Innovations in Applied Physics

With the help of 2D numerical model it has been investigated the nonlinear dynamics and generation of wideband chaotic signals in the generator based on electron beam with the virtual cathode. It has been discovered the strong influence of the external non­uniform magnetic field on the nonlinear dynamics of the virtual cathode in the system. It has been analyzed the physical processes responsible for the discovered dependency of dynamics of the electron beam with the virtual cathode on the parameters of the external non­uniform magnetic field.

The analytical estimation of the optimal parameters fulfilled for pulsed magnetrons with cold  secondary-emission cathodes, operating at a frequency of 32 GHz with anode voltage of 8 kV and  with magnetic field of about 0.4 Tesla. As shown, the geometry of the magnetron interaction space  can ensure an interaction between electrons and the high-frequency field as for the (−1)-th space  harmonic of π/2-oscillations, so for (+1)- th space harmonic π-oscillations in the drift-orbit  resonance mode.

Results of analytical consideration of the probability distribution density for Brown particle, subject to weak influence of the external force conditioned by a cosmic particle flow. It is shown that this influence, which is time­dependent, results in essential non­stationarity of the probability distribution, i.e. it becomes a sum of components caused by different astronomical factors: Earth revolution about inherent axes and the Sun, the motion of the Sun and stars and so on.

Phenomenon of the regular variability of the fine structure of the fluctuation in the amplitude distributions (shapes of related histograms) for the case of Brownian motion was investigated. We took an advantage of the dynamic light scattering method to get a stochastically fluctuated signal determined by Brownian motion. Shape of the histograms is most likely to vary, synchronous, in two proximally located independent cells containing Brownian particles. The synchronism persists in the cells distant at 2 m from each other, and positioned meridionally.

We present a numerical method for calculation the eigenmodes of the open resonator. We assume, that the resonator mirror has the finite conductivity. The new approach, based on the modified method of the field continuation, was suggested. The results obtained were compared with the asymptotic solution.

The three-dimensional excitation equations for the longitudinal-irregular circular waveguides with finite conductions of the walls by electron beams in completed form for self-consistent models of gyrotrons, peniotrons, relativistic TWT and BWO had been derived. The possibilities of improving the efficiency of millimeter-wave gyrotron with multimode interaction fields of whispering gallery waves and a relativistic helical electron beam were consider. It is shown that two-mode gyrotron, compared with single-mode allows you to raise the efficiency from 40 to 45%.

Anderson localization of electromagnetic waves incident on a disordered medium manifests itself in exponential decrease of the wave amplitude inwards the medium. Transparency of the medium is exponentially small if the medium thickness is large enough. However, there is a set of frequencies (resonances), specific for every random realization of the disordered medium, for which the medium is almost transparent. These sets are «fingerprints» of the media: every realization is characterized by its own unique set of resonances.

Theoretical research of dynamics of electron flow with virtual cathode in lowvoltage vircator under external harmonic force has been held in this work. The behavior of electron flow was considered within the framework of both stationary analytic model and numerical simulation of electron flow nonstationary processes. The increasing of lowvoltage vircator output power while increasing external force has been shown in both cases. The results of theoretical research let us to explain physical phenomenon leading to output power increasing.

Virtual cathode nonstationary dynamics has been numerically studied for the two counterstreaming electron beams. The variety of the virtual cathode oscillatory regimes has been discovered from regular to wide band chaotic oscillations. Connection between value of the largest Lyapunov exponent and output signal power has been revealed.

An approximate nonlinear theory of double-stream interaction is built. Based on this theory, calculation for double-stream amplifier gain was performed. It was shown, that 40 dB amplification can be obtained.