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卷 62, 编号 4 (2019)

Article

Methods for Measuring the Signal of the Phase Calibration of the VLBI Radio Telescopes

Nosov E.

摘要

In the majority of modern radio telescopes, which are used for radio interferometry with very long baselines, a special signal is introduced into the signal chain for the phase calibration of the equipment. This signal is used during the correlation processing of the radio-astronomy observations for obtaining a synthesized response when it is required to match the signals of several frequency channels by phase and delay and to ensure control over the working capacity of the equipment and the phase stability of the signal chain during the preparation and implementation of observations. Isolation of the phase-calibration signal in the recorded data requires considerable computation resources. In this case, the computation volume increases with increasing recorded frequency domain, which can amount to several gigahertz for modern radio telescopes, such as RT-13 of the “Quasar” VLBI network. In this work, the well-known methods for measuring the parameters of the phase-calibration signal are considered, their precision is estimated, the computation efficiencies are compared, and the disadvantages of the available measuring algorithms are shown. An improved method allowing one to significantly save the computation cost without the measuring-accuracy loss is proposed, which softens hardware requirements and speeds up computations.

Radiophysics and Quantum Electronics. 2019;62(4):237-249
pages 237-249 views

Volume Heating of a Vertical Air Column by Microwave Radiation in the Atmospheric Absorption Line

Krupnov A., Tretyakov M.

摘要

We propose a method of volume heating of a vertical air column by the vertically directed microwave radiation at the frequency of the spectral atmospheric-absorption line. The heating efficiency is estimated for the case of the molecular-oxygen absorption band near a frequency of 60 GHz. The proposed heating method can lead to the formation of new convection structures in an air column. Absence of natural ascending airflows with stationary heating over the entire flow length is noted.

Radiophysics and Quantum Electronics. 2019;62(4):250-256
pages 250-256 views

Reflection and Refraction of Harmonic Plane Acoustic Waves by a Plane Interface of Media with Arbitrary Acoustic Properties

Kobelev Y.

摘要

We propose universal formulas for the amplitudes of longitudinal and transverse plane acoustic waves, which are reflected and refracted by a plane interface of two media. The formulas are valid for liquid and gaseous media, as well as for elastic isotropic media. Advantages of these formulas are their relative clarity compared with the well-known and commonly accepted formulas, as well as a possibility to pass over from one scattering problem to another by simply replacing the corresponding wave numbers. Despite the well-known methods which are used in the calculations and rather have a methodical character, we manage to find a new type of surface waves at the interface of elastic media. These waves are characterized either by ratios of the wave numbers of transverse waves and densities, or by only the wave numbers of longitudinal waves and the ratio of the densities of media.

Radiophysics and Quantum Electronics. 2019;62(4):257-266
pages 257-266 views

Analytical Calculation and Monte Carlo Simulation of a Variation in the Shape of a Short Radio Pulse in the Case of Scattering in Urban Conditions

Gavrilenko V., Zhukov S., Zhukov M., Yashnov V.

摘要

We apply the corpuscular Monte Carlo method for the first time to calculate numerically the shape of an initially short radio pulse scattered in urban conditions. In the simplest two-dimensional case, which corresponds to a low elevation of the source and receiver with respect to building roofs, agreement of the results of the analysis and numerical calculations of the shape of the received pulse is demonstrated in the case of a single reflection of the pulse from building walls. The dependence of the pulse duration on various factors is analyzed with allowance for multiple reflections and diffraction by the roofs of urban structures.

Radiophysics and Quantum Electronics. 2019;62(4):267-276
pages 267-276 views

Optimization of a High-Power Subterahertz Gyrotron Tunable in a Wide Frequency Range Allowing for the Limitations Imposed by the Magnetic System

Zuev A., Zapevalov V., Plankin O., Semenov E.

摘要

We present a version of the frequency-tunable gyrotron operating in a wide frequency range (0.1–0.26 THz) with an output radiation power of up to 260 kW. Multilevel analysis and combined optimization of its electron-optical and electrodynamical systems are performed. The gyrotron is designed for operation with the JASTEC-10T100 cryomagnet or its analogs. Efficiency of single-stage recovery in this system is analyzed. A collector system is proposed, which is capable of collecting electron beams effectively during gyrotron operation in the entire specified frequency range.

Radiophysics and Quantum Electronics. 2019;62(4):277-285
pages 277-285 views

Method for Studying the Dynamics of Fast Frequency Sweeping Events in the Spectra of Non-Thermal Electromagnetic Plasma Emission

Viktorov M., Ilichev S.

摘要

We developed an algorithm for processing of the dynamic spectra of plasma emission, which makes it possible to extract chirped elements with both increasing and decreasing frequencies. The algorithm was tested on a set of experimental data obtained by studying the emission spectra of the rarefied plasma of an electron cyclotron resonant discharge in an open magnetic trap. The efficiency of the method is close to 100% for signals with a signal-to-noise ratio of more than 30 dB and about 50% with a signal-to-noise ratio of 20 dB. This method can be used for automated analysis of dynamic emission spectra of both laboratory and space plasmas.

Radiophysics and Quantum Electronics. 2019;62(4):286-292
pages 286-292 views

Crossover of Quasiparticles and Statistics of Bose-Einstein Condensate with Increasing Interaction: from an Ideal Gas to a Thomas-Fermi Regime. The Case of a One-Dimensional Flat Trap

Tarasov S., Kocharovsky V., Kocharovsky V.

摘要

A change-over of the quasiparticle wave functions and spectrum under a variation in an interparticle interaction in a Bose-Einstein condensed gas of bosons confined in a one-dimensional trap with a flat potential and impermeable walls is studied analytically and numerically. An efficient approximate method of analysis is developed. It yields a solution to the self-consistent Bogoliubov and Gross-Pitaevskii equations for quasiparticles and the condensate that describes a crossover from the regime of a gas of noninteracting bosons to the regime of a gas with the interaction being strong enough to reach a Thomas-Fermi asymptotics. As a result, the characteristic function of the total number of noncondensed particles is found which, for the first time, allows one to figure out how the quantum statistics of fluctuations of the number of particles in the condensate depends on its inhomogeneity and the interparticle interaction in the case of the flat trap. The qualitative features of this dependence as well as a possibility of an experimental observation of the predicted effects in the actual traps are discussed.

Radiophysics and Quantum Electronics. 2019;62(4):293-310
pages 293-310 views