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Plasma potential is a key parameter in plasma discharge or fusion plasma to control plasma–wall interaction or ExB drift. The magnitude of plasma potential depends on the overall energy transmitted to the plasma via direct current (dc) or radio frequency (RF) devices such as electrodes or antennas. Knowing the plasma potential from the exciting source is useful to prevent high energetic fluxes to the wall or to improve the plasma confinement or explaining shear velocity. The aim of the present model is to calculate this plasma potential with respect to a dc or RF source in a magnetized or unmagnetized plasma. This double saturated probe (DSP) model takes into account the electron saturation current and is able to derive the plasma potential as a function of the electrode/wall area ratio for a dc or RF discharge in a helium/argon plasma with or without a magnetic field. The results of the model are compared with Aanesland’s model in the case of unmagnetized capacitive sheath and particle-in-cell (PIC) simulations. The magnetized model is applied to a plasma column with a perpendicular capacitive current in an RF discharge. It appears that the plasma potential can increase to almost the RF potential value at a low wall/electrode area ratio ($A_{\text {wall}}/A_{\text {el}}$ lower than 5), while the same potential collapses as soon as the area ratio (perpendicular over the parallel current area) is higher than the electron/ion saturation current ratio. This is directly due to the saturation of electron current, preventing the plasma potential from following the imposed RF potential by the electrode, so that the maximum value can be as lower as the floating potential. The perpendicular current involved is mainly a conduction current modeled as a resistive collisional current. In fusion plasma, the maximum plasma potential can rise to higher values than in plasma discharges, but the collapse of the potential still occurs for long collisional biased flux tubes. [ABSTRACT FROM AUTHOR]

The problem of dust-ion-acoustic (DIA) solitons is addressed in an electronegative collisionless dusty plasma with the presence of trapped-nonthermal electrons. To do this, we revisited the Cairns–Gurevich distribution that describes, concurrently, the evolution of the energetic electrons and those trapped in the plasma potential and analytically expressed its corresponding density. The modifications, due to the presence of this trapped nonthermal density, arising in small-amplitude DIA solitons propagation associated with both space and experimental plasmas are analyzed. In particular, we have found that, in both cases, a proportion of trapped nonthermal electrons relatively significant makes the solitary structure less spiky. Besides, we have shown that the amplitude and width of the experimental plasma soliton seem more affected due to the low ionic mass ratio. [ABSTRACT FROM AUTHOR]

In this article, a numerical model is presented, where the self-consistent spatial distribution of the plasma potential near isolated dust particles is calculated. The dust particles shape is ellipsoid of revolution. This article demonstrates large-scale studies of the characteristics of the “dust particle—ion cloud” system measured for the various parameters of dusty plasma. These parameters are the shape and size of dust particles, the strength of the external electrostatic field, and the ion mean free path. The approximations describing the system characteristics on the plasma parameters are presented. [ABSTRACT FROM AUTHOR]

This study investigates different geometry configurations for obtaining photoplasma in a gas cell of Na–Ar mixture. For this purpose, 2-D simulations with the fluid model of plasma have been conducted for single-chamber and two-chamber cells. For the studied range of pressure, the drift-diffusion approximation has been used. The simulation model is based on solving the continuity, momentum balance for charged particles, coupled with electron energy balance equation and the Poisson equation. Detailed plasma chemistry has been considered, and plasma parameters have been obtained, such as electron density and temperature, and the electric potential of the plasma. The obtained results show the effectiveness of the two-chamber cell configuration over the single-chamber one in generating a notable electromotive force (EMF). [ABSTRACT FROM AUTHOR]

Langmuir probe (LP) diagnostics is performed on an inductively coupled plasma (ICP) generated using a flat spiral antenna. The current–voltage (I - V) characteristics are measured using a radio frequency (RF) compensated LP to mitigate the effect of RF distortion in I - V measurements. All-important plasma parameters such as electron density (ne), electron temperature (Te), plasma potential (Vp), and electron energy distribution function (EEDF) are measured in a cylindrical-shaped ICP. The plasma is generated by feeding RF (13.56 MHz) current in the planer multiple spiral antennas. It is seen that the plasma is uniform over an area with 200 mm diameter, with an electron number density in the range from ~ 1011 to 1012 cm−3. Typically for plasma processing of materials, the required density fall in that region. Variation of plasma parameters is investigated as a function of applied RF power and operating pressure and the observed results are discussed. [ABSTRACT FROM AUTHOR]

Amorphous silicon (a-Si:H) thin films are deposited on silicon substrates by inductively coupled plasma chemical vapor deposition (ICP-CVD) using a flat spiral antenna and SiH4 as the precursor gas. The films are deposited at operating pressure of 20 mTorr and 50-W radio frequency (13.56 MHz) power fed to the antenna. Films are deposited by varying the distance (ds) between the dielectric (quartz) plate that isolates the flat spiral antenna from the chamber and the substrate location. Diagnostics of the Argon plasma generated under similar experimental conditions are performed using RF compensated Langmuir probe to get an idea about the variation in plasma parameters (plasma density, electron temperature, and plasma potential) along the axial direction (with the increase in ds). The deposited films are characterized for their thickness and various physical and electronic properties. It is observed that there exists a discernible dependence of the film characteristics and the coil to substrate distance (ds). It is also found that there is a correlation between the microstructural parameters and the optoelectronic properties as well as the electronic defect density in the films with the coil to substrate distance. An attempt has been made to correlate these observations to the plasma parameters studied by the Langmuir probe. [ABSTRACT FROM AUTHOR]

CO2 gas is being considered as one of the potential plasma forming gases in plasma arc material processes due to its thermophysical properties, cost, and easy availability. The understanding of the thermal behavior of CO2 plasma arc is essential for an effective utilization of it. However, the studies on CO2 arc characteristics are scanty. In this study, a 2-D axisymmetric model is built for the simulation of CO2 and Ar arcs with and without evaporation of anode. The thermal characteristics of CO2 arc are compared with those of Ar arc at different arc currents and anode materials. CO2 arc possesses higher temperature compared to Ar arc and the arc current strongly influences the temperature of CO2 arc. The anode flux in CO2 arc is higher compared to that of Ar arc and the effects of arc current and nature of the anode material on the same are stronger in CO2 arc. The arc heating efficiency in CO2 is higher than that in Ar and it reduces with increasing arc current. [ABSTRACT FROM AUTHOR]

To improve the technology of glow discharge polymer (GDP) thin film deposition and provide theoretical support for the deposition mechanism of GDP thin films, the plasma properties in a special cylinder (radial small size) inductively coupled plasma (ICP) reactor were investigated. High electron energy was observed in this reactor in contrast to radial large reactors. The electron energy relaxation length $\lambda _{\varepsilon } $ in the elastic range was calculated to determine the electron kinetics transition pressure. The electron energy probability functions were found to change from a bi-Maxwellian distribution to a Maxwellian distribution and then into a Druyvesteyn-like distribution. Furthermore, we observed the association ions $\text{Ar}^{+}(+$ Ar) generated by ion-molecule association reactions. In addition, the profiles of plasma parameters, such as the plasma potential $V_{p}$ , the electron density $n_{e}$ , and the effective electron temperature $T_{\mathrm {eff}}$ , were experimentally investigated with increasing gas pressure. [ABSTRACT FROM AUTHOR]

Modeling the dynamics of charged dust particles, confined in a glass box placed on the lower electrode of a Gaseous Electronics Conference cell, requires that the interactions between the charged dust, plasma, and boundaries need to be accounted for in a self-consistent manner. The charged lower electrode affects the plasma conditions throughout the glass box, altering the electron and ion densities and temperatures within the plasma sheath. These plasma characteristics determine the charge collected on the walls of the surrounding glass box, the electric potential within the glass box, the dust charge, and ultimately the dynamics of the dust. This paper describes the steps taken to build a simple model of the relationship between the plasma conditions and the potential within the box as well as the expected dust charge near the center of the box. The calculated potential and dust charge are used to construct acceleration maps for the dust, which are compared to experimentally measured acceleration of the dust within the box. [ABSTRACT FROM AUTHOR]

Helicon plasma sources are capable of efficiently ionizing propellants and have been considered for application in electric propulsion. The literature suggests that the ion acceleration mechanism is a current-free double layer. Previous work shows that single-stage helicon thrusters can produce thrust in the range of 1–6 mN, but it is unknown whether the thrust contribution is due to direct ion acceleration versus thermal expansion. The ion energy and current density profiles in the plume of a helicon plasma source are measured across a range of operating conditions: 343–600 W RF power at 13.56 MHz, 50–350 G, and 1.5-mg/s Ar at a pressure of 1.6\times 10^-5 torr-Ar. The plasma potential, electron temperature, and ion number density are also measured inside the discharge chamber and in the plume up to 60 cm downstream of the exit plane and 45-cm radially outward from the device axis. Ions are found to have energies in the range of 20–40 V, with total beam currents in the range of 7–47 mA. The plume has an average divergence half angle of 82°, either evenly distributed across all angles or focused at large angles to the centerline. From these measurements, it is found that the estimated thrust due to ion acceleration is far less than what has been directly measured on the same device in previous work. [ABSTRACT FROM PUBLISHER]

A heated emissive probe is a smart diagnostic tool for acquisition of the plasma potential in the discharge and in the plume of a Hall thruster. However, measurements of high-frequency oscillations of the potential require a specific electrical circuit with a low $RC$ time constant. We developed and tested an emissive probe system with a cutoff frequency of 1 MHz. Details about the low-pass filter design as well as first experimental outcomes obtained in the plume of a 200 W permanent magnet Hall thruster are given in this paper. [ABSTRACT FROM PUBLISHER]

An experimental investigation is carried out to quantify the potential of the plasma plume emitted by an ion thruster type plasma source. A capability for efficient 2-D measurements of the plume profile is developed. The effects of plume expansion, plume charge-exchange (CEX) plasma, and facility background plasma on plume potential are investigated. For plasma source and vacuum chamber operating conditions considered in this paper, we find that the propellant CEX plasma is the primary factor that terminates the plume expansion process, and thus largely controls the magnitude of the plume potential with respect to the ambient. [ABSTRACT FROM PUBLISHER]