Plasma Physics Reports最新文献

The work presents the results of experiments on the study of fast particle losses to the wall in the Globus-M2 tokamak under conditions of excitation of toroidal Alfvén instabilities using a pyrometer developed at the Ioffe Institute. Data on the time evolution of the wall temperature and local heat flux to the wall during the instability development are presented. The origin of the separation of these quantities into coherent and incoherent components is discussed. Experimental dependences of the increase in wall temperature and heat flux on the instability amplitude are considered. The results of the simulation of fast particle losses during the development of Alfvén-type instabilities are analyzed. Based on these results and experimental data, conclusions are drawn regarding the mechanism of fast particle losses during the interaction with an Alfvén wave.

Stationary states of electron beam with arbitrary velocity spread in a vacuum diode are studied. The velocity distribution function of beam electrons is assumed to be constant over a certain velocity range. The limiting current as a function of the velocity spread was obtained. It was ascertained that, within a certain range of parameters, stationary states with two types of virtual cathodes can exist.

Geometric parameters and shape of the RF antenna must be optimized precisely for efficient ion cyclotron resonance (ICR) heating of plasma by the magnetic beach method in electrodeless plasma thrusters (EPT). To this end, in the present work, we carried out full-wave simulation of the excitation of eigenmodes of the magnetized plasma column by ion-cyclotron (IC) antennas taking into account the radial inhomogeneity of the plasma column and spatial dispersion of the electron and ion dielectric response. Both the total energy deposited by the antennas into plasma and its distribution between the Alfvén eigenmodes of the plasma column and the Alfvén continuum were obtained as a result of the simulation. The simulation was performed for three most popular types of antennas used for the ICR plasma heating in the PS-1 setup. The efficiencies of these types of antennas are compared and the optimal length of each of them is determined.

This work presents a laboratory experiment on the formation of dusty plasma and the visualization of flows of charged dust particles ranging in a diameter from 10 to 100 µm. These particles consist of silicon dioxide, a component of lunar regolith. The influence of near-surface plasma simulated using an electrostatic field and ultraviolet radiation (UV) on the dynamics of regolith-analog particles is examined. Particle trajectories and changes in the surface topography of the particles are visualized, and estimates of their takeoff velocities are obtained. It is shown that the pattern of the particle motion in dusty plasma depends on the presence of UV radiation and the size of the particles themselves. The results of this study are of interest for understanding the physical processes occurring near the surface of the Moon and other atmosphereless bodies in the Solar System, such as Mercury, asteroids, and the moons of Mars.

Currently, the National Research Center “Kurchatov Institute” is developing an ion-cyclotron resonance (ICR) heating system for the T-15MD tokamak. The ICRF (ion cyclotron range of frequency) system is to be used to heat the ion component of the plasma and generate a non-inductive current (drag current). The total power of the system is 6 MW with a pulse duration of up to 30 s. Under these parameters, reflected power could lead to failure of the ion-cyclotron resonance heating (ICRH) of the system. Therefore, matching the load (plasma) to the generator requires special attention. This work presents a numerical study of the antenna–plasma coupling efficiency for a three-loop antenna developed for ICRF plasma heating in the T‑15MD tokamak. The dependence of the antenna impedance on plasma parameters, its position, and the phasing of the antenna excitation currents is studied.

In experiments on plasma heating during the passage of a relativistic electron beam with a current ~10 kA through a plasma column, the electric and magnetic fields of the beam have to be compensated by the current induced in the plasma, i.e., the so-called charge and current neutralizations of the beam have to occur. In the earliest experiments on injection of high-current relativistic electron beams into a plasma with a magnetic field, the effects of plasma neutralization of the electron beam’s internal electromagnetic field were observed. At the same time, the dynamics of these neutralization processes also depends on the ratio between the duration of the leading edge of the beam current and the flight time of its electrons along the plasma column length. This work describes the results of two substantially different series of experiments on the neutralization of an electron beam with a current of about 10 kA in a plasma column under a strong (4 T) leading magnetic field. In the first series of experiments, the leading edge of the beam current was ≈5 ns and its duration was about 50 ns. In the second series of experiments, the leading edge of the current beam was ~0.1 μs and its duration was ≈5 μs.

Traditional microwave resonator methods for plasma diagnostics face fundamental limitations at high plasma densities (n_e > 10¹¹ cm^–3) due to the response nonlinearity and resonant peak broadening. The search for alternative approaches that provide accurate measurements over a wide range remains a topical issue. In this work, the feasibility of using the TM₁₁₀ (E₁₁₀) mode of a cylindrical resonator (radius R = 45 mm, length H = 30 mm) to measure the electron density in a gas-discharge plasma excited by a surface electromagnetic wave is studied experimentally and numerically. It is found that the coupling coefficient C_v for the TM₁₁₀ mode remains constant in the range n_e = 10¹¹–10¹² cm^–3, ensuring a linear dependence of the resonant frequency shift on the plasma density. The TM₁₁₀ mode demonstrates resistance to the resonant peak degradation at high plasma densities n_e, in contrast to the TM₀₁₀ mode, where the signal suppression was observed already at n_e ≈ 3 × 10¹¹ cm^–3. The obtained measurement results are in good agreement with the results of plasma density measurements using the transmitted wave method and the integrated plasma luminosity, as well as with literature data. The proposed modification of the method is suitable for noninvasive diagnostics of the longitudinal electron density distribution of gas discharge plasma, including plasma antennas.

We investigate the formation of damped oscillatory shock structures in a cold, weakly collisional plasma using the hydromagnetic Adlam–Allen (AA) model. By incorporating a small, constant dissipation term (nu ) motivated by effective electron–ion scattering in the transverse direction, we derive a nonlinear second-order differential equation governing the magnetic field evolution. Using the Sagdeev pseudo-potential method and Jacobian linearization, we systematically classify the resulting structures in the phase space, revealing the conditions under which stable spiral and saddle-type solutions arise. Furthermore, by linearizing the governing equation near equilibrium points, we obtain explicit expressions for the field amplitudes, which exhibit damped harmonic behavior. Our analytical results offer a complementary perspective to prior numerical studies and provide deeper insight into the nature of weakly damped hydromagnetic shock waves relevant to space and laboratory plasmas.

The radial distribution of gas temperature in a DC glow discharge in pure oxygen in a Pyrex tube was measured in different discharge regimes in the pressure range 1–5 Torr. Analysis of the obtained results allowed us to determine the thermal accommodation coefficient for oxygen molecules on Pyrex: 0.26 ± 0.02. The thermal accommodation coefficient determines the spatial distribution of temperature in the plasma-chemical reactor, the kinetics of reactions with heavy particles in the discharge, and the rate of plasma-chemical processing of materials.