S. Avtaeva - Academia.edu (original) (raw)

Papers by S. Avtaeva

Contributions to plasma physics, Feb 5, 2024

Plasma Chemistry and Plasma Processing, 2022

The asymmetric pulse-periodic dielectric barrier discharge (DBD) in a mixture of argon with sulfu... more The asymmetric pulse-periodic dielectric barrier discharge (DBD) in a mixture of argon with sulfur vapor exhibits the emission spectrum of the discharge with intense bands of S 2 molecules (B 3 Σ − > X 3 Σ transition) in the visible region. The modeling of the discharge characteristics in Ar-S 2 mixture within the 1D fluid model is presented showing that during a voltage pulse (150 ns), an electropositive plasma is formed in the entire discharge gap with the electron number density reaching values above 1.5*10 18 m −3 at the maximum under the mean electron energy of about 3 eV. The high electron number density during the current pulse leads to efficient excitation of sulfur dimers, as a result, their radiative efficiency during the voltage pulse reaches approximately 4%. The discharge is considered as promising one for creating radiation source in visible region of spectrum.

2018 International Conference Laser Optics (ICLO), 2018

Characteristics of nitrogen and helium pulse supersonic jets serving as target for realizing the ... more Characteristics of nitrogen and helium pulse supersonic jets serving as target for realizing the laser driven electron acceleration at interaction of a high intensity ultra-short laser pulses with a gas jet are presented. Evolution of the jets in time and effect of backing pressure and a nozzle dimensions on jet characteristics were studied.

Characteristics of the DBD in Xe-Cl2 mixtures were simulated using the 1D fluid model at gas pres... more Characteristics of the DBD in Xe-Cl2 mixtures were simulated using the 1D fluid model at gas pressure 150-300 Tor and chlorine concentration in the mixtures 0.1- 5%. The discharge gap is fixed at 4 mm. Two dielectric layers have an identical thickness 2 mm and relative permittivity 4. The source voltage US=U0sinφt with f=100 kHz and U0=4.25 or 5 kV is applied to the electrodes. Simulations show at all chlorine concentrations in the Xe-Cl2 mixtures the most abundant negative species in the discharge are Cl^- ions, the most abundant positive ions are Xe2^+. At the current pulse densities of electrons and Xe^+ ions near the dielectric barrier sharply increases. The potential drop across the discharge gap increases and the magnitude of the current pulse falls with chlorine content in the mixture. Power deposited into heating of positive and negative ions grows with chlorine concentration; power deposited into electrons mainly decreases with chlorine concentration. Growth of the chlorine...

IEEE Access, 2022

This paper presents a new composite grid electrode structure for the generation of plasma that is... more This paper presents a new composite grid electrode structure for the generation of plasma that is suitable for modeling microwave radiation transmission through atmospheric plasma. The new grid anode-composite cathode (GA-CC) structure is to be contrasted with the ordinary grid anode-cathode plate (GA-CP) structure. It is found that the breakdown voltage of the new GA-CC electrode structure is lower than that of the GA-CP structure and is a bit shifted to the right on the Pd-axis. An advantage of the GA-CC structure over the GA-CP structure is that it requires a lower voltage to generate the same current. It is found that plasma generated by the new GA-CC structure selectively strengthens electromagnetic waves attenuation in the frequency range of 9-12 GHz. INDEX TERMS Grid anode, composite cathode, microwave attenuation, Paschen curves, current-voltage characteristics.

Plasma Chemistry and Plasma Processing

A one-dimensional fluid model of a dielectric-barrier discharge (DBD) in Ar–S2 mixtures is develo... more A one-dimensional fluid model of a dielectric-barrier discharge (DBD) in Ar–S2 mixtures is developed, and the properties of the discharge are modeled. The discharge in a 3-mm-long gas gap between 2-mm-thick quartz layers covering metal electrodes is considered. The DBD spatiotemporal characteristics are simulated at gas pressures of 300 Torr for the case in which a 20-kHz harmonic voltage with amplitude of 8 kV is applied to electrodes. It was shown that the discharge active phase at S2 fraction of 0.1% in Ar–S2 mixture is characterized by the presence of multiple current spikes, which is explained by weak ionization waves. The cycle-averaged dissociation degree of S2 molecules is ~ 0.05–0.3% in Ar–S2 mixture with S2 fraction of 0.1–1% and degree of gas ionization is 2 × 10–8–4 × 10–7. The plasma is electronegative due to the fast attachment of electrons to sulfur molecules: e + S2 → S2–. The radiative efficiency of S2* excited molecules at S2 fraction of 0.5 and 1% is about two times higher than at S2 fraction of 0.1% and reaches about 0.8%. At S2 content in Ar–S2 mixture of 0.1% the main contribution in the discharge emission make argon resonance atoms (70%), while at 1%S2 the main contribution in the emission make sulfur excited atoms (95%), which radiative efficiency abruptly increases. The optimal S2 fraction in Ar–S2 mixture for developing DBD radiation source based on emission of S2* molecules is about 0.5%, when the 98% of discharge emission distributes between Ar* (44%), S2* (42%) and Ar2* (12%).

AIP Advances, 2022

In a previous study, the characteristics of plasma generated by fast electrons behind a grid anod... more In a previous study, the characteristics of plasma generated by fast electrons behind a grid anode with short glow discharge were studied using numerical simulation. The source of the post-anode plasma electrons is considered to be the direct current glow discharge itself in the gap between a cathode and a grid anode. However, the electron attenuation of the microwave radiation in the post-anode space measured in experiments does not correspond to the numerical predictions. In this paper, the current–voltage characteristics of the short glow discharge with a grid anode and the spectral characteristics of the discharge in both the electrode gap and the space behind the grid anode are studied; the effective thickness of the plasma in the post-anode space is estimated using a spectral method.

Plasma Physics Reports, 2021

A grid anode glow discharge is a promising source of plasma for absorbing electromagnetic radiati... more A grid anode glow discharge is a promising source of plasma for absorbing electromagnetic radiation. This paper presents an experimental study of a large-area dc grid anode glow discharge in helium. The behavior of the helium discharge was studied at pressures in the range of 2–50 Torr and discharge voltages up to 1500 V. It was observed that the discharge completely covered the cathode surface at helium pressures of 2–25 Torr. For all pressures, voltage increases as current increases, which typical for anomalous glow discharge. The electron density in the post-anode plasma and attenuation of the microwave radiation by the plasma were measured using microwave diagnostic methods. It was found that the electron density and degree of helium ionization decrease with increasing helium pressure and increase with increasing discharge current. The electron density in the post-anode plasma is not high: ne is about 2 × 109–6 × 1010 cm–3, corresponding to a degree of ionization of about 10–7–10–6. It is shown that the maximum attenuation of 10-GHz microwave radiation is about 6% at a helium pressure of 2 Torr.

Journal of Physics: Conference Series, 2017

Study of the large area low-pressure arc discharge plasma in Ar and Ar-N 2 mixtures is presented.... more Study of the large area low-pressure arc discharge plasma in Ar and Ar-N 2 mixtures is presented. The low-pressure arc discharge in large chambers was ignited between planar vacuum arc cathode with magnetic steering of arc spots and surrounding grounded primary anode while long-length remote arc discharge is extended toward remote linear anode parallel to the cathode plate. The arc column was moving up and down perpendicular to the cathode-to-remote anode direction, following the movement of the cathodic arc spots. I-V characteristics of the remote arc discharge were studied by electrophysical measurements. Electron density, electron temperature, and dissociation of nitrogen molecules in the low-pressure DC arc discharge in pure argon and Ar-N 2 mixtures at pressures ranging 1-20 mTorr were studied by electrostatic probes, MW resonant probe, ion energy analyzer and spectral methods at various remote anode currents and gas composition.

Composition of the high current low pressure arc discharge in a large chamber (0.5 m in diameter)... more Composition of the high current low pressure arc discharge in a large chamber (0.5 m in diameter) in Ar-H 2 mixtures was studied by optical emission spectroscopy methods and was modeled utilizing thermodynamic and fluid models. The dissociation degree of molecular hydrogen was estimated using I Hα /I H2 intensity ratio of H α line and Q1(0-0) line of the H 2 Fulcher's α-system. In addition, atomic hydrogen density was estimated using optical actinometry method from intensity ratio I Hα /I ArI of the H α and ArI 750 nm lines. Moreover, the H 2 dissociation degree across the discharge tube was modeled using LTE calculation based on minimization of isobaric-isothermal potential of the closed thermodynamic system with the help of commercial software TERRA. Alternatively, hydrogen thermal dissociation was calculated in an axially-symmetrical one fluid, one temperature approximation using commercial software COMSOL FEM; the thermal dissociation model relies on solving an advection-diffusion-reaction (ADR) equation for atomic hydrogen that is produced by Ar or H 2 impact and is lost in three-body recombination. The results of the comparison of hydrogen dissociation degree across the arc column demonstrate reasonably good agreement both with experimental findings and between two modeling approaches.

The dielectric barrier discharge (DBD) between plane electrodes covered with dielectric layers in... more The dielectric barrier discharge (DBD) between plane electrodes covered with dielectric layers in the 95% neon-5% xenon mixture is studied within a one-dimensional drift-diffusion model. The DBD has the following parameters. The thickness of identical barriers is 0.2 mm, the gap length is 0.4 mm, and the gas pressure is 350 Torr. The discharge is fed with 400 V ac voltage at a frequency of 100 kHz. A self-consistent one-dimensional model is based on a continual description of plasma with the use of a drift-diffusion approximation for particle flows. The description of electrons is based on a "hybrid" approach. An electric field is found from the Poisson's equation. A set of kinetic equations is used to characterize the evolution of the populations of atom and excimer excited states leading to VUV emission. The kinetic scheme includes 62 reactions and describes the kinetics of the 17 species.

Plasma Chemistry and Plasma Processing, 2021

A comprehensive study of the reversed arc plasma enhanced CVD (RACVD) reactor utilizing an Ar + H... more A comprehensive study of the reversed arc plasma enhanced CVD (RACVD) reactor utilizing an Ar + H2 + CH4 plasma-creating mixture in the pressure range 1–100 Torr with a plasma flow direction opposite to the direction of the arc current was carried out. The reversed arc discharge has rising current–voltage characteristics showing voltage increasing with pressure and hydrogen concentration. The spectrum of the Ar-H2-CH4 plasma column includes CH, C2, and H2 molecular bands, in addition to Hα, Hβ, Hγ, and Hδ lines. The dissociation degree of H2 was estimated from the intensity ratio IHα/IArI of the Hα and ArI 750 nm lines using the optical actinometry method, yielding an average dissociation degree of hydrogen in the arc plasma of 15–20%. The average vibrational and rotational temperatures of CH radicals are Tv = Tr = 3000 K ± 300 K. The dissociation degree of hydrogen in the reversed arc discharge was calculated by the advection–diffusion-reaction model and showed reasonably good agre...

Effects of xenon concentration and the reduced electric field on electron swarm parameters in Xe-... more Effects of xenon concentration and the reduced electric field on electron swarm parameters in Xe-Ne mixtures are numerically studied. The increase in xenon concentration in the mixture over ~10 % leads to sharp delay in growth of excitation rates of xenon atoms. Ionization efficiency increases at increase in xenon concentration up to ~7 %. When an electric field increases the share of electron energy, spent for xenon excitation, decreases and more energy is put in ionization of xenon, excitation and ionization of neon. Predictive force of the calculation of electron swarm parameters allows limiting the xenon concentration in Xe-Ne mixtures optimal for generation of VUV radiation to a range of 110 %.

Journal of Physics: Conference Series, Nov 1, 2017

View the article online for updates and enhancements. Related content Efficient chemical oxygen-i... more View the article online for updates and enhancements. Related content Efficient chemical oxygen-iodine laser with a high total pressure of the active medium M V Zagidullin, V D Nikolaev, M I Svistun et al.-Molecular tagging velocimetry in nitrogen with trace water vapor Carl A Hall, Marc C Ramsey, Darin A Knaus et al.-Emission and laser-induced fluorescence measurements in a supersonic jet of plasma-heated nitrogen

Optics and Spectroscopy, 2017

Luminescence spectra of a longitudinal pulse-periodic discharge in xenon mixture with rubidium br... more Luminescence spectra of a longitudinal pulse-periodic discharge in xenon mixture with rubidium bromide vapors (Xe-RbBr) are studied experimentally at low pressures. The conditions leading to the appearance of intense bands of ultraviolet radiation of exciplex XeBr* molecules in the spectral interval between 200 and 400 nm are found. The highest yield of UV radiation of XeBr* molecules is achieved when the temperature of discharge-tube walls is equal to 750°C. A maximum power of UV radiation from the entire plasma volume as high as 4.8 W is obtained.

Journal of Physics D: Applied Physics, 2020

Plasma Chemistry and Plasma Processing, 2020

The discharge in mixtures of inert gas with sulfur vapors is an effective source of radiation spe... more The discharge in mixtures of inert gas with sulfur vapors is an effective source of radiation spectrum, which is similar to solar in the wavelength range of 280-600 nm due to strong emission of S 2 molecules (B 3 → X 3-transition). This phenomenon is utilized in microwave sulfur lamp. Despite a number of advantages microwave sulfur lamps have disadvantages that prevent their widespread use. This paper presents optical properties of the pulsed-periodic discharge in mixtures of argon with sulfur vapour in UV and visible spectral region and a global model of the discharge. Emission of the pulsed-periodic discharge in argon-sulfur vapour mixtures was studied at argon pressure up to 100 Torr and pressure of sulfur saturated vapors determined by temperature of gas-discharge tube walls varied due self-heating from the room temperature up to 160 °C. It is shown that strong band of S 2 molecules are observed in the discharge emission in the wavelength range of 300-600 nm and S and Ar lines are predominate in the wavelength range of 600-1000 nm. Effect of the discharge conditions on emission spectra was investigated. Time profiles of plasma species densities under various Ar-S 2 mixture compositions and voltage pulse up to 15 kV with duration ~ 10 μs were calculated using the global model. It is shown, that densities of S 2 * molecules fast increases at the voltage pulse beginning and reach maximum after ~ 2 μs, so strong radiation of S 2 * is characteristic for the time interval, then S 2 * density fast decreases.

Spectrochimica Acta Part B: Atomic Spectroscopy, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.