Radiophysics and Quantum Electronics最新文献

There is currently a significant gap in understanding the effects of astro- and geophysical factors such as ionizing and non-ionizing radiation, including electromagnetic fields, on living organisms. The effects caused by these factors are important for planning scenarios in which significant changes in the intensity of such factors can be expected both on the Earth and during space missions. There is a reason to believe that, of all the indicators of the functioning of living organisms, the signaling systems responsible for the perception, processing, and amplification of the incoming stimulus are the most sensitive. In this work, we have studied the effect of increased levels of ionizing radiation (β radiation, dose rate of 31.3 μGy/h) and hypomagnetic conditions (induced magnetic field 0–1.5 μT) on electrical signals of plants caused by an additional stimulus. To conduct the experiments, a setup based on triaxial Helmholtz rings was created, which permits one to set and maintain altered conditions of the electromagnetic environment with high accuracy. The work showed that an increased level of ionizing radiation strengthens, while the near-null level of magnetic field weakens electrical signals in plants. It is assumed that the mechanism of action of such factors is their effect on a single component of stress signaling, namely, concentration of reactive oxygen species. The observed effects open up a new way for studying the mechanisms of the influence of ionizing and non-ionizing radiation on the state of living organisms.

One of the approaches to enhance the performance of a subcarrier wave quantum communication system is to modify the underlying detection principles. In this study, we investigate heterodyne detection using a balanced photodetector as an alternative to a single-photon detector. A heterodyne detection scheme was implemented for a subcarrier wave quantum key distribution system. The experimental operation of this scheme was demonstrated, and measurements of the phase shift—which can be used to encode information—were carried out.

Installation of the gyrotron complex on the T-15MD tokamak is planned for additional plasma heating and non-inductive current drive, as well as for pre-ionization of gas at the initial stage of the discharge. Safe and reliable operation of gyrotrons requires effective protection measures not only from microwave radiation, but also from X-ray radiation generated by the gyrotrons. The article presents the results of the X-ray radiation measurements when operating a 82.6 GHz gyrotron (with a power of up to 1 MW and a pulse duration of 1 s). NaI(Tl) and LaBr3(Ce) scintillation detectors are used for recording the X-ray radiation spectra. The spectrometric analysis carried out in the gyrotron operating mode with an accelerating voltage up to U=47.6 kV showed a continuous energy distribution of X-ray radiation with a maximum in the range 15–20 keV. In standard operating modes, the maximum radiation intensity is observed near the collector, at the microwave exit window, and in the lower part of the gyrotron. Installation of protective lead shields (up to 4 mm thick), covering the entire collector area and the area of the exit window of the microwave path, provides effective shielding from the X-ray radiation.

We consider the problem of interpolation of equidistant redundant series of samples, i.e., recovery of the values of a function with finite spectrum at any moment of time using an infinite series of discrete samples. A method for construction of appropriate functions is indicated. Asymptotic estimates of the rate of decrease at large times for the constructed functions are obtained. It is shown that the resulting functions decrease faster than those proposed earlier.

We study the radiation of whistler waves by a circular phased array of electric dipoles in a homogeneous cold magnetoplasma. It is assumed that the dipole sources of the array are electrically short and aligned with an external magnetic field. Using the expansion of the excited field in terms of cylindrical vector eigenfunctions of a magnetoplasma, rigorous integral representations of the total radiated power of the array are obtained along with its partial radiated powers going to waves with different values of the azimuthal index. For the ionospheric plasma conditions, the total and partial radiation resistances corresponding to these powers are calculated. Conditions are determined under which the array can excite selectively whistler waves with a given azimuthal index in a magnetoplasma.

We present the results of studying experimentally how axial misalignment of the cathode unit in a magnetron-injection gun affects the parameters of the helical electron beam and the efficiency of a two-resonator gyroklystron. The gyroamplifier uses an electron gun, whose design makes it possible to move the heated cathode. Four screws, which are located at an angle of 90° to each other, are used to move the cathode in a radial plane perpendicular to the axis of the system. The electron distribution functions in longitudinal velocities in the electron beams formed by different areas of the cathode are studied in an adjusted electron-optical system and at two values of the radial displacement of the cathode from the optimal position. It is shown that the pitch factor of the entire beam depends weakly on this displacement, while the spread of the longitudinal velocities increases sharply when the symmetry of the cathode unit is violated. The velocity spread increases due to the displacement of individual distribution functions of the electron beams emitted by different sections of the cathode into the regions of the longitudinal velocities, which are opposite to each other relative to their position in the adjusted electron-optical system. In addition, the increase in the spread is associated with the influence of the variable fields of the longitudinal low-frequency space charge oscillations, which are accumulated in the trap between the cathode and the magnetic mirror, on the passing beam. The main reason for the observed experimental drop in the efficiency with the increasing bias is determined by the spreading of the phase bunches of the grouped beam in the drift space, when the electrons arriving at the output cavity have significantly different longitudinal velocities due to a large velocity spread, which results in that some of them fall into non-optimal phases of the high-frequency field of the working cavity mode.

We propose a method for calculating the directional characteristics of a planar adaptive antenna array, with the weighting coefficient vector optimized via the Howells–Applebaum algorithm, and present the results of the corresponding modeling. The directional characteristics of the antenna array is obtained in the form of a level pattern. Differences in the directionality between planar and linear antenna arrays are discussed.

We consider the electrodynamic characteristics of slow spatial traveling harmonics in periodic waveguides. It is shown that for the electronic systems based on the stimulated Čerenkov radiation, as well as for the most devices of other types, there exists a region of parameters with a low (up to zero) coupling resistance for transverse magnetic waves. A physical interpretation of this phenomenon is given, and a generalized condition for its existence is obtained.

We consider the problem of electromagnetic wave scattering from 3D arbitrary shaped inhomogeneties located on the surfaces of a large body. To solve the problem, a combined method which combines the method of physical optics with the method of integral equations is proposed. An overridden system of linear algebraic equations is compiled to calculate surface currents. The block least squares method is used to solve it. Samples of calculation are given. To calculate surface currents, an overdetermined system of linear algebraic equations is obtained.

We analyze the results of a full-scale experiment on two-dimensional direction finding (with respect to the azimuth and the elevation angle) in a passive radiotelemetric complex in the decimeter-wave range. The complex includes an adaptive antenna array, whose sheet has rectangular topology. Direction finding objects transmit both a tone signal and a phase-manipulated signal, which is in most demand in modern telemetry complexes. Scenarios with one, two, or three sources on the air are considered. Special attention is paid to cases where two sources are located in the main beam of the directional pattern. The work proposes a number of approaches which allow one to reduce the computational complexity of the processing method. The experimental results confirm their applicability for real-time operation in domestic complexes of this type.