No 6 (2025)

The synthesis of fullerenes C₆₀ and C₇₀ in an electric arc in the atmospheres of various gases: argon, helium, krypton and hydrogen at pressures in the range of 0.01–0.1 MPa was investigated in this work. A stronger influence of gas-dynamic forces compared to the pinch effect on the possibility of obtaining a cathode deposit and a fullerene-containing soot with a falling volt-ampere characteristic was shown. The parameters of the electric arc, the structure of the cathode deposit and the possibility of its production in various gases were determined. Spectral analysis of gas samples after experiments using hydrogen did not reveal the presence of hydrocarbons in the working atmosphere of the reactor. Selective deposition on a metal substrate under the action of a high-voltage electric field made it possible to separate a finely dispersed mixture of fullerenes C₆₀ and C₇₀ contained in the arc discharge plasma. It was found that the fractional composition of the C₆₀/C₇₀ fullerene mixture changes depending on the value of the substrate potential.

Two interference techniques for measuring the surface profile of extended samples from 60 to 200 mm in length are developed. The profile is reconstructed by gluing separate frames taken with overlapping. It has been found that the angular reproducibility of the reconstructed profile in both techniques is less than 10 urad, which corresponds to a profile height difference of about 10 nm. When measuring surfaces with curvature radii R > 1 m, it is recommended to use the stitching technique on a highly coherent Zygo Verifire 4 interferometer, which provides a complete surface map. For surfaces with curvature radii R < 1 m, only the stitching technique on a SuperView W1 white light interferometer is suitable. For particularly important measurements, it is advisable to use both methods to achieve maximum measurement accuracy. The results of the study confirm the effectiveness of the proposed approaches in the field of interference metrological control.

The data from the LASCO/C3 space telescope onboard the SOHO space observatory are used to investigate the effect of solar energetic particles on the telescope's CCD detector. A special feature of the instrument is that it is located at the L₁ Lagrange point of the Sun–Earth system at a distance of 1.5 million km from the planet and is not protected from charged particles by the Earth's magnetic field. In the period from 2018 to 2024, a decrease in the instrument's sensitivity was detected at a rate of 0.94 ± 0.03% per year and an increase in the signal dispersion at a rate of 4.9 ± 0.1% per year. The main probable reason is an uneven decrease in the photometric sensitivity of the detector in different pixels. The effect of charged particles produced during large solar flares on the sensitivity of CCD detector was also studied. According to the data obtained, the influence of individual flares on the detector's sensitivity is insignificant and cannot be detected within the measurement error. However, this effect can accumulate, resulting in significant changes in CCD sensitivity over several years or more.

The paper presents the theoretical modeling results of the multilayer mirrors reflectivity based on rubidium and its compounds, designed to operate in the wavelength range of 11.4–17 nm and of interest to modern lithography and X-ray astronomy. Using a genetic algorithm, the problem of optimizing the multilayer design of such mirrors to achieve maximum reflection is solved, and a comparison of the theoretical reflection coefficients obtained in this work with modern developments of multilayer X-ray mirrors in the characteristic radiation regions of 11.4, 13.5, and 17 nm is presented. Due to the high chemical activity of pure rubidium, it is proposed to use a more stable compound for the potential practical implementation of rubidium-containing mirrors. It is shown that the use of boron carbide between the main layers of the mirror leads to a significant increase in their final reflection coefficient of the final mirrors and can be considered as a barrier method to prevent mutual diffusion between materials, however, experimental verification of this hypothesis is required. The integral reflection of an optical system containing a few multilayer mirrors significantly depends on increasing the reflectivity of a single mirror, thus justifying the prospects of using the proposed mirrors in the optical system of a modern lithograph.

The article simulates graphene moire patterns on an Ir(111) substrate. The difference in substrate and graphene periods leads to the formation of a moiré superstructure. This superstructure is periodic vertical deformations with hexagonal symmetry. The interaction between carbon atoms in graphene is significantly stronger than with substrate atoms. Therefore, graphene is not stretchable. Van der Waals forces determine the interaction between carbon atoms and substrate atoms. Lennard-Jones' potential models these forces. Surface potential replaces substrate exposure to carbon atoms. Our model calculates the surface potential in one unit cell and translates it using parallel transfer. The surface potential is the sum of the two-particle potentials for the atomic interaction. Comparison with experimental data and unification rules set Lennard-Jones potential parameters. The minimum energy determines the position of the graphene atoms. The simulation describes different orientations of the graphene crystal lattice relative to the substrate lattice. If the main directions of the two lattices coincide, then the period of the moire pattern has a maximum value of (2.54 ± 0.02) nm. This value is in good agreement with the experimental period 2.52 nm. The height of the graphene film above the substrate surface is calculated to be (0.330 ± 0.001) nm. Experimental measurements and ab initio calculations give a value (0.330 ± 0.005) nm. Rotation of the graphene relative to the principal directions of the substrate lattice results in a shorter moire period. A study of the dependence for the moire pattern period on the angle of rotation for the graphene crystal lattice relative to the substrate showed a nonlinear decreasing law.

Hydride phases TiZrTaV(Mo_1–xNb) and TiZrTaNb(Mo_1–xNi) (x = 0.2, 0.4, 0.6, 0.8) have been synthesized on the basis of a series of high-entropy alloys with a body-centered cubic lattice. The phase composition and type of crystal lattices of hydride samples were studied by X-ray diffraction. It has been established that the substitution of molybdenum with niobium or nickel in alloys leads to the formation of hydrides samples with crystal lattices of various types.

The paper presents the results of an experimental study of the integral characteristics of a laboratory model of a radio-frequency ion thruster with a beam diameter of 80 mm operating on krypton. A comparison of the obtained characteristics with the results of tests of the laboratory model using xenon as a propellant is carried out. The computational studies result to assess the impact of the transition to krypton on the accelerating grid resource of the thruster ion-extraction system and the efficiency of ion beam focusing are presented. The results of modeling the erosion process of the accelerating grid surface under the influence of the corresponding ions falling on the grid during operation are presented for xenon and krypton, taking into account the operating modes of the radio-frequency ion thruster laboratory model considered during the experiments. A number of studies have made it possible to evaluate the change in the integral characteristics of a radio-frequency ion thruster in the event of a transition to using a cheaper propellant compared to xenon. The obtained results can be used to optimize existing radio-frequency ion thruster models for krypton in order to achieve the highest operating efficiency.

The problem of contamination of the inner surface of the gas-discharge chamber of a high-frequency ion thruster with sputtered material of the accelerating electrode is considered. A physical and mathematical model of electrode surface sputtering by secondary ions is formulated using the sputtering indicatrix. The motion of sputtered atoms through the flow of primary beam particles is considered, and the conditions for the penetration of sputtered material into the plasma of the gas-discharge chamber are determined. The motion of impurity atoms through the gas-discharge plasma is considered taking into account the possibility of impurity ionization. It is also assumed that all impurity atoms reaching the chamber surface are condensed. Numerical modeling of surface contamination for a spherical gas-discharge chamber using carbon and titanium as the material of the accelerating electrode of the ion-optical system is performed, regardless to the chamber material. The angular distribution of particles penetrating the chamber is obtained, and the maximum velocity and localization of particle deposition on the surface of the gas-discharge chamber are estimated. The results are in satisfactory agreement with published experimental data.