Plasma Physics Reports最新文献

The formation of plasma on the surface of BaTiO₃ ferroelectric ceramics in an argon atmosphere in the pressure range 1 × 10^–5–1 × 10^–2 Torr has been experimentally studied. Based on the discharge voltage and current, the energy supplied by the driving pulse generator for plasma formation was investigated. It is shown that at argon pressures ≥10^–3 Torr, the fraction of energy spent on plasma formation increases significantly due to the growth of the discharge current. The elemental composition of the plasma was examined by optical emission spectroscopy, and the electron temperature and density were determined from analysis of Ar II ion spectral lines, taking into account the optical thin condition of the plasma and the McWhirter criterion. Local thermodynamic equilibrium in the plasma is achieved at argon pressures ≥10^–3 Torr. The dependence of the electron temperature and density on argon pressure has been determined. As the argon pressure increases, the electron temperature rises from 0.8 to 1.2  eV, while the electron density reaches (2‒5) × 10¹⁵ cm^–3. The concentration ratio of argon ions Ar II to Ba II and Ti II ions in the plasma has been determined over the studied pressure range.

Photoionization, the same as impact ionization, is one of the key processes affecting the development of streamers of both polarities in air and nitrogen–oxygen mixtures. To study the streamer dynamics in detail, a series of numerical experiments are being conducted in this work. The computational algorithm is based on a drift–diffusion model, in which the photoionization term is calculated in two ways: using an integral model (the Zheleznyak approach) and a differential model (a set of Helmholtz equations). The problems are solved in an axisymmetric setting in a cylindrical coordinate system on a uniform Cartesian grid. A constant potential difference of 25 kV is applied to plane circular electrodes with the radius of ({l_r} = 0.2;{text{cm}}) located at a distance of ({l_z} = 0.5;{text{cm}}). The interelectrode gap is filled with nitrogen under normal conditions with a small oxygen admixture of 0.05%. In all problems, the results obtained using both photoionization models are compared (the closeness of the solutions found is noted). The photoionization process is studied by the example of a cathode-directed streamer, and the photoionization and impact ionization rates are analyzed by simulating a two-headed streamer. The dynamics of a cylindrical discharge initiated at the anode from a ring of quasi-neutral plasma is studied.

PIC modeling of the formation of plasma current sheets has been carried out on the basis of laboratory experiments at the TS-3 facility. The study has been carried out using a hybrid method in the linear approximation, in which transverse plasma fields have been considered negligible, and the influence of the initial plasma parameters and external magnetic fields on the evolution of the sheet has been analyzed. The paper evaluates the influence of the studied parameters on the formation of the current sheet. The results obtained are necessary for a deeper understanding of the physics of solar flares and magnetospheric substorms, as well as for predicting their impact on the Earth’s magnetosphere.

The Cherenkov interaction of a relativistic electron beam with a magnetized, spatially confined plasma in a waveguide is numerically simulated using the KARAT code. This interaction underlies the operation of plasma masers, which are sources of broadband high-power microwave radiation. The study aims to verify the theoretical assumption that the radiation efficiency reaches a maximum when the ratio of the electron beam current to the maximum vacuum transport current is close to unity. However, the numerical simulation reveals that even doubling the current ratio does not cause substantial changes in radiation efficiency.

A detailed analysis of gas heating resulting from Joule dissipation in plasma produced by a helium dielectric barrier discharge (DBD) reactor is crucial for optimizing the operating regime and performance of the DBD system. The influence of gas heating on helium discharge characteristics was investigated experimentally and using a one-dimensional fluid model. Experimental study examines the visible light emission of a helium DBD lamp and evaluates the effects of applied voltage and frequency to optimize performance as an eco-friendly lighting alternative. The developed lamp is an efficient, mercury-free light source capable of replacing incandescent, fluorescent, and certain LED lamps that may contain toxic or heavy metals. The gas temperature evolution in the DBD discharge was determined using the heat conduction equation. To account for Joule heating, the heat transport equation was solved along the discharge gap distance. Coupling a 1D fluid model with the thermal conduction equation allowed us to calculate the temperature profile of the helium gas in the DBD discharge. We analyzed a DBD excited helium lamp under controlled conditions of 200 mbar pressure, 1500 to 2000 V sinusoidal voltages, and 20 to 50 kHz frequencies. The visible light intensity increases with applied voltage. Electrical measurements confirmed that the discharge operates in a homogeneous glow mode under optimal conditions. The plasma emission is due to the electronic relaxation of excited helium atoms and collisions with residual impurities such as oxygen. Helium’s ionization energy enables cold plasma generation, which reduces thermal effects and material degradation.

The formation and characteristics of cylindrical dust-acoustic (DA) solitary pulses are investigated in an unmagnetized warm complex plasma system consisting of adiabatic positively charged dust grains and nonthermal distributed electrons, ions, and positrons. By applying the reductive perturbation technique, the set of fluid equations in cylindrical coordinates that describes the plasma system under consideration is reduced to a ((3 + 1))-dimensional cylindrical Kadomtsev–Petviashvili (cKP) equation. An exact analytical stationary solitary wave solution obtained from the cKP equation is reported. It is found that our plasma system supports both compressive and rarefactive solitary pulses. The adiabaticity of positive dust grains and the nonthermal distributions of plasma species are shown to significantly modify the fundamental characteristics of positive and negative DA solitary pulses. These results provide deeper theoretical insight into dust-acoustic solitary excitations in nonthermal dusty plasmas, with relevance to both astrophysical and laboratory environments.

A theory of rotating partially ionized space and astrophysical plasma flows in the presence of density stratification is developed. For this very purpose, the anelastic approximation is implemented for the equations of Hall magnetohydrodynamics of rotating viscous and thermally conducting partially ionized plasmas. The theory developed considers large-scale compressibility of partially ionized plasma, though neglects the acoustic waves. In the case of no density stratification, the equations of Hall magnetohydrodynamics in the anelastic approximation reduce to the equations in the Boussinesq approximation for rotating partially ionized plasmas. Stratified inertial gravity waves, stratified whistler waves, stratified Alfvén waves and stratified magneto-gravity waves in the presence of rotation are found in the linear theory.

One of the most effective tools for depositing high-quality diamond films is plasma-enhanced chemical vapor deposition using microwave discharge. This paper examines the presence of an intense continuous spectrum in the radiation of such a plasma, the shape of which is similar to the Planck spectrum. It has been shown that the source of this radiation can be carbon nanoparticles, hypothetically present in the plasma volume. The temperature of the particles in the center of the plasma, estimated from the position of the maximum of the continuous spectrum, turned out to be about 2600 K, which, within the error limits, coincides with the gas temperature. Spatial measurements of both temperatures showed that the particles are in local thermodynamic equilibrium with the gas throughout the plasma volume. The spatial temperature profile of the particles shows a uniform zone with a radius of about 1 cm in the center of the discharge, the boundaries of which correspond to the region of uniform growth of the diamond film, both in thickness and in structure. The relationship between continuous emission of carbon particles in plasma and the homogeneity of growth conditions opens the possibility of using near-infrared spectroscopy for real-time monitoring of key parameters of the deposition process, which can be used to improve the reproducibility of the synthesis of high-quality diamond films.

For measuring the plasma ion temperature profile in the L-2M stellarator, passive spectroscopic diagnostic system in the visible spectral range was developed. The ion temperature profile in the ohmic heating regime was reconstructed using data on the Doppler broadening of the impurity ion lines: C III (464.7 nm), O II (441.5 nm), and O II (441.7 nm). Original computational code was developed for reconstructing the ion temperature profile. The radial intervals of correct reconstruction of the ion temperature profiles extend from the maximum of the radial intensity distribution of the corresponding lines to the plasma boundary. The ion temperature profiles reconstructed from the spectra of the C III (464.7 nm) and O II (441.5 nm) lines are in good agreement with each other.

A single-fluid theory of two-component rotating fully ionized space and astrophysical plasma is proposed. From the equations of two-fluid description of plasma, the equations for center of mass of the rotating plasma are obtained. In the obtained single-fluid equations, both the momentum conservation law and generalized Ohm’s law are modified because of the difference of ionic and electronic component’s masses. It is shown that the equations obtained describe the effects of skin-depth on plasma dynamics because of the consideration of electron inertia. New types of waves caused by extra restoring force because of rotation are studied: inertial whistler waves, inertial magnetosonic waves, and inertial Alfvén waves. It is found that considering the skin-depth effects in inertial whistler waves is crucial, since neglecting the depth of the skin-depth leads to the absence of rotation effects on the electronic component.