Plasma Physics Reports最新文献

An estimate was made of the operational and measurement range for the “Reflectometry for the Electron Density Profile Measurements” diagnostics that is being developed for the T-15MD device. The latest changes related to the design of the diagnostics are discussed, parameters of the diagnostics components are presented, and the expected signal-to-noise ratio is given. Also, an assessment of the maximum tolerable level of density fluctuations for diagnostics is presented and compared with measurement results obtained on the other devices. This study is of interest for professionals who develop microwave diagnostics for fusion machines.

Proceeding from the Boltzmann kinetic equation for electrons, the system of multigroup equations for the zeroth, first and second moments of the electron distribution function is derived. The system includes equations for the balance of concentration, flux density and momentum flux density of electrons, and it is intended for numerical simulations of transport and kinetics of low-energy electrons in weakly ionized cold plasmas. The results of numerical calculations of electron swarm development in a uniform electric field in neon according to the developed multigroup model are compared with the results obtained by the Monte Carlo method to demonstrate the accuracy of the proposed model.

The paper presents the results of a study on the mass-to-charge composition of ions in the beam plasma generated during the evaporation of a solid-state ceramic target made of yttria-partially stabilized zirconia (YSZ) in an environment of inert and reactive gases by an electron beam in the forevacuum pressure range. Monitoring of the mass-to-charge composition of beam plasma ions was carried out using a modernized RGA-300 residual atmosphere mass analyzer. The influence of the working gas composition on the mass spectra of ions of the evaporated target material is shown.

An experimental and numerical study of the velocity field in distilled water occurring at the pre-breakdown stage when a voltage pulse is applied to the electrode-needle at different immersion depths has been carried out. The results obtained are analyzed in terms of the extremum (maximum) of the flow velocity achieved in the observation area in the immediate vicinity of the high-voltage electrode. Satisfactory agreement between the experimental and numerical time dependences of the velocity extremum and the calculation is obtained. It is shown that the maximum velocity in the emerging flow is achieved at later times with increasing immersion depth. A decrease in the immersion depth leads to an electric discharge when the high-voltage electrode loses contact with water because of the flow occurring near it. The studies performed show the further direction of the development of the constructed physical and mathematical model.

The present paper investigates the dynamical properties of dust-ion-acoustic (DIA) solitary waves propagating obliquely to an external magnetic field in a three-component plasma system containing positive inertial ions, inertialess electrons, and negatively charged stationary dust grains. The electrons are assumed to obey the Kaniadakis distribution as governed by the deformation index (kappa ), which varies between ( - 0.4) and (0.4). Applying the appropriate reductive perturbation method, the Korteweg–de Vries (KdV) and modified KdV equations are derived, and their soliton solutions are numerically investigated. The influences of ion temperature, obliqueness angle, dust concentration, external magnetic field, and (kappa )-deformed parameter on the propagation properties such as amplitude, speed, and width of DIA solitary structure are analysed in detail. It is observed that there can be both compressive and rarefactive DIA solitary structures admitted by the KdV equation due to the variation of dust concentration. As to the mKdV equation, which is valid only in a specific dust concentration, it permits the coexistence of compressive and rarefactive DIA solitary structures with finite amplitude in the plasma. The implication of the outcomes of this investigation may be admissible for understanding the behaviour of nonlinear electrostatic localized waves in space and astrophysical dusty plasma environments.

The radiation power of a high-current vacuum arc burning on copper electrodes has been measured. The radiation measurement range has been 100 nm ≤ λ ≤ 1100 nm. The developed measurement technique has made it possible to analyze the change in the radiation power depending on the arc current in the visible and ultraviolet parts of the spectrum, as well as in the vacuum ultraviolet region. The analysis of the obtained results indicates that the radiation power spectrum is redistributed in a vacuum arc with a strong anodic activity. The obtained results make it possible to estimate the fraction of radiation in the arc energy balance.

Results of spectroscopic measurements of the plasma radiation in microwave discharges in experiments on the synthesis of micro- and nanosized catalytic structures under the action of powerful microwave radiation pulses produced by a gyrotron (the wavelength of 4 mm, the pulse duration of 2–8 ms, and the power of up to 500 kW) on the mixture of magnesium Mg and titanium oxide TiO₂ powders have been presented. The experiments have been carried out in air. The radiation spectra of the microwave discharges have been recorded by a set of AvaSpec spectrometers of different types in the wavelength range from 219 to 920 nm. Spectral lines of neutral atoms and singly ionized ions of magnesium and titanium were recorded. The characteristics of the spectral lines are studied during the interaction of the microwave radiation pulse with the powder mixture and after its termination. The analysis of the obtained results shows that for titanium atoms, the condition of the local thermodynamic equilibrium (LTE) is fulfilled, which allows one to make reliable estimates of the electron temperature of the plasma, which varies from 0.2 to 0.4 eV. At the same time, for titanium ions, the LTE condition is not fulfilled in the microwave discharge. The comparable intensities of the atomic and ionic titanium lines in the discharges at the electron temperature of 0.2–0.4 eV, which is more than one order of magnitude lower than the ionization potential of titan, indicate that the plasma of the microwave discharge in the powder mixture is strongly inhomogeneous. The bands of titanium monoxide TiO recorded in the radiation of the microwave discharge indicate that plasma-chemical reactions occur in the discharge.

In a brief review, we discuss the processes associated with plasma self-organization in tokamaks, and the model of the self-consistent pressure profiles formation used in the energy and particle balance equations. Plasma self-organization can be interpreted as the formation of a structure consisting from chain of magnetic islands, each of which can form a self-consistent pressure profile. The convergence of island chains leads to anomalous transport, and their divergence leads to the formation of transport barriers. In the proposed model, the total energy flux Γ consists of two main parts: Γ₀ and Γ₁, where Γ₀ corresponds to a self-consistent pressure profile, and the anomalous turbulent flux Γ₁ appears, when the pressure profile is distorted by additional heating/cooling, as well as the neoclassical flux Γ_neo. The electron pressure profiles obtained by Thomson scattering in plasmas with magnetic islands and the effect of sawtooth oscillations on the anomalous Γ₁ flux are analyzed. We present examples of the plasma confinement deterioration due to the nonoptimal deposition of additional heating power, and the confinement improvement due to increased radiation losses at the edge, leading to diminishing the level of magnetic fluctuations, which can be associated with the divergence of the chain of magnetic islands or with a decrease in the size of the islands.

A movable assembly of a Langmuir probe and a fiber optic sensor was used to simultaneously measure the electron energy distribution function (EEDF) f(u), electron concentration N_e, and the plasma emission spectra I(λ) with a spatial resolution in a discharge in inert gases with reduced pressure supported by a hollow cathode. The dynamic range of the f(u) measurements was 5 orders of magnitude, and the observed spatial measurement ranges for N_e and I(λ) were up to 3 orders of magnitude. It was found that even small additions of xenon to helium resulted in significant changes in the EEDF shape, including spatial changes. The coronal model (CM) was used to calculate the spatial profiles I(λ) for a number of Xe lines in the discharge in the He–Xe (99 : 1) mixture using the measured f(u) and N_e. Even this simple model provides calculated intensities that, on the whole, agree satisfactorily with the measured intensities. The common method of measuring the electron temperature using the relative intensities of the spectral lines of atomic transitions is also discussed.

A chromatographic study of atmospheric pressure glow discharge products in a mixture of CO₂ and CH₄ has been carried out. The discharge has been ignited using a source at a frequency of 50 Hz and a discharge voltage of up to 10 kV. The main gas products at the discharge output are H₂ (∼55%) and CO (∼40%). It is shown that the discharge properties are determined by the ratio of CO₂ and CH4 consumption at the reactor input. Soot particles are formed in the discharge in addition to gas products at the same CO₂ and CH₄ consumption at the reactor input. The soot formation is suppressed and water vapor appears in the discharge when in the CO₂ content in the mixture increases. The discharge current and voltage oscillograms have been analyzed and the energy required to obtain hydrogen and spent on decomposition of СО₂ have been estimated.