Pulsed Gas Discharge Research Articles

Development of an Environmentally Friendly, Economical and Effective Method for Pre-sowing Treatment of Cotton Seeds with a Pulsed Electric Field

The aim of this work is to study the effect of electric pulse gas discharge on cotton seeds in pre-sowing processes in grass-grass-gray soils. The studies were conducted on cotton seed samples brought from the Saatli district of the Azerbaijan Republic. Cotton seed samples were treated with pulse gas discharge at 14 kV for 15 minutes at atmospheric pressure and room temperature. As a result of agrotechnical measures in cotton agrocenosis, the living conditions of microorganisms change dramatically. The number of microorganisms increases. Processing seed in the electric field of pulse discharge helps to reduce the number and harmfulness of phytophages by 46.5-68.3% and 13.1-88.5%, respectively.

Pulsed processing by cold plasma, applied to industrial emission control.

A promising pollution control technology is cold plasma driven chemical processing. The plasma is a pulsed electric gas discharge inside a near atmospheric-pressure-temperature reactor. The system is energized by a continuous stream of very short high-voltage pulses. The exhaust gas to be treated flows through the reactor. The methods applied involve the development of robust cold plasma systems, industrial applications and measuring technologies. Tests of the systems were performed at many industrial sites and involved control of airborne VOC (volatile organic compound) and odor. Electrical, chemical and odor measuring data were collected with state-of-the-art methods. To explain the test data an approximate solution of global reaction kinetics of pulsed plasma chemistry was developed. It involves the Lambert function and, for convenience, a simple approximation of it. The latter shows that the amount of removal, in good approximation, is a function of a single variable. This variable is electric plasma power divided by gas flow divided by input concentration. In the results sections we show that in some cases up to 99% of volatile pollution can be removed at an acceptable energy requirement. In the final sections we look into future efficiency enhancements by implementation of (sub)nanosecond pulsed plasma and solid state high-voltage technology and by integration with catalyst technology.

Characterizing air-coupled gas discharge acoustic transducers by using scanning laser Doppler refracto-vibrometry

Scanning laser Doppler vibrometry (SLDV) is an effective tool for characterizing acoustic transducers and visualizing acoustic waves, in particular, when using air-coupled ultrasonic emitters. Refraction of laser beams in the areas of oscillating air pressure enables measuring amplitude-frequency parameters of propagating waves in a wide range of frequencies. The technique of refracto-vibrometry has been used for non-contact measurement of phase and frequency parameters of vibration signals generated by a pulsed gas discharge in the ambient air. The proposed gas discharge acoustic transducer operates on the base of the electro-thermoacoustic effect accompanying the flow of spark discharge current in the air at atmospheric pressure. A feature of the proposed device is that the emitter membrane contains a central through-hole that allows the discharge plasma to propagate beyond the electrode space of the emitter. Such configuration of the emitter allows the generation of acoustic waves in the ultra-wide frequency range from 50 Hz to 4 MHz. The spectrum of generated oscillations is essentially non-uniform that is explained by the presence of both resonance peaks and absorption bands of acoustic waves in the device elements. The proposed technique was checked in the inspection of impact damage in a hybride CFRP/flax composite.

Erosion mechanisms of DLC coatings deposited on polyimide and silica substrates when exposed to a pulsed gas discharge

The influence of spark discharges on the surface morphology and chemical composition of resistive diamond-like carbon (DLC) coatings designed to prevent breakdowns in gas electron multipliers (GEMs) has been studied. DLC coatings with thicknesses of approximately 200 nm and 66 nm were deposited in an inert argon atmosphere on polyimide substrates by high current pulsed magnetron sputtering and on silica (silicon oxide) substrates by vacuum arc method. Based on the analysis of images of optical and scanning electron microscopy, it was established that, the region of interaction between the gas discharge channel and the coating surface presents an accumulation of erosion craters with a characteristic linear size in the range of 20–40 μm. The value of current density passing in the region of interaction between the plasma in spark discharges and the sample is estimated to be of the order of 105 A/cm2, which is sufficient to ablate the coating and create thermal stresses of magnitude ∼4 GPa at the interface between the coating and the substrate. Thus, pulsed surface erosion, insufficient adhesive strength of the coating to the substrate, and poor thermal conductivity should be considered as the key reasons for destruction of the DLC coating.

The spectroscopic investigation of broad C I and C II lines emitted from pulsed atmospheric pressure gas discharge source in argon and argon‑hydrogen mixture

The spectroscopic investigation of pulsed atmospheric pressure needle-to-cylinder (NTC) gas discharge source with graphite cathode in argon and argon‑hydrogen mixture is performed. Numerous C2 molecular bands, of interest for rotational temperature Trot measurement, are recorded in the optical region of NTC discharge spectrum. Due to strong interference with C2 bands, the full set of C I and C II lines are not recorded. Nevertheless, we succeeded to obtain the spectra of broad C I multiplet at 477.0 nm, C II 274.7 nm line, and C II doublet at 283.7 nm. In addition, the hill-shaped-spectrum is recorded in the range 709–714 nm which is most probably the superposition of broad C II lines. Applying the appropriate fitting function on C II lines, the Stark broadening full-width-at-half-maximum (FWHM) is obtained and electron number density Ne estimated. The gas temperature Tg = 3500–4500 K, an important parameter for Ne diagnostics, is estimated from Trot calculated using C2, CH and CN molecular bands in the course of this study. The Ne ≈ 3 × 1016 cm−3 and Ne ≈ 1.5 × 1017 cm−3 are determined, which is consistent with our previous study with brass and stainless steel cathode NTC gas discharge.

Pulsed Gas Discharge Driven by Bipolar Solid-State Linear Transformer Driver

Pulsed gas discharge has been studied using a pulsed power generator with a bipolar solid-state linear transformer driver (SSLTD) scheme. Taking advantage of the output flexibility of the bipolar SSLTD, we have studied the residual charges phenomenon by the coaxial discharge load. The experiment result shows that for two consecutive positive pulses discharge, the current of the second positive pulse is usually lower than that of the first pulse for the same voltage amplitude. However, a middle negative pulse applied between the first and second pulse can increase the current of the second positive pulse. An explanation for this phenomenon has been explored using a 1-D model that considers the effect of residual charge left by the previous pulse discharge. According to the explanation of our 1-D discharge model, this phenomenon may be caused by the residual charge distorting the discharge electric field strength. The findings obtained by this article will help us understand the fundamental characteristics of pulsed atmospheric pressure gas discharge.

Hydrogen sorption by nanostructures at low temperatures (Review article)

The features of hydrogen sorption by a wide range of nanostructures — fullerite C60, carbon nanotubes, graphene structures, nanodispersed carbon, including Pd-containing nanoclusters, ordered silicon-oxide-based nanostructures (the MCM-41 family) and silicon-oxide aerogel — have been reviewed. Special attention is given to the sorption characteristics of carbon nanostructures that have been exposed to various modifying treatments (oxidation, gamma-ray irradiation in gas atmosphere, action of pulsed high frequency gas discharge). Two mechanisms of physical low-temperature sorption of hydrogen have been revealed to predominate in such nanostructures in different temperature intervals. At the lowest temperatures (8–12 K), the sorption can actually proceed without thermal activation: it is realized through the tunnel motion of hydrogen molecules along the nanostructure surfaces. The periodic structure of the potential relief, allowed by the surface frame of carbon and silicon-oxide nanostructures, along the rather low interpit barriers are beneficial for the formation of low-dimensional (including quantum) hydrogen-molecule systems practically without thermally activated diffusion. In such nanostructures, the hydrogen diffusion coefficients are actually independent of temperature at 8–12 K. At higher temperatures (12–295 K), a thermally activated mechanism of hydrogen diffusion prevails. The periodic structure of fullerite C60 contains periodic interstitial cavities, separated by rather low potential barriers. Their sizes are sufficient to accommodate impurity hydrogen molecules and, thus, allow diffusion processes, which can also have a tunnel nature. It is shown that gamma-irradiation and high-frequency gas discharge processing increase markedly the quantity of hydrogen strongly bonded to carbon nanostructures.

The spectroscopic study of metallic lines emitted from a pulsed atmospheric pressure gas discharge source with brass and stainless steel cathodes

Numerous metallic lines are recorded from atmospheric pressure μs-pulsed NTC discharge in argon and an argon–hydrogen mixture to measure Te and Ne in the cathode region of plasma.

Mechanism of runaway electron generation in nanosecond pulsed plate-plate discharge at atmospheric-pressure air

Classical discharge theory (Townsend theory and streamer theory) has limitations in explaining nanosecond pulsed gas discharge. In recent years, the research on nanosecond pulsed gas discharge theory based on the high-energy runaway electrons has attracted extensive attention. But so far, there have been few studies of the generation mechanism of runaway electrons in atmospheric-pressure-air nanosecond pulsed plate-to-plate discharge, which seriously hinders the application and development of nanosecond pulse discharge plasma. In this paper, a one-dimensional implicit particle-in-cell/Monte Carlo collision (PIC/MCC) model is developed to investigate the mechanism of runaway electron generation and breakdown in a 1 mm-long atmospheric-pressure-air gap between the plate electrode and plate electrode driven by a negative nanosecond pulse voltage with an amplitude of 20 kV. The results show that under the influence of space charge dynamic behavior, the electric field enhancement region appears between the plate electrode and plate electrode, so that electrons can satisfy the electron runaway criteria and behaves in the runaway mode. In addition, it is also observed that the pre-ionization effect of the runaway electrons in front of the discharge channel can cause the secondary electron avalanches. As the secondary electrons avalanche and the discharge channel continues to converge, the discharge is guided and accelerated, eventually leading to the breakdown of the air gap. This study further reveals the mechanism of nanosecond pulsed plate-plate discharge, expands the basic theory of nanosecond pulsed gas discharge, and opens up new opportunities for the application and development of nanosecond pulsed discharge plasma.

Pulsed inductive CO2 laser with radio-frequency excitation and influence of the H2 content on the efficiency and lasing temporal characteristics

In 2021, data on the effective pulsed gas discharge inductive CO2 laser with radio-frequency (RF) excitation were published with a pulse output energy of E∼ 1 J (the efficiency η∼ 14.5%) on the gas mixture He:N2:CO2 = 8:2:1. The efficiency of the developed CO2 laser had exceeded the value η∼ 21% at E∼ 350 mJ. At the beginning of 2022, it was shown that xenon addition (Xe = 4%) to the gas mixture made it possible to achieve an efficiency of η∼ 27% at an output energy of E∼ 600 mJ. For the first time, the effect of hydrogen additives in the active medium (He:N2:CO2:H2 and N2:CO2:H2 gas mixtures) was investigated for a pulsed inductive CO2 laser with RF excitation depending on the RF-pumping pulse duration value (τ), which allows the energy and temporal radiation characteristics of the laser to be controlled over a wider range. In addition to those already published, new experimental data have been obtained, namely the output beam profile of the inductive CO2 laser based on He:N2:CO2 = 8:2:1 gas mixture depending on the τ value. The new data will improve our understanding of inductive CO2 laser physics and of the plasma–chemical processes occurring in its active medium. RF current pulses propagated along inductor wires and, thus, an inductive discharge was formed to create a population inversion by IR transitions of CO2 * molecules.

Vacuum as a continuum medium forming energy inhomogeneities with high energy density in the liquid phase

A method for the formation of metal nanoparticles in a localized volume with a high energy density due to the flow of a pulsed electric discharge and the effect of cavitation has been studied. The mechanism of formation of energy inhomogeneities, which provides the generation of nanoparticles with high specific energy intensity, is considered. The formation of dynamic heterogeneity is carried out in three stages. There is a breakdown of the interelectrode space and the formation of a vacuum volume, which is filled with a vapor-gas medium. As a result of an increase in pressure in the bubble, a pulsed gas discharge is ignited, which leads to the generation of metal nanoparticles. As a result, there is a localized volume in which the energy in the discharge reaches a value of up to 106 K. The growth of energy in the bubble leads to its collapse and metal nanoparticles pass from a medium with high energy (106) into water at room temperature, which leads to their hardening. Particularly pure nanoparticles of various metals with a size of 5–15 nm are obtained, which can be grown on a single-crystal silicon surface at room temperature and positioned on the surface of porous materials and products of complex configuration.

Vacuum as a continuum medium forming energy inhomogeneities with a high energy density in the liquid phase

A method for the formation of metal nanoparticles in a localized volume with a high energy density due to the flow of a pulsed electric discharge and the cavitation effect was studied. The mechanism of the formation of energy inhomogeneities providing for the generation of nanoparticles with a high specific energy intensity was considered. Dynamic heterogeneity forms in three stages. There is a breakdown of the inter-electrode gap and the formation of a vacuum volume filled with a vapor-gas medium. When the pressure inside the bubble increases, a pulsed gas discharge is ignited, thus generating metal nanoparticles. This leads to the formation of a localized volume in which the discharge energy reaches values of up to 106 K. The increase in energy in the bubble leads to its collapse, after which the metal nanoparticles pass from the high-energy (106) medium into water at room temperature, resulting in their hardening. Highly pure nanoparticles of various metals 5–15 nm in size are obtained; these can be grown on a single-crystal silicon surface at room temperature and positioned on the surface of porous materials and products of complex configuration.

Controlling the breakdown delay time in pulsed gas discharge

In experiment and 2D3V PIC MCC simulations, the breakdown development in a pulsed discharge in helium is studied for U = 3.2 kV and 10 kV and P = 100 Torr. The breakdown process is found to have a stochastic nature, and the electron avalanche develops in different experimental and simulation runs with time delays ranging from 0.3 to 8 μs. Nevertheless our experiments demonstrate that the breakdown delay time distribution can be controlled with a change of the pulse discharge frequency. The simulation results show that the breakdown process can be distinguished in three stages with (a) the ionization by seed electrons, (b) the ions drift to the cathode and (c) the enhanced ionization within the cathode sheath by the electrons emitted from the cathode. The effects of variation of seed electron concentrations, voltage rise times, voltage amplitudes and ion–electron emission coefficients on the breakdown development in the pulsed gas discharge are reported.

Development of a Probe System for Measuring the Plasma Parameters and the High-Energy Part of the Electron-Energy Distribution Function

—A probe system has been developed on the basis of an external ADC/DAC module (ADC is the analog-to-digital converter and DAC is the digital-to-analog converter). Using this system, it is possible to determine all the main plasma parameters of continuous and pulsed gas discharges. A program for the Windows operating system has been developed in C++ to control the probe system. The probe system can be used for diagnostics of plasma devices and can be included in modern microplasma analyzers of gas mixtures.

Pulsed RF excitation inductive discharge CO-=SUB=-2-=/SUB=- laser with the radiation energy of 1 J and high efficiency

An efficient pulsed gas-discharge inductive CO2-laser with a radiation energy of 1.05 J has been developed for the first time. In this case, the pulse duration of the laser radiation was about 10 msec. The maximum efficiency of 21.1% was obtained at a radiation energy of 340 mJ. HF current pulses propagated along the inductor conductor and, thus, an inductive discharge was formed to create a population inversion at the infrared (IR) transitions of CO2* molecules. The temporal and energy characteristics of the radiation of the inductive CO2-laser depending on the duration of the pump pulse are investigated. The spatial characteristics and spectrum of the radiation of the developed laser are estimated. The divergence of the laser radiation was 0.52 mrad. The cross-sectional dimension of the laser output beam was about 35 mm in diameter. Keywords: inductive discharge in a mixture of gases, high-frequency modulation of the pump voltage, population inversion, output characteristics of laser radiation.

Импульсный индукционный CO-=SUB=-2-=/SUB=--лазер с энергией излучения 1 J и высоким КПД с ВЧ возбуждением

An efficient pulsed gas-discharge inductive CO2-laser with a radiation energy of 1.05 J has been developed for the first time. In this case, the pulse duration of the laser radiation was about 10 msec. The maximum efficiency of 21.1% was obtained at a radiation energy of 340 mJ. RF current pulses propagated along the inductor conductor and, thus, an inductive discharge was formed to create an inverse population at the infrared (IR) transitions of CO2* molecules. The temporal and energy characteristics of the radiation of the inductive CO2-laser depending on the duration of the pump pulse are investigated. The spatial characteristics and spectrum of the radiation of the developed laser are estimated. The divergence of the laser radiation was 0.52 mrad. The cross-sectional dimension of the laser output beam was about 35 mm in diameter.

Study of the effects of ultra-low intensity electromagnetic fields on biological objects

The object of research is the efficiency of exposure to electromagnetic field (EMF) of ultra-low intensity on biological objects, which is formed by a generator of broadband radiation. The principle of action of the generator is based on formation of electromagnetic radiation induced by periodic pulsed gas discharge in coaxial system of electrodes, which is loaded on a dielectric rod antenna. The method of selection of signals and corresponding equipment, which energy characteristics of radiation correspond to the criterion of non-thermal influence on bioobjects, is developed for obtaining a comparative assessment of influence bioefficiency. The proposed new method for processing experimental data using statistical calculations that meet the requirements for the processing and interpretation of the results. The seeds of wheat and interaction of millimeter range electromagnetic oscillations with bone marrow cells of rats were used as biological objects for investigating the effect of millimeter range electromagnetic oscillations. A biosensory effect was obtained when exposed to broadband radiation of ultra-low intensity, compared to the control sample. A change in the properties of the seeds, in particular, heat resistance, is observed. According to the experimental data, seeds turn out to be less susceptible to heat as a result of their pretreatment with EMF. The biological response is observed to depend on the frequency and time of irradiation. Also, the dependence of the decrease in the number of dead cells on the time of EMF irradiation was experimentally proved. The equation of dependence of selective average proportion of dead cells in rat bone marrow on irradiation time was calculated. Biosensory effect of exposure to broadband ultra-low intensity EMF of the developed emitter was revealed. It was established and statistically proved that the minimum time with the maximum positive effect of exposure to electromagnetic radiation of millimeter range on bone marrow cells of rats is 30 minutes, compared with an unirradiated sample. The results make it possible to evaluate the positive effect of electromagnetic oscillations on biological objects and propose the results of studies for practical use in the development of medical systems.

Empirical dependence of the probability of blocks rotations on the diffusion coefficient in a cellular automaton with a Margolus neighbourhood

The paper considers a cellular automaton approach to modeling physical processes, in particular, the diffusion of pulsed periodic gas discharges in plasma. An attempt to determine the dependence of the probability of the block rotation on the diffusion coefficient for a cellular automaton diffusion model with a Margolus neighborhood is describe. Some features of the tensor approach to the implementation of random block cellular automata are described. The results of computer experiments are presented. The analysis of this results indicates that the data from the literature sources differ from the data obtained during the experiment.

On the consistency between ionization and trapped runaway electron acceleration in a pulsed discharge

Runaway electrons accelerated in the electric field of a pulsed discharge may substantially change the discharge properties. The existence of this acceleration mechanism is indicated by the x-rays emitted from the discharge and by the increasing propagation velocity of the ionization front. An enhanced non-uniform electric field arises naturally due to the field distortion by the high-density plasma. A simple model is proposed to describe consistently the electron impact ionization, the electric field enhancement by the space charge of the discharge plasma, and the acceleration of runaway electrons to about 100 eV in the enhanced field. Optimal conditions for acceleration, ionization and field enhancement have been found at the plasma density level ∼1015–1016 cm−3 and the energy of hundreds of eV. This energy corresponds to trapped runaway mode of acceleration then the electrons produce maximal ionization instead of continuous acceleration to the anode and x-rays production. Obtained estimations count towards revisiting the role of the runaway electrons in pulsed gas discharge.

Optically pumped argon metastable laser with repetitively pulsed discharge in a closed chamber

The optically pumped rare gas laser (OPRGL) is an innovative type of gas laser, which has the potential to be a candidate for high-energy lasers (HELs), in which metastable rare gas atoms generated by gas discharge are used as active particles. To realize these kinds of lasers as HELs in field application, high efficiency and low cost are necessary. For this purpose, we demonstrated a closed-chamber operation with repetitively pulsed gas discharge for an OPRGL of argon metastables. The pulsed discharge was powered by a home-made LC generator, which provided a high efficiency for the deposition of electric energy. The metastable density produced was higher than 1012 cm−3, quite enough for efficient laser operation. The dependencies of laser radiation on the parameters of discharge voltage, gas pressure, and argon concentration were studied, which showed an optimized argon concentration of 1%. Long-time operations were also performed, which demonstrated the practicability of the operation of OPRGL in a closed chamber, with the avoiding of the running away of rare gases in the open cycle of flowing operation.