Primary Streamer Research Articles

Various Kinds of Streamers in Atmospheric Pressure Oxygen Dielectric Barrier Discharge

An atmospheric pressure oxygen dielectric barrier discharge had been simulated using two dimensional fluid model. Three kinds of streamers had been obtained, and they are primary, small and secondary streamers. The electron density of small and secondary streamers is lower than that of primary streamers. But it was found that generation of ozone was significantly affected by these three streamers.

Secondary reverse streamer observed in an ester insulating liquid under negative impulse voltage

The so-called ‘secondary reverse streamer (SRS)’ in this study depicts a newly observed streamer-in-liquid phenomenon which subsequently occurs well after the extinction of the primary streamer (PS) propagation within a single shot of negative impulse voltage and has reverse polarity to the PS. Tests were carried out in a synthetic ester liquid at a 50 mm needle–plane gap under negative impulse voltages up to 140 kV. Based on the current and light waveforms as well as the photographic images, two types of SRS were found: one has a bright trunk with a high velocity of 9.79 km s−1 belonging to the 3rd mode streamer; and the other has a weak tree-like channel with a low velocity of 1.28 km s−1 resembling the 2nd mode streamer. It should be emphasized that SRS under negative impulse voltages has positive polarity being opposite to the negative PS, which is believed to be due to the reverse electric field induced by the residual space charges left by the PS. This has been confirmed by further verification tests under tail-chopped impulse voltages, for SRSs are significantly enhanced in both axial and lateral directions after the early removal of the external applied field.

Dependence of Ozone Generation on Gas Temperature Distribution in AC Atmospheric Pressure Dielectric Barrier Discharge in Oxygen

AC atmospheric pressure multi-filament dielectric barrier discharge in oxygen has been simulated using two dimensional fluid model. In the discharge, three kinds of streamers have been obtained. They are primary streamers, small scale streamers and secondary streamers. The primary streamers are main streamers in the discharge and the small scale streamers are formed after the ceasing of the primary streamers. And the secondary streamers are formed on the trace of the primary streamers. In these streamers, the primary and the small scale streamers are very effective to generate O(3P) oxygen atoms which are precursor of ozone. And the ozone is generated mainly in the vicinity of the dielectrics. In high gas temperature region, ozone generation decreases in general. However, increase of the O(3P) oxygen atom density in high gas temperature region compensates decrease of ozone generation rate coefficient. As a result, amount of ozone generation has not changed. But if the effect of gas temperature was neglected, amount of ozone generation increases 10%.

Modeling of a Streamer Plasma Reactor Energized by a Pulse Compression Modulator

This paper presents a semi-empirical model for a wire-wire corona reactor driven by a capacitive storage solid-state pulse generator. The reactor electrode system is configured as a checker mesh of potential and grounded threaded electrodes, and the pulse generator is based on a modern magnetic pulse compression topology. This presentation considers the effect of the geometrical parameters of the reactor (the total length of the high-voltage electrode surrounded by its grounded counterparts and the gap between the high-voltage and grounded electrodes) on the operation of the atmospheric pressure streamer plasma system. The model analyzes the discharge processes in the reactor by distinguishing between four phases, each being represented by an equivalent circuit: before the streamer generation, during the primary streamer propagation, after the primary streamers have crossed the interelectrode gaps, and after the plasma conductivity quenching. The new reactor model is realized on the PSpice platform, and the simulations are done using an improved pulse modulator model. The simulation results are compared with the experimental data, showing the model validity. Based on the simulated model, a better matching between the wire-to-wire reactor load to the pulse generator may be achieved.

Evaluation of density in nitrogen streamer discharges

Available experimental data on the number density of metastable molecules in channels of primary streamers in pure nitrogen and its mixtures with small amount of oxygen are re-evaluated in the framework of an approach that accounts for strong radial non-uniformity of plasma parameters in the channels. The obtained values are compared with an estimate based on the results of streamer simulations.

Gas density in a pulsed positive streamer measured using laser shadowgraph

Gas density in a pulsed positive streamer is quantitatively measured using a laser shadowgraph. The discharge occurs in a point–plane gap of 13 mm in humid air. After the onset of the streamer, the gas density decreases in two steps. The first step is a rapid decrease in gas density, which is caused by gas heating owing to electron impact onto molecules. This step is significant within 1 mm from the anode, although it occurs throughout the gap. The second step is a gradual decrease in gas density after the streamer pulse, which is caused by gas heating due to vibration-to-translation energy transfer. This step takes place mainly in the secondary streamer channel, not in the primary streamer channel. When the discharge voltage is 32 kV, the decrease in gas density reaches 30% of the ambient density. This large decrease in gas density affects the rate of various chemical reactions in the postdischarge period.

레이져 유기형광법을 이용한 펄스 배리어 방전 공간에서의 NO분자에 대한 시·공간적 밀도변화 측정

This paper tried to find out NO generation and removal mechanisms in the space of the atmospheric pulsed barrier discharge using laser induced fluorescence method, which is a very effective approach to the measurement of spatio-temporal density of specific molecules. The propagation velocity of the primary streamer reaches about [m/s] and the secondary streamer is produced in the vicinity of positive electrode after the primary streamer finished. In this work, pulse Nd:Yag and Dye lasers are used for generating the specific wavelength of 226[nm], which is possible to excite NO molecules into (0,0) and fluorescence signals as the transition of (0,2) is measured. For the effective removal of NO molecules in the plasma discharge process, the lower oxygen contents are needed and the influence of secondary streamer for the reduction mechanism of NO molecules is important

Drift and reactions of positive tetratomic ions in dry, atmospheric air: Their effects on the dynamics of primary and secondary streamers

The ion swarm data, namely, the reduced mobility, diffusion, and reaction rates of the positive tetratomic ions O4+ and N2O2+ in N2 and O2 have been determined from a Monte Carlo simulation using calculated and fitted elastic and inelastic cross sections. The elastic momentum transfer cross sections have been determined from a semiclassical Jeffreys-Wentzell-Kramers-Brilouin (JWKB) approximation based on a rigid core potential model well adapted for polyatomic ions. The inelastic cross sections have been approximated from considerations based on the N4+/O2 and N4+/N2 systems. The validated cross section sets in pure N2 and O2 have been used to determine the O4+ and N2O2+ swarm data in dry air over a large E/N range up to 1000 Td. However, due to the lack of experimental ion transport coefficients necessary for a more rigorous cross section validation, the present data, validated only at low E/N, should be regarded as a first approximation, susceptible to improvements as soon as measurements of ion transport coefficients become available in the literature. Then, the present data are used in a two-dimensional discharge dynamics fluid model for the simulation of the primary and secondary streamers for the case of a positive point-to-plane corona discharge in dry air. Relevant characteristics such as discharge current, charged particle densities, space charge electric field and the variation in active species like N and O radicals (very useful in many nonthermal plasma applications) are analyzed and discussed with and without the consideration of three positive tetratomic ions (N4+, O4+, and N2O2+). More particularly, the non-negligible effect of O4+, in the dynamics of the primary and secondary streamers during the discharge propagation and relaxation stages is highlighted with an emphasis on the role of the related kinetic reactions occurring between the different charged particles.

Gas Temperature of Steady Glow and Streamer Discharges in Atmospheric Air Gap

In order to analyze independently the various discharges of a point-to-plane air gap (steady glow, primary streamer, and secondary streamer discharges), the gas temperature in each of discharge region should be determined accurately by using the spectrum emitted from the second positive system bands of N2. In this experiment, we investigate the laser triggered streamer discharge with a repetition frequency of 10 Hz from the dc positive glow corona. The results show that the temperatures of the glow, primary streamer and secondary streamer are in the range of 316∼356K, 335∼350K and 370∼390K, respectively, and are considerably lower than the value of the high-stable dc positive repetitive streamer corona published in the previous references.

X-ray emission in streamer-corona plasma

X-ray emission has been detected occasionally during the streamer-corona propagation in a wire-plate corona reactor open to ambient air. A 65 kV pulse with 15 ns rise time is applied to the wire anode superimposed on a 20 kV dc bias. The duration of the driving voltage pulse (110 ns) is less than 2.5 times the primary streamer transit time. Under this condition no arc discharge occurs between the wire and the cathode plates separated by 6 cm air. The onset of x-ray emission coincides with the initiation of the primary streamers near the wire anode. No x-rays were detected later, during or after the primary or secondary streamer development. X-ray energies ranged between 10 and 42 keV, as detected by a LaBr3 (Ce) scintillator–photomultiplier combination. Time resolved imaging of the streamer propagation highlights the different stages in the streamer discharge process. The energetic electrons originate near the anode, at the moment of streamer initialization.

Measurement of metastable in N2 pulsed positive corona discharge with trace amounts of additives

The density of metastable is measured in various gases (N2/O2, N2/NO, N2/NO2, N2/H2O, N2/CO) after pulsed positive corona discharge using time-resolved laser-induced fluorescence (LIF) under atmospheric pressure. The density in N2/O2(0.25%) is uniformly distributed along the axis of the discharge gap (point-to-plane, 12 mm). This result indicates that is mostly generated in the primary streamer channels. The absolute density is measured by calibrating the LIF signal intensity. When the discharge voltage is 21.5 kV, the density immediately after the discharge pulse is estimated to be (2–3) × 1013 cm−3. The reaction rate constants of with O2, NO, NO2, H2O and CO are roughly estimated using the decay rate of density after the discharge pulse, and are compared with reference values. production is increased approximately twofold when hundreds of ppm of O2, NO or NO2 molecules are added to N2.

Two-photon absorption laser-induced fluorescence of atomic oxygen in the afterglow of pulsed positive corona discharge

Atomic oxygen is measured in the afterglow of pulsed positive corona discharge using time-resolved two-photon absorption laser-induced fluorescence. The discharge occurs in a 14 mm point-to-plane gap in dry air. After the discharge pulse, the atomic oxygen density decreases at a rate of 5×104 s−1. Simultaneously, ozone density increases at almost the same rate, where the ozone density is measured using laser absorption method. This agreement between the increasing rate of atomic oxygen and decreasing rate of ozone proves that ozone is mainly produced by the well-known three-body reaction, O+O2+M→O3+M. No other process for ozone production such as O2(v)+O2→O3+O is observed. The spatial distribution of atomic oxygen density is in agreement with that of the secondary streamer luminous intensity. This agreement indicates that atomic oxygen is mainly produced in the secondary streamer channels, not in the primary streamer channels.

Measurement of vibrationally excited O2(v = 6) in the afterglow of pulsed positive corona discharge

The density of vibrationally excited O2(v = 6) in the afterglow of a pulsed positive corona discharge is measured using time-resolved laser-induced predissociation fluorescence. Discharge occurs in a 13 mm point-to-plane gap in humid air under atmospheric pressure. When the discharge voltage is 32 kV, the O2(v = 6) density at a distance of 2.5 mm from the anode tip is 4 × 1014 cm−3 at t = 2 µs, where t is the postdischarge time, then decreases to 3 × 1013 cm−3 by t = 15 µs. The corresponding vibrational temperatures of O2, Tv, are 1400 K at t = 2 µs and 1100 K at t = 15 µs, which are calculated by assuming the vibrational equilibrium of O2. It is shown that the Tv of O2 in the secondary streamer channel is much higher than that in the primary streamer channel. Since the cross section of dissociative attachment (e + O2 → O + O−) for a low electron energy (<5 eV) increases markedly with the Tv of O2, the high Tv in the secondary streamer may lead to a marked increase in O atom production in the secondary streamer in spite of its low mean electron energy (1–2 eV).

Experimental analysis and modelling of positive streamer in air: towards an estimation of O and N radical production

This paper is mainly devoted to the comparison between the calculation and experimental results of primary and secondary streamer development in a point-to-plane positive corona discharge in dry air at atmospheric pressure. The qualitative agreement between experimental and calculation results based on the hydrodynamics approximation shows that the O radical is mainly produced in the secondary streamer which is in good agreement with the recent literature measurements using TALIF diagnostics. However, the O radical production yield (in terms of radicals produced per energy injected) is more efficient in the primary streamer than in the secondary one. The main positive corona discharge characteristics are revisited using fast electrical and optical ICCD and streak camera measurements. The calculation shows two streamer radii of, respectively, 10 µm (associated with the radial extension of a high electron density region) and 200 µm (corresponding to the extension of the radial space charge electric field).

Primary and Secondary Streamer Dynamics in Pulsed Positive Corona Discharges

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Preliminary comparisons between numerical simulation and experimental results are obtained under pulsed applied voltages in the case of positive point to plane corona discharges in dry air at atmospheric pressure. The experimental conditions correspond to 7 mm interelectrode distances with a tip radius of 20 <formula formulatype="inline"><tex>$\mu\hbox{m}$</tex></formula>. The calculations are based on a first-order 2-D electrohydrodynamic model including the main charged-particle/gas reactions occurring in dry air discharge. The development of the corona discharge is analyzed using streak camera pictures. The transition from the branching structure to the monofilamentary one is described. An interesting comparison is performed between the streak camera pictures and the spatiotemporal evolution of the calculated ionization rate. This shows a qualitative agreement in the development of both primary and secondary streamers. </para>

Optical and electrical analyses of DC positive corona discharge in N2/O2/CO2gas mixtures

This paper presents an experimental analysis of the electrical and optical behaviour of positive point-plane corona discharges. The measurements of the instantaneous corona current and the current-voltage characteristics are used with the imagery analyses (CCD and streak camera) to determine the streamer properties such as the streamer morphology and velocity with the primary and secondary streamer developments. These analyses are performed first in synthetic air as a function of operating parameters such the applied voltage. Then the effect of gas mixtures (several proportions of N 2 , O 2 with or without CO 2 ) is analysed. When the gas concentration is varied the discharge morphology, the shape and amplitude of the corona current are significantly affected due to the variation of the gas electronegativity following its composition and concentration.

Positive- and Negative-Pulsed Streamer Discharges Generated by a 100-ns Pulsed-Power in Atmospheric Air

A Blumlein generator that has a pulsewidth of 100 ns was used to investigate the process of streamer discharge propagation in a coaxial cylindrical reactor using a streak camera. Both positive and negative polarities of the streamer discharges were performed in air at atmospheric pressure. The results showed that the primary and secondary streamers propagated with increasing velocity from the central rod to the outer cylinder electrode in both positive and negative polarities of applied voltages to the rod electrode. The propagation velocity of the streamer heads was in the range of 0.8-1.2 mm/ns for a positive peak applied voltage in the range of 43-60 kV and 0.6 mm/ns for a negative peak applied voltage of -93 kV, respectively. The electric field at streamer onset was calculated to be 12 and 20 MV/m for positive and negative applied voltages, respectively.

Underwater streamer propagation analyzed from detailed measurements of pressure release

In this paper we describe experimental observations connected with the propagation of primary and secondary streamers in water. Using a Mach-Zehnder interferometer we determined the pressure field surrounding the streamer channel at a given instant in time with high temporal and spatial resolution. This pressure field contains information on the time evolution of the pressure pulse inside the discharge channel. The pressure history in the channel has been reconstructed by comparing the experimentally obtained fringe shifts in the interferograms with those derived from one-dimensional hydrodynamic calculations in cylindrical geometry. Assuming different trial pressure pulses, it has been possible to establish the channel pressure iteratively. A reproduction of the experimental data from secondary streamers requires short (2–3ns) pressure pulses with amplitudes of 2–3GPa. These findings are inconsistent with the assumption of bubble-initiated propagation of secondary streamers. It has also been inferred from estimates of the channel diameter that self-propagation of secondary streamers occurs at field strengths at the streamer tip of more than 2GV∕m. We can therefore conclude that field induced dissociation and ionization of molecules in the bulk liquid are the most likely mechanism for secondary streamer propagation. Rather high electrical conductivity (&amp;gt;0.2S∕m) is achieved at fields of 2GV∕m and an ionization wave is launched from the streamer tip into the liquid. To advance the streamer the electric field must be expelled from the newly generated section. This occurs with the Maxwellian relaxation time of a few nanoseconds. During this time the region of high conductivity is transformed into a plasma channel of lower density and a pressure wave is launched into the liquid. A different mechanism is suggested for primary streamer formation. Because of the low conductivity in the channels it is more likely that gas bubbles or phase instabilities are involved in this case.

Subnanosecond spectral diagnostics of streamer discharges: I. Basic experimental results

We have carried out cross-correlated high-resolved electrodynamical and spectro-optical measurements of different characterizations in a high-stable regime of the dc positive streamer corona in short gap in atmospheric density laboratory air. Special attention was paid to the measurement of absolute intensities of the second positive (SPS) and first negative (FNS) systems of molecular nitrogen as well as for further improvement in the spatiotemporal resolution along with high synchronization and stability. In the cathode region, the FNS and SPS emission temporal waveforms during primary streamer development have been recorded with the cross-correlated synchronization not worse than 0.1 ns and spatiotemporal resolution around 0.01–0.1 mm along the axis and 0.2–0.4 ns in the multiphoton mode of the PMT-based detector and in the single pulse acquisition mode of the measuring system. The shortest rise-times of the corresponding voltage waveforms were found to be around 0.3–0.4 ns for the SPS (0,0)-band and 0.2–0.3 ns for the FNS (0,0)-band, the full widths at the half-altitude ranging around 1.4–1.5 ns and 0.5–0.6 ns, respectively. Again, the absolute values and the ratio of the synchronized temporal waveforms of the SPS to the FNS (0,0)-bands have been recorded across the entire gap in the accumulation and averaging acquisition mode of the measuring system with somewhat worse temporal resolution but with adequate stability and stochasticity. Various supporting characteristics such as the synchronous anode and cathode electric current waveforms, the streamer velocity and the gas temperature within the streamer channel region have been measured and presented as well. All the data in the aggregate allow reconstruction of the 2D structure of the streamer head generally and of the electric field and the electron number density partially.

Ozone production process in pulsed positive dielectric barrier discharge

The ozone production process in a pulsed positive dielectric barrier discharge (DBD) is studied by measuring the spatial distribution of ozone density using a two-dimensional laser absorption method. DBD occurs in a 6 mm point-to-plane gap with a 1 mm-thick glass plate placed on the plane electrode. First, the propagation of DBD is observed using a short-gated ICCD camera. It is shown that DBD develops in three phases: primary streamer, secondary streamer and surface discharge phases. Next, the spatial distribution of ozone density is measured. It is shown that ozone is mostly produced in the secondary streamer and surface discharge, while only a small amount of ozone is produced in the primary streamer. The rate coefficient of the ozone production reaction, O + O2 + M → O3 + M, is estimated to be 2.5 × 10−34 cm6 s−1.