Radio physics and electronics

Number 23(3), 2018

3-8
THERMAL ACTION OF MICROWAVE RADIATION ON A VERY THIN CONDUCTING FIBRE

Authors: N. G. Kokodii, M. V. Kaydash, S. V. Pogorelov

Abstract

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The subject and purpose. The experimental findings of a new physical effect of a strong interaction of microwave radiation with very thin (d << l) conducting fibers are presented in the paper. The calculations show that the absorption efficiency factor of fiber of a diameter of several micrometers when exposed to radiation in the centimeter range can reach the value of several hundred. It was found that the effect can be enhanced by oblique incidence of the radiation beam. An experiment to measure the absorption of microwave radiation with a wavelength of 1 cm in a graphite fiber with a diameter of 12 μm has been carried out. Methods and methodology. To determine the absorption of radiation in a fiber the change in the resistance of the fiber when heated by radiation was measured. To reduce the error of the results, the average value of resistance for 1 minute was measured. The resistance was measured at a frequency of 2 Hz. A thermal picture of the heated fiber was observed by means of a thermal imager. A mathematical model of the fiber heating process by the radiation beam is developed. Results. The experiment has showed that a graphite fiber with a diameter of 12 μm absorbs about 10 % of the energy of the incident microwave beam with a wavelength of 1 cm. The heating temperature at the place of incidence of the beam reaches 200 °C. The developed mathematical model describes the interaction process of radiation and fiber well. Conclusion. The results of the study confirmed the existence of a strong interaction of microwave radiation with very thin conducting fibers. The effect can find application in installations where it is necessary to transfer energy of electromagnetic radiation to small targets. Another area of usage of this effect is the creation of protective screens against the effects of microwave radiation on a person or on different installations.

9-39
Clinotronic effect application in vacuum sources of terahertz electromagnetic oscillations (To the 100th anniversary of G. Ya. Levin, the inventor of the O-type BWT-clinotron)

Authors: V. D. Yeryomka, O. F. Pishko

Abstract

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Number of views: 207

Subject and purpose. In the vacuum microwave electronics, with increasing the operating frequency of the source electromagnetic oscillations, most attention is paid to increasing the efficiency of electron-wave interaction on the Vavilov-Cherenkov effect of rectilinear electronic flows with a slow spatial harmonic of electromagnetic waves in metallic periodic slowing structures (PSS). At the same time, isufficient attention was paid to the study of the effect of the coefficient of the use of rectilinear electronic flows on the frequency energy Cherenkov oscillators and amplifiers of electromagnetic oscillations. Clinotron effect, reveated in 1956 in the process of development and research of O-type backward wave tubs (O-type BWT) of short-wave ranges Institute for Radiophysics and Electronics of Academy of Sciences of the Ukrainian SSR, demonstrated a significant influence of the utilization factor of a spatially developed rectilinear electronic flows on the frequency-energy characteristics of the O-type BWT. Methods and methodology. There is no publication in the scientific literature that summarizes the results of research into the frequency-energy characteristics of vacuum sources of terahertz (THz) electromagnetic oscillations with spatially developed electron currents, created during the last 50 years and differing in the principle of action, by theoretical and experimental methods of influence of the clinotronic effect on the frequency-energy characteristics. Results. The analysis of the frequency-energy characteristics of THz BWT-clinotrons, THz-clinoorotrons, THz-gyroclinotrons, THz-clinoorbictrons was carriedout. Based on the analysis of the results of the research, there is a conclusion about the existence of a close relationship between the value of the coefficient of the use of spatially-developed electron flows and frequency-energy and also the mass-size characteristics of vacuum sources of THz electromagnetic oscillations. Сonclusions. The use of the clinotronic effect in vacuum sources of electromagnetic oscillations with spatially developed electron currents contributes to the creation of compact generators and signal amplifiers in the "THz slit" of the spectrum of electromagnetic oscillations.

40-64
SOLID-STATE COMPONENTS AND DEVICES OF TERAHERTZ ELECTRONIC TECHNOLOGY IN UKRAINE

Authors: N. F. Karushkin

Abstract

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Number of views: 207

Subject and purpose. One of the main problems arising in the implementation of the terahertz range is associated with the need to provide the advanced equipment developed in this frequency band with effective electronic components. Methods and methodology. This paper provides a comparative analysis of the characteristics of the terahertz range components, based on the solid-state elements and waveguide electrodynamic structures. Results. The features of design solutions in the process of creating semiconductor components and devices, such as oscillators, amplifiers, frequency multipliers, power meters, transmission lines, and devices for modulating electromagnetic waves using p–i–n-structures, are shown. The main directions of the practical application of apparatus and equipment of the terahertz range are considered. Conclusions. The attractiveness of the terahertz range to create high-speed communication systems, high-resolution radar, radio vision systems, remote identification devices of substances, and other special and civil engineering, is shown. The provided data indicate the potential capabilities of leading Ukrainian enterprises in solving the problems of mastering the terahertz frequency interval.

65-76
Particularities of the influence of electromagnetic field mediated by water on wheat seeds

Authors: O. I. Kovalenko

Abstract

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Number of views: 208

Subject and purpose. Particularities of the targeted modification of functionals of the wheat seeds state by irradiation with a low-intensity electromagnetic field (EF) were investigated. The aim of the work was to investigate the effectiveness of low-intensity electromagnetic field mediated by water on wheat seeds depending on their initial state, evaluated statistically as “norm” and “pathology”, and to study the possibility of functional reconstruction of the wheat seeds with the “pathology” state. Methods and methodology. The work is experimental. Approved radio-physical, radio-technical, biological methods and techniques were used in this work. Generators Г4-141 (37.5…53.57 GHz) and Г4-142 (53.57…78.33 GHz) were used for electromagnetic field irradiation. Efficiency of the electromagnetic field influence was evaluated using functionals of the seed state: energy of growing, average length of roots and seedlings in each portion. Statistical methods were used in the processing and the analysis of the obtained results. Results of work. The possibility of a targeted modification of the functional parameters of wheat seeds upon their interaction with water, previously irradiated with EF, was established. Differences in the effectiveness of the water-mediated influence of EF depending on the frequency and exposure of the signal were shown. We found the dependence of biological reaction of the wheat seeds on the electromagnetic field irradiation mediated by water. The reaction depends on the initial state of the seeds: those in the “norm” state get oppressed, while those in the “pathology” state are stimulated. The application of water-mediated electromagnetic field influence on wheat seeds in the “pathology” state was shown to be promising for restoring of the lost functional properties. Efficient regimes of electromagnetic field influence mediated by water were established. Conclusion. Water-dissipative model of the electromagnetic field interaction with substance was confirmed. Method of the electromagnetic field influence mediated by water on wheat seeds was proposed. It allows stimulating their lost properties, which is promising for development of agricultural technologies.

77-83
DEPENDENCE OF FLUORESCENT CHARACTERISTICS OF NANOCOMPOSITES ON THE BASIS OF DYE MOLECULES AND SILVER NANOPARTICLES ON THE OPTICAL DENSITY OF COMPONENTS

Authors: S. V. Nikolaev, V. V. Pozhar, M. I. Dzyubenko, K. S. Nikolayev

Abstract

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Number of views: 171

Subject and purpose. It is known that the addition of plazmon metal nanoparticles to active media can be used to improve the radiative characteristics of the medium. However, the problem of the influence of the component ratio on the intensity of the nanocomposites fluorescence, which is relevant from an applied point of view, has not been sufficiently investigated and requires additional studies. Methods and methodology. In this paper fluorescence of solutions of Rhodamine 6G and Rhodamine C dyes in the presence of silver nanoparticles at different excitation wavelengths was studied. The effect of the mixture components concentration on the fluorescence amplification coefficient of the dye molecules was studied. Results. It is shown that as a generalized parameter determining the fluorescent characteristics of nanocomposites, one can consider the relative optical density of the mixture components, which is the ratio of the optical density of the nanoadditive to the optical density of the dye at the excitation wavelength. The relative optical density increases with an increase in the concentration of nanoparticles, a decrease in the concentration of the dye, or in the case of excitation by radiation with the spectrum closest to the maximum of plasmon resonance of nanoparticles. In this case, an increase in the fluorescence amplification coefficient was observed. If the pump spectrum is far from the maximum wavelength of the plazmon resonance, the concentration of the nanoparticles is low, and the dye concentration is high, then the relative optical density is small, the fluorescence intensification becomes insignificant, and even its quenching may occur. Conclusions. The results of these studies allow us to formulate a general approach to assessing the effect of the components ratio of mixtures composed of dye molecules and metallic nanoparticles on the fluorescence intensity of fluorophore molecules.