Theoretical Plasma Model Research Articles

Modulated dust-ion-acoustic waves result from Earth's magnetosphere and lunar ionosphere interactions

The Earth's magnetosphere's modulational amplitude dust-ion-acoustic waves are studied. When the moon passes through the Earth's magnetotail, its dust grains may interact, causing these waves. The theoretical plasma model for this study includes positive ionospheric ion fluids, isothermal electrons, and fluid-negative dust grains on the moon. A perturbation technique derived the nonlinear Schrödinger equation, which exhibited dispersion and nonlinear effects. The nonlinear and dispersion term coefficients' polarity may predict stable and unstable pulse domains. A numerical study was performed to identify unstable pulse domains and their connections with bright and rogue unstable modes. The effects of critical plasma conditions on these pulses' basic features have been studied. This study showed that increasing the ratio of ions to electrons temperature and density reduces system nonlinearity. Consequently, shorter unstable pulses are formed. Amplification of plasma unstable waves results in an increase in their intensity and energy, potentially impacting any device traveling through the area of impact.

Study on the Expansion Kinetics of Plasma and Absorption Wave Induced by Millisecond-Nanosecond Combined Pulse Lasers in Fused Quartz

The transient temperature field, the velocity and pressure of plasma, and the absorption wave of fused quartz induced by millisecond-nanosecond combined pulse lasers are simulated. The theoretical model of plasma and absorption wave produced by fused quartz irradiated by a millisecond-nanosecond pulsed laser is established, in which pulse delay and laser energy are essential variables. The results show that the damaged effect of the millisecond-nanosecond combined pulse laser is different under the damaged effect of different pulse delay conditions. When the energy densities of millisecond-nanosecond combined pulse lasers are 800 J/cm2 and 20 J/cm2, respectively, the range of pulse delay is 0 ms < Δt ≤ 3 ms, and the energy coupling efficiency is the highest when Δt = 1 ms. The addition of a nanosecond pulsed laser causes more obvious thermal damage and optical breakdown to fused quartz. The high pressure is concentrated at the plasma expansion interface or the shock wave front. The results can optimize the simulation parameters and be applied to laser plasma processing technology.

Computational Study of Charge Density Produced in N2:H2 Plasma Actuator

Numerical simulation of charge density produced in plasma actuators is dependent upon the development of models dealing with electrical properties. The main aim of this work is to investigate the characteristics surface charge density and space charge density of DBD plasma actuator. A simple design of surface dielectric barrier discharge plasma actuator is used in the study. The discharge gas was N2:H2 mixture with applied voltage equal to 1.5 kV. A theoretical plasma model is used to establish the charge density details. Results show that surface charge density increased in value and spread in width alone the exposed electrode as the voltage increased and reached to the amplitude value.
 HIGHLIGHTS
 
 In plasma diagnostics studies, charge density is one of the important parameter
 The paper includes simulation to charge density in plasma actuator with two gases which are N2 and H2
 The results very useful to follow up the electric field and flow of gases

Computational Study of Charge Density Produced in N2:H2 Plasma Actuator

Numerical simulation of charge density produced in plasma actuators is dependent upon the development of models dealing with electrical properties. The main aim of this work is to investigate the characteristics surface charge density and space charge density of DBD plasma actuator. A simple design of surface dielectric barrier discharge plasma actuator is used in the study. The discharge gas was N2:H2 mixture with applied voltage equal to 1.5 kV. A theoretical plasma model is used to establish the charge density details. Results show that surface charge density increased in value and spread in width alone the exposed electrode as the voltage increased and reached to the amplitude value.
 HIGHLIGHTS
 
 In plasma diagnostics studies, charge density is one of the important parameter
 The paper includes simulation to charge density in plasma actuator with two gases which are N2 and H2
 The results very useful to follow up the electric field and flow of gases
 
 GRAPHICAL ABSTRACT

Nonlinear electrostatic waves in the auroral plasma

Nonlinear electrostatic waves in a two-component magnetized plasma comprising of cold ions and suprathermal electrons following κ-distribution have been analyzed. The nonlinear electrostatic waves are considered to be propagating at an oblique direction to the ambient magnetic field. A parametric study of the effect of initial driving electric field amplitude (E0), wave Mach number (M), spectral index (κ), propagation angle (α) and ion drift velocity (δ) on the evolution and the existence domain of nonlinear electric field structures is carried out. The theoretical plasma model is able to generate electrostatic ion cyclotron and ion acoustic waves, with the variation in the initial driving electric field amplitude and Mach number. It is observed that with increase in the driving strength, the electric field structures evolve from sinusoidal to sawtooth to highly spiky bipolar waveforms. The presence of κ–electrons is perceived to reduce the initial driving strength required to generate spiky bipolar electric field structures as compared to Boltzmann-electrons. Further, the period of the waveforms were found to decrease with increase in κ. The electric field amplitude and the phase speed of the bipolar structures predicted by the theoretical model is found to be in the range of observed electric field and speed in auroral region by the FAST satellite.

Resonant instabilities of kinetic Alfvén waves in the Earth's magnetosphere with superthermal electrons

A theoretical plasma model for the generation of kinetic Alfvén waves (KAWs), having background Maxwellian ions, κ-electrons, and drifting Maxwellian beam ions, is discussed. The ion beam streams along the ambient magnetic field, whereas velocity shear is perpendicular to it. The role played by nonthermal electrons in the excitation of resonant KAWs with the velocity shear in the ion beam as the free energy source is examined. In the presence of κ-electrons, the effect of plasma parameters such as propagation angle, ion beam temperature, number density, and ion plasma βi on the growth of the KAWs is analyzed. It is found that nonthermal electrons restrict the excitation of KAWs by reducing the growth rate of the waves. It is inferred that a high velocity shear and ion beam density are required to excite KAWs in the presence of nonthermal electrons. The model is capable of producing waves with frequencies up to ≈18 mHz in the auroral region of Earth's magnetosphere.

Theoretical and experimental studies of the radiative properties of matter at high energy densities and their application to the problems of inertial confinement fusion

The paper presents the results of theoretical and experimental studies of the radiative properties of plasmas produced by heating and compression of various materials to high energy densities. The specific features of the theoretical plasma model known as the ion model, which is used to calculate the radiative characteristics of plasmas of complex chemical composition, are discussed. The theoretical approach based on this model is applied to the plasma produced during the explosion of the X-pinch wires. The theoretical estimate of the radiation efficiency is compared with the experimental data on the total energy yield from an X-pinch made of two different wires (NiCr and Alloy 188). The radiative characteristics of (C12 H16 O8) and (C8 H12 O6) plasmas are calculated for the temperature diagnostics of plasmas produced from porous targets employed in inertial confinement fusion experiments with the use of laser radiation and heavy-ion beams.

Mechanisms of a linear hollow cathode used for the production of a helium plasma sheet

A hollow-cathode device has been shown to operate as a plasma reflector for radar electronic beam steering using helium in the 0.2-0.5 Torr pressure range. Compared to former experiments, the use of this light gas reduces significantly spurious sputtering effect on the cathode materials. In a previous paper, a semi-quantitative physical model was developed to calculate the time evolution of the sheet reflectivity from the experimental current Id(t) measured across the discharge. A self-consistent, numerical, stationary model is now developed to describe the main physical mechanisms that govern the hollow-cathode source. The model describes the coupling between the high-voltage collisional sheath and the magnetized plasma through the hollow cathode. The cold electron creation rate includes the efficiency of ionization from the fast secondary electrons emitted from the surface of the cathode, lowered by the three-body recombination process in volume and by the ejection of a part of these fast electrons out of the cathode plasma. As the recombination rate scales as Te-9/2, the energy balance of the electrons must be solved precisely, so that the collisional-radiative exchanges in Helium are included in the model. The results are then compared to the experimental V-I characteristics for different pressures of the neutral gas; there is good agreement between the theoretical plasma model and the experiment.

Plasma dynamics from laser ablated solid lithium

Emission plasma plume generated by pulsed laser ablation of a lithium solid target by a ruby laser (694 nm, 20 ns, 3 J) was subjected to optical emission spectroscopy: time and space resolved optical emission was characterised as a function of distance from the target surface. Propagation of the plume was studied through ambient background of argon gas. Spectroscopic observations can, in general, be used to analyse plume structure with respect to an appropriate theoretical plasma model. The plume expansion dynamics in this case could be explained through a shock wave propagation model wherein, the experimental observations made were seen to fit well with the theoretical predictions. Spectral information derived from measurement of peak intensity and line width determined the parameters, electron temperature (Te) and electron number density (ne), typically used to characterise laser produced plasma plume emission. These measurements were also used to validate the assumptions underlying the local thermodynamic equilibrium (LTE) model, invoked for the high density laser plasma under study. Some interesting results pertaining to the analysis of plume structure and spatio-temporal behaviour of Te and ne along the plume length will be presented and discussed.

Observations of low-frequency mode in a multicomponent plasma with negative ions

Based on linear perturbation theory, a dispersion relation for low-frequency (LF) electrostatic waves has been derived in a multicomponent plasma containing negative ions. To relate the theoretical observations with experiments on the LF wave, the slower mode has been studied extensively for various plasma models. The experiment was carried out in Ar, F, and electron plasma in a double plasma device. The experimental observations on LF electrostatic waves yield the qualitative frequency variations due to the presence of negative ions. In the region of lower negative ion concentration, the mode decreases with the addition of a higher percentage of negative ion concentration while later, in the higher region of negative ion concentration, the variation shows the asymptotic behavior with negative ion concentration. Both the observations, theoretical and experimental, have shown a good agreement with each other. Moreover, a theoretical model of plasma with heavy negative ions has also been presented.

Analysis of DC magnetron discharges in Ar- gas mixtures. Comparison of a collisional-radiative model with optical emission spectroscopy

DC magnetron discharges in argon-nitrogen gas mixtures have been characterized by optical emission spectroscopy (OES). Optical lines from the cathode species (aluminium) and the gas mixture (argon, nitrogen) have been measured at constant total pressure, as a function of the gas mixture composition and electrical power. The experimental data are compared with results of a theoretical plasma model which solves self-consistently the Boltzmann equation for electrons and the kinetic equations for aluminium, argon, molecular and atomic nitrogen states. The emission intensity variations of plasma species have been analysed versus the nitrogen relative concentration and electrical power and compared with calculated populations of emitting species with a satisfactory agreement. The variation of aluminium density versus the nitrogen concentration has been deduced by using the line intensity and excitation rates given by the model.