D. A. Lukovnikov

Bio: D. A. Lukovnikov is an academic researcher from Russian Academy of Sciences. The author has contributed to research in topics: Waveguide & Gyrotron. The author has an hindex of 5, co-authored 11 publications receiving 78 citations.

Resonant reflectors for free electron masers

Abstract: A new type of a waveguide reflector is discussed. Its operating principle is based on the effect of resonant reflection of a wave from a cavity when there is coupling between the wave and an eigenmode of the cavity. The resonant reflectors are very attractive for the use in microwave systems of free electron masers due to their high reflection coefficients and narrow frequency bands at comparatively short lengths. Results of calculations and measurements of some resonant reflectors and a microwave system for KA-band cyclotron autoresonance masers are presented.

Minimization of Diffraction Losses in Big Gaps of Multi-Mode Waveguides

Abstract: A systematic approach to design of low-loss miter bends and quasi-optical gaps in multi-mode waveguides is proposed. Several examples illustrate the approach. A mode filter based on a quasi-optical gap in the 31.75 mm diameter corrugated waveguide at frequency 84 GHz has been tested in low (mW) and high-power (200 kW, CW) experiments.

Simple millimeter wave notch filters based on rectangular waveguide extensions

Abstract: A new efficient notch filter is proposed. Some details of notch filter operation at millimeter waves are discussed. A 110 GHz notch filter is numerically and experimentally tested.

On the resonant scattering at guide dielectric windows

Abstract: The effect of output wave resonant scattering at vacuum window of a microwave device caused by high-quality dielectric window eigenmodes excitation is studied. These negative resonant effects can seriously influence the device operation. The numerical calculation results are confirmed by a model experiment.

Oversized $Ka$ -Band Traveling-Wave Window for a High-Power Transmission

Abstract: A new millimeter-wave barrier window in an oversized metallic circular waveguide has been developed for high-power transmission. The novel design utilizes the traveling-wave regime in an oversized profiled guide and synthesized TE0n mode mixing to minimize field intensity at the alumina ceramics surface. Proper choice of ceramics thickness provides necessary broadening of the operation frequency band. Low-power measurements show a reflection level below -25 dB at the operating frequency band of 34.272 plusmn 0.06 GHz

State-of-the-Art of High-Power Gyro-Devices and Free Electron Masers

Abstract: This paper presents a review of the experimental achievements related to the development of high-power gyrotron oscillators for long-pulse or CW operation and pulsed gyrotrons for many applications. In addition, this work gives a short overview on the present development status of frequency step-tunable and multi-frequency gyrotrons, coaxial-cavity multi-megawatt gyrotrons, gyrotrons for technological and spectroscopy applications, relativistic gyrotrons, large orbit gyrotrons (LOGs), quasi-optical gyrotrons, fast- and slow-wave cyclotron autoresonance masers (CARMs), gyroklystrons, gyro-TWT amplifiers, gyrotwystron amplifiers, gyro-BWOs, gyro-harmonic converters, gyro-peniotrons, magnicons, free electron masers (FEMs), and dielectric vacuum windows for such high-power mm-wave sources. Gyrotron oscillators (gyromonotrons) are mainly used as high-power millimeter wave sources for electron cyclotron resonance heating (ECRH), electron cyclotron current drive (ECCD), stability control, and diagnostics of magnetically confined plasmas for clean generation of energy by controlled thermonuclear fusion. The maximum pulse length of commercially available 140 GHz, megawatt-class gyrotrons employing synthetic diamond output windows is 30 min (CPI and European KIT-SPC-THALES collaboration). The world record parameters of the European tube are as follows: 0.92 MW output power at 30-min pulse duration, 97.5% Gaussian mode purity, and 44% efficiency, employing a single-stage depressed collector (SDC) for energy recovery. A maximum output power of 1.5 MW in 4.0-s pulses at 45% efficiency was generated with the QST-TOSHIBA (now CANON) 110-GHz gyrotron. The Japan 170-GHz ITER gyrotron achieved 1 MW, 800 s at 55% efficiency and holds the energy world record of 2.88 GJ (0.8 MW, 60 min) and the efficiency record of 57% for tubes with an output power of more than 0.5 MW. The Russian 170-GHz ITER gyrotron obtained 0.99 (1.2) MW with a pulse duration of 1000 (100) s and 53% efficiency. The prototype tube of the European 2-MW, 170-GHz coaxial-cavity gyrotron achieved in short pulses the record power of 2.2 MW at 48% efficiency and 96% Gaussian mode purity. Gyrotrons with pulsed magnet for various short-pulse applications deliver Pout = 210 kW with τ = 20 μs at frequencies up to 670 GHz (η ≅ 20%), Pout = 5.3 kW at 1 THz (η = 6.1%), and Pout = 0.5 kW at 1.3 THz (η = 0.6%). Gyrotron oscillators have also been successfully used in materials processing. Such technological applications require tubes with the following parameters: f > 24 GHz, Pout = 4–50 kW, CW, η > 30%. The CW powers produced by gyroklystrons and FEMs are 10 kW (94 GHz) and 36 W (15 GHz), respectively. The IR FEL at the Thomas Jefferson National Accelerator Facility in the USA obtained a record average power of 14.2 kW at a wavelength of 1.6 μm. The THz FEL (NOVEL) at the Budker Institute of Nuclear Physics in Russia achieved a maximum average power of 0.5 kW at wavelengths 50–240 μm (6.00–1.25 THz).

Relativistic X-band BWO with 3-GW output power

Abstract: Results from a study of a relativistic X-band backward-wave oscillator (RBWO) with 3-GW output microwave power are presented. The RBWO was driven by the high-current electron accelerator SINUS-7. The dependence of radiated microwave pulse duration on microwave power was obtained. Pulse shortening occurring at the higher power levels is probably attributable to explosive electron emission from the slow wave structure (SWS). An increase in the cross section of the electrodynamic structure seems to be a way to increase the microwave pulse duration. Experimental results from a moderately oversized X-band RBWO using a resonance reflector are described. This tube can be operated with a low external magnetic field.

A multigigawatt X-Band relativistic backward wave oscillator with a modulating resonant reflector

Abstract: Effective generation regime with a high output pulse power has been experimentally realized in a relativistic backward wave oscillator (RBWO) with a resonant reflector and a slow-wave system having a diameter 1.6 times the radiation wavelength. At a guiding magnetic field of 4.5 T, the maximum peak power amounted to 4.3 GW at a frequency of 9.4 GHz, an efficiency of 31%, and a microwave pulse duration of 22 ns.

Frequency-tunable CW gyro-BWO with a helically rippled operating waveguide

Abstract: Operation of a continuous wave gyrotron backward-wave oscillator (gyro-BWO) with a helically rippled operating waveguide has been experimentally studied. The gyro-BWO exploits a dc oil-cooled magnet with magnetic field up to 0.5 T and utilizes a weakly relativistic (20 keV) electron beam produced by a magnetron injection gun. Stable generation at the second cyclotron harmonic with a maximum power of 7 kW and an efficiency of 15% at a frequency of 24.7 GHz was achieved. Smooth oscillation frequency tuning by varying the magnetic field was measured to be as wide as 5% at the half-power level. The first gyro-BWO operation with a single-stage energy recovery system was realized. The use of a depressed collector provided an efficiency increase up to 23% and an opportunity for reduction of the main power supply voltage down to 10 kV.

State-of-the-Art of High Power Gyro-Devices and Free Electron Masers. Update 2011. (KIT Scientific Reports ; 7606)

Abstract: This report gives an update of the worldwide experimental achievements in the development of long-pulse gyrotron oscillators for fusion plasma heating, plasma diagnostics and materials processing. In addition, this work gives a short overview of the present development status of coaxial-cavity multi-megawatt gyrotrons, gyrotrons for technological and spectroscopy applications, relativistic gyrotrons, quasi-optical gyrotrons, cyclotron autoresonance masers, gyro-amplifiers, gyro-BWO's, free electron masers and of vacuum windows for such high-power mm-wave sources.