Vitalii I. Shcherbinin

Bio: Vitalii I. Shcherbinin is an academic researcher from Kharkov Institute of Physics and Technology. The author has contributed to research in topics: Gyrotron & Waveguide (acoustics). The author has an hindex of 10, co-authored 45 publications receiving 277 citations. Previous affiliations of Vitalii I. Shcherbinin include Jilin University.

Effect of Cavity Ohmic Losses on Efficiency of Low-Power Terahertz Gyrotron

Abstract: The problem of power degradation due to the dominant ohmic losses in gyrotron cavity is considered. As an example, the operating performances of the FU CW III gyrotron of Fukui University are investigated numerically. It is found that, for this gyrotron, there is a significant divergence between the classical and the self-consistent computations of the loss-induced power degradation. The reason is that the former computations ignore the effect of the cavity ohmic losses on beam-wave interaction efficiency.

Cylindrical Cavity with Distributed Longitudinal Corrugations for Second-Harmonic Gyrotrons

Abstract: Metallic cavity with distributed longitudinal corrugations is proposed and studied for the use in a subterahertz second-harmonic gyrotron. The corrugated conducting walls are treated as a homogeneous surface with effective (averaged) anisotropic impedance. The theoretical study incorporates both single-mode and coupled-mode approaches. It is shown that the distributed longitudinal corrugations provide several-fold increase in the Q-value of the operating mode with respect to that of the fundamental competing mode at a reasonable level of ohmic losses and mode conversion in the gyrotron cavity.

On the theory of longitudinally inhomogeneous waveguides with impedance walls

Abstract: The Maxwell equations for longitudinally inhomogeneous (irregular) waveguides with impedance walls are reduced equivalently to a system of ordinary differential equations by applying transverse expansions. The obtained system of equations for amplitudes of the coupled modes is used to analyze gyrotron cavities. Specifically, the effect of mode conversion and ohmic losses on the eigenfrequencies, quality factors, and field distributions in the gyrotron cavities operating in the submillimeter range is investigated.

Improved Cavity for Broadband Frequency-Tunable Gyrotron

Abstract: Cavity modification is proposed with the aim of enhancing the continuous frequency tunability of a gyrotron. The modification can be applied to both uniform and tapered gyrotron cavities and involves just using an additional cavity section. It ensures larger effective cavity length and thus lower starting current for higher order axial modes. As a consequence, the frequency tuning band of the gyrotron can be increased significantly. Moreover, the proposed cavity modification is beneficial for smoothing the variations of output power within the tuning band.

Linear and nonlinear theory of the Doppler-shifted cyclotron resonance maser based on TE and TM waveguide modes

Abstract: This paper presents a comprehensive theory of the cyclotron resonance maser (CRM) interaction in a circular waveguide. The kinetic theory is used to derive the dispersion relationships for both TE and TM modes. The TE mode case has been investigated by several authors, but there has been comparatively little work on the TM mode case. However, the TM mode interaction competes effectively with the TE mode interaction at relativistic electron energies. The conditions for maximum temporal and spatial growth rates are shown. The TM mode growth rates are found to vanish when the RF wave group velocity equals the beam axial velocity (‘grazing incidence’). The single particle theory is used to derive a compact set of self-consistent non-linear equations for the TE and TM mode interactions. These equations are particularly appropriate for the cyclotron auto-resonance maser (CARM) regime but applicability extends to other regimes as well. The conditions for optimum efficiency are investigated for oscillator and amp...

Geometrical structure, multifractal spectra and localized optical modes of aperiodic Vogel spirals.

Abstract: We present a numerical study of the structural properties, photonic density of states and bandedge modes of Vogel spiral arrays of dielectric cylinders in air. Specifically, we systematically investigate different types of Vogel spirals obtained by the modulation of the divergence angle parameter above and below the golden angle value (≈137.507°). We found that these arrays exhibit large fluctuations in the distribution of neighboring particles characterized by multifractal singularity spectra and pair correlation functions that can be tuned between amorphous and random structures. We also show that the rich structural complexity of Vogel spirals results in a multifractal photonic mode density and isotropic bandedge modes with distinctive spatial localization character. Vogel spiral structures offer the opportunity to create novel photonic devices that leverage radially localized and isotropic bandedge modes to enhance light-matter coupling, such as optical sensors, light sources, concentrators, and broadband optical couplers.

Metamaterials and Metasurfaces: A Review from the Perspectives of Materials, Mechanisms and Advanced Metadevices

Abstract: Throughout human history, the control of light, electricity and heat has evolved to become the cornerstone of various innovations and developments in electrical and electromagnetic technologies. Wireless communications, laser and computer technologies have all been achieved by altering the way light and other energy forms act naturally and how to manage them in a controlled manner. At the nanoscale, to control light and heat, matured nanostructure fabrication techniques have been developed in the last two decades, and a wide range of groundbreaking processes have been achieved. Photonic crystals, nanolithography, plasmonics phenomena and nanoparticle manipulation are the main areas where these techniques have been applied successfully and led to an emergent material sciences branch known as metamaterials. Metamaterials and functional material development strategies are focused on the structures of the matter itself, which has led to unconventional and unique electromagnetic properties through the manipulation of light—and in a more general picture the electromagnetic waves—in widespread manner. Metamaterial’s nanostructures have precise shape, geometry, size, direction and arrangement. Such configurations are impacting the electromagnetic light waves to generate novel properties that are difficult or even impossible to obtain with natural materials. This review discusses these metamaterials and metasurfaces from the perspectives of materials, mechanisms and advanced metadevices in depth, with the aim to serve as a solid reference for future works in this exciting and rapidly emerging topic.

Analysis of the wide band gyrotron amplifier in a dielectric loaded waveguide

Abstract: The effect of broadening the bandwidth with a dielectric load in a cylindrical gyrotron is investigated for a hollow electron beam. The linear dispersion relation for the azimuthally symmetric, transverse electric (TE) modes is obtained by the method of the wave impedance matching. It is found that the TE perturbations exhibit three unstable modes characterized by their phase velocities vph : one fast wave, the long wavelength mode (LWM, vph ≳c), and two slow waves, the intermediate (IWM, c≳vph ≳ce−1/2) and the short (SWM, vph