Estimation of Plasma Parameters using Radio-Frequency Resonance Technique

Numerical simulations and experimental measurements were combined to determine the ability of a plasma impedance probe (PIP) to measure plasma density and electron collision frequency in a plasma containing spatial gradients as well as time-varying oscillations in the plasma density. A PIP is sensitive to collision frequency through the width of the parallel resonance in the Re[Z]-vs.-frequency characteristic, while also being sensitive to electron density through the zero-crossing of the Im[Z]-vs.-frequency characteristic at parallel resonance. Simulations of the probe characteristic in a linear plasma gradient indicated that the broadening of Re[Z] due to the spatial gradient obscured the broadening due to electron collision frequency, preventing a quantitative measurement of the absolute collision frequency for gradients considered in this study. Simulation results also showed that the PIP is sensitive to relative changes in electron collision frequency in a spatial density gradient, but a second broadening effect due to time-varying oscillations made collision frequency measurements impossible. The time-varying oscillations had the effect of causing multiple zero-crossings in Im[Z] at parallel resonance. Results of experiments and simulations indicated that the lowest-frequency zero-crossing represented the lowest plasma density in the oscillations and the highest-frequency zero-crossing represented the highest plasma density in the oscillations, thus the PIP probe was found to be an effective tool to measure both the average plasma density as well as the maximum and minimum densities due to temporal oscillations.

Terahertz communication is thought of as a viable solution to the blackout issue induced by the presence of a plasma sheath. Previous studies have mainly focused on the external conditions such as the aerodynamic configuration and vehicle velocity on the terahertz communication, while neglecting the influence of spatiotemporal variations during the plasma evolution process and the angle of attack (AOA). In this work, the effect of plasma flow evolution and AOA on the terahertz communication is studied. Electron density and collision frequency distributions exhibit significant spatiotemporal variations during the plasma evolution process, leading to time-varying characteristics in terahertz propagation. And the steady-state of plasma sheath has a lower attenuation compared to the early and mid-stages. Furthermore, the influence patterns and mechanisms of AOA on the terahertz transmission are further explored. On the windward side, an increase in the AOA leads to higher electron density and collision frequency, while the plasma sheath thickness decreases, and the opposite trends are observed on the leeward side. Additionally, the electron density and collision frequency on the leeward side are significantly lower than those on the windward side, leading to reduced terahertz attenuation, and the lowest terahertz attenuation is observed at a smaller AOA of 4°. For an antenna position of L = 0.8 m, the critical terahertz communication frequencies for the leeward and windward sides are determined to be 0.1 THz and 0.16 THz. Finally, a communication scheme is proposed, recommending the leeward side as the communication end, combined with a smaller AOA of 4° and a frequency of 0.1 THz.

The research is focused on determining the plasma parameters such as electron temperature and density, and plasma and collision frequencies, that can be applied on plasma antenna simulation. From the characteristics of plasma parameters obtained, the antenna parameters are then investigated. The Ar-Hg discharge tube is used, and energized by using a high voltage power supply. The plasma parameters are obtained by using numerical programming namely Glomac based on the different voltage, current, pressure and size diameter of the discharge tube. Plasma antenna parameters are characterized by using Computer Simulation Technology (CST) software with different plasma frequency, gas pressure, tube size and material used to analyze the antenna performance. The plasma and collision frequencies are calculated based on the plasma parameter obtained from Glomac programming. It shows that the electron temperature decrease while electron density increase when the current is increased. The gas pressure and diameter of tubes are also influences the plasma parameters. From CST simulation, the antenna's performance can be analyzed in terms of return loss, resonant frequency, bandwidth, gain, and radiation pattern. The plasma frequency increase when the electron density increases. By changing the plasma frequency, gas pressure and tube diameter, the antenna performance can be improved in particular at their return loss, gain, directivity and conductivity. In addition, the efficiency of the plasma column as a radiating element is related to the conductivity of the plasma. From this study, the characteristics of the monopole plasma antenna is investigated and evaluated.

The refractive index n for electromagnetic waves in isotropic ionized mediums is given by [e. g., Budden, 1961a] n2=1−X/(1−iZ) where X = Ne2/ϵ0mω2, Z = v/ω, and the fields have the time factor eiωt, ω being the angular frequency. In these expressions, e and m are the charge and mass of an electron, N and v are the electron density and collision frequency, and ϵ≥1 and an approximate expression for n2 is often obtained by neglecting unity compared with iZ: X/(1−iZ)≐˙iX/Z Use of this in (1) gives n2≐˙1−i(ωr/ω) where ωr = e2N/ϵ0mv [e.g., Budden, 1961a, p. 103, and 1961b, p. 96]. For a medium with conductivity σ and relative permittivity ϵr, the refractive index n is given by n2=er−i(σ/ωe0) Thus, according to (3), the ionosphere at VLF can be represented by the quantities er≐˙1 σ≐˙e0ωr which are real and independent of frequency.

Solitary waves in a symmetric pair-ion plasma are studied as affected by various plasma parameters, e.g., electron density, collision frequency, ion temperatures, (r, q)-distributed electrons. In this regard, plasma fluid equations have been used to simulate the plasma system for which a reductive perturbation technique is applied to derive the relevant damped Korteweg–de Vries equation. The effects of spectral indices, collision frequency, ion-electron temperature ratios, and density on the time evolution of perturbed potential profile have been illustrated and benchmarked with Boltzmann distributed electrons. It is observed that the nonthermal population significantly affects the soliton amplitude, which increases with r and q. Furthermore, it also grows with electron density and ion temperature; however, there is a in the slowing down rate in the case of the latter. An increase in the collision frequency leads to faster damping in both the amplitude and speed of the solitary potential profiles. This work will be useful in the determination of plasma dynamics for pair-ion plasma systems containing nonthermal electrons, especially with flat-topped distribution functions, e.g., as found in Earth's magnetosheath and magnetotail, as well as in laboratory experiments with the fullerene plasma. To the best of our knowledge, a general description for pair ion plasmas using (r, q) distribution has never been reported. This study can explore a huge variety of velocity distribution functions—via the two index nonthermal parameters, in contrast to single index counterparts.

A 2mm microwave transmission interferometer is used to measure the electron density, collision frequency and electron temperature in order to study the expanding plasma of BSG I device. The electron density is above 2.5×1020m-3 at the peak and the microwave beam is cut off. The density decay below cut off is obtained from the phase shift and the density profile measured by floating double probes. Oversized waveguide of 10Ge/s, standard pyramidal horns of 25db gain andteflon lenses about 60mm infocal distance are used.

Electron temperature and density in pure He, Ar, and Xe plasmas are estimated by zero-dimensional particle and power balance equations and measured by a Langmuir probe. Both of the modeling and experimental results show that the He (Xe) plasma has the highest (lowest) electron temperature and lowest (highest) electron density for a given fill pressure and source power. We find that the electron temperature is weakly dependent on the rf power, and thus the electron density can be controlled using the rf power. The electron temperature and density are also modeled and measured in mixtures of two noble gas species. We find that the electron temperature can be controlled by altering the composition of the noble gas mixture. Thus modulation of noble gas admixture ratios and rf power allows the electron density and temperature to be controlled independently. This independent control is shown to maintained with the addition of up to 20% partial pressure of oxygen, suggesting binary noble gas admixtures may provide additional control of dissociation kinetics.

An experimental investigation of the impedance characteristic of a spherical plasma probe has been carried out for a quantitative assessment of theoretical work, and of hydrodynamic or fluid theory in particular. A stable, low temperature (T ∼ 500°K) plasma was produced in nitrogen by a cold cathode discharge, with a plasma frequency of the order of 15 MHz and with an electron collision frequency in the range of 106 to 107 sec−1. The probe consisted of two hemispheres, one serving as a guard to eliminate the effects of the connecting leads; this geometry provided an almost purely radial electric field over the test hemisphere. Probe diameters ranged from 7 to 20 mm (10 to 30 Debye lengths). Hydrodynamic probe theory was tested against the experimental results for the specific cases corresponding to the probe at floating potential and at space potential. Good agreement was obtained for both the real and imaginary parts. The real part of the impedance shows a peak near the plasma frequency, a small shift being explicable in terms of realistic sheath profiles. Electron density can thus be deduced rather accurately, and electron temperature approximately, on the basis of hydrodynamic theory. Accurate values of the electron‐neutral collision frequency were also obtained for plasmas where the collision frequency was larger than 0.4 times the radian plasma frequency. At lower pressures the presence of collisionless or Landau damping was clearly established, and the more accurate kinetic theory is necessary to explain the experimental results.

This paper presents an experimental study of an RF-DBD plasma, establishing how variations in operational parameters affect its characteristics and discharge behavior. The study identified the optimal parameters for plasma ignition – including pressure, applied power, and gas flow rate – and quantified their influence on key plasma characteristics, namely electron temperature, electron density, and Hα emission intensity as an optical indicator of hydrogen-containing species. Emission spectroscopy was employed to characterize the argon and argon-methane plasmas, with particular attention paid to the hydrogen Hα line (656.2 nm) in the mixture. For argon plasma, the electron temperature increased from ~ 0.98 eV to ~ 1.08 eV as the pressure was raised from 0.5 to 1.0 Torr at a constant discharge power of 4 W. Under the same pressure and power conditions, the electron temperature for an argon-methane plasma was approximately ~ 1.2 eV. A further increase in both power and gas flow rate leads to a decrease in electron temperature. Concurrently, the electron density was found to be on the order of 1014– 1015 m− 3. Material properties were examined using scanning electron microscopy (SEM) for morphology and Raman spectroscopy for structural analysis and defect characterization. The deposited carbon-based materials – films on the RF electrode and particles on the reactor wall – exhibited an amorphous structure. These findings elucidate the fundamental relationship between plasma parameters and gas conversion efficiency, providing a valuable framework for the controlled hydrogen production for energy applications.

Differential equation associated with electromagnetic waves in an inhomogeneous medium where ∇ε( r)· E vanishes

The influence of electric fields and neutral particles on the plasma sheath at ITER divertor conditions

Spectroscopic measurements are carried out to investigate the effect of plasma oxide surface coating of electrodes on impurity concentration and plasma parameters (electron temperature and density). Optical spectra (380–700) emitted from argon glow discharge plasma are recorded as a function of plasma oxidation time of electrodes. Emission intensity of the selected aluminum lines is measured as a function of electrodes oxidation time to study its effect on impurity concentration. Significant decrease in the impurity concentration is observed due to plasma oxide surface coating. The electron temperature is deduced from the ratio of Ar-I emission lines whereas the electron density is determined from the ratio of Ar-I and Ar-II emission lines. Both the electron temperature and density are found to increase with plasma oxidation of electrodes.

Kinetic Vlasov equation for collisional plasmas with BGK (Bhatnagar-Gross-Krook) collision integral is used. The case of arbitrary temperature (i.e. arbitrary degree of degeneration of electronic gas) is considered. From kinetic Vlasov equation the distribution function in square-law approximation on size of transversal electromagnetic field is received. The formula for calculation electric current is deduced. This formula contains one-dimension quadrature. It is shown, that the nonlinearity account leads to occurrence the longitudinal electric current directed along the wave vector. This longitudinal current is perpendicular to the known transversal classical current, received at the linear analysis. When frequency of collisions tends to zero, all received results for collisional plasma pass in known corresponding formulas for collisionless plasma. The case of small values of wave number is considered. It is shown, that the received quantity of longitudinal current at tendency of frequency of collisions to zero also passes in known corresponding expression of current for collisionless plasmas. Graphic research of dimensionless density of the current depending on wave number, frequency of oscillations of electromagnetic field and frequency of electron collisions with plasma particles is carried out.

There appears the elliptically rotated Faraday effect for microwaves transmitted through lossy plasmas with magnetic field. The detector signal of an electric field component of the wave through plasmas oscillates for the monotonous decrease of the plasma electron density, where the cyclotron frequency is higher than the applied frequency. It is shown that the electron density and the collision frequency can be cletei-Tnined from the maxima and the minima of the detector signal.From the detected microwave signal through an afterglow plasma in a waveguide in pressures of 2 and 5 mmHg in Neon or Argon, the electron density decays from 1012-1010cm-3 with time are determined for different magnetic fields from 3400 to 6000 Gauss. These decays show, reasonable values of trio recombination coefficient in the later period, where the electron energy rel, sxes to the thermal equilibrium with the gas temperature, because the recombination loss predominates for these afterglow plasmas with radial diffusion suppressed by the strong magnetic field.The collision frequencies of electrons with ions, which predominate over those with neutral atoms under this experimental condition are determined and plotted versus the electron density. A plausible explanation is discussed for these values somewhat higher than the theoretical ones.

This work used spectroscopic plasma emission analysis to investigate the parameters of ZnTi plasma formed in the atmosphere by a Q-switched Nd:YAG nanosecond laser system emitting infrared (1064 nm) laser light with an energy output spanning 200-500 mJ. The spectrometer was used to examine and record the emission spectrum profiles of (ZnTi), which helped to extract crucial plasma characteristics (i.e., [Formula: see text] and [Formula: see text]. The electron density was measured using the Stark broadening, and the plasma temperature was calculated using the Boltzmann plot technique. The electron temperature was between 2.04 and 2.15 eV, and the electron density was between (15.72 and 18.99) × 10[Formula: see text] cm[Formula: see text]. The Debye length ([Formula: see text], the number of particles in the Debye sphere ([Formula: see text], and the plasma frequency ([Formula: see text] can all be estimated from the electron temperature ([Formula: see text] and the electron density ([Formula: see text] ([Formula: see text].