Plasma Physics Reports最新文献

The effect of the dust grain flows on a spatial dusty structure in a stratum of a glow discharge in two inert gases (neon and argon) in a weak magnetic field was studied. The discharge parameters were determined that are necessary for the creation of three-dimensional dusty structures made from dust grains of the same size in both gases in a magnetic field. The dependences were obtained of the angular velocities of the dusty structures in the two gases on the magnetic field and on the gas pressure. The rotation speeds of the dust grains in the magnetic field were used to compare the ion fluxes acting on the dust formations.

A microwave discharge inside of a methane bubble in boiling water is modeled in a 0D approximation taking into account the change in the size of the plasma bubble. The process of quenching the reaction products after the bubble detaches from the electrode surface is also simulated. The working pressure is 1 atm. It is shown that the main reaction products are H₂, CO₂, and CO. The ratio of CO₂ and CO concentrations depends on the ratio of the initial flows of water vapor and methane. The calculated concentrations of the main decomposition products of methane and water are in good agreement with experimental data.

We calculate the photorecombination emission intensity, which determines emission from a hot plasma at thermodynamic equilibrium at a noticeable degree of ionization. In the case of air, the contribution of the short-wavelength emission in the range 60–100 nm to the total emission power is about 90%. Above 10 kK, this contribution is temperature-independent.

The most interesting new results are discussed that were presented at the LI International Zvenigorod Conference on Plasma Physics and Controlled Fusion, held from March 18 to 22, 2024 in Zvenigorod, Moscow region. The achievements in the main fields of research in plasma physics in Russia were analyzed and compared with those obtained abroad.

The results of the first gyrokinetic calculations of anomalous heat fluxes in the T-10 tokamak plasma obtained for typical conditions of a discharge no. 71 568 with ohmic heating are presented. The calculations have been performed at the Kurchatov Institute Supercomputer Center. The experimentally measured electron density and temperature profiles, ion temperature profiles with a large gradient leading to the so-called ion temperature gradient (ITG) turbulence, and also the profiles of carbon and oxygen impurity densities measured using the charge exchange recombination spectroscopy (CXRS) active diagnostics are used as input data. The “experimental” electron and ion heat fluxes are estimated from the heat balance condition using the ASTRA transport code. The analytical dependence of heat fluxes on the effective plasma charge is presented. Gyrokinetic calculations of anomalous electron and ion heat fluxes are performed for the T-10 tokamak for the first time. The well-known gyrokinetic GENE code is used in the so-called linear and nonlinear approximation with fixed density and temperature gradients taking into account the influence of carbon and oxygen impurities. A linear dependence of heat fluxes on the effective plasma charge is found, and the sensitivity of the results to input parameter errors is investigated. The results of gyrokinetic calculations for the T-10 tokamak are compared with the results obtained for facilities with similar input parameters. A comparison is made of gyrokinetic calculations of heat fluxes performed using the GENE code with the results of calculations by the CONTRA-T code, intended for the self-consistent simulation of low-frequency turbulence and transport processes in tokamaks with a large aspect ratio. Good agreement obtained in the work between the results of transport calculations using the ASTRA, GENE, and CONTRA-T codes based on various transport models for the ohmic discharge of the T-10 tokamak with a circular cross section, provides grounds for the further simulation of transport processes in plasma with additional heating and a more complex cross section shape of the plasma column.

In studies of impurity transport in quasi-stationary hot plasma, the initial kinetic equation and the diffusive-convective transport model take into account ionization and recombination as “sources and sinks” of particles. Due to the incompatible representation of the radial dynamics and charge kinetics of impurity charge states, this approach and the results obtained appear to be out of system. The basis for their systematic criticism is the ideas of the theory of random processes proposed by M.A. Leontovich in 1935 as a theoretical alternative to the gas-kinetic equation. In this case, the charge-radial transport of an impurity in a quasi-stationary plasma is defined as a syncretic vector random Markov process of charge state transport. Its coupling (ergodicity) in a two-dimensional Markov system excludes “sources and sinks” from it in principle, and the relaxation convergence is directed to the formation of equilibrium invariant density profiles. The impurity equilibrium and density profiles are specified by a system of invariant functions that provide analysis of any types of density profiles observed in experiments. Modeling of radial profiles of helium, boron and carbon impurities allows us to find variants of their transformation from accumulation in the center to concentration near the plasma edge, transport coefficients and systematic connection with plasma parameters.

The results of flyer acceleration up to the velocity of 10 km/s at the Angara-5-1 facility at the current of 5 MA by the magnetic field pressure are presented. 1D and 2D simulation of aluminum flyer acceleration is performed. The simulation results agree with each other and with the experimental data.

Selection of dust particles in three-dimensional plasma–dust trap in the electrodeless radio frequency inductive discharge in neon was studied for the first time. The discharge conditions and the discharge chamber design were chosen so that the dust structures of polydisperse quartz particles are created in the resulting dust trap. The structure lengths were of up to 1.5 cm and the number of particles in them was of up to 4000. Statistical analysis of the sizes of trapped particles has shown that under the conditions chosen the average particle size is close to 4 μm, and in a wide range from 0.25 to 1.0 Torr, it weakly depends on neon pressure. It was found that in the three-dimensional dust structure formed, the longitudinal interparticle distance changes in anomalously wide range, as compared to the dust structures formed in plasma of glow discharge. The characteristic size of the trapped particles was estimated based on the vertical balance of forces acting on dust particle. It was shown that, in terms of a number of parameters, the method of particle selection in radio frequency inductive discharge is preferable, as compared to similar method used in glow discharges in strata, and the dust trap applied can be used for studying three-dimensional dusty plasmas in the magnetic field.

The problem of calculating kinetic characteristics during electron drift in inert gases in a wide range of the reduced electric field strength: 0.001 Td < E/N < 10 000 Td is considered. For the case of a weak field E/N < 0.01 Td, there is little reference data, and the drift velocity, average energy, longitudinal and transverse diffusion coefficients and ionization coefficient for the cases of a weak field and a moderately strong field E/N < 100 Td were calculated using the method of dynamics of many particles involving collisions in accordance with the Monte Carlo procedure. For the cases of strong and superstrong fields 100 Td < E/N < 10 000 Td, the results of calculations for two models of electron departure from the system were considered and analyzed for the first time: (1) an avalanche model with multiplication; (2) a model with the most energetic electron in the system leaving the wall during the act of ionization or transition to the escape mode. Taking into account the appearance of new electrons in the system during ionization events under stationary current conditions made it possible to include the departure of electrons from the system to the wall with the determination of its potential into the consideration and, by analogy with the ionization coefficient, to introduce the definition of the electron runaway coefficient. For these two models, tabulated values of the electron runaway coefficient were obtained. An analysis and comparison of the calculation results with the table data was carried out. In addition, we present analytical approximations of the elastic and inelastic cross sections of electron–atom collisions depending on the collision energy that we obtained based on an analysis of the available theoretical and experimental data. They have physically reasonable asymptotics and can be recommended by us for widespread use.

Deuterium Z-pinch experimental studies [1] were carried out at the Angara-5-1 facility at a current of 2–2.5 MA with 100 ns rise time. Neutron yield in experiments ranged from 5 × 10¹⁰ to 8 × 10¹¹ neutrons per pulse. In order to explain experimental results, the two-dimensional MHD calculations were performed taking into account the generation of DD-neutrons using thermonuclear and beam-target mechanisms. MHD calculations of pinch dynamics, carried out taking into account the deuterium density distribution in the gas puff, satisfactory agree with voltage measurements. The neutron yield in the calculations ranges from 4 × 10¹⁰ to 1.5 × 10¹¹ depending on the deuterium density and the time delay between the start of gas puff and the moment of generator start-up. The energy of accelerated deuterons, which lead to neutron generation in the beam-target mechanism, is calculated to be from 55 to 900 keV, which is in satisfactory agreement with the estimates obtained [1]. An important difference between neutron generation in a fast gas Z-pinch and neutron generation in a dense plasma focus is that the contributions of thermonuclear and beam-target mechanisms to neutron generation in a fast gas Z-pinch are comparable, whereas in a dense plasma focus the main neutron generation mechanism is the beam-target mechanism.