formation. It is found that patterns in both glow and streamer DBDs can be homogenized by decreasing the driving frequency to a low level. But filamentary streamers can still appear at low frequency when the voltage is much higher. With an additional lateral electric field, patterns in both regimes can be homogenized. However, an axial magnetic field makes the glow DBD homogeneous, while the streamer DBD decreases in filamentary size. In both regimes, dynamics and distribution of the space charges, rather than the surface charges, play the predominant role in the formation of DBD patterns. But the surface charges may also play an important role in pattern formation, especially in streamer DBD.

Pattern formation based on complex coupling mechanism in dielectric barrier discharge

The pattern formation of cinque-dice square superlattice pattern (CDSSP) is investigated based on the complex coupling mechanism in a dielectric barrier discharge (DBD) system. The spatio-temporal structure of CDSSP obtained by using an intensified-charge coupled device indicates that CDSSP is an interleaving of two kinds of subpatterns (mixture of rectangle and square, and dot-line square) which discharge twice in one half voltage, respectively. Selected by the complex coupling of two subpatterns, the CDSSP can be formed and shows good stability. This investigation based on gas discharge theory together with nonlinear theory may provide a deeper understanding for the nonlinear characteristics and even the formation mechanism of patterns in DBD.

Three-dimensional patterns in dielectric barrier discharge with “H” shaped gas gap

Three-dimensional (3D) patterns are obtained for the first time in dielectric barrier discharge by a special designed device with “H” shaped gas gap which consists of a single gas layer gap and two double gas layer gaps. Three dimensional spatiotemporal characteristics of discharge are investigated by photomultiplier and intensified charge-coupled device camera. Results show that the discharge first generates in the single gas layer gap and the coupled filaments in the double gas layer gap present the simultaneity characteristics. The formation of 3D patterns is determined by the distribution of the effective field of the applied field and the wall charge field.

Formation mechanism of concentric-ring pattern in dielectric barrier discharge

Concentric-ring pattern is observed in an Ar/air mixture dielectric barrier discharge. The discharge images within one half voltage circle are taken by an intensified-charge coupled device camera, indicating that the discharge filaments are the basic units of the concentric-ring pattern. By comparing the six instantaneous images corresponding to three successive positive and negative half voltages, it is proved that the concentric-ring pattern seen with naked eyes is formed by the numerous discharge filaments located at different positions during successive acquisition intervals. With applied voltage increasing, concentric-ring pattern can transform into spiral, and then into concentric-ring pattern again. By analyzing the features of formation and transformation of these two patterns, it is inferred that the two patterns have similar dynamic mechanisms. Discharge powers of concentric-ring pattern and spiral are calculated respectively, and the results show that the power increases linearly approximately with applied voltage increasing. The correlation coefficients of concentric-ring pattern are compared with those of spiral, and the results show that the correlation coefficient of concentric-ring pattern is relatively low and irregular, while the correlation coefficient of spiral is relatively high and has an oscillatory characteristic.

Formation mechanism of dot-line square superlattice pattern in dielectric barrier discharge

We investigate the formation mechanism of the dot-line square superlattice pattern (DLSSP) in dielectric barrier discharge. The spatio-temporal structure studied by using the intensified-charge coupled device camera shows that the DLSSP is an interleaving of three different subpatterns in one half voltage cycle. The dot square lattice discharges first and, then, the two kinds of line square lattices, which form square grid structures discharge twice. When the gas pressure is varied, DLSSP can transform from square superlattice pattern (SSP). The spectral line profile method is used to compare the electron densities, which represent the amounts of surface charges qualitatively. It is found that the amount of surface charges accumulated by the first discharge of DLSSP is less than that of SSP, leading to a bigger discharge area of the following discharge (lines of DLSSP instead of halos of SSP). The spatial distribution of the electric field of the surface charges is simulated to explain the formation of DLSSP. This paper may provide a deeper understanding for the formation mechanism of complex superlattice patterns in DBD.

Study on formation process of honeycomb pattern in dielectric barrier discharge by optical emission spectrum

The authors report on the first investigation of the variations in the plasma parameters in the formation process of the honeycomb pattern in a dielectric barrier discharge by optical emission spectrum in argon and air mixture. The discharge undergoes hexagonal lattice, concentric spot-ring pattern and honeycomb pattern with the applied voltage increasing. The molecular vibration temperature, electron excitation temperature and electronic density of the three kinds of patterns were investigated by the emission spectra of nitrogen band of second positive system (C3pi(u) --> B3 pi(g)), the relative intensity ratio method of spectral lines of Ar I 763.51 nm (2P(6) --> 1S(5)) and Ar I 772.42 nm (2P(2) -->1S(3)) and the broadening of spectral line 696.5 nm respectively. It was found that the molecular vibration temperature and electron excitation temperature of the honeycomb pattern are higher than those of the hexagonal lattice, but the electron density of the former is lower than that of the latter. The discharge powers of the patterns were also measured with the capacitance method. The discharge power of the honeycomb pattern is much higher than that of the hexagonal lattice. These results are of great importance to the formation mechanism of the patterns in dielectric barrier discharge.

Investigation on collisions of filament pairs in dielectric barrier discharge

Collisions of filament pairs in a hexagonal superlattice pattern in dielectric barrier discharge are investigated on different timescales. In the evolution of the pattern, the space scale of each hexagon cell decreases with the increasing voltage. The duration of one collision is seven half voltage cycles at least. Two stable orientations of a pair are approximately perpendicular to each other and the orientational changes occurring during the entire colliding process should be a multiple of 30°. The time interval between two consecutive collisions decreases with the increasing voltage. The distance between the paired spots decreases nonmonotonically. Based on the discharge order of the pattern, it is inferred that the collision should be the interaction between a discharging filament and the surface charges deposited by another discharged filament, and the nonmonotonic decrease of distance D is explained.

Formation of spiral patterns in dielectric-barrier discharge investigated by an intensified-charge coupled device

The formation of the spiral patterns in dielectric-barrier discharge is investigated through instantaneous pictures at successive driving half cycles taken by an intensified-charge coupled device (ICCD). The filaments discretely distributed in each instantaneous picture corresponding to one discharge pulse indicate that they are the basic unit of the spiral patterns. An individual filament can undergo two movement states within continuous discharges: pinning at the same locations and shifting along the arm with a small displacement (less than the filament radius), which results in the formation of smooth arms. The averaged correlation time between the instantaneous patterns is found to be about two driving half-cycles by the cross-correlation calculations.

Applications of autocorrelation function method for spatial characteristics analysis of dielectric barrier discharge

In this paper, spatial characteristics of dielectric barrier discharge (DBD) are analyzed using autocorrelation function (ACF) method. The filamentary, homogeneous and periodic discharge produced in a plate and mesh electrode, respectively, are quantitatively identified by analysis of the spatial structure of the discharge images in DBD with the ACF method. The influences of the size of the mesh electrode on spatial characteristics of discharge in DBD are also investigated by using the ACF, current waveform and Lissajous figures measurements. Moreover, the spatial structure and evolution of patterns in DBD are studied using this method. The results show that an exponential decay and random oscillation are exhibited in the radial and angular distribution of the ACF in a filamentary discharge, respectively. Both the radial and angular distribution of the ACF display a periodic oscillation in a periodic discharge. while the radial and angular distribution of the ACF are both approximately to 1 in a homogeneous discharge. With the decrease of mesh size, it can be seen from the corresponding radial distribution of the ACF that the discharge transits from a periodic discharge with its discharge period gradually decreasing to a filamentary discharge in air at atmospheric pressure when the voltage is kept fixed. It means that there is a optimal mesh size for the formation of the homogeneous spatial structure. Furthermore, the radial distribution of the ACF transits from a exponential decay, an periodic oscillation and into approximately to 1 with the increase of the applied voltage in air/argon mixture. It indicates that the discharge transit from the filamentary mode, the periodic patterned mode into the homogeneous mode. Moreover, two different periodic patterned discharge, the hexagon pattern and the square pattern are recognized quantitatively from the angular distribution of the ACF, which are coincident with the known experimental results. These results demonstrate that the ACF is a simple and effective method to analyze the spatial characteristics of DBD.

Pattern formation in dielectric barrier discharges with different dielectric materials

The influence of dielectric material on the bifurcation and spatiotemporal dynamics of the patterns in dielectric barrier discharge in argon/air at atmospheric pressure is studied. It is found that pattern bifurcation sequences are different with different dielectric materials. The spatiotemporal dynamics of the hexagonal pattern in dielectric barrier discharge depends on the dielectric material. The hexagon pattern with glass dielectric is an interleaving of two rectangular sublattices appearing at different moments. The hexagon pattern with quartz dielectric is composed of one set of hexagonal lattice discharging twice in one half cycle of the applied voltage, one is at the rising edge and the other at the falling edge. It results in that the accumulation of wall charges in individual microdischarges in a hexagon pattern with quartz dielectric is greater than that with glass dielectric, which is in agreement with the electron density measurement by Stark broadening of Ar I 696.54 nm.