Plasma Physics Reports最新文献

The set of equations is obtained that describes the nonlinear three-dimensional dynamics of magnetosonic waves. Plane solitary waves propagating at a small angle to the guiding magnetic field have been studied. Three-dimensional spatially localized waves have been qualitatively studied.

Plasma was heated at the second harmonic of electron cyclotron resonance (ECR) in the L-2M stellarator and the T-10 tokamak. The concept of equivalent tokamak and stellarator discharges was extended to the case of both full and partial absorption of EC power. Comparison of experimental electron temperature profiles with profiles calculated using the canonical profiles transport model allows us to estimate the efficiency of ECR heating in the L-2M discharges without suprathermal electrons, which distort the distribution function, preventing reliable measurements of temperature. The dependence of the ECR heating efficiency on the plasma density was obtained, describing experiments on the L-2M and TJ-II stellarators, and on the T-10 tokamak. The energy characteristics (the stored energy and the confinement time) for L-2M discharges were calculated. Predictions for ECR heating in the T-15MD tokamak are considered. The features of solving the ill-posed transport problem for the L-2M are discussed.

The results of a study of a pulsed short-arc unlimited high-pressure xenon discharge as a source of UV radiation are presented. A theoretical analysis of the possibility of increasing the efficiency of xenon discharge radiation in the UV region of the spectrum is performed, the design of a three-electrode flash lamp is described, and the electrical, brightness and spectral characteristics of the source being developed are studied.

A method for activating water by plasma of an electrodeless torch discharge in a microwave electromagnetic field in argon in an environment of water vapor, at atmospheric pressure, to obtain a pure solution of hydrogen peroxide H₂O₂ without impurities in distilled water is proposed. It is shown that the main mechanism for the formation of atomic hydrogen H^• and hydroxyl HO^• radicals in the water decomposition is photolysis under the influence of excimer vacuum ultraviolet radiation of argon plasma. Hydrated electrons can be an additional source of radicals in liquid water when the plasma torch comes into contact with the water surface. Today plasma technologies are widely used to produce activated water containing hydrogen peroxide, to solve environmental problems, to increase productivity in agriculture, and for medical use.

The effect of the spatial distribution of electric potential on the separating properties of the plasma mass separator that operates in a configuration with crossed radial electric and longitudinal magnetic fields is studied. The single-particle approximation is used to obtain analytical expressions that connect the electric potential distribution and the angular mass spectrum. A mathematical algorithm is described that allows one to recover the distribution of electric potential from the given shape of the mass spectrum. It is shown that the local inhomogeneity of the electric potential profile allows one to achieve the deposition of mass groups in the diametrically opposite regions of the separator. Data is presented that confirms the possibility of creating experimentally both the positive and the negative local inhomogeneity of the potential. The results of this work can be used to increase the efficiency of the process of plasma mass separation of ions of different elements.

A one-dimensional (1D) fluid model is developed to investigate the effect of multi-frequency excitation consisting of (N) consecutive harmonics on the charge of a single dust grain in a weakly collisional capacitively coupled plasma discharge. The spatial distributions of the electron density, the electrons temperature, and the charged particle flux are obtained and analyzed under the effects of the number of harmonics. It is shown that the number of harmonics considerably affects the discharge properties and the sheath thickness. In order to analyze the charge of an injected dust particle under the effect of different operating parameters, the model takes into account the electron and ion currents, as well as the effect of collisions between ions and neutral atoms. The results showed that as the number of harmonics increases, the particle charge increases in the powered sheath region while it decreases in the grounded sheath due to the electrical asymmetry effect. However, the charge remains constant in the central region where the electron temperature is constant. The present study further shows that the gas pressure and the driving frequency affect the dust charge oppositely, where an increase in pressure leads to a decrease in the dust charge, especially in the sheath regions, while the particle charge negatively increases as the driving frequency increases for all excitation waveforms.

Using chromatography, the gas composition in a cold plasma jet, which is a flowing afterglow of a microwave glow discharge at atmospheric pressure, is analyzed. The plasma jet is formed by the interaction of the discharge plasma with atmospheric air behind the outlet of the 6-electrode plasma torch, electrical power to which is supplied from the waveguide microwave (2.45 GHz) plasmatron. An analysis of the gas samples of the jet shows that when plasma-forming argon flows through the microwave discharge, hydrogen and methane are formed behind the discharge region, and the concentration of carbon monoxide increases by 5–6 times. The reactive oxygen species in the cold plasma jet is studied using liquid chromatography of an aqueous solution of isopropyl alcohol after treatment with the plasma jet. It is found that because of plasma treatment, partial oxidation of isopropyl alcohol to acetone occurs. This makes it possible to consider acetone as an indicator of reactive oxygen species (hydroxyl radicals, atomic oxygen and ozone) in a cold plasma jet.

Using a numerical solution of the Boltzmann equation, the electron drift velocity, the coefficients of their longitudinal and transverse diffusion, as well as the ionization and dissociative attachment coefficients in weakly ionized plasma of mixtures of air with water vapor are calculated in a wide range of reduced electric fields (1–650 Td, 1 Td = 10^–17 V cm²) and mole fractions of water vapor (0–1). The calculation results are compared with new experimental data, and good agreement between them is obtained. It is shown that for all coefficients and the average electron energy, their dependence on the gas composition changes with increasing electric field. At low reduced fields, an increase in the content of H₂O water molecules in mixtures leads to a decrease in the transport coefficients and average electron energy, while the opposite trend is observed at high fields. It is shown that for the drift velocity and electron attachment coefficient there are electric fields, in which these coefficients in gas mixtures can be greater than the coefficients in dry air and water vapor. A qualitative explanation is given for the obtained dependences of the electron coefficients on the electric field and H₂O content in the mixtures.

The problem of signal amplification in a plasma microwave amplifier is considered in the linear approximation and with allowance for nonlinear effects leading to saturation of instability. The solutions of the exact dispersion equation and an approximate dispersion equation used in calculation of parameters of plasma microwave amplifiers are compared. It is shown that the solutions of these equations in the region of high frequencies are significantly different. Nonlinear dynamics of beam–plasma instability in plasma microwave amplifiers is described by a system of differential equations which is obtained by the slowly varying amplitude method and yields an approximate dispersion equation when it is linearized. A method for modifying parameters of a nonlinear system of differential equations to make it consistent with the exact dispersion equation is proposed and the calculation results are demonstrated.

Proceeding from the Boltzmann kinetic equation for electrons, the system of multigroup equations for the zero and first moments of the distribution function of low-energy electrons is derived within the Lorentz approximation. The system includes the balance equations for concentration and flux density of electrons and is intended for numerical simulation of the transport and kinetics of electrons in the energy range from zero to several tens of electron volt where the angular distribution of electrons is weakly anisotropic. Results of the numerical calculations of electron transport in helium in homogeneous and inhomogeneous electric fields according to the developed multigroup model are compared with results obtained by the Monte Carlo method.