Model Of Glow Discharge Research Articles

Analytical model of a short DC glow discharge in the presence of significant radial ambipolar diffusion losses

We present a simple analytical model of a short direct-current glow discharge (without positive column) that is applicable for the case of narrow discharge tubes when radial losses of charged particles due to ambipolar diffusion significantly influence discharge properties. The model is based on the analytical parameterization of the non-local ionization produced by fast electrons, which allows obtaining an exact solution of the ambipolar diffusion equation with radial particle losses written in the τ-approximation. Analysis of the spatial distribution of electron density in the near-cathode plasma regions of a discharge allow obtaining an explicit expression for the position of electric field reversal in the negative glow that is independent of electron temperature and interelectrode distance. The latter fact makes the model viable for description of near-cathode plasma regions in the general case of a discharge with a positive column. The procedure for obtaining quantitative estimates and interpretation of experimental data on discharge properties using the proposed model is presented and discussed in detail.

Mechanism Analysis of the Effect of Axial Magnetic Field on Low Pressure Glow Discharge

The effect of axial magnetic field on glow discharge parameters at low pressure is studied in this article. First, Paschen&#x2019;s law under axial magnetic field is modified. The results show that under the same conditions, the magnetic field will increase the breakdown voltage of glow discharge. The experimental results are consistent with the theoretical analysis, but the experimental value is higher than the theoretical value. Second, the physical model of parallel field glow discharge is established, and the plasma density of glow discharge under different pressure, discharge spacing, and magnetic field is studied. The results show that the plasma density increases with the increase in magnetic field at low pressure; at high pressure, the larger the magnetic field, the smaller the plasma density. At the same position, the plasma density increases with the increase in discharge spacing in weak magnetic field, and it decreases with the increase in discharge spacing in strong magnetic field. When the surface area of the magnet is only 20&#x0025; of the surface area of the anode and cathode, the radial nonuniformity of the magnetic field makes the plasma density reach the maximum when the radial <inline-formula> <tex-math notation="LaTeX">$r =0$ </tex-math></inline-formula>.

Modeling of DC glow discharges in low-pressure CO2

A simple model of glow discharges in CO2 is presented. In the framework of this model, analytical expressions for plasma characteristics (the electric field, the electron density, the gas temperature, the vibrational temperature of asymmetric mode) and for the molar fraction of CO molecules produced at CO2 dissociation by electron impact have been obtained. The plasma characteristics have been estimated for CO2 discharges at pressures 0.4–5 Torr and currents 10–50 mA. The estimates are consistent with recent experimental results obtained in DC discharges in the indicated pressure and current range.

Theoretical Study on Characteristics of Glow Discharged Neon Gas and Its Interaction With Terahertz Waves

Discharge gases have been used to detect terahertz (THz) waves, however, there are few relevant theoretical studies. The neon glow discharge model is established by COMSOL Multiphysics software, the characteristics of glow discharged neon and the interaction of the discharged gas with THz waves were investigated. The results show that with the increase of THz wave’s frequency, the transmittance increases, the change of plasma discharge characteristics caused by THz wave can be used for THz wave detection. The results provide a theoretical basis for the development of cheap, room temperature THz wave detector with fast response speed, and high sensitivity.

Numerical modeling of a DBD in glow mode at atmospheric pressure

In this work, a fluid model of helium glow discharge at atmospheric pressure in a dielectric barrier discharge configuration has been developed and the discharge was numerically simulated. The transport equations for charged and excited species are self-consistent coupled to the Poisson equation for the electrical field calculation. A finite difference method technique is adopted; a detailed numerical procedure modeling is given. The addition of some nitrogen impurities to the helium successfully reproduced the discharge evolution during the breakdown. The numerical results showed that the discharge has a structure similar to DC low-pressure glow discharges and confirms the establishment of the glow regime at atmospheric pressure under very adequate conditions. The profiles of physical and electrical discharge parameters knowing that, particle densities, electric field, drift velocity, voltages and discharge current are presented and analyzed. A detailed study was made of the effect of nitrogen impurities on the stability of the glow mode of the discharge, and on the evolution of its parameters.

Modeling of glow discharge in longitudinal gas flow in a plane channel of variable cross section

A two-dimensional model of glow discharge positive column in gas flow has been suggested in this paper. It is considered that the discharge maintained between the permeable mesh electrodes installed in the initial and end sections of the plane channel. In general case the channel width changing along the stream is accounted. The positive column in gas flow is described by integro-differential system of equations with an approximation of constant gas flow density. The border conditions for gas ionization degree and temperature in the initial section of channel are given by any functions. An analytical solution of that system was obtained and special cases of the boundary conditions analyzed.

Self-consistent modeling of self-organized patterns of spots on anodes of DC glow discharges

Self-organized patterns of spots on a flat metallic anode in a cylindrical glow discharge tube are simulated. A standard model of glow discharges is used, comprising conservation and transport equations for a single species of ion and electrons, written with the use of the drift-diffusion and local-field approximations, and the Poisson equation. Only processes in the near-anode region are considered and the computation domain is the region between the anode and the discharge column. Multiple solutions, existing in the same range of discharge current and describing modes with and without anode spots, are computed for the first time. A reversal of the local anode current density in the spots was found, i.e. mini-cathodes are formed inside the spots or, as one could say, anode spots operate as a unipolar glow discharge. The solutions do not fit into the conventional pattern of self-organization in bistable nonlinear dissipative systems; In particular, the modes are not joined by bifurcations.

Numerical study on discharge characteristics influenced by secondary electron emission in capacitive RF argon glow discharges by fluid modeling**Project supported by the National Natural Science Foundation of China (Grant No. 51172101).

A one-dimensional (1D) fluid model of capacitive RF argon glow discharges between two parallel-plate electrodes at low pressure is employed. The influence of the secondary electron emission on the plasma characteristics in the discharges is investigated numerically by the model. The results show that as the secondary electron emission coefficient increases, the cycle-averaged electric field has almost no change; the cycle-averaged electron temperature in the bulk plasma almost does not change, but it increases in the two sheath regions; the cycle-averaged ionization rate, electron density, electron current density, ion current density, and total current density all increase. Also, the cycle-averaged secondary electron fluxes on the surfaces of the electrodes increase as the secondary electron emission coefficient increases. The evolutions of the electron flux, the secondary electron flux and the ion flux on the powered electrode increase as the secondary electron emission coefficient increases. The cycle-averaged electron pressure heating, electron Ohmic heating, electron heating, and ion heating in the two sheath regions increase as the secondary electron emission coefficient increases. The cycle-averaged electron energy loss increases with increasing secondary electron emission coefficient.

Modeling of glow discharge in a gas flow

The discharge plasma of positive column in electronegative gas flow has been described by two-dimensional integro-differential system of equations written in the approximation of “narrow channel”. An efficient algorithm of solving this system of equations is suggested. In this work an implicit method is used of solution with selection gradient of the electric field along the channel. The simulation of discharge characteristics was conducted under various boundary conditions at the inlet of the discharge area and with various full discharge currents.

1D kinetic simulations of a short glow discharge in helium

This paper presents a 1D model of a direct current glow discharge based on the solution of the kinetic Boltzmann equation in the two-term approximation. The model takes into account electron-electron coulomb collisions, the corresponding collision integral is written in both detailed and simplified forms. The Boltzmann equation for electrons is coupled with continuity equations for ions and metastable atoms and the Poisson equation for electric potential. Simulations are carried out self-consistently for the whole length of discharge in helium (from cathode to anode) for cases p = 1 Torr, L = 3.6 cm and p = 20 Torr, L = 1.8 mm, so that pL = 3.6 cm·Torr in both cases. It is shown that simulations based on the kinetic approach give lower values of electron temperature in plasma than fluid simulations. Peaks in spatial differential flux corresponding to the electrons originating from superelastic collisions and Penning ionization were observed in simulations. Different approaches of taking coulomb collisions into account give significantly different values of electron density and electron temperature in plasma. Analysis showed that using a simplified approach gives a non-zero contribution to the electron energy balance, which is comparable to energy losses on elastic and inelastic collisions and leads to significant errors and thus is not recommended.

Computational model of a direct current glow discharge used as an ambient desorption/ionization source for mass spectrometry

A new model of a plasma ionization source anchored by experimental data giving a comprehensive view of the discharge mechanism.

Conversion of an atomic to a molecular argon ion and low pressure argon relaxation**Project supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Grant No. ON171025).

The dominant process in relaxation of DC glow discharge between two plane parallel electrodes in argon at pressure 200 Pa is analyzed by measuring the breakdown time delay and by analytical and numerical models. By using the approximate analytical model it is found that the relaxation in a range from 20 to 60 ms in afterglow is dominated by ions, produced by atomic-to-molecular conversion of Ar+ ions in the first several milliseconds after the cessation of the discharge. This conversion is confirmed by the presence of double-Gaussian distribution for the formative time delay, as well as conversion maxima in a set of memory curves measured in different conditions. Finally, the numerical one-dimensional (1D) model for determining the number densities of dominant particles in stationary DC glow discharge and two-dimensional (2D) model for the relaxation are used to confirm the previous assumptions and to determine the corresponding collision and transport coefficients of dominant species and processes.

Numerical simulation of the two-dimensional structure of glow discharge in molecular nitrogen in light of vibrational kinetics

A two-dimensional computer model of glow discharge in molecular nitrogen in axisymmetric geometry is presented. The glow discharge structure is described within the diffusion-drift model, while the kinetic parameters of the model used are calculated from the solution to the kinetic Boltzmann equation. Calculations of the energy accumulated on the electronically and vibrationally excited levels of molecules and the effectiveness of electron energy conversion to the Joule heat are performed. In the context of state-to-state kinetics of anharmonic oscillators, populations of vibrational levels of molecular nitrogen are calculated.

Model of glow discharge between an electrolytic anode and a metal cathode

The results of the numerical simulation of the glow discharge between the pin cathode and the electrolytic anode are presented. The electron concentration distribution for the different distances from the anode were calculated. The 2D distribution is calculated for the equipotential lines between the steel cathode and the electrolytic anode. The essentially nonuniform character of the electric field strength distribution along the discharge axis was discovered. The obtained distribution of the electric field strength between the metal cathode and the electrolytic anode is in a good qualitative agreement with the results of the experiments realized in the similar conditions.

Two-dimensional fluid modeling of DC glow discharge in argon at low pressure

The modeling of DC glow discharge in argon at the pressure p = 1.5 Torr and inter-electrode distance d = 1 cm was performed for different voltages and glow currents. For the first time, argon glow discharge is modeled using a two-dimensional (2D) fluid model with non-local ionization. A detailed numerical procedure for 2D fluid modeling is given. The 2D profiles of particle number densities and electric potential obtained from the fluid model with non-local ionization and the simple fluid model are presented and compared.

Effect of Secondary Electron Emission on Argon Glow Discharge Characteristics

The present work develops and tests a computationally model of a DC glow discharge in low pressure argon gas of collisionless electron plasma. In this work, we have chosen the fluid model described by a series of partial differential equations representing all the physical phenomena that occur in a landfill. Using these differential equations, the spatial distribution of electrons, electron mean energy and electric field distribution in the inter-electrode space of DC plasma discharge have been calculated by the finite differences method according to the exponential scheme. Argon is used as the working gas to investigate all the physical processes occurring in the glow discharge. We especially investigate the effect of the secondary emission of electrons from the electrode surface. We have performed a classification of the value of the secondary emission coefficient γ and the model was validated using the value of γ according to plasma potential. The value of γ has been shown to affects electric field behavior in the plasma sheaths.

Fluid model of dc glow discharge with nonlocal ionization source term

We developed and tested a simple hybrid model for a glow discharge, which incorporates nonlocal ionization by fast electrons into the fluid framework. Calculations have been performed for an argon gas. Comparison with the experimental data as well as with the hybrid (particle) and fluid modelling results demonstated good applicability of the proposed model.

Numerical simulation of rarefied dusty plasma in a normal glow discharge

A self-consistent model of a glow discharge, burning in a normal current density mode, with dust particles placed in it is presented. The model of a normal glow discharge is based on a diffusion-drift approximation. Within the framework of this model, the regions of a spatial charge are taken into account. The motion of dust particles in the glow discharge region is calculated using the method of molecular dynamics. The particle charge is estimated based on qualitative conceptions on the process of charging of solid particles. The proposed model is studied numerically, and the corresponding results are presented.

Modeling of glow discharge controlled by a dielectric barrier

Numerical calculations of spatio-temporal characteristics of the homogeneous barrier discharge in helium are performed by means of a one-dimensional fluid model. This model consists of the continuity equations for electrons, ions and excited atoms, with the current conservation equation and the electric field profile; the time evolution of the discharge current, gas voltage and the surface density of charged particles on the dielectric barrier were calculated. The simulation results showed that the peak values of the discharge current, gas voltage and electric field in the first half period are asymmetric to the second half. When the current reaches its positive or negative maximum, the electric field profile and the electron and ion densities represent similar properties to the typical glow discharge at low pressures. Key words: Atmospheric pressure glow discharge, numerical simulation, helium gas.

Thermal mechanism for formation of electrical prepeak and pressure waves in a microsecond direct current pulsed glow discharge with a Grimm-type source: a modeling investigation

A Monte-Carlo based model is developed for simulating the evolution of Ar concentration, temperature and flow in time and space. Potentially, the model could be used for gas simulations in a wide range of different applications. Here, the model is incorporated into an existing but modified model of a microsecond pulsed glow discharge (μs PGD) in a Grimm-type plasma excitation source. Results of the simulations reveal that a thermal mechanism is responsible for the formation of the electrical prepeak and pressure waves, two phenomena that take place at the leading edge of the μs pulse in this source.