Vol 61, No 9 (2016)

Laser irradiation of a molybdenum film on a quartz substrate is numerically studied. The simulated results prove the experimental effect lying in a threefold decrease in the size of the ablation region in comparison with the focal spot. The numerical experiment proves the hypothesis on the two-stage ablation of metal film with the primary formation of oxide phase. It is demonstrated that oxidation leads to a selective decrease in the thermal resistance of the film along the vertical direction, so that the anisotropic character of the ablation is enhanced.

We have reported on the results of a numerical simulation of high-gradient magnetic filtration of ultradisperse corrosion products from water coolants. These results have made it possible to establish optimal technical characteristics of high-gradient magnetic filters. The results have been used to develop test samples of high-gradient magnetic filters (HGMFs) with different magnetic systems to purify technological water media of atomic power plants from activated corrosion products.

The evaporation of water drops of initial mass 5–15 mg on a stationary graphite substrate, as well as inhomogeneous drops with solitary solid inclusions, during heating by high-temperature combustion products has been investigated experimentally. Experiments have also been carried out with analogous inhomogeneous drops moving through combustion products. The possibility of two mechanisms of phase transformations of inhomogeneous liquid drops has been established. The scales of the effect of the area of the inclusion surface (up to 20%) and the initial mass of water (up to 90%) on the characteristics of the evaporation of inhomogeneous drops have been determined.

The electric charge of a lightning ball is found by comparing the electrohydrodynamic stabilities of a charged drop in an electrostatic suspension and a lightning ball floating in a superposition of the gravitational field and the surface electric field. It has been assumed that the electric field strength at the surface is limited by a breakdown value. For a lightning ball radius of 15 cm, its charge is estimated as several microcoulombs. Accordingly, the density of electrostatic energy accumulated in the lightning ball is on the order of one-hundredth of a joule per square centimeter. The density of the material that constitutes the lightning ball has been estimated for the case when the electric field strength at the site of its origination is several times higher than that in fine weather. The density of the lightning ball turns out to differ from that of air by only a few percents.

The results of experiments on the formation of a low-impedance diode in a rod pinch diode configuration preliminarily short-circuited by a radial foil have been described. The low-impedance diode is formed as a result of detachment of the foil (accelerated by the current of a high-current generator) from the anode rod. It has been shown that, by changing the shape of the anode tip, the thickness of the aluminum foil, and its position relative to the anode tip as by reconnecting the current via the foil and rod plasma, it is possible to obtain from one to several sequential hard X-ray pulses.

Nanostructured titanium disilicide powders with semiconductor properties are synthesized and studied. The optical and electrophysical properties of TiSi₂ are found to be controlled by its crystallite size.

The influence of the transverse size of a composite wire based on a high-temperature superconductor on the dynamics of its thermoelectrodynamic properties at constant-rate current input has been studied. The physical mechanism behind the formation of stable regimes, which are characterized by the nonuniform distribution of the electric field and transport current over the cross-sectional area of the composite, has been determined. It has been shown that the critical current density of the superconducting composites determined from their current–voltage characteristic have lower and upper boundaries of electric voltages, which outline the allowable measurement range. It has been found that, when the input current completely penetrates into the composite, conditions for its stability are governed by the size effect. The essence of this effect is that conditions for current state stability in superconducting composites with the same cross-sectional area but various cross size differ. The conditions for the absence of unstable states in the composite the cross section of which is partially filled with the transport current have been formulated.

The hardness and Young’s modulus of the thin hydroxyapatite-based coatings deposited by RF magnetron sputtering onto magnesium alloy, titanium, and steel substrates are studied. As the penetration depth increases, the hardness and Young’s modulus of these coatings are found to tend toward the values that are characteristic of the substrates. It is shown that the difference between the values of hardness and Young’s modulus at small penetration depths (h < 80–100 nm) can be caused by the difference between the physicomechanical properties inside the coatings and that this difference at large penetration depths (h > 100 nm) can be induced by an additional effect of the strength properties of the substrate material.

Influence of acoustic anisotropy on acousto-optic interaction in optically and acoustically anisotropic media is theoretically and experimentally studied. A specific type of acousto-optic diffraction is analyzed with allowance for the phase-matching conditions for two diffraction maxima. Analytical expressions for the phase-mismatch parameters versus the angle between the phase and group velocities of acoustic wave are derived. Light intensity in the diffraction peaks is numerically calculated, and experimental data on the diffraction in the paratellurite crystal at an acoustic walk-off angle of 54° are presented.

Interference patterns of Bloch surface waves with a period that is significantly less than the wavelength of incident radiation are formed using dielectric diffraction gratings located on the surface of photonic crystal. The simulation based on electromagnetic diffraction theory is used to demonstrate the possibility of high-quality interference patterns due to resonant enhancement of higher evanescent diffraction orders related to the excitation of the Bloch surface waves. The contrast of the interference patterns is close to unity, and the period is less than the period of the diffraction structure by an order of magnitude.

Fabrication of efficient scattering materials based on uniform layer of metallized fine powder on the surface of thermoplastic polymer is analyzed. Spectra of diffuse reflection and scattering indicatrix of the materials in the near- and mid-IR spectral ranges are studied.

We have reported on the results of theoretical and experimental investigations of characteristics of aluminum and titanium foils used in devices to extract electron beams from wide-aperture low-energy accelerators with a high current density. The mechanical properties of foils at different temperatures and the electron beam transmission and absorption coefficients have been compared. The results of analyzing the dependences of the efficiency of the electron beam extraction from accelerators on the type of the electron–optical system, material, and thickness of the foil for various sizes of extraction windows and the same type of the slot support grids have been presented. We have proposed an analytic model for calculating the temperature of the foil in the unit cell of the support grid. The electron transmittance and absorbance, as well as the temperature regimes of the foils, have been calculated using different methods.

We have described the structure of the proton-beam writing channel as a continuation of a nuclear scanning microprobe channel. The problem of the accuracy of positioning a probe by constructing a new high-frequency electrostatic scanning system has been solved. Special attention has been paid to designing the probe-forming system and its various configurations have been considered. The probe-forming system that best corresponds to the conditions of the lithographic process has been found based on solving the problem of optimizing proton beam formation. A system for controlling beam scanning using multifunctional module of integrated programmable logic systems has been developed.

The moments in the theory of deceleration of fast charged particles colliding with an oscillator have been considered in the dipole approximation. In this approximation, the problem has been solved exactly, and the moment of the oscillator has been determined from the initial state |m> = |0> in the form of the sum of 1D integrals. The method considered here makes it possible to calculate the moments for ion velocities close to atomic velocities (v ~ v_a).

IR analysis and the plasma deposition of silicon-containing hydroxyapatite powder have been carried out. It has been shown that the coating exhibits developed morphology and consists of molten powder (including nanosize) particles uniformly distributed over the entire surface. The adhesion characteristics have been calculated and scanning electron microscope images of the resultant coating have been analyzed.

Computer simulation has been performed for a high-transmission electrostatic spectrograph, and charged particle energies in the range E_max/E_min = 25 and 50 have been measured simultaneously. The spectrograph has been designed in the form of two coaxial cylinders with plane endface electrodes; the cylinder of a larger diameter has been cut into fragments with a potential that varies according to a linear law. For this device, the geometric and electrical parameters that ensures a beam that focuses in the entire range of recorded energies with the energy resolution interval (0.4–1.1)% are determined in the regime when the object under investigation is placed outside the field.