Том 43, № 4 (2017)

The results of examination of the microwave-breakdown mode in an accelerating structure with parallel coupling are reported. It is demonstrated that breakdown normally occurs in a single cavity of the structure, while other cavities and the structure in general remain unaffected. This is attributed to the fact that neighboring accelerating cavities are almost independent of each other. This feature makes the structure more resistant to breakdown failure and may be used to increase the amplitude of the accelerating field in accelerators with a large number of accelerating structures.

A theory of acoustical vector solitons of self-induced transparency in anisotropic media is developed. It is shown that, in these systems, a two-component vector soliton oscillating with the difference and sum of the frequencies in the vicinity of the frequency of a carrying acoustic wave may arise. Explicit analytical expressions for the form and parameters of a nonlinear wave depending on the direction of pulse propagation are given.

The restructuring of the periodic structure of a turbulent streamline for a semicircular airfoil at a zero angle of attack with a system of slot suction from the circular cavern switched off is calculated. Multiblock numerical methods are applied for solution of Reynolds-averaged nonstationary Navier–Stokes equations closed using the modified shear-stress transfer model taking into account flow line curvature. The lifetime of a trapped vortex in a circular cavern is estimated.

A photoemissive “solar-blind” cell of a vacuum ultraviolet detector array for the 50–225 nm wavelength range is described. The cell is a cavity in the shape of frustum of a pyramid in a silicon wafer, the walls of which are coated by polycrystalline diamond film acting the part of a photosensitive cathode. The design of the cell allows one to manage the work of the detector in the “pass through” mode; i.e., photons fall to one side of the wafer, and photoelectrons release from its opposite side. Estimation of photosensitivity of the cell gives a value of about ten photons.

The method of “multistop” time-of-flight mass spectrometry has been used to study the mechanism of radiation damage to glycine molecules in the gas phase upon their interaction with He²⁺ ions with energy E_p = 4 keV/amu. The relative cross sections of various elementary processes occurring in single collisions of glycine molecules with the ions were measured for the first time. A difference was found between the fragmentations of intermediate doubly charged ions formed in capture of a single electron with ionization and in two-electron capture, which is accounted for by the difference between the excitation energies of molecular ions.

Investigation of temporal dependences of the voltage and current of high-voltage spark discharge over a dielectric surface in vacuum has shown that, in the presence of a longitudinal magnetic field, delay of the leading edge of the pulse-breakdown voltage takes place and the current, in turn, is converted from a well-defined impulse into alternating oscillations. Deceleration of the breakdown process in the presence of a low-current discharge that precedes the spark has been observed.

It is experimentally established and theoretically justified that a decreasing growth rate of carbon nanotubes (CNTs) on thin-film catalysts may be caused by the formation of intermetallic compounds that hinder supply of carbon from the bulk. In particular, the growth of CNTs on the Ti–Ni thin-film system is accompanied by the formation of a titanium carbide layer on the surface of a catalyst droplet. The kinetics of CNT growth under these conditions is calculated, and kinetic coefficients determining the growth rate are evaluated.

We present original results of an investigation of the specific features of optical electrochirality (electrogyration) in a lead tungstate crystal. Since this crystal exhibits neither the Pockels effect nor the inverse piezoelectric effect, the electrogyration effect can be used to create a fast-response electric sensor for remote monitoring of high-speed processes in high-voltage electric networks. A fiber-optic sensor prototype has been manufactured using optical elements intended for fiber communications.

We have experimentally studied the thermal and microwave properties of a nanoporous medium (silica gel) with hydrogen-filled pores. On cooling down to about −45°C at atmospheric pressure, the system exhibited chemical transformations, a first-order phase transition with heat evolution, and a sharp change in the power of microwave radiation at 34 GHz transmitted through a sample. It is concluded that this point on the phase diagram corresponds to a point on the Widom line featuring sharp increase in fluctuations of the entropy and density of supercooled water formed during hydrogen interaction with the surface of pores in silica gel. These results confirm the existence of a second critical point of water, from which the Widom line originates.

The evolution of three-dimensional (3D) ultimately short optical pulses propagating in silicene has been studied. An effective equation describing the dynamics of these pulses is obtained that has the form of a nonlinear wave equation with saturable nonlinearity. Pulses comprising one and two oscillations of a electromagnetic field have been studied.

We describe a series of high-frequency EPR/optically detected magnetic-resonance (ODMR) spectrometers operating in both continuous-wave and pulsed regimes in 2-, 3-, 4-, and 8-mm. The resonance signal can be monitored in both microwave and optical detection channels. The entire series of EPR/ODMR spectrometers has common design features.

Evolution of the structure and mechanical properties of a FeNi alloy annealed after megaplastic deformation (MPD) at room temperature in the Bridgman chamber has been studied by the transmission electron microscopy, electron backscatter diffraction, and microhardness measurement techniques. It is established that the primary recrystallization process during annealing is accompanied by growth of the recrystallized grains formed at the preliminary MPD stage. At the same time, the deformation fragments cannot grow because of the extremely low mobility of their boundaries.

The task of controlled variation of parameters of supersonic flow past a semicylindrical aerodynamic body is considered. The action of gas-discharge plasma on the flow by means of discharge-induced increase in the degree of nonequilibrium in the oncoming gas has been experimentally studied. For the flow parameters used in the experiment, the numerical simulation has been conducted for the thermal action of plasma upon the shock layer of a homogeneously heated region with the gas temperature equal to the electron temperature determined in the experiment. Comparison of the experimental and calculated data leads to the conclusion that the new mechanism based on increase in the degree of gas nonequilibrium in the source of energy supply can be used for controlling supersonic flows past aerodynamic bodies.