Low-temperature Gas Discharge Research Articles

Применение научной визуализации в моделировании низкотемпературной газоразрядной плазмы

This article discusses the importance of developing software and hardware complexes for data visualization and improving methods of presenting them in the modeling of low-temperature gas discharge plasma phenomena and related physical processes. In particular, issues related to creating a specialized distributed environment for solving gas discharge modeling tasks are considered. The use of computer graphics for visualization has allowed for a visual analysis of the obtained data and making necessary adjustments to the modeling process interactively with the data. The paper presents the results of visualizing a model of mercury-argon plasma in a coaxial microwave discharge. The application of local cross-sections of the computational domain for visualization has revealed the internal structure and peculiarities of the distribution of the electric field and electron concentration in the discharge tube. The obtained data served as the basis for creating an experimental prototype of a coaxial gas discharge optical radiation source.

Revisiting the numerical stability/accuracy conditions of explicit PIC/MCC simulations of low-temperature gas discharges

Particle-in-cell (PIC) with Monte Carlo collisions is a fully kinetic, particle based numerical simulation method with increasing popularity in the field of low temperature gas discharge physics. Already in its simplest form (electrostatic, one-dimensional geometry, and explicit time integration), it can properly describe a wide variety of complex, non-local, non-linear phenomena in electrical gas discharges at the microscopic level with high accuracy. However, being a numerical model working with discretized temporal and (partially) spatial coordinates, its stable and accurate operation largely depends on the choice of several model parameters. Starting from four selected base cases of capacitively coupled, radio frequency driven argon discharges, representing low and intermediate pressure and voltage situations, we discuss the effect of the variation of a set of simulation parameters on the plasma density distribution and the electron energy probability function. The simulation parameters include the temporal and spatial resolution, the PIC superparticle weight factor, as well as the electron reflection and the ion-induced electron emission coefficients, characterizing plasma–surface interactions.

Deposition of metal nanofilms on cylinder-shaped items

The use of the magnetron sputtering method ensures high adhesion of the applied thin nanoscale films and allows deposition of metal coatings (Cu, Ni, Ti, Ag, Au, etc.) on various substrates. The disadvantage of planar magnetron sputtering devices is the inability to apply coatings to the inner surface of cylindrical parts (for example, silvering of the inner walls of waveguides). The formation of such films is possible with the use of a rod cathode-target and a cylindrical anode-substrate coaxially located with it. In the space between the target cathode and the anode substrate, a low-temperature gas discharge plasma is created by applying a constant electric voltage, and a magnetic induction field perpendicular to the electric field is created by permanent magnets or solenoids located outside the cylindrical anode substrate. The disadvantages of such a device include the inability to control the characteristics of the permanent magnetic induction field in the case of permanent magnets and the inhomogeneous characteristics of the magnetic induction field in the case of solenoids. A significant disadvantage is the need to rebuild the entire system of external magnets in the event of a change in the requirements for the parameters of the magnetic induction field or a change in the configuration of the substrate. Therefore, it is necessary to exclude external sources of the magnetic induction field. In the proposed device, the magnetic induction field is created due to the flow of a constant current of the required value through the cathode. The use of alternating and direct current sources and a system of capacitors and chokes allows creating a controlled magnetic field of the required configuration and implementing a discharge in the crossed fields. This makes it possible to obtain a high-quality coating with heterogeneity of about 3% throughout the product.This paper was recommended for publication by the Organizing Committee of the International Conference Nanophysics and Nanomaterials (24–25 November 2021, Saint Petersburg, Mining University).

Kinetics of metastable N2(A3Σu + , v) molecules in high-pressure nonequilibrium plasmas

Absolute, time-resolved populations of N2(A3Σu +, v = 0–5) vibrational levels in high-pressure ns pulse discharge plasmas are measured by Tunable Diode Laser Absorption Spectroscopy (TDLAS). The diffuse plasma is generated by a repetitively pulsed, double dielectric barrier, ns discharge across a 10 mm gap in a plane-to-plane geometry, at pressures of up to 400 Torr. The results of TDLAS measurements in nitrogen and in H2–N2, O2–N2, and NO–N2 plasmas are compared with kinetic modeling predictions, identifying the mechanisms of N2(A3Σu +) generation and decay during the discharge pulses and in the afterglow. Comparison with the modeling predictions indicates that electron impact dissociation of N2 from the ground electronic state significantly underpredicts the yield of N atoms. The present data suggest that N2 dissociation in the plasma also occurs during the energy pooling process in collisions of two N2(A3Σu +) molecules. The results also show that high-pressure, high repetition rate, volume-scalable ns pulse discharges can be used for efficient generation of atomic species for plasma chemical and plasma catalysis syntheses. In an NO–N2 mixture, it is shown that the N2(A3Σu +) decay is controlled by the rapid energy transfer to NO, resulting in its electronic excitation and UV emission (NO γ bands). The diagnostics used in the present work can be used for the accurate characterization of both high-pressure, low-temperature gas discharge plasmas and high-temperature nonequilibrium flows generated in pulsed facilities such as shock tubes and expansion tunnels.

Investigation of parameters of low-temperature gas discharge plasma with liquid electrodes upon receipt of metal powder

Selective laser melting technologies are widely used in various industries and medicine. A gradual increase in the volume of manufactured products requires the creation of new cheap methods for producing metal powders. One of the new methods for producing powders is the plasma-electrolyte method. A feature of this method is the use of gas with liquid electrodes, which allows you to get a metal powder and quickly cool it in a liquid. The question of the influence of discharge parameters on the process of metal atomization remains open. The paper studies gas discharges with liquid electrodes under the conditions of atomization of a metal anode. A gas discharge between a liquid electrolyte and a metal electrode was studied experimentally in the voltage range 300 - 1000 V. Solutions of sodium chloride in distilled water were used as the electrolyte. The conditions are established under which a stable discharge column is formed and metal powder is sprayed. The regularities of the change in the CVC of the discharge depending on the interelectrode distance are determined. A splitting of the spectral lines of the yellow sodium doublet was found in the emission spectrum of a gas discharge.

ON MECHANISMS OF INCREASING HCL DISSOCIATION DEGREE IN GLOW DISCHARGE PLASMA

The influence of initial compositions of the binary HCl+Ar and HCl+O2 gas mixtures on the hydrogen chloride dissociation kinetics in low temperature gas discharge plasma was investigated. The experiments were carried out under the conditions of direct current glow discharge at constant total gas pressure (100 Pa) and discharge current (25 mA). The data on electro-physical plasma parameters and plasma composition were obtained by modeling procedure based on the simultaneous solution of Boltzmann kinetic equation and the equations of chemical kinetics for neutral and charged species in a steady-state approximation. It was found that an increase in the second component fraction in both gas mixtures results in the sufficient increase in the HCl dissociation degree (aHCl = 23–43% for 0–80% Ar and 23–90% for 0–80% O2), which is associated with different mechanisms. Particularly, in the HCl+Ar gas mixture, an effect of increasing aHCl is provided by an increase in the electron impact dissociation frequency due to the change in electro-physical plasma parameters, such as electron mean energy and electron density. For the HCl+O2 gas mixture, such mechanism is almost negligible because of the weak disturbances in both electron energy distribution and formation/decay balance for charged species in the combination of two molecular electronegative gases. At the same time, the HCl dissociation kinetics in this gas system appears to be strongly dependent on the gas-phase interactions with ground state of oxygen atoms O(3P), metastable atoms O(1D) and OH radicals. It was found that the rates of corresponding processes begin to exceed the HCl electron impact dissociation rate at 20% O2 in HCl+O2.Forcitation:Efremov A.M., Murin D.B., Belyaev S.V. On mechanisms of increasing hcl dissociation degree in glow discharge plasma. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 7. P. 61-66

A plasma device for increasing the hydrophilicity of paper products

The treatment of various materials using low-temperature gas–discharge plasma to clean their surface or change their structure is rather promising because of the generation of particles that react with molecules of impurities or base material. In addition, the molecules of the surface layer of material are exposed to the influence of ultraviolet and soft X-ray radiation generated in the cathode layer of the discharge. Only the volumetric gas–discharge can guarantee a high degree of uniformity of the material surface treatment. To increase the intensity of the plasma-chemical reactions, it is effective to increase the frequency of the supplied voltage of a discharge reactor or to use the pulse–periodic power-supply mode. The pulse frequency should be coordinated with the typical frequency of the plasma chemical reactions. Experimental installations that have a discharge reactor as their main element showed successful performance for the modification of the volumetric structure of a thin paper tape to increase its hydrophilicity.

5th International Congress on Energy Fluxes and Radiation Effects 2016

Special Issue of the Materials of the V International Congress on Energy Fluxes and Radiation Effects (Tomsk, Russia, 2016)Maksim Trigub, Georgiy Osokin, Alexander KonovodNational Research Tomsk Polytechnic University, 30, Lenin Avenue, Tomsk, Russiaemail: geosokin@tpu.ruThe present issue of the journal is based on the materials of the V International Congress on Energy Fluxes and Radiation Effects 2016 (EFRE 2016) that was held on October 2 to 7, 2016 in Tomsk (Russia). This large scientific forum gathers together scientists, developers and representatives of knowledge-intensive enterprises that have relevance to physics and technology. This year, the Congress was dedicated to the 120th anniversary of the National Research Tomsk Polytechnic University.The history of the Congress as a joint scientific event dates back to 2000; it traditionally includes three conferences: International Symposium on High-Current Electronics (SHCE), International Conference on Radiation Physics and Chemistry of Condensed Matter (RPC) and International Conference on Modification of Materials with Particle Beams and Plasma Flows (CMM). However, each of these large conferences has its own lasting history.In 2016, the International Symposium on High-Current Electronics was arranged for the 19th time. The participants have presented the results of fundamental studies and applied outcomes in the fields of high-power pulsed energy engineering and electronics (Pulsed Power), physics and application of high-power electron and ion beams, high- and low-temperature gas discharge plasma, physics of high-energy treatment and extreme states of matter, electric pulsed technologies. Noteworthy, the symposium took place in the year of the 40th anniversary of USSR scientific discovery of explosive electron emission. This physical phenomenon—being one of the basics of high-current electronics—determines the processes in pulsed vacuum discharge, enables the operation of high-current electron accelerators, finds application in beam pumping of high-power pulsed gas lasers, switches and other electric pulsed devices.The 17th International Conference on Radiation Physics and Chemistry of Condensed Matter is traditionally organised starting from 1969. This conference is the largest both on national and international scale in the fields of radiation physics and chemistry of inorganic substances, investigation of fundamental problems of elementary, nonlinear and catastrophic processes in condensed matter under fluxes of hard radiation.The International Conference on Modification of Materials with Particle Beams and Plasma Flows was held for the 13th time beginning from 1988. The high level of this event is due to the participation of the representatives of outstanding scientific schools that stand at the origins of this scientific and technological field.Regular organisation of EFRE Congress strengthens the interdisciplinary bonds between three grand fields of physics and technology playing increasingly important role in the technological development of society. Pulsed energy generation and high-current electronics provide equipment for electric discharge, plasma beam and radiation technologies that intensely fill and update the technological niches in various branches of industry, defence, chemistry, biology and medicine. The participants of the forums get comprehensive picture of scientific and applied problems and have an opportunity to look at them from the perspective of theoretical and experiment studies and engineering.The place of the event has been chosen for a reason: Tomsk is a city having strong scientific and educational network including outstanding physical and technological schools. It was Tomsk where many of the scientific topics of the Congress germinated. Each of the forums gathers the representatives of abundant student pool of Tomsk.The main organisers of the Congress—Tomsk Polytechnic University and Institute of High-Current Electronics of SB RAS, which soon will celebrate its 40th anniversary—have strong bonds in the field of scientific research, educational activities, management, and represent a splendid example of real integration of academic and university-level science.In 2016, the Congress gathered leading national and international scientists, manufacturers and consumers of vacuum and electron beam equipment, accelerators and radio-frequency devices, representatives of field-specific organisations and business-structures. The 500 participants of the Congress included specialists from Russia, Republic of Belarus, Brazil, Germany, Israel, Italy, Kazakhstan, People’s Republic of China, Republic of Korea, USA, Ukraine, France and Czech Republic.The conferences were conducted with the financial support of the Russian Foundation for Basic Research (projects nos. 16–02–20530, 16–08–20408, 16–02–20464).

Dependence of helium ion diffusion and drift characteristics in own gas on its temperature

The low-temperature gas discharge has a number of features which can appear in experimentswith dusty plasma. For example, at cryogenic temperatures of gas-discharge tube walls, the strong anisotropy of the velocity distribution function of ions takes place, which in turn can cause a significant change in dust structure properties. The dependences of the helium ion drift characteristics in a dc uniform electric field on the atomic temperature of own gas is analyzed.

Geochemistry of fluid discharges from Peteroa volcano (Argentina-Chile) in 2010–2015: Insights into compositional changes related to the fluid source region(s)

This study presents the first geochemical data of fluid discharges collected from February 2010 to March 2015 from the Planchón–Peteroa–Azufre Volcanic Complex (PPAVC), located in the Transitional Southern Volcanic Zone (TSVZ) at the border between Argentina and Chile. During the study period, from January 2010 to July 2011, Peteroa volcano experienced phreatic to phreatomagmatic eruption possibly related to the devastating Maule earthquake occurred on February 27, 2010. The compositional dataset includes low temperature (from 43.2 to 102°C) gas discharges from (i) the summit of Peteroa volcano and (ii) the SE flank of Azufre volcano, both marked by a significant magmatic fluid contribution, as well as bubbling gases located at the foothill of the Peteroa volcanic edifice, which showed a chemical signature typical of hydrothermal fluids. In 2012, strong compositional changes affected the Peteroa gases from the summit area: the acidic gas species, especially SO2, increased, suggesting an input of fluids from magma degassing. Nevertheless, the R/Ra and δ13C–CO2 values decreased, which would imply an enhanced contribution from a meteoric-hydrothermal source. In 2014–2015, the chemical and isotopic compositions of the 2010–2011 gases were partially restored. The anomalous decoupling between the chemical and the isotopic parameters was tentatively interpreted as produced by degassing activity from a small batch of dacitic magma that in 2012 masked the compositional signature of the magmatic fluids released from a basaltic magma that dominated the gas chemistry in 2010–2011. This explanation reliably justifies the observed geochemical data, although the mechanisms leading to the change in time of the dominating magmatic fluid source are not clear. At this regard, a geophysical survey able to provide information on the location of the two magma batches could be useful to clarify the possible relationships between the compositional changes that affected the Peteroa fluid discharges and the 2010–2011 eruptive activity.

Coulomb collisions in the Boltzmann equation for electrons in low-temperature gas discharge plasmas

This paper investigates the effects of electron-electron and electron-ion Coulomb collisions on the electron distribution function and transport coefficients obtained from the Boltzmann equation for simple dc gas discharge conditions. Expressions are provided for the full Coulomb collision terms acting on both the isotropic and anisotropic parts of the electron distribution function, which are then incorporated in the freeware Boltzmann equation solver BOLSIG+. Different Coulomb collision effects are demonstrated and discussed on the basis of BOLSIG+ results for argon gas. It is shown that the anisotropic part of the electron-electron collision term, neglected in previous work, can in certain cases have a large effect on the electron mobility and is essential when describing the transition towards the Coulomb-collision dominated regime characterized by Spitzer transport coefficients. Finally, a brief overview is presented of the discharge conditions for which different Coulomb collision effects occur in different gases.

Generation of low-temperature gas discharge plasma in large vacuum volumes for plasma chemical processes

In the paper the principles of generation of low temperature capacitively coupled in a vacuum chamber of a large size with the use of original low-pressure arc discharges are considered. The designs of plasma sources and their main parameters are described. Examples of effective use of the generated plasma in plasma chemical modification of the surfaces of materials and products are presented.

Electron energy distribution function control in gas discharge plasmas

The formation of the electron energy distribution function (EEDF) and electron temperature in low temperature gas discharge plasmas is analyzed in frames of local and non-local electron kinetics. It is shown, that contrary to the local case, typical for plasma in uniform electric field, there is the possibility for EEDF modification, at the condition of non-local electron kinetics in strongly non-uniform electric fields. Such conditions “naturally” occur in some self-organized steady state dc and rf discharge plasmas, and they suggest the variety of artificial methods for EEDF modification. EEDF modification and electron temperature control in non-equilibrium conditions occurring naturally and those stimulated by different kinds of plasma disturbances are illustrated with numerous experiments. The necessary conditions for EEDF modification in gas discharge plasmas are formulated.

Characteristics of low-energy ion beams extracted from a wire electrode geometry

Beams of argon ions with energies less than 50 eV were extracted from an ion source through a wire electrode extractor geometry. A retarding potential energy analyzer (RPEA) was constructed in order to characterize the extracted ion beams. The single aperture RPEA was used to determine the ion energy distribution function, the mean ion energy and the ion beam energy spread. The multi-cusp hot cathode ion source was capable of producing a low electron temperature gas discharge to form quiescent plasmas from which ion beam energy as low as 5 eV was realized. At 50 V extraction potential and 0.1 A discharge current, the ion beam current density was around 0.37 mA/cm(2) with an energy spread of 3.6 V or 6.5% of the mean ion energy. The maximum ion beam current density extracted from the source was 0.57 mA/cm(2) for a 50 eV ion beam and 1.78 mA/cm(2) for a 100 eV ion beam.

Self-Organized Patterns in Planar Low-Temperature AC Gas Discharge

Various partly strange self-organized patterns can be observed experimentally in the distribution of the luminescence radiation density and the corresponding current density in planar low-temperature dielectric barrier gas discharge systems.

Self-Organized Patterns in Planar Low-Temperature DC Gas Discharge

Self-Organized Patterns in Planar Low-Temperature DC Gas Discharge

Measurement of collisional quenching rate of nitrogen states N2(C 3Πu, v = 0) and

This paper presents an experimental investigation of the effect of the electric field strength on the collisional quenching rate of nitrogen states N2(C 3Πu, v = 0) and by nitrogen and oxygen molecules. In experiments, the pulses of non-self-sustained electrical discharge excite gas molecules. The range of reduced electric field strength is from 240 to 4000 Td at pressure range from 70 to 4300 Pa. The experiments show that the field strength has no effect on the quenching rate. The paper discusses the probable reasons for discrepancy of results obtained by different authors and proposes the preferable values for rate coefficients. These coefficients can be used for electric field determination in low temperature gas discharge plasmas via nitrogen emission spectrum, and are of interest to atmospheric air fluorescence investigations.

Electron impact ionization of metastable rare gases: He, Ne and Ar

Cross sections for ionization of atoms by electron impact are important quantities for modeling of low temperature plasmas and gas discharges. Although experimental and theoretical studies of ionization of atoms from their ground levels have been extensive, much less information is available about the larger cross sections for ionization from excited levels. We use the Binary–Encounter–Bethe (BEB) method of Kim and Rudd to calculate ionization cross sections from the 1s2s 3S level of He, the 2p 53s 3P levels of Ne, and the 3p 54s 3P levels of Ar. We compare our results with the few available experimental results and with results from other theoretical methods.

Natural evidence for rapid abiogenic hydrothermal generation of CH 4

Although recent hydrothermal experiments imply that abiogenic methane (CH 4) generation from hydrothermal reduction of CO 2 can occur, evidence from natural systems was still lacking. Based on the chemical and isotopic equilibrium signatures of low-temperature fumarolic gas discharges, we are able to provide hard evidence for its natural occurrence, namely in three subduction-related bi-phase hydrothermal systems of the Mediterranean, whose temperatures range from 260 to 470 °C. The attainment of equilibrium and the time spans of recent volcanic dormancy allowed us to calculate minimum rates for chemical and isotopic equilibration. These are significantly higher than those previously reported and might be due to the presence of a saturated water vapor phase in the investigated systems. The fact that nature provides conditions enabling relatively fast production of hydrocarbons from CO 2 strongly supports the concerns that were recently raised from laboratory experiments. These address the use of the carbon isotope composition of reduced carbon in Archean sediments as a tracer of early life and the occurrence of CH 4 on extraterrestrial planets as a bioindicator. In view of the potential role of abiogenic CH 4 as a precursor of life, we also present an estimate of abiogenic hydrothermal CH 4 fluxes throughout the Archean. It is not expected that these fluxes exceeded 80 Mt/yr during the past 4.0 Ga. This, however, would have been enough to facilitate HCN production on the prebiotic Earth.

Modelling electron transport in magnetized low-temperature discharge plasmas

Magnetic fields are sometimes used to confine the plasma in low-pressure low-temperature gas discharges, for example in magnetron discharges, Hall-effect-thruster discharges, electron-cyclotron-resonance discharges and helicon discharges. We discuss how these magnetized discharges can be modelled by two-dimensional self-consistent models based on electron fluid equations. The magnetized electron flux is described by an anisotropic drift–diffusion equation, where the electron mobility is much smaller perpendicular to the magnetic field than parallel to it. The electric potential is calculated either from Poisson's equation or from the electron equations, assuming quasineutrality. Although these models involve many assumptions, they are appropriate to study the main effects of the magnetic field on the charged particle transport and space charge electric fields in realistic two-dimensional discharge configurations. We demonstrate by new results that these models reproduce known phenomena such as the establishment of the Boltzmann relation along magnetic field lines, the penetration of perpendicular applied electric fields into the plasma bulk and the decrease in magnetic confinement by short-circuit wall currents. We also present an original method to prevent numerical errors arising from the extreme anisotropy of the electron mobility, which tend to invalidate model results from standard numerical methods.