Plasma Physics Reports最新文献

The breakdown and discharge ignition in discharge tubes with a diameter of about 1 cm and a length of 80 cm in inert gases (neon, argon, krypton, and xenon) at a pressure of about 1 Torr are studied experimentally. The tube is illuminated by radiation from continuous or pulsed light sources in the visible spectrum range. A ramp voltage with a small slope steepness (of about 50 V/s) is applied to the anode of the tube. Previously, the authors established that under these conditions external illumination can increase the breakdown voltage in several times. This effect was explained by the appearance of a charge on the tube wall as a result of photodesorption of electrons from its inner surface. In this work, it is found that charging the wall begins only when the anode potential approaches the breakdown potential measured without illumination. In addition, it is found that during the increase in the voltage on the anode and charging the wall, the anode potential differs from the breakdown potential by a constant and small value (less than 200 V).

The paper gives a systematic presentation of the Wigner function method (Weyl formalism) for modeling the propagation and absorption of electromagnetic waves in anisotropic and gyrotropic dissipative media with spatial dispersion. A general kinetic equation for the Wigner function (tensor) is formulated, and its asymptotic expansion up to the second order for smoothly inhomogeneous and weakly dissipative media is constructed. As a result, a modification of the method of the kinetic equation for rays is proposed, based on the stochastic description of rays, making it possible to increase the accuracy of numerical modeling of wave problems with strong transverse inhomogeneity of the absorption coefficient without increasing the amount of calculations. The technique developed can be used to describe the propagation, absorption, and scattering of electron-cyclotron waves in high-temperature plasma of magnetic traps for controlled fusion in cases where standard modeling methods do not provide the necessary accuracy.

The properties of a plasma sheath are investigated numerically by using a fluid model in which a monoenergetic electron beam is taken into account. To suit the realistic environment, secondary electrons emitted from the wall surface due to collision between the electrons and the wall surface is considered. The result reveals that the effective emission coefficient depends on the emission generated by a monoenergetic electron beam when the temperature of a monoenergetic electron beam is high. The effective emission coefficient of secondary electrons changes monotonically with the increase of emission coefficient generated by beam electrons. Using the Sagdeev pseudopotential method, a modified Bohm criterion can be obtained. It is found that the ion Bohm velocity increases with increasing beam electron energy and emission coefficient generated by a monoenergetic electron beam. Moreover, when the emission coefficient generated by a monoenergetic electron beam is small, the wall potential decreases with increasing beam electron energy and concentration. When the emission coefficient generated by a monoenergetic electron beam is large, the opposite is true. It is also shown that a monoenergetic electron beam can cause an increase in the critical effective secondary electron emission coefficient, and the increase is nonmonotonic.

Based on the two-dimensional resistive magnetohydrodynamics (MHD) model, this study explores the impact of shear flow on the resonant magnetic perturbation (RMP)-induced double tearing mode (DTM). The results indicate that the effectiveness of shear flow in suppressing the double tearing mode is primarily dependent on the flow velocity at the outer rational surface. A notable finding is that, with higher flow velocities, the double tearing mode is effectively suppressed. However, in cases of very weak flow velocities, the shear flow still exerts an influence, but with a limited suppression effect. Specifically, it can only inhibit the inner island, while the outer island continues to grow under the influence of the resonant magnetic perturbation.

The radiation field of a multi-dimensional plasma formation can be substantially asymmetrical. Often, the luminosity of such an object is determined using one-dimensional models with various correction factors to account for the nonsphericity. In this work, a model is presented for the determination of the luminosity of asymmetrical plasma formations based on consistent multi-dimensional radiation–hydrodynamics calculation on the example of the scenarios of supernovae with an equatorial disk. The simulations were compared with the observations of the supernova SN2009ip. The bolometric light curves were determined for the observation of this object in the disk plane and from the pole. A conclusion was made that it is impossible to describe the multi-dimensional structure of the radiation field within the framework of the one-dimensional model with correction factors and that, rather, a full three-dimensional simulation is required.

The ion-acoustic instability in the tails of meteoroids as a result of their passage through the Earth’s atmosphere is studied and the conditions under which it develops are given. The development of this instability occurs as a result of the relative motion of the plasma of meteoroid tails and the dusty plasma of the Earth’s ionosphere. Dust, in turn, creates conditions when this instability can develop in a situation of approximately equal ion and electron temperatures, which is observed in the plasma–dust system under consideration. The mechanism of the excitation of ion-sound waves as a result of the development of the ion-acoustic instability in meteoroid tails is shown. The growth rates of the ion-acoustic instability and the characteristic times of its development are found. It is shown that the instability has time to develop during the time of passage of a meteoroid body in the Earth’s atmosphere and the formation of a meteoroid trail, which has values much greater than the time of development of ion-acoustic instability in the system under consideration. The wave vectors and velocities of meteoric bodies, at which the development of the ion-acoustic instability is expected, are found. It is noted that the instability can reach a nonlinear regime at possible large wave amplitudes.

Electric field on the surface of a metal electrode covered by a continuous dielectric film and immersed in plasma is calculated at negative electrode potential Ψ when parameter eΨ substantially exceeds electron temperature T_e (left( {frac{{ePsi }}{{{{T}_{e}}}} gg 1} right)). It is established that strong electric field with a magnitude of 1–10 MV/cm can appear inside the film at plasma density of 10¹²–10¹³ cm^–3 and electron temperature of T_e = 10 eV as a result of charging of the outer film 10–1000 nm in thickness surface by a flux of positive ions from plasma. The magnitude of the electric field at film discontinuities is comparable to that inside the film. The magnitude of the electric field at the surface of the dielectric film and at the film-free clean metal surface in plasma is substantially lower than that inside the film. Strong electric fields inside the film and at its discontinuities can lead to electrical breakdown inside the film and at its discontinuities. The electrical breakdown of the dielectric film can initiate the unipolar arcing on metals, drive microplasma discharges and form centers of explosive electron emission on metal surfaces in plasma.

Physical principles and modern techniques for the formation of spontaneous vacuum ultraviolet radiation are described for three cases: the formation of line spectra of atoms, line spectra of multicharged ions and continuous spectra of excimer molecules. The parameters of the radiation sources are correlated with their applications: real and potential. The following schemes of the formation of vacuum ultraviolet radiation are described: H-type and E-type high frequencies discharges; discharge in a hollow cathode; glow, barrier, and arc discharges; high-voltage nanosecond discharge with a sharply inhomogeneous distribution of electric field strength in a gap; laser, discharge, and hybrid systems for multicharged ions formation; excitation of gas targets under conditions of gyrotron plasma heating. The review covers the state of the art over the last 20 years.

The formation of red plasma diffuse jets (PDJs) initiated by a capacitive discharge in air at pressures of 0.1–10 Torr is studied. Data on the dimensions and properties of plasma diffuse jets including counter-propagating ones with different and identical front polarities are obtained in a pulse-periodic discharge mode in a 15-cm-diameter tube. Photographs of the discharge glow in various modes are presented. It is confirmed that the emission of counter-propagating PDJs is suppressed at the same polarity of voltage pulses. It is shown that during a collision of unipolar PDGs formed from two generators the brightness of the discharge plasma between the ring electrodes increases.

The paper describes a method for generating aluminum and hydrogen plasma jets. It illustrates the formation mechanism of extended plasma structures produced during the combustion of a high-current vacuum-arc discharge. The current-carrying plasma front is shown to propagate at different velocities for aluminum plasma and hydrogen plasma. The hydrogen plasma has a substantially higher initial velocity (about 30 cm/µs) compared to the aluminum plasma (about 10 cm/µs). It is shown that the bulk velocity of the hydrogen plasma jet is about 9 cm/µs. It was proven by means of spectral diagnostics that the hydrogen plasma jet is indeed composed mainly of hydrogen.