Russian Physics Journal最新文献

The paper determines output characteristics of a photoconductive semiconductor switch with high gain and maximum pulse operating voltage of 32 kV at a load of 50, 25, 4.3 Ω and 42 mΩ at a 10 kV charge voltage when exposed to laser radiation with a wavelength of 355 nm and 25 µJ optical energy. The switch is irradiated with the laser beam with autograph in the form of an elongated ellipse ~300 µm wide and 14 mm long. The resulting output pulses are 56, 71, 106 A at a load of 50, 24.8, and 4.3 Ω, respectively. At these values, the current and resistance parameters change similarly to those observed at the coaxial line discharge to the load. In the case of switching to a 42 mΩ resistor or to a short-circuited section of coaxial line, a received bipolar signal matches the discharge duration of the forming line that strengthens the potential for switch application in a microwave compressor.

The behavior of carbon nanoparticles C₅₀ heated in a nitrogen atmosphere at a pressure of 0.1 MPa is studied using the method of computer thermodynamic modeling. The simulation consists in a complete thermodynamic analysis of the system using the TERRA software package. The temperature range of the experiment is from 273 K to 3373 K. A graph of the carbon balance in the C₅₀–N₂ system is constructed, and the ongoing physico-chemical processes, divided into four classes, are described. The equilibrium constants of the reactions with an isolation of the temperature intervals are calculated.

The paper presents testing results and certification of VMM3a integrated circuits, which are planned to be used in the data acquisition system in the spin physics detector experiment on the NICA collider. The key parameters of the circuits evaluated during testing, include the power consumption, amplitude and time measurement accuracy, response correctness in various operating modes. The obtained results are used to identify circuits matching the experimental conditions and units with defects.

The formation of a high-frequency electromagnetic pulse in a transmission line, partially filled with saturated ferrite surrounded by insulating dielectric, fed with a nanosecond-risetime high-voltage pulse, is studied in a numerical experiment based on solving the Landau–Lifshitz equation along with Maxwell’s equations. The ferrite dielectric properties are taken into account in a constant-permittivity approximation. An analysis of the energy exchange of the electromagnetic wave with the magnetization and dielectric polarization currents in the ferrite demonstrates that the energy is primarily transferred through the magnetization current wave. The role of the dielectric permittivity of the gyromagnetic medium, which is much higher than that of the surrounding dielectric, consists mainly in slowing down the wave, ensuring an effective excitation of gyromagnetic precession at the pulse front and its steepening.

The paper studies the interaction between the relativistic electron beam and electromagnetic resonances in the Cherenkov generator with the single-section slow-wave structure using the 2.5D hybrid particle-in-cell code. In numerical simulation, the tubular beam current of ≤ 25 kA and ≤ 490 keV energy are used to inject the electron beam into a homogeneous slow-wave structure of a diameter 40 mm with and without a diffraction reflector. The frequency range is 362 to 367 GHz. Parameter ranges are obtained for the stable radiation generation with synchronization of electromagnetic resonances by the electron beam and self-modulation of radiation power. With the diffraction reflector, the total power of stable radiation is 400 MW with the forward radiation power of 90%, regardless of power ohmic losses. Resonance magnification modes are detected for the radiation power in the narrow range of the electron energy, which match the radiation frequency near the third-order electromagnetic resonance with no electron beam.

The paper presents numerical simulation results of elastic deformation of cylindrical bodies during the dynamic impact against a rigid wall. Dependences are suggested for the recovery factor of the striker initial velocity and Poisson’s ratio of different materials. This recovery factor is defined as the energy expenditure of striking elements on strain potential energy which depends on Poisson’s ratio. The finite element method (FEM) is used to simulate an impact of plates, cylinders of a compact shape and thin cylinders against a rigid wall. Two series of calculations are carried out for different materials to study the influence of Poisson’s ratio on cylinder deformation. In the first series, the cylinder material is isotropic, while in the second, it is anisotropic auxetic with different orientations of symmetry axes relative to the loading axis. Tetrahedronal elements are used in FEM to simulate deformation. It is found that the higher Poisson’s ratio of the cylinder material, the more kinetic energy converts to potential energy.

In the present work, the deformation behavior of bimetal specimens consisting of BCC and FCC grains is studied by the molecular dynamics method. The influence of crystallographic orientation of grains on uniaxial compression and tension is analyzed. The α‑iron grains interfacing with copper or nickel are investigated. The choice of FCC metals is governed by different levels of the specific stacking fault energy. The results obtained show that deformation of bicrystals can develop either in one or both grains. This is determined not only by the material and its strength properties, but also by the crystallographic anisotropy of these properties with respect to the loading direction.

The paper evaluates the morphofunctional properties of silver nanoparticles in gel compositions using either sodium alginate or gelatin as a gelling agent. It is shown that gelatin in the concentration of 0.9%, enables the composition to incorporate a significant amount of the most functional silver nanoparticles, ranging in size from 1 to 15 nm (76.2%). In contrast, at 0.9% of sodium alginate, a substantial (over 50%) content of nanoclusters ranging in size from 41 to 100 nm, is observed on SEM images. This suggests the need to reduce the concentration of this gelling agent to form the basis for hydrogel wound dressings. In this case, it is necessary to account for the material properties (density, extensibility, and absorption capacity of wound exudate) and the kind of application of the end product containing silver nanoparticles, e.g., the wound process stage.

The influence of gamma radiation on the magnetoelectric properties of extruded samples of Bi_0.85Sb_0.15 <Pb_x> (0.001 ≤ x ≤ 0.05) solid solutions doped with lead at ~ 77–300 K and magnetic field induction of up to 1.0 Tl is studied. It is found out that at low doses of gamma irradiation of the Bi_0.85Sb_0.15 <Pb> solid solution, the simplest defects of individual interstitial atoms and individual vacancies are formed, leading to an increase in the concentration of free electrons n and electrical conductivity σ and a decrease in the thermopower coefficient α and R_H. It is shown that a higher irradiation dose in the course of subsequent restructuring during irradiation can cause the formation of complex defects, i.e. point defect clusters, thus decreasing the concentration of current carriers and giving rise to the changes in σ, α and R_H.

Dry sliding of sintered composites of Cu–Fe and Cu–RBS (RBS stands for recycled bearing steel) compositions against a quench-hardened steel is tested at a high-density alternating electric current. The contact layers are subjected to plastic deformation. This leads to the formation of transfer layers containing Cu, Fe, FeO, and CuFe₂O₄ phases. It is of scientific interest to determine the effect of cuprospinel (CuFe₂O₄) on the wear. It has been established that the average concentration of cuprospinel in the contact layers of Cu–RBS composites has higher values compared to that of the Cu–Fe composites. However, the wear of the Cu–RBS composites is higher than that of the Cu–Fe composites. The cuprospinel content varies in the range of (0–26) vol.% without any regularity. Therefore, it is not possible to determine the effect of cuprospinel on wear. The transfer layers contain more than 50 vol.% FeO. It has been noted that wear is reduced mainly due to an increase in the FeO concentration and thermal conductivity of the initial composite structure.