Half Cycle Of Voltage Research Articles

Characteristics of a micro-gap argon barrier discharge excited by a saw-tooth voltage at atmospheric pressure

Using two water electrodes, a micro-gap dielectric barrier discharge excited by a saw-tooth voltage is investigated in atmospheric pressure argon. Through electrical and optical measurements, it is found that, at a lower driving frequency, a stepped discharge mode is obtained per half voltage cycle. Moreover, the duration and amplitude of the current plateau increase with the increase in the applied peak voltage. With the increase in the driving frequency, the stepped discharge mode transits into a pulsed one after a multi-peak mode. During this process, a diffuse discharge at a lower frequency transits into a filamentary one at a higher frequency. Temporal evolutions of the discharges are investigated axially based on fast photography. It is found that the stepped mode is in atmospheric pressure Townsend discharge (APTD) regime. However, there is a transition from APTD to atmospheric pressure glow discharge for the pulsed mode. Spectral intensity ratio of 391.4 nm to 337.1 nm is used to determine the averaged electron energy, which decreases with increasing peak voltage or driving frequency.

Study on a new type of square superlattice pattern in dielectric barrier discharge

The new type of square superlattice pattern that big and small spots are not completely inserted into the center of each other is firstly observed in the mixed gas discharge with high argon content. Its spatial-temporal dynamics investigated by an intensified charge coupled device camera (ICCD) and photomultiplier (PMT) show that it is an interleaving of three different sub-lattices, and the discharge sequence of substructures in each half voltage cycle is: small spots, halos and central spots. In addition, the discharge current of central spots is corresponding to two distinct pulses at the negative edge of the each half voltage cycle, which indicates that discharge time is selective. The intensity of electric field is non-uniform around different central spots due to the selective discharge of central spots and different quantities of wall charges of the halo being consumed. Therefore, each small spot is not completely inserted into the center of four big spots during discharging.

Comparative investigation on the atmospheric pressure plasma jet excited by three types of waveforms

By using a rod-to-ring electrode geometry, an argon plasma jet excited by sinusoidal, triangular and square waveforms is developed to generate cone-shaped plasma plumes at atmospheric pressure. By electrical method, it is found that the discharge pluses excited by the three waveforms only appear in the positive half cycle of the applied voltage, however, there are no discharge pulses in the negative half cycle. Moreover, the discharge pulse number per half voltage cycle increases with increasing the peak voltage. For the multi-pulse discharge, the pulse intensity of the discharge increases in the rising edge of the applied voltage for the sinusoidal and triangular waveforms, while it keeps constant in the positive half cycle of the square voltage. Furthermore, the time interval of the adjacent pulses is larger for the square voltage than that for the sinusoidal or triangular voltages. The temporal evolutions of the plasma plumes excited by the sinusoidal and triangular voltages are investigated by high-speed photography. Result indicates that both of them are composed of a breakdown stage (a streamer developing stage) and an afterglow stage. The aforementioned experimental phenomena are discussed qualitatively by analyzing the discharge process.

A linear-field plasma jet for generating a brush-shaped laminar plume at atmospheric pressure

A linear-field plasma jet composed of line-to-plate electrodes is used to generate a large-scale brush-shaped plasma plume with flowing argon used as working gas. Through electrical measurement and fast photography, it is found that the plasma plume bridges the two electrodes for the discharge in the positive voltage half-cycle, which behaves like fast moving plasma bullets directed from the anode to the cathode. Compared with the positive discharge, the negative discharge only develops inside the nozzle and propagates much slower. Results also indicate that the gas temperature of the plume is close to room temperature, which is promising for biomedical application.

Spatio-temporal dynamics of the white-eye square superlattice pattern in dielectric barrier discharge

We report on the first investigation of the white-eye square superlattice pattern (WESSP) in a dielectric barrier discharge system. The evolution of patterns with increasing voltage is given. A phase diagram of WESSP as functions of gas pressure p and argon concentration φ is presented. The spatio-temporal dynamics of the WESSP is studied by using an intensified charge-coupled device camera and photomultipliers. Results show that the WESSP consists of four different transient sublattices, whose discharge sequence is small spots—spots on the line—halos—central spots in each half voltage cycle. The discharge moment and position of each sublattice are dependent upon the field of the wall charges produced by all sublattices discharged previously.

Evolution of a plasma vortex in air.

We report the generation of a vortex-shaped plasma in air by using a capacitively coupled dielectric barrier discharge system. We show that a vortex-shaped plasma can be produced inside a helium gas vortex and is capable of propagating for 3 cm. The fluctuation of the plasma ring shows a scaling relation with the Reynolds number of the vortex. The transient discharge reveals the property of corona discharge, where the conducting channel within the gas vortex and the blur plasma emission are observed at each half voltage cycle.

Dynamics of Atmospheric Pressure Plasma Plumes in the Downstream and Upstream Regions

A novel plasma jet driven by an alternating current voltage is developed to generate atmospheric pressure non‐equilibrium plasma plumes in the downstream region and in the upstream one of the argon flow. The angle between the rod electrode and the gas flow can be changed easily, and the plume lengths in the downstream and upstream regions are investigated as a function of the angle and the peak voltage. With increasing the peak voltage, the discharge pulse number tends to increase for every half voltage cycle. Using an intensified charge‐coupled device camera, the dynamics of the plasma plumes is also investigated in the downstream and upstream regions. The dynamics of the plumes is qualitatively explained by the streamer propagations influenced by residual charges.

Dielectric barrier discharge-based plasma actuator operation in artificial atmospheres for validation of modeling and simulation

We present an experimental case study of time-resolved force production by an aerodynamic plasma actuator immersed in various mixtures of electropositive (N2) and electronegative gases (O2 and SF6) at atmospheric pressure using a fixed AC high-voltage input of 16 kV peak amplitude at 200 Hz frequency. We have observed distinct changes in the discharge structures during both negative- and positive-going voltage half-cycles, with corresponding variations in the actuator's force production: a ratio of 4:1 in the impulse produced by the negative-going half-cycle of the discharge among the various gas mixtures we explored, 2:1 in the impulse produced by the positive-going half-cycle, and cases in which the negative-going half-cycle dominates force production (by a ratio of 1.5:1), where the half-cycles produce identical force levels, and where the positive-going half cycle dominates (by a ratio of 1:5). We also present time-resolved experimental evidence for the first time that shows electrons do play a significant role in the momentum coupling to surrounding neutrals during the negative going voltage half-cycle of the N2 discharge. We show that there is sufficient macroscopic variation in the plasma that the predictions of numerical models at the microscopic level can be validated even though the plasma itself cannot be measured directly on those spatial and temporal scales.

Square Grid Superlattice Pattern in Dielectric Barrier Discharge System

We report on the observation of the square grid superlattice pattern in dielectric barrier discharge system. Instantaneous images taken by an intensified charge-coupled device show that the pattern is an interleaving of four transient sublattices including three square sublattices and a cross-shaped halo sublattice. Comparing the single-frame instantaneous image with the 30-cycles integration image, it is found that the cross-shaped halo sublattice consists of several sporadic filaments. They discharge at different positions of the discharge-area in successive half-cycles of the applied voltage, which would have little influence on the following discharges. The calculation further verifies the significant influence of the wall charges which are accumulated in the first discharge on the following discharges during each half voltage-cycle.

Honeycomb superlattice pattern in a dielectric barrier discharge in argon/air

We report on a honeycomb superlattice pattern in a dielectric barrier discharge in argon/air for the first time. It consists of hexagon lattice and honeycomb framework and bifurcates from a hexagon pattern as the applied voltage increases. A phase diagram of the pattern as a function of the gas component and gas pressure is presented. The instantaneous images show that the hexagon lattice and honeycomb framework are ignited in turn in each half voltage cycle. The honeycomb framework is composed of filaments ignited randomly. The spatiotemporal dynamics of honeycomb superlattice pattern is discussed by wall charges.

White-Eye Hexagonal Pattern in Dielectric Barrier Discharge

The white-eye hexagonal pattern (WEHP) is firstly observed in a dielectric barrier discharge system and its structure is investigated using a high speed framing camera and a lens-aperture photomultiplier tube system. It bifurcates from a honeycomb pattern as the applied voltage is increased. A phase diagram of the pattern types as a function of gas pressure and gas content is presented. The frames integrated 15 and 100 of voltage cycles respectively show that the WEHP is an interleaving of two hexagonal sub-structures, one of which consists of central spots and the other consists of diffusion rings. The frame corresponding to the second current pulse in each half voltage cycle indicates that the diffusion ring is composed of several filaments, which is further confirmed by the light signals of the white-eye. The results show that wall charges play an important role in the formation of the white-eye hexagonal pattern.

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.

Spectroscopic Investigation of a Dielectric Barrier Discharge

Vibrational temperatures of , reduced electric fields , and relative number densities of and have been measured for the positive and negative voltage half-cycles of a surface dielectric barrier discharge (SDBD) using optical emission spectroscopy. The measurements were performed for a sinusoidally driven SDBD having amplitudes of 4450 and 5900 V and a frequency of 5000 Hz. The relative number density profiles of and , as a function of voltage, show the difference in discharge structure of the two voltage half-cycles, as well as a transition in discharge structure during the negative voltage half-cycle. The transition in discharge structure was also evident in the results. The transition in discharge structure occurred by increasing the applied voltage, resulting in the presence of weak and strong tufts at 4450 and 5900 V, respectively. In particular, the presence of strong tufts resulted in a localized enhancement in the production of by a factor of 6 and in by a factor of 1.8, as well as an increase in the by a factor of 1.6, within the electrode gap.

介质阻挡放电中点线超四边形发光斑图研究

The spatio-temporal structures and plasma parameters of the dot-line square superlattice luminous pattern are investigated by using photomultiplier and spectrograph. Optical signals from the discharge filaments show that the dot-line square superlattice pattern is an interleaving of four different transient sub-lattices,three of them occur at the rising edge and one of them at the falling edge in each half voltage-cycle. And the discharge sequence is followed as the small-dot square sub-lattice,the big-dot line sub-lattice,big-dot halo sublattice and the small-dot square sub-lattice located in the center of each big-dot. The emission spectra of the N2 second positive band( C3Πu→B3Πg)are collected and used to calculate the molecular vibration temperatures of the four transient sub-lattices in this pattern. Measurements show that different sub-lattices almost have the same molecular vibration temperature. The influence of the wall charge distribution on the formation process and the spatio-temporal dynamics of the dot-line square superlattice pattern are discussed. It is found that wall charges deposited on the dielectric surface have a great influence on discharge process.

Temporal and spectral characteristics of atmospheric pressure argon plasma jet

An investigation of atmospheric pressure argon DBD plasma jet generated at 6 kHz sinusoidal voltage was carried out. On the basis of recorded electrical, optical and spectral characteristics spatiotemporal evolution of plasma jet in negative and positive half-cycles of voltage was studied. It was found that the dynamics of argon jet propagation outside the tube differs considerably from that found by other authors in the case of helium jet. The difference was explained with the influence of Penning reactions between metastable state He atoms and air molecules in He jet. On the basis of radiative transitions N2 (C-B, 0-0) and OH(A-X, 0-0) the rotational temperatures of N2(C, 0) and OH(A, 0) were estimated along jet axis. In regions where Ar-air mixing was negligible or low, the rotational temperatures of both molecules coincide and were close to the gas temperature.

Spectroscopic Study of Low-Frequency Helium DBD Plasma Jet

Atmospheric-pressure helium plasma jet has been studied by optical emission spectroscopy and electrical measurements. Streamer/bullet properties of the plasma jet are observed in the positive voltage half cycle, whereas in the negative jet, they operate more as a glowlike atmospheric-pressure discharge. This is revealed by spatially resolved measurements of intensity distribution of typical excited species and by electric field measurements based on Stark polarization spectroscopy. Obtained radial distribution of the axial electric field of the bullet shows that the ring-shaped structure of the light emission is a consequence of such electric field distribution. Gas temperature distribution over the jet is obtained by Boltzmann plot of rotational lines of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{N}_{2}^{+}$</tex></formula> and OH bands. Gas temperature is found to be about 310 K, favorable for the biomedical applications.

Motion of rotating pairs in a hexagonal superlattice pattern within dielectric barrier discharge

Stochastic rotation of rotating pairs in a hexagonal superlattice pattern is observed in a dielectric barrier discharge system. It is found that the pairs rotate with orientation and diameter randomly changing by observing a series of frames recorded by a high speed video camera. Frames recorded by a high speed framing camera with an exposure time corresponding to current pulse phases in one half cycle of the applied voltage show that one rotating spot, six small spots, and another rotating spot in one cell discharge successively. Based on this discharging sequence, forces exerted on a rotating spot are analyzed at different discharging stages in a half voltage cycle. A resultant force on a rotating spot with both magnitude and direction varied leads to the stochastic rotation.

Numerical simulation of operation modes in atmospheric pressure uniform barrier discharge excited by a saw-tooth voltage

The characteristics of dielectric barrier discharge excited by a saw-tooth voltage are simulated in atmospheric pressure helium based on a one-dimensional fluid model. A stepped discharge is obtained per half voltage cycle with gas gap width less than 2 mm by the simulation, which is different to the pulsed discharge excited by a sinusoidal voltage. For the stepped discharge, the plateau duration increases with increasing the voltage amplitude and decreasing the gas gap. Therefore, uniform discharge with high temporal duty ratio can be realized with small gap through increasing the voltage amplitude. The maximal densities of both electron and ion appear near the anode and the electric field is almost uniformly distributed along the gap, which indicates that the stepped discharge belongs to a Townsend mode. In contrast to the stepped discharge with small gas gap, a pulsed discharge can be obtained with large gas gap. Through analyzing the spatial density distributions of electron and ion and the electric field, the pulsed discharge is in a glow mode. The voltage-current (V-I) characteristics are analyzed for the above mentioned discharges under different gas gaps, from which the different discharge modes are verified.

Simulation of transition from Townsend mode to glow discharge mode in a helium dielectric barrier discharge at atmospheric pressure

The dielectric barrier discharge characteristics in helium at atmospheric pressure are simulated based on a one-dimensional fluid model. Under some discharge conditions, the results show that one discharge pulse per half voltage cycle usually appears when the amplitude of external voltage is low, while a glow-like discharge occurs at high voltage. For the one discharge pulse per half voltage cycle, the maximum of electron density appears near the anode at the beginning of the discharge, which corresponds to a Townsend discharge mode. The maxima of the electron density and the intensity of electric field appear in the vicinity of the cathode when the discharge current increases to some extent, which indicates the formation of a cathode-fall region. Therefore, the discharge has a transition from the Townsend mode to the glow discharge mode during one discharge pulse, which is consistent with previous experimental results.

Analytical estimation of the thrust generated by a surface dielectric barrier discharge

The thrust induced by a set of microdischarges forming a surface dielectric barrier discharge (SDBD) at sinusoidal alternating voltage is estimated analytically by a phenomenological model based on available experimental data and achieved understanding of SDBD physics. Qualitative coincidence between theoretical predictions and experimental observations for thrust dependence on voltage at different dielectric thicknesses and its relative permittivity is demonstrated by the developed phenomenological model. The volumetric force is primarily induced by the negative voltage half-cycle. The origin of the force is the accumulation of volumetric negative charge carried by negative long-lived and ions. This accumulation is proportional to the third power of discharge length giving a strong force dependence on applied voltage. The directions of further SDBD investigation and actuator performance improvement are discussed.