Slow-wave System Research Articles

Collective quantum dynamics with distant quantum emitters in slow-wave nanoplasmonic waveguides

We consider a slow-wave nanoplasmonic waveguide system with spatially separated (distant) quantum emitters. Based on a nanoplasmonic waveguide quantum electrodynamic theory the emerging non-Markovian collective plasmon-polariton dynamics directly reflects the spatial positioning of the quantum emitters. A phase-space analysis allows us to distinguish between collectivity and cooperativity and the transition between these regimes. For distant emitters, temporal decoherence is reflected in anomalous phase-space evolution. In the spectral domain, collectivity emerges as a resonant single Lorentzian peak with two weak sidebands, while cooperativity manifests as a Fano-like resonance normal-mode splitting. Remarkably, even for distant quantum emitters, we achieve collective multiple quantum emitter dynamics with non-vanishing excitation and vanishing instantaneous emission, establishing an interaction-based quantum nanoplasmonic memory with key relevance in quantum nanoplasmonic networks.

The development of W waveband diffraction radiation oscillator

This study presents the development of a continuous wave diffraction radiation oscillator utilizing a sheet electron beam. The oscillator comprises a slow-wave system formed by double-comb gratings, an open resonant cavity consisting of a spherically curved mirror and a cylindrically curved mirror, and a sheet electron beam generated by a diode gun. A permanent magnetic focusing system stabilizes the transmission of the sheet electron beam within the slow-wave system. Through a combination of mechanical and electronic tuning, the oscillator generates stable signal output in the TEM00q mode. The oscillator's frequency tuning range spans from 87 to 97 GHz, achieving a maximum output power of 13.5 W.

Microwave Methods and Technologies for Monitoring Electrical Activity of the Skin

The paper presents the analysis of the existing solutions for measuring the electrical activity of the skin using traditional methods, which include the use of direct current sensors, and also proposes new promising solutions related to the use of sensing elements based on slow wave systems. The questions of practical realization of electrodes, in particular materials and topologies providing mechanical strength and ergonomics of elements of wearable devices are considered. It is shown that the use of microwave sensors allows to increase the sensitivity of the device in comparison with the existing analogs on direct current, and also possess the desired mechanical properties, allowing them to be resistant to deformations.

Development and research of a slow-wave system for a miniature W-band multibeam traveling wave lamp

The results of the development of a meander-type slow-wave system (SS) with metal supports for a miniature high-power W-band traveling wave lamp (TWT) with two ribbon electron beams are presented. Using a three-dimensional finite element software package, the electrodynamic parameters of the GS were studied. A two-section model of a TWT amplifier with a discontinuity has been developed to prevent self-excitation. Three-dimensional modeling of electron-wave interaction was carried out. It was found that with a total beam current of 200 mA in linear mode, the gain exceeds 30 dB in the frequency band 95.4...97.75 GHz, and the output power in saturation mode reaches 120 W. A technology for manufacturing SS based on laser microprocessing of thin copper plates is proposed. Test samples of the SS were manufactured and verified using optical and scanning microscopy.

Оптимизация полосы пропускания в лампе бегущей волны О-типа террагерцового диапазона

For developing terahertz O-type traveling wave tube amplifiers, as a rule, models are used that take into account only interaction of electron beam with electromagnetic wave in slow-wave system, without considering influence of areas occupied by electron gun and collector on these processes. However, if resonance occurs within volumes occupied by electron gun and collector, then this may lead to distortion of the slow-wave system bandwidth, thereby degrading the device performance. Reflectors using can significantly improve this situation, as thanks to reflectors, electromagnetic waves don't pass inside these areas, and absorbing layer inside them suppresses the resonance possibility. As a result, the device becomes more stable and efficient as an electromagnetic wave amplifier. This paper presents the numerical simulation results of processes in terahertz TWT model, including the entire device volume without exceptions, based on the Finite-Difference Time-Domain (FDTD) method for Maxwell equations and the Particle-In-Cells (PIC) method for calculating electron beam dynamics.

Development of Powerful Spatially Extended W-Band Cherenkov Maser of Planar Geometry With Two-Dimensional Distributed Feedback

A powerful spatially extended planar Cherenkov maser project operating in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${W}$ </tex-math></inline-formula> -band is under development in collaboration between Budker Institute of Nuclear Physics of the Russian Academy of Sciences (BINP RAS) (Novosibirsk) and Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS) (Nizhny Novgorod). The ELMI accelerator (1 MeV/5–7 kA/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3~\mu \text{s}$ </tex-math></inline-formula> ) forms a sheet electron beam with the transverse size (width) of up to 18 cm, which serves to drive the oscillator. The electrodynamic system of this Cherenkov maser is based on doubly periodical structure, which combines the properties of a slow wave system that realizes conditions for an effective Cherenkov interaction with a high-current rectilinear sheet electron beam and a high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> resonator that implements the mechanism of two-dimensional distributed feedback and provides selective excitation of the operating mode in the strongly oversized interaction space. In this article, the crucial elements and design parameters of the oscillator are discussed, and the results of simulations are presented to demonstrate the possibility of achieving a stable narrow-band generation regime for a transverse system size reaching about 50 wavelengths and a gigawatt output power level. To provide a single-directed output of radiation, a planar Bragg reflector is elaborated for installation at the cathode side of the interaction space. A mode converter formed by a slowly tapered waveguide section for transformation of the radiated wavebeam into a Gaussian-type wavebeam was designed to be installed at the oscillator output. In the electron-optical experiments, the formation of a large-width sheet electron beam with parameters acceptable to drive designed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${W}$ </tex-math></inline-formula> -band Cherenkov maser is demonstrated.

Планарные замедляющие системы для ЛБВ миллиметрового диапазона длин волн

Achievements, problems and features in the development of planar slow-wave systems for TWTs in the millimeter range are considered. In this article, a review of the characteristics of planar slow-wave systems for mm-band TWTs manufactured using photolithography is presented, which provides the opportunity for researchers and manufacturers to select high-tech designs of planar slow-wave systems for creating efficient broadband TWTs.

Compact High Efficiency Relativistic Magnetron With TE11 Mode Output

A compact high-efficiency GW-level <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula> -band relativistic magnetron (RM) with TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode output is proposed. In order to achieve high efficiency and high power, an eight-cavity slow wave system with rectangular vanes is adopted, which can provide a larger resonant system where the high-frequency energy is directly stored. All cavity axial extraction (ACAE) is applied with four 90° sector waveguides arranged azimuthally around the anode block. The four 90° sector waveguides play a significant role in converting sector waveguide TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode to circular waveguide TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode. The entire tube is designed without any increase in the radial dimension, which is propitious to a compact and lightweight magnet system design. In particle-in-cell (PIC) simulations, the proposed rectangular vane-type 8-cavity (R8) RM with ACAE can generate a microwave power of 2.1 GW with a pure TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode at the frequency of 2.475 GHz when the applied voltage is 460 kV and the axial magnetic field is 0.46 T, and the power conversion efficiency is 68.4%.

Generation of a Periodic Sequence of Ultrashort Electromagnetic Pulses in a Scheme with Two Parallel Radiating and Absorbing Electron Beams

We demonstrate the possibility of generating a periodic sequence of ultrashort electromagnetic microwave pulses in a scheme with two parallel coaxial electron beams formed by a common cathode and transported via common vacuum channel. The external cylindrical tubular beam ensures the amplification of radiation during rectilinear propagation along periodic slow-wave system, while the internal (paraxial) beam accounts for the nonlinear cyclotron-resonance absorption.

Development of Electrodynamic Components for Microwave Electronic Devices Using the Technology of 3D Photopolymer Printing with Chemical Surface Metallization

We study the possibility of using the technology of 3D photopolymer printing with subsequent metallization of working surfaces for developing electrodynamic components of microwave devices. The technology applicability is considered by examples of mockups of a profiled helical waveguide for a microwave undulator of a Compton free-electron laser and a periodic slow-wave system of a backward-wave oscillator with a ribbon electron beam. The results of “cold” measurements of the parameters of these electrodynamic systems are presented and good agreement with the simulation results is obtained, which confirms the prospects of using additive technologies for developing components of the vacuum microwave electronic devices.

Multi-pass relativistic traveling-wave tube with simultaneous operation on symmetric and asymmetric modes

The advantages of using symmetrical and asymmetric eigenmodes of a slow-wave system (SWS) in a relativistic traveling-wave tube (TWT) with multi-pass amplification are discussed. The nonlinear theory of such a TWT amplifier is developed. The parameters of the SWS of the Ka-band TWT amplifier based on a combination of the lower symmetric E01 mode and the asymmetric hybrid HE11 mode are calculated. The calculated efficiency of the amplifier reaches 28% with a gain of about 40 dB. The results of the calculations are confirmed by 3D particle-in-cell (PIC) simulation, in which an output power of 200 MW and a total gain of about 40 dB are obtained when the amplifier is driven by a 500 keV/2 kA hollow electron beam with a total pulse duration of 25 ns. Amplification of short millimeter-wave pulses is also demonstrated in PIC simulations, in which an output peak power of about 180 MW with a pulse duration of the order of 1 ns is obtained.

High-Efficiency Relativistic Generators of Nanosecond Pulses in the Millimeter-Wavelength Range

We propose and study a scheme of a microwave pulse generator operating in the frequency ranges near 37 and 73 GHz, in which the electron interaction with both the (−1)st harmonic of the counterpropagating TM02 mode and the synchronous slowed-down TM01 mode is combined in a sectionalized slow-wave system with an average diameter of 2.5λ. An efficient current modulation at the input of the slow-wave system is ensured in the region of the cathode–anode gap and the matching section, which reduces the diffraction loss of the energy flow directed towards the cathode. Numerical modeling shows that the efficiency of converting the electron-beam power to microwave radiation is up to 50%. Experiments demonstrate a stable regime of generation of subgigawatt pulses at an efficiency of more than 40% in the upper part of the millimeterwavelength range, which have a reproducible spatial wave structure corresponding predominantly to the TM01 mode at the input of the emitting horn.

Hybrid Vircator Microwave Oscillator with a Nonlaminar Electron Beam and an Electrodynamic Section

A vircator-based microwave oscillator with a nonlaminar electron beam and an extended matched section of a helical slow-wave system was studied numerically and experimentally. It is shown that the oscillator efficiency in the frequency range of 1–3 GHz reaches 20%.

Проектирование замедляющей системы для ЛБВ Ku диапазона с полосой рабочих частот не менее 16,5% и коэффициентом усиления не менее 30 дБ.

Проектирование замедляющей системы для ЛБВ Ku диапазона с полосой рабочих частот не менее 16,5% и коэффициентом усиления не менее 30 дБ.

Designing a Beam-Plasma Traveling Wave Tube

The method of equivalent systems is used to simulate resonator slow-wave structures of beam-plasma devices. A collisionless plasma is considered as a filler for the drift channel. The adequacy of the model is shown by comparing the calculation results with known experimental data. The dispersion characteristics of slow-wave systems are analyzed. The structure of the high-frequency unit of a beam-plasma traveling wave tube is developed, and the parameters of the tube are evaluated using the VEGA code.

Slow-Wave System of Double Shifted Impedance Comb

Using the partial domain method, surface integral equations are obtained for slow-wave systems of double shifted combs taking dissipation on all metal surfaces into account. The case of aliquot comb periods is considered. The quadratic functionals are proposed as dispersion equations. A method to solve complex dispersion equations in the form of functionals for complex constants of propagation is proposed by means of their joint iterations with integral equations. The results of calculating the dispersion with allowance for dissipation in several structures considered are presented.

Electron Orbital Motion and the Threshold Voltage for Spatial-Harmonic Magnetrons

The Buneman-Hartree relation is a condition that determines the excitation of oscillations in magnetrons. However, experiments of different years indicate that for a whole class of similar generators, it is not accurate enough. In particular, this is observed for the so-called spatial-harmonic magnetrons, which have significant advantages over conventional ones in millimeter and subterahertz ranges. The operating parameters of these generators are close to the Hull cutoff parabola, i.e., they have substantially larger transverse dimensions of the interaction space for the same values of the operating voltage and magnetic field, and accordingly, a larger-sized slow-wave system is possible. The results obtained in the development of spatial-harmonic magnetrons for radars can serve to estimate the limits of applicability of the Buneman-Hartree condition. Experiments show that the initial voltage at which generation occurs is significantly higher than the value calculated from the conventional formula. Probable causes are a change in the pattern of motion of an electron near the Hull cutoff parabola and the possibility of exciting gyroresonances. The analysis of the experiments fully confirms that even for millimeter-band magnetrons operating under purely drift (conventional) resonance, an analytical model that takes into account the orbital motion of electrons more accurately describes the physical processes near the cutoff parabola and significantly improves the accuracy of the choice of generator parameters and operating modes.

Замедляющая система двойная сдвинутая импедансная гребенка"

AbstractUsing the partial domain method, surface integral equations are obtained for slow-wave systems of double shifted combs taking dissipation on all metal surfaces into account. The case of aliquot comb periods is considered. The quadratic functionals are proposed as dispersion equations. A method to solve complex dispersion equations in the form of functionals for complex constants of propagation is proposed by means of their joint iterations with integral equations. The results of calculating the dispersion with allowance for dissipation in several structures considered are presented.

Effect of Mode Transformation in THz Clinotron

Extension of the theory of a clinotron is developed by use of the scattering matrix of an oversized T-junction on the ends of a slow wave system. The matrix contains elements corresponding to the transformation of slow grating modes into fast ones and vice versa. Those fast waves with low ohmic losses provide strong resonant properties of a clinotron even in the case of strong attenuation of the surface mode. Results of the theoretical simulation are compared with experimental ones and obtained dependencies explain strong resonances in sub-THz clinotrons.

Slowing designer surface plasmons in a surface-wave photonic crystal.

We propose and experimentally demonstrate a broadband slow-wave system in a surface-wave photonic crystal based on a non-uniform line-defect waveguide with graded metallic pillars, whose dispersions and cutoff frequencies vary gradually along the waveguide. Since the group velocity of designer surface plasmons at the cutoff frequencies is zero, we show that surface waves can be slowed and stopped at different positions under different frequencies. Experimental evidence including transmission measurements and direct near-field profile imaging performed in the microwave frequencies validate the stopping of surface waves in a broadband range within the forbidden bandgap of the surface-wave photonic crystal. This proposal is a promising candidate for slow-wave devices implemented on a single metal surface in both the microwave and terahertz frequency ranges.