In the present paper kinetics of emission spectra of the high voltage erosive water discharge at near ultraviolet and visible spectral ranges has been investigated. Obtained results show a similarity of physical properties of this discharge (and of corresponding plasmoids) to that of some other types of erosional discharges which also result in the formation of dust-gas fireballs.
The non-stationary mode of radial-slotted erosive discharge was considered. The existence condition of the relatively steady multiarc regime has been found. Experimentally it has been shown that this discharge has been corresponding to the required condition at the sufficiently large current. The oscillograms of commutation of lightning impulse on the simulative test facility with the equivalent of a high-voltage transmission line are presented. The obtained results indicate the ability of erosive discharge, when using within the framework of the complex lightning protection facility, to fast …
New non-stationary non-contracted form of the erosive radially-slotted discharge as a thin round sheet with the current of the azimuth direction have been discovered, its existence beings stipulated by a radial transport-wave fluxes. Characteristic features of this discharge is self-confinement of the discharge current magnitude, corresponding decrease of the current pulse duration and occurrence of an energy and substance ejection with rather unusual properties. Measurements of kinetics of the discharge current, the plasma radiation intensity and an electrical probe signal, as well as the tra…
Main results of researches of the electric erosive discharge afterglow plasma, of the fireballs being formed by this plasma and having some particular but deep similarities to the ball lightning are given. The analysis of our results and results of some other authors has allowed to specify the nature of radiation and stability of the shape for a dust-gas chemical fireball, to make series of assumptions concerning the mechanism of these properties. The experimental results and considerations of the given work can be interesting for physics of plasma with different kinds of condensed state, for …
We propose a method for generation of long-living autonomous fireball-like objects via a pulse erosive discharge between tin alloy electrodes. The objects are similar to the natural ball lightning in some properties, in particular, they have high energy density and are capable to burn through thin metal foils. The dynamics of the objects are studied using high speed videorecording. During their lifetime the fireballs generate aerogel threads. The studies of their structure by scanning electron microscopy reveal the presence of tin oxide nanoparticles and nanowhiskers.
In this paper we present the results of the spectral studies of erosive discharge with tin alloy electrodes and of the generated JFs, and experimentally determine internal energy of JFs using the calorimetric technique.
The effects of the discharge voltage on the formation and nature of electric field transients in a symmetric, collisionless, very high frequency, capacitively coupled plasma are studied using a self-consistent particle-in-cell (PIC) simulation code. At a driving frequency of 60 MHz and 5 mTorr of argon gas pressure, the discharge voltage is varied from 10V to 150 V for a fixed discharge gap. It is observed that an increase in the discharge voltage causes filamentation in the electric field transients and to create multiple higher harmonics in the bulk plasma. Correspondingly, higher harmonics,…
A subnanosecond breakdown in high-voltage pulse discharge is studied in experiment and in kinetic simulations for mid-high pressure in helium. It is shown that the characteristic time of the current growth can be controlled by the secondary electron emission. We test the influence of secondary electron yield on plasma parameters for three types of cathodes made from titanium, silicon carbide and CuAlMg-alloy. By changing the pulse voltage amplitude and gas pressure, the area of existence of subnanosecond breakdown is identified.
A new type of pulse high voltage electric discharge through a thin conducting layer on the surface of glass plate has been investigated. The afterglow plasma of this discharge forms quasi-spherical object with a lifetime about 0.2-0.3 s. Electric properties of the objects were studied by electric probe method. Measurements of plasma radiation spectra kinetics at visible and near ultraviolet spectral ranges have been carried out. Comparative analysis of the physical properties of the plasmoids appearing in this discharges and of ones generated via thin metal wires burning is given. Possible mec…
We investigate the energy and angular distributions of the ions reaching the electrodes in low-pressure, capacitively coupled oxygen radio-frequency discharges. These distributions, as well as the possibilities of the independent control of the ion flux and the ion energy are analysed for different types of excitation: single- and classical dual-frequency, as well as valleys- and sawtooth-type waveforms. The studies are based on kinetic, particle-based simulations that reveal the physics of these discharges in great details. The conditions cover weakly collisional to highly collisional domains…
In this paper, we use a fluid model to simulate the excitation of a hydrogen radio-frequency discharge, and employ tailored voltage waveforms to assess the effect of charged species transport properties. Results of the fluid simulation are compared with experimental data and previous results obtained with a hybrid model. Several expressions for electron and ion transport coefficients are compared, and their impact on the self-bias potential is studied. The self-bias is shown to be insensitive to the choice of electron transport coefficients, while remarkably sensitive to variations in ion mobi…
Two-dimensional capacitively coupled radio frequency discharge in methane is simulated by PIC-MCC method. The results were obtained in pressure range 50-300 mTorr and voltage range 40-180 V for discharge frequency 13.56 MHz. The electron energy and electron--methane reaction rates spatial distributions show existence of two regimes of discharge glow: a) with active sheaths, when electrons are hot in electrode sheaths and cold in the middle of discharge so the electron-neutral reactions strongly dominate in sheaths regions; b) with volume domination, when the electron energy is more uniform and…
Controlling streamer morphology is important for numerous applications. Up to now, the effect of the voltage rise rate was only studied across a wide range. Here we show that even slight variations in the voltage rise can have significant effects. We have studied positive streamer discharges in a 16 cm point-plane gap in high-purity nitrogen 6.0, created by 25 kV pulses with a duration of 130 ns. The voltage rise varies by a rise rate from 1.9 kV/ns to 2.7 kV/ns and by the first peak voltage of 22 to 28 kV. A structural link is found between smaller discharges with a larger inception cloud cau…
The characteristics of atmospheric-pressure microdischarges excited by nanosecond high-voltage pulses are investigated in helium-nitrogen mixtures, as a function of the parameters of the excitation voltage pulses. In particular, cases of single-pulse excitation, unipolar and bipolar double-pulse excitation are studied, at different pulse durations, voltage amplitudes, and delay times (for the case of double-pulse excitation). Our investigations are carried out with a particle-simulation code that also comprises the treatment of the VUV resonance radiation in the plasma. The simulations allow g…
An influence of a high-voltage (3-17 kV) 20 ns pulse on a weakly-ionized low-pressure (0.1-10 Pa) capacitively-coupled radiofrequency (RF) argon plasma is studied experimentally. The plasma evolution after pulse exhibits two characteristic regimes: a bright flash, occurring within 100 ns after the pulse (when the discharge emission increases by 2-3 orders of magnitude over the steady-state level), and a dark phase, lasting a few hundreds μs (when the intensity of the discharge emission drops significantly below the steady-state level). The electron density increases during the flash and remain…
The dynamical characteristics of a single frequency low pressure capacitively coupled plasma (CCP) device under varying applied RF voltages and driving frequencies are studied using particle-in-cell/Monte Carlo collision simulations. An operational regime is identified where for a given voltage the plasma density is found to remain constant over a range of driving frequencies and to then increase rapidly as a function of the driving frequency. The threshold frequency for this mode transition as well as the value of the constant density is found to increase with an increase in the applied volta…
We use the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 to explore the charged particle densities, the electronegativity, the electron energy probability function (EEPF), and the electron heating mechanism in a single frequency capacitively coupled oxygen discharge when the applied voltage amplitude is varied. We explore discharges operated at 10 mTorr, where electron heating within the plasma bulk (the electronegative core) dominates, and at 50 mTorr where sheath heating dominates. At 10 mTorr the discharge is operated in combined drift-ambipolar (DA) and …
The plasma-liquid interaction is an important issue in plasma technology. The simulation of discharge in spherical bubbles in the water that produced plasma-activated water (PAW) is investigated using finite element methods (FEM) for a simulated 2D dielectric barrier discharge in three different geometries. The electron density changes with voltage, frequency, dielectric thickness, and bubble radius are investigated in different time duration. The results show that electron density increases linearly by increasing voltage, frequency and bubble radius, while it is vice versa for dielectric thic…
Discharge characteristics and parameter diagnosis of dielectric barrier discharge patterns in double-gap configuration
College of Physics Science and Technology, Hebei University(河北大学物理科学与技术学院);Engineering Research Center of Zero-carbon Energy Buildings and Measurement Techniques, Ministry of Education(教育部零碳能源建筑及测量技术工程研究中心)
To find a viable alternative to SF6 with growing climate change regulations, proper evaluation of alternatives such as compressed air ought to be done. For medium voltage applications, the withstand voltage is used as the dimensioning criteria and this is dependent on the initiation and propagation of streamers which are precursors to electrical breakdown. For design optimization, a thorough understanding of the initiation and propagation mechanisms of such electrical discharges under different stresses, pressure etc. ought to be studied experimentally and numerically also via a predictive mod…
We investigate structure and evolution of long positive spark breakdown; and we study at which stage pulses of hard X-rays are emitted. Positive high-voltage pulses of standardized lightning impulse wave form of about 1 MV were applied to about 1 meter of ambient air. The discharge evolution was imaged with a resolution of tens of nanoseconds with an intensified CCD camera. LaBr3(Ce+) scintillation detectors recorded the X-rays emitted during the process. The voltage and the currents on both electrodes were measured synchronously. All measurements indicate that first a large and dense corona o…
The Floating Potential Fluctuations (FPF) observed in a dc glow discharge plasma powered with two sources is modeled using an anharmonic oscillator with two forcing terms. In the discharge system, one of the electrode is biased to a negative voltage source (i.e. cathode), and the second electrode is biased to a positive voltage source (i.e. anode), while the stainless-steel vacuum chamber is grounded. The dc glow discharge plasma is generated by the application of negative voltage on the cathode with respect to the grounded chamber using one of the power supplies. On the application of positiv…
The investigations of powerful discharge in high density hydrogen were carried out on an installation with preliminary adiabatic compression. The experiments were performed under the following conditions: stored energy of the capacitive storage - 140-450 kJ, charging voltage - 8.0-14.0 kV, discharge current amplitude- 200-600 kA, current rise rate - 10^9-10^10 A/s. The maximum particle density nmax, achieved just before the discharge, was about 2.0x10^22 cm-3. It was observed one or several compression of the discharge channel. The moments of contractions corresponds a increase of voltage on d…
In this paper, a coaxial pulsed plasma thruster was designed, built, and tested. This design confirmed PPT operation at substantially reduced discharge voltages of 100 to 200 V across the discharge plasma at a discharge current level of 10.4 kA similar to magnetoplasmadynamic arcs. The PPT cathode was imaged with an ICCD camera over a wide range of pressures, and the photos indicated "spotless" diffuse arc attachment to the cathode at higher pressures, and the appearance of conventional cathode spots at lower pressures. Cathode erosion rate measurements support the conclusion of "spotless" ope…
We apply particle based kinetic simulations to explore the characteristics of a low-pressure gas discharge driven by high-voltage ( $\sim$ kV) pulses with alternating polarity, with a duty cycle of $\approx$ 1% and a repetition rate of 5 kHz. The computations allow tracing the spatio-temporal development of several discharge characteristics, the potential and electric field distributions, charged particle densities and fluxes, the mean ion energy at the electrode surfaces, etc. As such discharges have important surface processing applications, e.g. in the treatment of artificial bones, we anal…
Data on the observation of neutron bursts in the process of high-voltage discharge in the air at an average electric field strength ~ 1 MV/m and discharge current ~ 10 kA are presented. Two independent methods (CR-39 track detectors and plastic scintillation detectors) registered neutrons within the range from thermal energies up to the energies above 10 MeV with the flux of >= 1E6 neutrons per shot into 4π solid angle.
A 2D approach is used to simulate the properties of positive and negative streamers emerging from a high-voltage electrode in a long (14 cm) air gap for standard pressure and temperature. The applied voltage varies from 100 to 500 kV. To reveal the influence of photoionization, the calculations are made for various rates of seed electron generation in front of the streamer head. The difference between the properties of positive and negative streamers is associated with the different directions of the electron drift ahead of the streamer head. As a result, the peak electric field at the streame…
The new results concerning neutron emission detection from a laboratory high-voltage discharge in the air are presented. Data were obtained with a combination of plastic scintillation detectors and $^3$He filled counters of thermal neutrons. Strong dependence of the hard x-ray and neutron radiation appearance on the field strength near electrodes, which is determined by their form, was found. We have revealed a more sophisticated temporal structure of the neutron bursts observed during of electric discharge. This may indicate different mechanisms for generating penetrating radiation at the tim…
A parametric study of an underwater pulsed plasma discharge in pin-to-pin electrode configuration has been performed. The influence of two parameters has been reported, the water conductivity (from 50 to 500 $μ$S/cm) and the applied voltage (from 6 to 16 kV). Two complementary diagnostics, time resolved refractive index-based techniques and electrical measurements have been performed in order to study the discharge propagation and breakdown phenomena in water according to the two parameters. A single high voltage of duration between 100 $μ$S and 1 ms is applied between two 100 $μ$m diameter pl…
In this work, the effect of flashing corona enhancement by introducing Teflon dielectric enclosure in vicinity to the electrode assembly was studied. The discharge operating in air without the dielectric was able to operate within a very narrow voltage range of approximately 200 V. The pulsing frequency was below 1.2 kHz and current peaks were below 14 mA. Increasing the applied voltage onto the positive electrode beyond this range would result in sparks between the electrodes. When the Teflon tube enclosure surrounding the high voltage electrode was used, the window of stable flashing corona …
This paper demonstrates and studies helium atmospheric pressure plasma jet comprised of series of repetitive streamer breakdowns, which is driven by a pure DC high voltage (auto-oscillations). Repetition frequency of the breakdowns is governed by the geometry of discharge electrodes/surroundings and gas flow rate. Each next streamer is initiated when the electric field on the anode tip recovers after the previous breakdown and reaches the breakdown threshold value of about 2.5 kV/cm. Repetition frequency of the streamer breakdowns excited using this principle can be simply tuned by reconfiguri…
The propagation mechanisms of plasma streamers have been observed and investigated in a surface dielectric barrier discharge (SDBD) using 2D particle in cell simulations. The investigations are carried out under a simulated air mixture, 80\% N$_2$ and 20\% O$_2$, at atmospheric pressure, 100$\,$kPa, under both DC conditions and a pulsed DC waveform that represent AC conditions. The simulated geometry is a simplification of the symmetric and fully exposed SDBD resulting in the simultaneous ignition of both positive and negative streamers on either side of the Al$_2$O$_3$ dielectric barrier. In …
Transition from chaotic to ordered state has been observed during the initial stage of a discharge in a cylindrical dc glow discharge plasma. Initially it shows a chaotic behavior but increasing the discharge voltage changes the characteristics of the discharge glow and shows a period substraction of order 7 period $\to$ 5 period $\to$3 period $\to$1 period i.e. the system goes to single mode through odd cycle subtraction. On further increasing the discharge voltage, the system goes through period doubling, like 1 period $\to$ 2 period $\to$ 4 period. On further increasing the voltage, the sys…
Proof of operation of a micro-hollow cathode discharge driven by a true ns-pulsed high voltage: emission properties and atomic nitrogen production
Laboratoire des Sciences des Procédés et des Matériaux (LSPM), CNRS, Université Sorbonne Paris Nord(材料过程与科学实验室,法国国家科学研究中心,索邦巴黎北大学);Laboratoire Energétique Moléculaire et Macroscopique, Combustion (EM2C), CNRS, Université Paris Saclay(分子与宏观能量、燃烧实验室,法国国家科学研究中心,巴黎萨克雷大学)
Packed bed plasma reactors (PBPRs) inherently have complex geometries where the volume between the electrodes is filled with dielectric/catalytic pellets to form an array of voids and cavities. This design generates multiple length scales i.e. the dimension of the plasma region (of the order of centimeters), of the dielectric/catalytic pellets (of the order of millimeters) and of the void between the dielectrics (or cavities) and/or surface pores that can reach micrometer dimensions. The plasma is formed as an array of connected or segmented microdischarges. The understanding of plasma propaga…
In this work, the influence of crossed magnetic fields (B=100 Gauss) on the UV-vis and NIR spectra and breakdown voltages of nitrogen and oxygen at a pair of parallel plane copper electrodes with a spacing d=2 cm and diameter R= 2.2 cm are studied. Working pressures of the gases are kept between 0.1 and 1 Torr. The breakdown voltage measurements across the electrodes are conducted by Tektronix P6015 high voltage probe connected to a Tektronix 2430A oscilloscope. The Spectra of discharge plasmas in the absence and presence of magnetic fields are recorded between 200-1100 nm. by AvaSpec-ULS3648.…
In this study, we investigate the responsible species and processes involved in repetitive pulsed streamer inception in CO$_{2}$. We applied a 10 kV high-voltage pulse with a repetition frequency of 10 Hz and pulse width of 1 ms to a pin electrode which is placed 160 mm apart from the grounded plane electrode. We measured the inception times (delay between the rising edge of the high-voltage pulse) by a photo-multiplier tube for 600 high voltage cycles. We observed one peak in the histogram of inception times with a median of 1.2$μ$s. To identify the source of this peak, we applied a negative …
Variation of voltage profiles with different time scales leads to the redistribution of deposited energy as well as electro-hydrodynamic forces, while the mechanism and scaling law is still unknown. On the basis of theoretical and numerical analysis, we show that a secondary surface ionization wave forms during the voltage rising slope when electron density decreases to a critical level while the voltage is still rising. A characteristic map of energy and electro-hydrodynamics force in time scales between 1~ns and 0.1~s at atmospheric pressure is proposed, opening the door towards the target--…
We present an one-dimensional particle-in-cell Monte-Carlo model for capacitively coupled radio-frequency discharges in oxygen. The model quantitatively describes the central part of the discharge. For a given voltage and pressure, it self-consistently determines the electric potential and the distribution functions for electrons, negatively charged atomic oxygen, and positively charged molecular oxygen. Previously used collision cross sections are critically assessed and in some cases modified. Provided associative detachment due to metastable oxygen molecules is included in the model, the el…
This study is designed to explore the two dimensional temperature maps of the atmospheric argon discharge consisting of pin-to-plane electrodes supplied by a high voltage DC source. After checking the stability of the micro discharge, the two dimensional image plane focused by a quartz lens was scanned by the fiber probe driven by a 3D Mobile Platform. The rotational and vibrational temperatures are calculated using nitrogen emissions collected by the high resolution spectrometer and high sensitive intensified charge coupled device (ICCD). The rotational temperature varies from 1558.15 K to 26…
In this contribution, nanosecond pulsed discharges in N$_{2}$ and N$_{2}$/0.9% H$_{2}$O at atmospheric pressure (at 300 K) are studied with time-resolved imaging, optical emission spectroscopy and Rayleigh scattering. A 170 ns high voltage pulse is applied across two pin-shaped electrodes at a frequency of 1 kHz. The discharge consists of three phases: an ignition phase, a spark phase and a recombination phase. During the ignition phase the emission is mainly caused by molecular nitrogen (N$_{2}$(C-B)). In the spark and recombination phase mainly atomic nitrogen emission is observed. The emiss…
Peterson et al. [2009] intend to determine the NOx production of sprites and blue jets from laboratory experiments. Sprite discharges are known to be physically similar to streamer discharges at standard temperature and pressure. However, streamer experiments that simulate geophysical discharges require voltage pulses of one polarity, in contrast to the oscillating voltages of Peterson et al. Furthermore, Peterson et al. make errors in their comparison of current densities, sprite volumes and gas densities. Finally, there is a calculation error of 6 orders of magnitude in an important result.
The pilot system development in metre-scale negative laboratory discharges is studied with ns-fast photography. The systems appear as bipolar structures in the vicinity of the negative high-voltage electrode. They appear as a result of a single negative streamer propagation and determine further discharge development. Such systems possess features like glowing beads, bipolarity, different brightness of the top and bottom parts, and mutual reconnection. A 1D model of the ionization evolution in the spark gap is proposed. In the process of the nonlinear development of ionization growth, the mode…
The results of the experiments on recording hard gamma radiation and measurements of its angular distribution at the initial stage of a laboratory high-voltage atmospheric discharge are presented. The experiments were performed on an ERG installation at a voltage of $\sim 1$ MV, an atmospheric discharge current of up to 12 kA, and a gap of 0.55 m. The duration of the voltage pulse was about 1~$μ$s with a pulse rise time of 150-200 ns. The radiation was recorded by an assembly of 10 identical scintillation detectors installed each 10$^\circ$ around the circumference of a quarter of a circle wit…
Parameters of a high frequency capacitive discharge in argon in axially symmetric chambers of different geometries are studied in experiments and by means of two-dimensional kinetic modeling by the Particle-in-Cell method. It is demonstrated that a change in the ratio of the areas of the driven and grounded electrodes can substantially increase the ion energy on the electrode practically without disturbing the plasma parameters. Particular attention is paid to studying the self-bias voltage and the ion distribution function on the electrode for gas pressures ranging from 15 to 70 mTorr. The re…
In this series of three papers we present results from a combined experimental and theoretical effort to quantitatively describe capacitively coupled radio-frequency discharges in oxygen. The particle-in-cell Monte-Carlo model on which the theoretical description is based will be described in the present paper. It treats space charge fields and transport processes on an equal footing with the most important plasma-chemical reactions. For given external voltage and pressure, the model determines the electric potential within the discharge and the distribution functions for electrons, negatively…
Spectroscopic characterization of a specific case of the atmospheric pressure air jet plasma in the transverse cw dc arc discharge of high voltage was done. Within the spectrum of wavelengths from 200 to 1100 nm all remarkable emissions were monitored, and all excited atomic lines of N, O, H and molecular bands of NO, N2, O2, OH, CO, CN were identified. Using relative intensities of analytical CuI lines 510.5, 515.3, 521.8 nm (the product of electrode emission) and N2 2+ -system band at 337.1 nm (the dominating component of plasma-forming gas), the temperature of electronic excitation of free …
Glow discharge plasmas exhibit various types of self excited oscillations for different initial conditions like discharge voltages and filling pressures. The behavior of such oscillations associated with the anode glow have been investigated using nonlinear techniques like correlation dimension, largest Lyapunov exponent etc. It is seen that these oscillations go to an ordered state from a chaotic state with increase in input energy i.e. with discharge voltages implying occurrence of inverse bifurcations. These results are different from the other observations wherein the fluctuations have bee…