Yu. V. Tkach

Studies of the Parameters of a Spark Discharge Between an Artificial Charged Water-Aerosol Cloud and the Ground

The optical and current characteristics of spark discharges between a grounded electrode and a strongly charged artificial water-aerosol cloud are studied experimentally. The spectral characteristics of the discharge current are investigated using wavelet and Fourier analyses. Three main types of discharge with different final stages are revealed and investigated. It is found that the parameters of a discharge in its final stage depend substantially on the discharge trajectory and the depth to which it penetrates into the aerosol cloud. It is shown that the parameters of the most powerful type of discharge (the brightness of the discharge channel, the current growth rate in the final stage, and the penetration depth into the charged aerosol cloud) are close to the discharge parameters in the main stage of natural lightning. It is also shown that such a discharge neutralizes up to 5% of the cloud charge. In contrast to Fourier analysis, wavelet analysis shows that the signal amplitude (i.e., the energy deposition rate in the discharge channel) is maximum at high frequencies for all types of discharge. Of special interest is the most powerful type of discharge, in which the signal amplitude (which is one to two orders of magnitude larger than in other discharges) is maximum at frequencies of several hundred megahertz.

Generation of fractal-spectrum signals

Development of communications systems reliably operating in an unfavorable electromagnetic environment is today a challenging problem because of a high density of interfering signals generated by numerous radioelectronic systems (especially in cities) and a large amount of electromagnetic noise of different natures. The search for new types of noise-immune signals is a key direction in designing communications system reliably operating in a noisy environment. Using a fractal wavelet signal as an example, we consider the theoretical and experimental data on synthesizing wide-band fractal signals on a 2-GHz sinusoidal carrier and discuss their basic properties. It is shown that such signals have self-similar fractal spectra and a high noise immunity and, therefore, can be applied in noise-immune communications.

Removal of asphalt-paraffin deposits in oil pipelines by a moving source of high-frequency electromagnetic radiation

A new method for removing asphalt-paraffin and gasohydrate plugs in oil pipelines with a movable source of electromagnetic radiation, electromagnetic pig, is suggested. The pig melts the plug when the latter absorbs intense electromagnetic radiation and heats up. Effective melting of the dielectric plug is achieved with the source moving along the pipeline as the solid-liquid interface propagates. The time of paraffin plug removal and the dependence of this time on the radiation frequency are found with the model suggested. The efficiency of the method is estimated.

An ultrarelativistic fel: Physics and prospects

Abstract Theoretical calculations and experimental data of an ultrarelativistic free electron laser are compared to define the number of coherently radiating particles in pumping e-beams.

Fractal communication system

Complex electromagnetic situation and the need in protecting information from unauthorized access require new engineering solutions in the development of communication system. One of such approaches is associated with fractal communication systems (FCSs) employing antijamming waveforms with fractal spectra as information carriers. Basic concepts of an FCS are considered and the results of its practical implementation for computer communication via an aerial or a coaxial cable are discussed.

Theory of microwave amplification in a coaxial ubitron

Results are presented from a theoretical study of the microwave amplification process in a coaxial ubitron with an undulator based on permanent annular magnets. Such an undulator is used for both focusing of a high-current relativistic electron beam (REB) and excitation of microwave radiation. The spatial structure of the magnetic field in a coaxial undulator is obtained. It is shown that optimum transport of the REB is possible under certain conditions for the parameters of the coaxial undulator (the intensity of the magnetic field and the undulator period).

High-power coaxial microwave ubitron : Simulation by the particle-in-cell method

Results of complete numerical simulation of a high-power coaxial microwave ubitron are reported. The simulation uses a 2.5-dimensional numerical electromagnetic code based on the particle-in-cell method and is performed for the amplification and oscillation operating modes. The results of our numerical simulation are compared with analytical results and results following from the nonlinear theory that are obtained by partial computer simulation.

PIC simulation of powerful microwave coaxial ubitron

Results of numerical simulation of a powerful coaxial UHF-ubitron are given. We received these results using the numerical 2.5-dimensional electromagnetic code, which we developed. This code is based on the PIC method. In the work the algorithm adapted to the coaxial ubitron geometry is described. The numerical analysis of ubitron operation in amplification and in generation regimes is given.

Transportation of high current relativistic electron beams in coaxial drift chambers

The process of high-current relativistic electron beam propagation in a coaxial drift chamber located in homogeneous magnetic fields has been studied theoretically.

Spectral characteristics of spark discharge processes in artificial aerosol clouds

Artificial charged aerosol clouds represent a complicated physicochemical system whose properties approach such little-studied states of matter as aerosol plasma. In this paper the spectra of electromagnetic radiation accompanying discharge processes are discussed. These results are important within the framework of EMC problems.