Volume 62, Nº 2 (2017)

Kinetic methods are used to derive the transport equations, virial equation, dynamic equilibrium condition, and the equation of the envelope of an axially symmetric paraxial relativistic electron beam propagating in an Ohmic plasma channel during the evolution of resistive firehose instability. The equation of the beam envelope is generalized by taking this instability into account.

Random energies of electrons that escape from the source in the course of field emission are simulated using energy spectra. A relationship of the random values of total energy and the energy related to the normal (with respect to surface) component of momentum is established. A family of quadrature formulas needed for the integration of the distribution density of particles is analyzed. A hypothesis on the compliance of selected random energies with desired distribution laws is statistically tested.

Combined action on a source that flows into a submerged area or vacuum in the constant Mach number regime has been studied. The action by an external force has been defined with a constant distribution function (the force is given per unit volume) and with a distribution function proportional to the gas density (the force is given per unit mass). The investigations have been carried out for cylindrical and spherical sources. Similarity and differences, advantages and drawbacks of the above-mentioned cases and variants have been analyzed. It has been shown that the enthalpy increases significantly in subsonic flow (for the Mach number smaller than unity) by several times in the cylindrical source and by more than an order of magnitude in the spherical source. The total enthalpy increment increases with the length of the action zone or with the coordinate of the closing section.

We have studied the generation of the beam plasma formed by a forevacuum plasma source of a ribbon electron beam in the conditions of its transportation without an accompanying magnetic field. The ignition conditions in the beam transportation region of the beam–plasma discharge producing a plasma formation of the plasma sheet type with a plasma concentration of ~10¹⁶ m^–3 and an electron temperature of 1–2.5 eV have been determined. The attained values of parameters and the sizes of the plasma formation make it possible to use it in technologies of the surface modification of planar extended articles.

An original technique of differential thermal analysis for studying thermal properties of samples loaded with a tangential stress has been created. In a series of experiments studying the direct martensitic transformation B2 → B19′ in titanium nickelide during cooling under constant stress, it has been found that the enthalpy of transformation linearly decreases with an increase in stress and, at a stress of 100 MPa, it is 30% less than that of the sample in a free state.

Novel, small-sized broadband matched loads in the form of disordered photonic crystals containing nanometer metallic and insulating layers have been developed. It has been proposed to form insulating layers with different permittivities and low dissipation factors in both centimeter and millimeter wavelength ranges from the composites that consist of insulating matrices filled with air inclusions.

The influence of growth conditions on the carbon dendrite structure has been investigated. The threshold values of the ratio between electron temperature T_e and kinetic temperature T of the gas near a needle electrode and of the discharge current density, which are necessary for dendritic growth, have been determined. It has been shown that the hexagonal structure of submicron carbon particles arises when a number of hydrocarbons are used to synthesize dendrites. It has been found that the degree of order in the carbon structure can be controlled by applying external actions at the stage of graphite particle nucleation. The characteristic frequencies of inertial actions that may be energetically appropriate must exceed 10 kHz.

Experiments and numerical simulation show that the irradiation of alkali-containing glasses using electrons at an energy of 35 keV and the subsequent thermal processing at a temperature above the vitrification point lead to the formation of spherical metal (lithium, sodium, and potassium) nanoparticles with oxide sheaths that exhibit plasmon resonances in the visible spectral range. Glasses containing two alkali metals exhibit mutual effect of metals on the formation of nanoparticles with two compositions due to the difference of ion radii and mobilities of metal ions.

The results of investigating the effect of nanosize modifiers of a polymer matrix on the nanostructural self-organization of polymer composites and dynamic adaptation of metal–polymer tribosystems, which considerably affect the wear resistance of polymer composite materials, have been analyzed. It has been shown that the physicochemical nanostructural self-organization processes are developed in metal–polymer tribosystems with the formation of thermotropic liquid-crystal structures of the polymer matrix, followed by the transition of the system to the stationary state with a negative feedback that ensures dynamic adaptation of the tribosystem to given operating conditions.

Nanocomposites consisting of a polymethylmethacrylate or polystyrene matrix with embedded silicon dioxide nanoparticles surface-modified by silazanes have been prepared by melting technology. The influence of particles on viscoelastic properties of the nanocomposites has been studied using dynamic mechanical analysis. It has been revealed that the addition of 20 wt % of SiO₂ raises the flexural modulus of the nanocomposites by 30%.

The results of studies of the physical nature of emissions produced in polymethyl methacrylate excited by electron beams of a subnanosecond or a nanosecond duration are presented. The spatial, amplitude, and spectral-kinetic properties of emissions have been examined under an electron beam energy density varying from 10^–4 to 4 × 10^–1 J/cm². It has been found that cathodoluminescence is the primary type of emission under low energy densities of the electron beam. When the energy density of a nanosecond electron beam and/or the number of pulses of excitation by a subnanosecond electron beam were increased, an electrical breakdown of polymethyl methacrylate occurred in the irradiated region. This process was accompanied by a burst of emission of dense, low-temperature plasma.

The possibility of the standardless mass spectrometric analysis of the elemental composition of solids has been discussed. The effect of each stage of the laser plasma expansion on the formation of the coefficient of relative sensitivity of elements in the sample has been studied theoretically and experimentally. It has been shown that the stages of ionization and detection make the main contribution to the formation of the coefficient of relative sensitivity. It has been proposed to separate dissociation and ionization processes in time and/or in space. To compensate for the energy spread of ions at the output of the analyzer, a circuit has been proposed for aligning the energy of ions before their detection.

Peak force measurements with the aid of atomic force microscopy are used to quantitatively map nanomechanical properties of intact erythrocytes of rats under conditions that are close to physiological conditions. Erythrocytes that are immobilized on the substrate preliminary processed using poly-L-lysine predominantly exhibit plane shape. However, cells may also exhibit stepwise transformation to semispherical objects with an increase in volume and hardening. Possible reasons for such transformations are discussed.

The results of examining and analyzing the interrelation between the processes of polarization and structuring in magnetic fluid microlayers under the influence of the temperature, external electric and magnetic fields, and variations in the structure and amount of stabilizer have been presented.

A project of the source of ultracold neutrons for the WWR-M reactor based on superfluid helium for ultracold-neutron production has been developed. The full-scale source model, including all required cryogenic and vacuum equipment, the cryostat, and the ultracold-neutron source model has been created. The superfluid helium temperature T = 1.08 K without a heat load and T = 1.371 K with a heat load on the simulator of P = 60 W has been achieved in experiments at a technological complex of the ultracold-neutron source. The result proves the feasibility of implementing the ultracold-neutron source at the WWR-M reactor and the possibility of applying superfluid helium in nuclear engineering.

It has been demonstrated experimentally that the local irradiation of a thin gold film on glass with electrons with an energy of 5 keV led to an increase in the thickness of the irradiated area. When the film was subjected to local irradiation with electrons with an energy of 25 keV, the irradiated region became thinner and a gold ring was formed along the perimeter of this region. At high densities of the electron current, thickened regions of the film assumed the shape of fractal nanostructures. The observed effects were induced by the formation of a negative charge region on the surface of glass (or in the bulk of it) and the migration of positive gold ions into this region.

We have derived the formulas for calculating the force of the interaction of a relativistic electron beam with an ion plasma channel in the case of the beam transportation during ion focusing. The dependence of the difference in radial profiles of the beam and the ion channel on this force for different amplitudes of beam deviations from the channel symmetry axis has been studied.