Structure Of Glow Discharge Research Articles

Influence of A.C. Frequency on Hollow Magnetron Sputtering Discharge Parameters

In the present work, optical emission spectroscopy was used to diagnose the influence of A.C. power source frequency on the hollow magnetron sputtering discharge parameters (such as discharge emission, discharge current and voltage, glow discharge structure, temperature (Te) and electron number density (ne), Debye length (λD), and plasma parameter (ND) of constant pressure. The electron temperature and number density were determined using the Boltzmann plots and the Stark broadening methods, respectively. The results illustrate that the normal glow discharge structure is similar to the D.C. discharge mode. The magnetic field has no impact on the fundamental discharge parameter in both A.C. frequencies under study. On the other hand, the other discharge parameters (Te, ne, λD and ND) increase with increasing the magnetic field in both discharge frequencies. In addition, the increase in the frequency of the A.C. source current led to an increase in the discharge intensity emission and the other discharge parameters being studied. In this case, in frequency 7 kHz, Te surged from 0.685 eV to 0.839 eV, and ne experienced an increase from 3.088 x 1018 m-3 to 4.902 x 1018 m-3. At a frequency of 9 kHz, the electron temperature surged from 0.711eV to 0.911 eV. ne experienced an increase from 3.615 x 1018 m-3 to 6.749 x 1018 m-3.

Evolution of Negative Corona in the Discharge-Current Limitation Mode: Transition from the Pulsed-Periodic Mode to Steady-State Burning

The evolution of burning modes of a weak-current corona discharge in a diode filled with atmospheric air, having a pointed cathode and a flat anode, has been investigated. A theoretical description is performed in terms of an axisymmetric multifluid plasma model, including the kinetics of 9 types of particles and 25 plasma-chemical reactions. A discharge in a gap 10 mm long, with a needle-like cathode having a tip curvature radius of 100 μm, a source voltage of 8 kV, a ballast capacitance of 100 pF and a circuit ballast resistance of 1 MΩ, is described in detail. It is shown, both experimentally and theoretically, that the discharge has a lifetime of 180 μs and occurs in four clearly different stages under these conditions: (1) dark breakdown delay phase (0–20 μs); (2) Trichel pulse phase with a variable on–off time ratio and quasi-steady-state corona current component (20–80 μs); and (3) intermediate phase of monotonically rising weak current (80–130 μs), which ends with a vibrational transition to the (4) steady-state phase (130–180 μs), having a typical structure of glow discharge. The tendencies to a change in the corona discharge parameters with a variation in the feed voltage are analyzed. The results of theoretical calculations are in good agreement with the experimental data.

On the Issue of Effect of Magnetic Field on Characteristics of Dust Structures in Glow Discharge

On the Issue of Effect of Magnetic Field on Characteristics of Dust Structures in Glow Discharge

Hypersonic Flow past Sharp Plate and Double Wedge with an Electromagnetic Actuator

The two-dimensional problem of hypersonic flow past a sharp plate and a double wedge on whose surfaces there are electrodes meant for generation of d.c. glow discharge that has a thermal and force influence upon compressed gas flow near the surface is considered. The problem is solved in the self-consistent formulation in which the gas discharge parameters are determined by the gas flow and boundary layer conditions and the flow field structure depends on the local force and thermal impacts generated by the discharge. Therefore, the system of the Navier–Stokes equations and the energy conservation equation for viscous heat-conducting gas is integrated together with the system of equations of the diffusive-drift model for description of the electrodynamic glow discharge structure in gas flow. The influence of the external magnetic field with the vector of magnetic induction perpendicular to the vector of gas flow velocity is taken into account. The effect of the glow discharge parameters on the structure of shock-wave interaction on the sharp plate and the double wedge is investigated.

Synthesis of nanoclusters and quasy one-dimensional structures in glow discharge at T ≈ 2 K

The present article considers the phenomena observed in ultracold multimodal dusty plasma generated in the glow discharge cooled with superfluid helium. It was shown that intense sputtering of the clay insert due to focused beams of low energy electrons and ions produces a total flow ∼100 ng s−1 of sputtered materials at the power released in the discharge less than 0.1 W at T ⩽ 2 K. The synthesis rates for nanoclusters (∼10 ng s−1) and filaments (∼1 ng s−1) were estimated for the first time. Fast growth of quasy one-dimensional structures, the filaments with high aspect ratio, ∼100, in ultracold plasma was explained by self-assembly of polarizable materials in strongly inhomogeneous electric fields. The intense broadband emission stimulated by laser excitation of the filaments synthesized was assigned to carbon quantum dots, domains enriched with carbon. The key parameters of the nanocluster cloud were determined for the first time. The nanocluster concentration was estimated as high as 1012÷1013 nanocluster/m3. Charging of nanoclusters in plasma produced a stable uprising nanocluster flow (∼108 cluster/s) driven by external electrostatic field and observable due to laser light scattering on dust acoustic waves developed within the flow. Temporal variations of the nanocluster concentration caused changes of the interparticle distance in the dusty plasma structure composed of CeO2 particles. It was found that the particles trapped in the structure had the mean size of about 2 μm and much narrower size distribution in comparison with the very broad initial distribution.

Double-hole anode glow discharge in axial magnetic field at low pressures

The influence of magnetic field on glow plasma was studied by the self-designed double-hole anode discharge device, and the relationship between ignition voltage and gas pressure under different magnetic fields is obtained. In addition, the influence of magnetic field on the spatial distribution of plasma density is studied by changing different magnetic field configurations. The results show that under the same pressure, the magnetic field can effectively reduce the glow discharge ignition voltage and increase the plasma density; the enhancement of magnetic field is similar to the increase in air pressure in the double-hole anode glow discharge structure; the hole anode and magnetic field are indispensable conditions for glow generation at low pressure; and different magnetic field configurations control the plasma density distribution.

Influence of nitrogen impurities on the performance of multiple-current-pulse behavior in a homogeneous helium dielectric-barrier discharge at atmospheric pressure

A systematic investigation regarding the influence of nitrogen impurities on the evolution of multiple-current-pulse (MCP) behavior in a homogeneous dielectric-barrier discharge is carried out via fluid modelling. By gradually up-regulating the N2 content from 0.1 ppm to 10 000 ppm, the discharge evolves from MCP mode into a single-pulse mode, and finally returns to MCP mode. Analyses reveal that Penning ionization plays an important role in regulating the MCP performance. Under 10 ppm nitrogen content, the direct electron impact ionization predominates the total ionization process while Penning ionization is negligible. A relatively low pre-ionization level and seed electron level of incipient pulse (ne0) in this stage induce a strong incipient current pulse as well as MCP. As N2 content increases, the pre-ionization level and ne0 are enhanced due to the elevation of Penning ionization rate, leading to the smoothing of gap voltage profile and the annihilation of MCP at 10 ppm. Above 100 ppm, Penning ionization becomes the dominant ionization channel. As N2 content exceeds 300 ppm, the MCP reappears, which is believed to be resulted from a slump in metastable density owing to the excessive dissipation by Penning ionization. Beyond 1000 ppm, the strengthening of glow discharge structure at the incipient current peak phase contributes to the further increase of Jpm as well as pulse number.

Numerical investigation on the dynamics and evolution mechanisms of multiple-current-pulse behavior in homogeneous helium dielectric-barrier discharges at atmospheric pressure

A systematic investigation on the dynamics and evolution mechanisms of multiple-current-pulse (MCP) behavior in homogeneous dielectric barrier discharge (HDBD) is carried out via fluid modelling. Inspecting the simulation results, two typical discharge regimes, namely the MCP-Townsend regime and MCP-glow regime, are found prevailing in MCP discharges, each with distinctive electrical and dynamic properties. Moreover, the evolution of MCP behavior with external parameters altering are illustrated and explicitly discussed. It is revealed that the discharge undergoes some different stages as external parameters vary, and the discharge in each stage follows a series of distinctive pattern in morphological characteristics and evolution trends. Among those stages, the pulse number per half cycle is perceived to observe non-monotonic variations with applied voltage amplitude (Vam) and gap width (dg) increasing, and a merging effect among pulses, mainly induced by the enhanced contribution of sinusoidal component to the total current, is considered responsible for such phenomenon. The variation of incipient discharge peak phase (Φpm) is dominated by the value of Vam as well as the proportion of total applied voltage that drops across the gas gap. Moreover, an abnormal, dramatic elevation in Jpm with dg increasing is observed, which could be evinced by the strengthened glow discharge structure and therefore enhanced space charge effect.

Dusty plasma in a glow discharge in helium in temperature range of 5–300 K

Dusty plasma structures in glow discharge in helium in the temperature range of 5–300 K are investigated experimentally. We have described the experimental setup that makes it possible to continuously vary the temperature regime. The method for experimental data processing has been described. We have measured interparticle distances in the temperature range of 9–295 K and compared them with the Debye radius. We indicate the ranges of variations in experimental parameters in which plasma–dust structures are formed and various types of their behavior are manifested (rotation, vibrations of structures, formation of vertical linear chains, etc.). The applicability of the Yukawa potential to the description of the structural properties of a dusty plasma in the experimental conditions is discussed.

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.

Glow Discharge Characteristics in Transverse Supersonic Air Flow

A low pressure glow discharge in a transverse supersonic gas flow of air at pressures of the order 1 torr has been experimentally studied for the case where the flow only partially fills the inter electrode gap. It is shown that the space region with supersonic gas flow has a higher concentration of gas particles and, therefore, works as a charged particle generator. The near electrode regions of glow discharge are concentrated specifically in this region. This structure of glow discharge is promising for plasma deposition of coatings under ultralow pressures

Glow discharge in a transverse supersonic gas flow at low pressures

A low-pressure glow discharge in a transverse supersonic gas flow was experimentally studied for the case where the flow only partially fills the interelectrode gap. It is shown that the space region with supersonic gas flow has a higher concentration of gas particles and, therefore, works as a charged particle generator. The near-electrode regions of glow discharge are concentrated specifically in this region. This structure of glow discharge is promising for plasma deposition of coatings under ultralow pressures.

Efficient simulation of drift–diffusive discharges: application of the ‘complete flux scheme’

Fluid models have successfully explained the physics of a variety of plasmas. To solve the fluid model, the discretization scheme commonly used is the exponential difference scheme (EDS) (Sharfetter D et al 1969 IEEE Trans. Electron Devices 16 64–77). We present an extension of the EDS, the complete flux scheme (ten Thije Boonkkamp J H M et al 2011 J. Sci. Comput. 46 47–70) and show that for typical glow discharge models it is ten times more accurate.The Péclet number is the key parameter throughout the paper. A new interpretation of this number is presented. It is then used to explain the glow discharge structure and to formulate a necessary condition for the validity of the local field approximation.

On the spatio-temporal dynamics of a self-pulsed nanosecond transient spark discharge: a spectroscopic and electrical analysis

A self-pulsing discharge in flowing argon is investigated by means of electrical, optical and spectroscopic methods. The dependence of the discharge self-pulsing frequency on external parameters (applied negative dc voltage, gap dimensions) is determined, and optical and spectroscopic methods are used to investigate the discharge development with high spatial and temporal resolution. High-resolution spectroscopic measurements at several wavelengths reveal the complex dynamics of the transient spark discharge: a pre-phase at the needle tip and capillary edge, propagation of positive and negative streamers, creation of a transient glow discharge structure and a long-lasting afterglow. Excited plasma species necessary for the treatment of an exposed sample continue to be present even 80 µs after the breakdown of the active plasma.

Analysis of Dusty Plasma Structures Using Spatial Spectra of Their Images

Advantages of dusty plasma structure analysis using spatial spectra received by means of fast Fourier transform of dusty structure image are illustrated by simulated experiments and by processing actual images of dusty structures in glow discharge in inert and molecular gases. It is shown that this method allows discovering a hidden order in a dusty structure and that it is highly robust against noise.

Magnetic Force Microscopic Description of the Structure of Glow Discharge Nitrided Layers Produced on Ni27Ti2AlMoNb Steel

The paper analyzes the magnetic properties and stability of austenite, athermal martensite, and deformation martensite that form in Ni27Ti2AlMoNb steel subjected to glow discharge assisted nitriding, and also of nitrogen austenite (S phase with various lattice constants) which occurs when the nitriding process is conducted below the temperature As. The analysis of these structural components and their morphology was performed using a magnetic force microscope (MFM), whereas the phase composition of the nitrided layers produced on this steel was determined by X-ray diffraction.

Dusty plasma structures in He-Kr DC glow discharge

Ion drift in gas mixtures has certain properties that can be used to generate ion flows with desired characteristics. For example, when the field is strong, ion heating is significant, and there is a large difference in atomic weight between ions and atoms, the ion velocity distribution can be highly anisotropic. Ion distribution anisotropy, in turn, can cause a substantial change in properties of dust structures in plasmas. Experiments on dusty plasma structures in glow discharge in mixtures of light and heavy gases (helium and krypton) are performed, and results of numerical simulations of ion and electron drift in the mixture are presented.

DC atmospheric pressure glow microdischarges in the current range from microamps up to amperes

Electrical and spectroscopic results of comprehensive investigations of microdischarges in atmospheric pressure helium, argon, nitrogen and air at gaps less than 1 mm and over a large current range from microamperes up to amperes are presented. At distance shorter than 1 mm, electrodes influence the normal glow discharge structure and their electrical and optical parameters. Two oscillation discharge regimes were revealed in discharge current range comparable or less than the low-current limit of normal glow discharge.

Space–time development of low-pressure gas breakdown

In this paper we present an analysis of time- and space-resolved development of several regimes of low-pressure dc discharges in argon. These regimes include low current Townsend discharge, oscillations and constrictions of discharge and high current diffuse glow discharges. Our work is based on ICCD recordings of the discharge structure, synchronized with current and voltage measurements. Measurements were made at three different pressure × electrode gap parameters (pd = 250, 150, 45 Pa cm), at three gaps (d = 1.1, 2.1, 3.1 cm). Special attention is given to radial effects and the influence of dielectric walls during the development of the glow discharge structure. We were able to show how the space time-resolved structure of the discharge can lead to an understanding of the physics of the initial stages of gas breakdown and formation of different regimes of low-pressure discharge. The results also give the basis for interpreting formative time delays associated with gas breakdown.

Spatiotemporal Development of Low-Pressure Gas Discharges

We present an analysis of time and space resolved development of all typical regimes of low-pressure DC discharge in argon - low current Townsend discharge, oscillations and constrictions of discharge and high current glow discharges. Our work is based on time-resolved ICCD recordings of the discharge structure, synchronized with current and voltage measurements. Special care is given to radial effects and influence of dielectric walls during development of the glow discharge structure.