Linear theory of interaction between two infinitely thin sheet electron beams has been built in hydrodynamic approximation. It’s supposed that electron beams move in space between two conducting planes. Research takes into account the effect of space charge and finite longitudinal focusing magnetic field. The considered model allows to describe instability to high-frequency (HF) perturbations in the given system. The eight-power dispersion equation has been derived for given system. Since it’s not possible to write down its analytical solution, that dispersion equation has been solved graphically. From the point of view of the theory of coupled waves four waves can be exited in each of the beams – fast and slow space-charge waves and fast and slow cyclotron waves. The effect of finite magnetic field on development of the instability has been investigated in case of two interaction electron beams on bases of dispersion equation solution. Investigation of the dispersion characteristics allow to conclude that presence of the permanent longitudinal magnetic field leads to occurrence of new instability regions, that is caused by not only interaction of space-charge waves, but also cyclotron waves in beams.
Show AbstractThe characteristics of output radiation of gyro-amplifiers (such as gyroklystron and helical waveguide gyro-TWT) with delayed feedback and gyrotron, operated at the regime of high exceeding of the threshold, were studied. It was shown, that this devices could produce wideband chaotic oscillations with a relative spectrum width up to 10% at the millimeter wavelength. In all cases these regimes are referred to as hyperchaos.
Show AbstractIn present paper, we observe physical processes leading to the emission of the powerful microwave radiation in vircator system, which contains relativistic electron beam in case of simultaneous development of Bursian and shear instability. We have studied the influence of beam dynamics on the output radiation characteristics via 3D particle-in-cell simulation.
Show AbstractThe conditions of instability of horizontal surface of low-viscous liquid are calculated analytically. The flaws of calculation methodic admitted by other investigators are corrected.
Show AbstractTheoretical investigation of two-dimensional few-cycle optical pulse (light bullet) dynamics in heterogeneous medium of carbon nanotubes in the presence of an external constant magnetic field parallel to the axis of nanotubes. Electromagnetic field of pulse describes classically, on basis of Maxwell equation, and carbon nanotubes give dispersion law for electrons, which interacting with pulse. The dispersion law is written in the close-coupling approximation of the analysis of the dynamics -electrons, which interact with the electromagnetic field of extremely short pulse. The initial condition for the vector potential of the electric field of an extremely short optical pulse is chosen in the Gaussian form. The time and coordinate steps were determined from the standard stability conditions and sequentially halved until the solution changed in the eight decimal sign. As shown by the results of numerical calculations, the propagation of two-dimensional extremely short optical pulse in the presence of the magnetic field is stable, and also able to establish the impact of the period of the inhomogeneity of the medium on the velocity of propagation of extremely short optical pulse, namely, by increasing the lattice period is extremely short optical pulse is spreading most rapidly.
Show AbstractIt was experimentally found that when the ambient temperature changes from 260 K to 345 K, the peak wavelength of the spectral characteristic of a laser diode with a frequency doubler on a KTP crystal is practically not shifted relative to the position it occupied at room temperature. The justification of this phenomenon is given.
Show AbstractAn analytic and numerical study of the dynamics of parameters of a super-Gaussian pulse, whose spectrum can fit both in the region of normal and anomalous dispersion of the group velocity, is carried out. An analytical solution is found for the parameter characterizing the evolution of the degree of the super-Gaussian momentum.
Show AbstractIn the article integrated ferroelectric device of new type namely homogeneous circuit with ferroelectric capacitors with a negative capacitance has been considered. Under the great number of such capacitors in the circuit in the framework of the Witham theory propagation of nonlinear modulated waves in this system has been described.
Show AbstractA noncontact method for determination of recombination parameters of p(n) layer local spaces of silicon n+-p(n)-p+ structures is considered. The method is based on local illumination of investigated structure by two different absorbed light beams. At first both beams illuminate simultaneously one side of the local space of this structure and then - another side. The intensities оf the light beams are modulated so that the sum of the alternative photo-voltage becomes equal zero. Under these condi-tions the ratio of the modulation amplitudes of this light beam intensities are measured. Using such values we calculated nomograms for separate determination of the nonequilibrium charge carrier lifetimes of the illuminated p(n) local space and its surface recombination velocity at the rear side. The nomograms were calculated at wave lengths 1064 and 808 nm for thicknesses 0.4 and 0.2 mm of the p(n) layer
Show AbstractFormation of single two-dimensional waveguides and multi-element (3 and 5 waveguides) of such waveguides within a bulk of undoped lithium niobate has been experimentally demonstarated. Waveguide structures with a channel size of 8, 12, 23 μm have been formed by the bright spatial solitons obtained at the compensation of the diffraction divergence of light beams in the crystal due to the contribution of the pyroelectric effect into the nonlinear response. The light wavelength were 532 and 633 nm and the optical power was ranged from 50 to 200 μW in experiments. The total compensation of the diffraction divergence at uniform heating of the crystal sample to the temperature from 35 to 55 degrees Celsius.
Show AbstractThe paper discusses propagation of optical beams through a Bose-Einstein condensate. With the help of numerical simulation shows that the optical beam is focused or defocused depending on the sign of the detuning of the laser frequency from the atomic transition frequency. Established analytical and numerical models describing the evolution of a wave beam in the BEC. For was based on the semiclassical model, in which the condensate is considered from the quantum point of view, and the wave beam classic. This model allows to take into account not only the changes of the wave beam, but also changes in the wave functions of the condensate. The paper considers two models: taking into account spontaneous emission and without. BEC behaves as a medium with the Kerr nonlinearity, the sign of which depends on the sign of the detuning from the resonance frequency. For negative detuning there is a trend towards the focusing of the beam, while for positive detuning there is a defocusing. The wave function of the ground state BEC does not undergo significant changes, while the wave function of the excited state performs oscillations (in the case of resonance with the Rabi frequency). In addition to storing the total number of atoms in the system is the law of conservation of energy for the entire system. The reduction in beam energy leads to the growth of the population of the excited level, and a reduction of the population of the excited level, respectively, leads to an increase in beam energy. For a wide beam in the case of a positive detuning from the resonance is observed in its cleavage.
Show AbstractThree-dimensional light beams-pulses, known as light bullets, are studied analytically and numerically. Using the method of the averaged Lagrangian obtained analytical solution describing a bullet in nonlinear parametric interaction. The obtained conditions for sustainable spread of bullets, which is a ratio between diffraction, dispersion and nonlinear lengths. Analytical conclusions are confirmed in the process of computer simulation. The calculations demonstrate that the light bullet extends to a distance far exceeding the dispersion and diffraction lengths in the anisotropic medium. Separately the cases of stable propagation of two-component three-dimensional light bullets, as well as the formation of the beam pulse by generating the second optical harmonic.
Show AbstractA study was made of the formation of solitary waves in a ring aerobasin. It is shown that when wind speed is increased in "deep water" conditions, groups of waves with one maximum wave height (the analog of the ninth shaft) are formed first and then, when the wavelength is greater than the depth of the liquid, several solitary waves arise, the interaction between which leads to the appearance of one Solitary wave.
Show AbstractThe study of influence of external harmonic signal on generation in low-voltage vircator with magnetron-injection gun as source of electron beam are carried out. The classical phenomenon of synchronization in the distributed electron-wave system are observed. The possibility of vircator output signal power increasing with the frequency of external signal changing are shown.
Show AbstractIn this paper, we investigated the processes of synchronization and the formation of structural patterns in a multilayered network of dynamic elements. The layers compete for an optimal topology, where elements interactions within the layer occurs according to the principles of additivity and homeostasis.
Show AbstractIn this paper, we describe an approach to the analysis of stability, based on an analysis of the dynamics of a set of the small perturbations of an inhomogeneous distribution of the electric field in superlattice. It has been found that zero value of the real part of the coefficient characterizing the propagation of the perturbation indicates the development of space-time instability. In this case, the value of the imaginary part, which determines the frequency of oscillations of the perturbation, corresponds to the frequency of the voltage fluctuations in the system. The application of the proposed technique allows us to take into account the properties of the injecting contact on the stability of the stationary distribution of the electric field. It has been found, that a decrease in the differential conductivity of the contact makes it possible to stabilize the field distribution in the system for certain values of the applied voltage.
Show AbstractIn this study, we investigated the processes of clustering in multilayered social networks of collaborations and professional interactions. We have identified the basic principles that are responsible for the interconnection of topology and dynamic characteristics in such kind of networks.
Show AbstractThe results of approbation of the method for the quantitative determination of 2H by NMR spectroscopy using a lanthanide shifting reagent added to the probe as an external NMR standard against which the measurement is performed are presented. In the course of the studies, it was confirmed that europium (III) trifluoromethanesulfonate is the most suitable chemical compound for creating a reference sample. It was found that the highest content of deuterium was in the juice of the Argentine pear (144.6 ± 2.3 ppm), the lowest concentration of deuterium was found in the russian and egyptian potato juices (≈100 ppm).
Show AbstractA method of constructing a low-level quantum system for a one-dimensional spin lattice consisting of N particles is proposed. In the Bernasconi model, the problem of constructing the simplest quantum system in the form of a one-dimensional Ising model reduces to the problem of constructing binary sequences with the lowest side-lobe energy. In this paper, we provide a computationally effective method of exhaustive search for binary sequences with a low level of side lobes. Examples of low-level one-dimensional spin lattices of record lengths N > 80 are synthesized and presented
Show AbstractThe numbered iteration algorithm for polyphase sequence constructions with low level sidelobes of aperiodic autocorrelation function is offered. The example of polyphase sequence for the length N = 512 with peak sidelobe of aperiodic autocorrelation function with PSL = 1.763 is demonstrated. Polyphase sequences with a low level of side lobes AACF are widely used as modulating signals in radar systems for various purposes. A low level of side lobes provides detection of targets with a low effective scattering area (ESA) against the background of high ESA targets.
Show AbstractWe investigated the collective dynamics of nanoscale heterostructures semiconductor superlattices, which which adaptively coupled by an external resonant circuit. It is shown that the interaction of the active medium through the resonant circuit leads to emergence of broad areas of chaotic dynamics and broadband generation.
Show AbstractThe problem of calculating the stable resonators of solid-state lasers forming a Gaussian beam with variable spatial parameters (waist diameter, confocal parameter, angular divergence) with the energy parameters of the radiation unchanged is considered. The scheme of the optical system of a resonator of a solid-state laser to solve this task is presented. By the ray bundle method and on the base of scalar diffraction theory, the problem of calculating the characteristics of a laser beam formed by linear resonators of arbitrary configuration taking into account the aberrations of its elements is considered. The results of modeling the mirror-lens resonator scheme for varying the spatial parameters of the output beam by the ray bundle method are presented. For stable resonators approximate analytical expressions are obtained, which allow to calculate the distribution of the complex amplitude on mirrors and in an arbitrary cross section of the resonator, the spatial parameters of beam and the frequency spectrum of the radiation for a rectangular and circular aperture of mirrors. The configurations of resonators in which the aberrations of the shape of the surface of mirrors have a significant effect on the characteristics of the formed laser radiation are determined.
Show AbstractFeatures of functioning of optical systems of the process equipment on the basis of powerful fiber lasers are considered. The experimental results show that the distribution of the power density of the laser radiation and the temperature distribution on the optical element of the laser head can be approximated by the Gaussian function. The results of experimental studies of the heating of optical elements from high-purity quartz glass of the Russian production of the grade KS-4V are presented in the formation of radiation from a CW high-power fiber laser. The maximum heating temperature of optical elements at various laser power densities are determined. Expressions are given for analyzing the thermal-optical distortions of the beam at the output of the optical system of laser equipment for technological processes of material processing. Analysis of the optical systems calculated has shown that when heating of lenses made of quartz glass under the influence of high-power laser radiation, the output waist is shifted closer to the protective glass, and its diameter remains practically unchanged. The researches show that when designing of laser optics for the modern technological equipment on the basis of powerful fiber lasers the account of heating of lenses is very important.
Show AbstractPhysical Principles of Setting (PPS) of Apparatus Functions (AF) of measuring systems (PPS AF) on the sizes of domains of determination AF are proposed. Sizes of AF O definition region are chosen so that its inverse resolving function R = O-1 in the chosen discrete domain has a minimal norm. In the PPS AF method, the result is reversible; there is no "a priori smoothness of solutions" with a residual error, as in the regularization method. Action of PPS method is demonstrated on the example of the Sun radio image super-resolution in comparison with a result obtained by regularization one.
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