Plasma Physics Reports最新文献

The possibility of implementing the magnetic beach method in the GOL-NB facility is analyzed. Based on the analysis of plasma transparency regions and numerical modeling in two-dimensional cylindrical geometry, the possibility of excitation of an Alfvén wave in GOL-NB plasma has been studied. For heating, it is proposed to use electromagnetic waves with a frequency of 13.56 MHz (resonance with protons in a magnetic field of 0.89 T). The antenna will be placed in a magnetic field of 1.3 T. It is shown that heating can be realized up to plasma densities of ~10¹⁹ m^–3, which will make it possible to significantly expand the range of plasma parameters available for the GOL-NB experiment. At a design density of 3 × 10¹⁹ m^–3 the introduction of RF power can help to heat the plasma periphery and improve the retention of hot ions in the trap.

The results of experiments on studying the plasma flow parameters in the strong-field sections of the GOL-NB open trap are presented. The strong-field sections were connected forming either uniform magnetic field (long magnetic mirrors) or the multiple-mirror configuration (the corrugation period was 22 cm, the number of corrugation periods was 13, and the corrugation depth was 1.4). The plasma flow parameters were studied using the Mach and Langmuir probes. The experiments were carried out at the electron and ion temperatures of T_e ≈ 20 eV and T_i ≈ 6 eV, respectively. In the output strong-field section, the on-axis plasma density was (1–3) × 10¹⁹ m^–3 at the end of the density accumulation stage and (3–5) × 10¹⁸ m^–3 in the decay stage. In this case, the plasma flow along the magnetic field was generally collisional, with the free path of ions being less than the corrugation period of the magnetic field. The differences in plasma accumulation and decay processes in the central trap, plasma flow in the output strong-field section, and MHD stability of plasma in the solenoidal and the multiple-mirror configurations are discussed. Possible ways for reaching plasma parameters required for efficient operation of multiple-mirror sections are considered.

The scheme and design features of classical multi-grid analyzers of charged particles are considered and their operation is analyzed. The errors in measuring the energy spectrum of charged particles in isotropic plasma using analyzers with cylindrical geometry are determined. It is established that the errors in recording the particle spectrum are caused by the small angular aperture of the classical analyzer, which is determined by the input aperture and the size of the collector. A new scheme of a multi-grid analyzer with a spherical collector, grids, and large angular aperture is proposed. It has been shown that a spherical grid analyzer allows for the measurement of the energy spectrum of charged plasma particles without significant distortion in the energy range from 1 to 1000 eV.

Under non-static limiting and non-steady conditions as well as the framework of non-extensive statistic, a novel set of nonlinear coupled equations describing the interaction between a space vehicle and wake-plasma is derived. Then the characteristics of modulation instability for both transverse and longitudinal perturbation modes is systematically studied. It is shown that the transverse modes play a major role in the formation of nonlinear localized structures. As the non-extensive parameter increased, the growth rates of the instability increased, while the characteristic scales of density cavitons and localized field decreased. And as the non-extensive parameter (q = 1), the results of Maxwellian case will be recovered. Furthermore, it is also found that the influences of the non-extensive parameter on transverse modes’ instability are more significantly than that of longitudinal modes. Therefore, selectively injecting energetic electrons into the wake region alters the characteristics of nonlinear localized density cavitons to make the stealth space vehicle difficult to detect accurately. For potential application of spacecraft stealth technology in ionospheric and plasma environments, the present work provides a significant theoretical basis for anti-detection.

The Moon’s exosphere contains dust particles originating from the lunar surface. Photoelectrons, electrons, and ions from the solar wind, as well as charged dust particles, form a plasma–dust system near the surface of the Moon. In dusty plasma near the surface of the Moon, the development of linear and nonlinear wave processes can be expected. This paper considers nonlinear waves: dust acoustic solitons and nonlinear periodic waves. The potential profiles of large-amplitude solitons and nonlinear periodic waves have been obtained, and the conditions under which the formation of such structures is possible have been determined.

Ultra-high-frequency 0.6-GHz modulation of a beam of high-energy electrons with an energy an order of magnitude larger than the charge–voltage product produced by the generator has been measured for the first time in the high-voltage diode of the Katran pulsed high-current relativistic electron beam generator (250 kV, 50 kA, 10^–7 s). The phenomenon is associated with the limitations of the operation of the generator’s high-voltage diode, whose current exceeds the Alfvén level. The operation scenario for high-current generators operating on a vacuum diode and a plasma load is being clarified.

This article presents the results of numerical simulation and an evaluation of the influence of several factors on the angular divergence of the electron beam velocities generated in a diode with a hot cathode and a plasma anode. The beam is designed to enhance the parameters and improve the transverse stability of the plasma in the GOL-NB open plasma trap. The aim of the study was to estimate the fraction of the beam current reflected by the trap input magnetic mirror. The limiting beam and plasma parameters specified in the model correspond to experimental data and estimates obtained by probe and other measurements. The combined effect of the cathode surface temperature and roughness, as well as the inclination of the external and beam magnetic fields to its plane, on the angular distribution of electron velocities is considered. The calculations show that for the cathode center with the greatest roughness, almost complete beam passage into the magnetic mirror with an aspect ratio of 60 is expected; the fraction of reflected electrons obtained was approximately 1%. For the rest of the cathode surface, the fraction of reflected electrons is negligible.

Studies have been conducted on a discharge with a hollow rectangular cathode and a mesh anode in a vacuum chamber, the dimensions of which significantly exceed the discharge geometric aperture. The measurements have been carried out using a combined optical-electrical probe along the discharge central axis both between the electrodes and in the post-anode plasma. For various plasma-forming gases (He, Ne, Ar, and Xe), spatial distributions of the following parameters were obtained: plasma potential U_p, concentrations N_e and medium energy (leftlangle u rightrangle ) of electrons, and the intensities of the luminescence of individual spectral lines. It has been established that for all plasma-forming gases, the region of plasma existence significantly exceeds the region limited by the aperture of the discharge system and a significant concentration of electrons is observed in the region behind the anode.

The dissipative-radiative instability (the effect of amplification on radiation) upon propagation of an electron beam in an infinite dielectric medium is analyzed. It is demonstrated that this type of instability can be interpreted as an instability of the slow wave emitted by the electron beam. The transformation of the stimulated Cherenkov effect in a slow-wave electrodynamic system into the effect of amplification on radiation with an increase in the transverse size of the system is analyzed. It is demonstrated that the nonlinear saturation of the dissipative-radiative instability is caused by the deceleration of the electron beam to the phase velocity of the slow electromagnetic wave, in contrast to an ordinary dissipative beam instability, the saturation of which is associated with the breaking of the slow wave of the electron beam.

Properties of nonlinear muon-acoustic waves (MAWs) propagating in three-component e^‒μ^‒i⁺‑plasma were studied. Linear analysis of MAWs was performed and the dispersion equation was derived. The analysis performed resulted in obtaining the exact expression for the linear velocity of muon-sound waves. By means of normalizing soliton velocity to this expression, its Mach number was obtained. Nonlinear analysis was performed involving the Sagdeev pseudopotential method. It was found that in the e^‒μ^‒i⁺-plasma, the stationary periodic subsonic MAWs can propagate, as well as supersonic muon-acoustic solitons (MA-solitons). It was also found that in MAWs, the muon and electron plasma components change in antiphase with each other. It was shown that in the e^‒μ^‒i⁺-plasma, in the case of relative electron density being equal to unity or somewhat less, the Mach numbers of muon-acoustic solitons can be abnormally high. Profiles of physical parameters in such hypersonic MA-solitons were calculated. It was demonstrated that the amplitudes of physical parameters characterizing hypersonic MA-solitons can be giant.