Vol 51, No 4 (2025)

The applicability of several signal processing methods is analyzed for local magnetic probes experimental data aimed at determining the poloidal mode number (m) of MHD perturbations in the plasma of a tokamak with a non-circular cross-section. These include two-dimensional Fourier decomposition, the Hilbert transform method, singular value decomposition, and the phase matrix method. These methods have been applied under the conditions of the D-shaped cross-section of the T-15MD vacuum chamber and have shown good results in determining the poloidal wave numbers of MHD perturbations for both synthetic and experimental local magnetic probes signals. The results of processing experimental data from local magnetic probes demonstrate good agreement with those obtained using the T-15MD soft X-ray diagnostic.

A deterministic numerical model is proposed for the time-evolution of the ion distribution function in an axially symmetric open trap. The model assumes the only flux tube with a uniform distribution of parameters over the cross-section. The phase space is parameterized by the total energy and magnetic moment. The Rosenbluth-Trubnikov potentials are calculated using angle-averaged distribution functions. The Maxwellian distribution of electrons with the same temperature in the entire computational domain is assumed.

Relativistic self-trapping of a relativistic-intensity laser pulse during its propagation in a transparent high-density plasma is accompanied by the generation of ultra-bright synchrotron (betatron) radiation of the super-hard X-ray range. The paper studies the effect of the duration of a laser pulse of a given energy on the characteristics of such radiation. It is shown that the already available compression of powerful laser pulses significantly increases the efficiency of conversion into synchrotron radiation, and also increases the brightness of the X-ray source by an order of magnitude.

Phobos and Deimos are atmosphereless celestial bodies with a weak gravity. Their surfaces consist of small regolith grains that are not connected to one another and have appeared due to bombardment with micrometeorites. Their weak gravity makes these bodies interesting for piloted flights and increases the role of dust, since even a small perturbation leads to the creation of massive dust clouds above their surfaces. The surfaces of these satellites of Mars are charged by the electromagnetic radiation from the Sun and the plasma of the solar wind. The dust grains located at the surface and in the near-surface layer absorb the photons, photoelectrons, electrons, and ions of the solar wind, and, as a result, they obtain electric charge. The action of the electrostatic force under the weak gravity conditions leads to the detachment of dust grains from the surface and the creation of a dusty plasma system together with the electrons and ions. In the dusty plasma system above the surfaces of Mars's satellites, dust acoustic waves can propagate. In this work, we consider nonlinear periodic and solitary dust acoustic waves with an arbitrary amplitude, which can propagate near the surface of Phobos and Deimos, and discuss the possibility of observing these structures.

The paper presents the results of one of the first experimental campaigns on the experimental stand HPS-2 (helicon plasma source, 2 kW) for studying the plasma-material interactions, designed and manufactured at the NRC “Kurchatov Institute”. The discharge parameters were measured using a set of probe diagnostics. Based on the obtained experimental data, the optimal values of the magnetic field and the flow rate of the working gas for this configuration of the device were selected, the possibility of obtaining plasma with a density of about 1011 cm-3 was demonstrated. The influence of the position of the RF antenna in a decreasing magnetic field relative to its maximum was studied.

The probability of heterogeneous recombination of hydrogen atoms, γH , on the surface of a Pyrex tube in a direct current medium-pressure pure hydrogen (2–7 Torr) glow discharge was measured in dependence on the pressure and discharge current for two wall temperatures. It was found that there is no dependence of the recombination probability on the pressure and discharge current provided that the tube is pre-trained in a hydrogen discharge. During the tube training, γH decreases with a characteristic time to reach a steady-state value of ~30 minutes. Analysis of the possible recombination mechanism using quantum chemical methods revealed that the recombination of hydrogen atoms on the Pyrex surface is associated with OH radicals and oxygen vacancies on the surface, and the dynamics of γH can be explained by the recombination of surface OH radicals during tube training.