Том 64, № 3 (2019)

Investigation results of the effect of electron cooling are considered. The current state-of-the-art is analyzed. The possibilities are discussed for the experimental study of the electron cooling phenomenon using a large shock tube and plasma-gas-dynamic stand at the Ioffe Institute.

A general approach to analyzing eigenmodes in anisotropic and gyrotropic 3D photonic crystals based on dielectric and magnetic media is proposed. This approach is based on the representation of stationary macroscopic Maxwell equations in the operator form corresponding to the quantum-mechanical equation for a photon with spin s = 1. In these equations, the strengths of electric and magnetic fields are put into correspondence with state vectors in the complex Hilbert space. The permittivity and permeability serve as operators acting on these vectors. It is shown that the problem of determining the eigenmodes of a photonic crystal is reduced to searching for eigenvectors and eigenvalues of the Hermitian operator characterizing the spin–orbit interaction of a photon in the periodic anisotropic medium under study. It is proposed to use photon states with a certain wave vector (certain momentum) and a certain linear or circular spin polarization as a basis for the representation operator equations. One-dimensional photonic crystals are considered as an example. The influence of anisotropy and gyrotropy on the dispersion of eigenmodes in these crystals is investigated. The group velocity of the eigenmodes, momentum transferred by them, and spin angular momentum are analyzed for the case of gyrotropic media.

We have measured the absolute values of total cross sections of capture of one and two electrons by He²⁺ ions from argon atoms. The differential scattering cross sections have been determined for fast atoms and singly charged helium ions formed in each of these processes (without and with additional ionization of the formed slow argon ion). Measurements have been taken for He²⁺ ions with kinetic energy of 6 keV in scattering angle range 0–2.5°. Based on the measured differential cross sections using different model atomic particle interaction potentials, we have calculated the cross sections of these processes as functions of the impact parameter. The probabilities of realization of these processes with electron density distribution in different shells in the target atom have been compared. The applicability of the expressions for the screened Coulomb interaction potentials in the description of scattering of particles that have captured electrons has been demonstrated.

The numerical simulation of gas-dynamic processes accompanying the transverse injection of a gas jet into the supersonic part of a nozzle is considered in the context of creating steering forces in rocket engines. Numerical calculations are conducted based on various turbulence models at different mass flow rates of the injected gas. The calculation results obtained for the non-viscous, laminar, and turbulent formulation of the problem are compared with each other and with the physical experiment data. The formation of a shock wave and vortex flow pattern is discussed. Conclusions about the effect of problem input parameters on the thrust gain coefficient are made.

The disintegration of a plane nonconductive jet of a high-permittivity liquid has been studied. The jet moves with constant velocity in a gas that is quiescent at infinity in the presence of a perpendicular electrostatic field. Initially, the boundaries of the jet are parallel to each other. Its thickness is much smaller than the capillary constant. The gas density has been included into the list of governing parameters. The case has been considered when aerodynamic forces arising from wave disturbance of the gas–liquid interface make a greater contribution to the dynamics of the liquid than capillary forces. It has been shown that when the jet is aerodynamically unstable, the application of a perpendicular electric field with moderate intensity considerably decreases fragments of the jet after disintegration.

We have considered basic theoretical models describing various aspects of the formation and acceleration of plasma in pulsed accelerators. The discharge current, magnetic field, and plasma bunch velocity have been determined experimentally at different initial gas pressures in the accelerator chamber. We have considered the correspondence of some theoretical models of plasma acceleration to experimental data obtained in a KPU-30 coaxial accelerator. It is shown that the formation of the plasma in the coaxial accelerator depends on the plasma density, and acceleration processes at densities higher and lower than a certain transient density value on the order of 10¹¹–10¹² cm^–3 are different. At a density higher than this critical value, the plasma is accelerated by a magnetic force. At the same time, at a low plasma density, plasma can be accelerated by an internal electric field.

In this paper, we obtained intensity distributions of beams of positively charged ions emitted from the surface of uniaxially compressed granites under the effect of a shock wave. The intensity of beams decreases exponentially with an increase in the number of shock waves. The ions fly out at the moments when the dislocations reach the surface moving in intersecting slip planes. A compressive load suppresses the dislocation release and the intensity of ion beams.

A brief review and results of experimental investigation of the properties of energy-saturated nanoporous silicon-based composites are presented. Various types of oxidants used in the composites are examined. Calcium perchlorate has been used as an oxidant. The energy-saturated composite under study is shown to exceed in several parameters the primary explosive, mercury fulminate and brisant explosive, RDX.

IR photodetectors have been made on Pb/δ-layer/p-Pb_{1 –x}Sn_xTe_{1 –y}Se_y/p⁺-Pb_0.8Sn_0.2Te/Au and Au/δ-layer/n-Pb_{1 –x}Sn_xTe_{1 –y}Se_y(BaF₂)/Pb surface-barrier structures prepared by liquid-phase epitaxy and thermal evaporation. At ~170 K, peak wavelength λ_p ~ 7.9–8.2 μm, and cutoff wavelength λ_c ~ 8.2–8.5 μm, the former surface-barrier structure has product R₀A (where R₀ is the zero-bias differential resistance and A is the active surface area) = 0.31–0.97 Ω cm², peak quantum efficiency η_λ = 0.32–0.48, and specific detectability \(D_{\lambda }^{*}\) = (0.72–1.83) × 10¹⁰ cm Hz^1/2 W^–1. For photodiodes made on the latter surface-barrier structure, these parameters measured at ~80 K are R₀A = 1.71–2.72 Ω cm², η_λ = 0.34–0.49, and \(D_{\lambda }^{*}\) = (3.02–4.51) × 10¹⁰ cm Hz^1/2 W^–1 at λ_p ~ 8.6–12.3 μm and λ_c ~ 9.2–12.9 μm.

The elastic (G) and inelastic (Q^–1) properties of Co_x(PZT)_{100 –x} nanocomposites (x = 23–76 at %) obtained by ion-beam sputtering have been studied in the temperature range 200–900 K. Internal friction peaks associated with Co atom hopping inside metallic granules have been discovered at 236 K. It has been found that the peak height grows with metallic phase concentration. Above 750 K, curve Q^–1(T) rises considerably because of vacancy diffusion in Co granules under conditions of confined space.

Single-pass free-electron lasers (FELs) with harmonic multiplication in the X-ray range are studied theoretically with the objective of producing intense radiation with the minimum possible FEL length, beam energy, and seed laser frequency. A cascade FEL with a two-frequency undulator for electron bunching at wavelengths of higher harmonics is proposed. The dynamics of radiation power in a FEL with harmonic multiplication cascades is investigated based on a well-proven phenomenological FEL model that covers all major losses for each harmonic in each FEL cascade. The effect of the beam quality on X-ray generation in a FEL is examined. It is demonstrated that electron beams with energy spread σ_e ≤ 0.0002 are required for efficient use of harmonics in a cascade X-ray FEL. The evolution of power of harmonics in several cascade FELs at wavelengths of ~2–3 nm with multiplication of seed harmonics at a wavelength of 13.51 nm (Mo/Si reflection peak) and 11.43 nm (MoRu/Be reflection peak) is studied. It is demonstrated that the power increases to ~1 GW at a FEL length up to 40 m. In addition, the operation of multicascade FELs with a seed F₂ excimer 157-nm UV laser and harmonics of lasers with CO₂ and C₂H₂ at 30 nm with a beam of electrons with an energy of ~0.6 GeV and a current of ~1 kА is studied. The power of the modeled X-ray radiation of these FELs at λ = 2.5 and 3.3 nm increases to ~0.5 GW at ~30 m.

We report on the results of the 3D numerical simulation of perspective design of an oscillator based on an external-feedback virtual cathode (virtode), as well as optimization of characteristics of its generation. We have analyzed the effect of beam parameters on the virtode output characteristics. In particular, we have obtained the dependence of the efficiency on the feeding voltage and on the current being injected. We have studied the effect of beam velocity premodulation and electron velocity spread on virtode generation characteristics. It has been established that the introduction of premodulation sharply increases the generation efficiency up to 13% for optimal parameters. The possibility of stable generation in the virtode at relatively large spread in electron velocities has been demonstrated.

Effect of ultrabroadband radiation and bremsstrahlung on a complicated device (ATmega8515) placed in a radio-transparent housing is studied. Similar results are obtained in the two cases: short-term malfunction or hangup. A particular scenario depends on the moment of irradiation relative to the phase of the meander generated by the microcontroller. In the presence of bremsstrahlung, the effect depends on the exposure dose, so that an increase in the duration of the generated phase or hangup can be obtained.

The formation of a surface layer with silver and sodium concentration gradients in K8-grade glasses as a result of ion exchange is demonstrated by scanning electron microscopy (SEM) and electron probe X-ray microanalysis. The silver ions enriched layers with different thicknesses, depending on the duration of the ion exchange from the silver melt, are visualized in the secondary electrons mode. SEM data on the thickness of the silver enriched layer are in good agreement with the results of calculation from the diffusion equation for silver in glass. The dependence of the silver concentration on the diffusion depth is obtained using elemental composition mapping over the glass cross section. The presence of a layer with a silver concentration gradient leads to formation of a gradient waveguide. Discrete peaks in silver concentration profiles, caused by specific features of mutual diffusion of sodium and silver ions in glasses, are found.

A bifurcation analysis of a nociceptive neuron model was performed to study how the firing activity pattern changes when an antinociceptive response to damaging pain stimulation arises in rat dorsal ganglia. Ectopic train activity was found to arise in the model. Suppression of train activity was demonstrated to proceed solely through modification of the activation gating structure of the Na_V1.8 slow sodium channel in response to comenic acid, which exerts an analgesic effect and is an active ingredient of the new nonopioid analgesic Anoceptin.

Storage cells for ultracold neutrons (UCNs) are crucial parts of the experimental setup used to measure the electric dipole moment (EDM) of a neutron. The effect of the technology of preparation and sputtering of elements of UCN storage cells on the limiting operating voltage and on the capacity of these cells for long-term operation under high voltage with polarity switching was studied. A voltage magnitude of ±250 kV was obtained in tests of a neutron storage cell for the EDM spectrometer with a cell height of 9 cm.