Showing papers by "G. G. Denisov published in 2016"
TL;DR: In this article, the development of radiation sources and present the most notable examples of the use of gyrotrons in spectroscopy and material diagnostics are reviewed and discussed, as well as the near-term development prospects for high-frequency gyrotrajectory.
Abstract: We review the development of radiation sources and present the most notable examples of the use of gyrotrons in spectroscopy and material diagnostics. We describe the main features of terahertz gyrotrons, present the most prominent examples of modern continuous-wave and pulsed gyrotrons for a specified frequency range, examine a number of topical applications, and discuss near-term development prospects for high-frequency gyrotrons.
54 citations
TL;DR: The electron cyclotron (EC) heating and current drive (H&CD) system developed for the ITER is made of 12 sets of highvoltage power supplies feeding 24 gyrotrons connected through 24 transmission lines (TL), to five launchers, four located in upper ports and one at the equatorial level as mentioned in this paper.
Abstract: The electron cyclotron (EC) heating and current drive (H&CD) system developed for the ITER is made of 12 sets of high-voltage power supplies feeding 24 gyrotrons connected through 24 transmission lines (TL), to five launchers, four located in upper ports and one at the equatorial level. Nearly all procurements are in-kind, following general ITER philosophy, and will come from Europe, India, Japan, Russia and the USA. The full system is designed to couple to the plasma 20 MW among the 24 MW generated power, at the frequency of 170 GHz, for various physics applications such as plasma start-up, central H&CD and magnetohydrodynamic (MHD) activity control. The design takes present day technology and extends toward high-power continuous operation, which represents a large step forward as compared to the present state of the art. The ITER EC system will be a stepping stone to future EC systems for DEMO and beyond. The development of the EC system is facing significant challenges, which includes not only an advanced microwave system but also compliance with stringent requirements associated with nuclear safety as ITER became the first fusion device licensed as basic nuclear installations as of 9 November 2012. Since the conceptual design of the EC system was established in 2007, the EC system has progressed to a preliminary design stage in 2012 and is now moving forward toward a final design.
31 citations
TL;DR: In this paper, a non-linear saturable absorber is installed in the feedback loop of an electron oscillator to increase the peak power of a periodic train of powerful ultrashort microwave pulses.
Abstract: A periodic train of powerful ultrashort microwave pulses can be generated in electron oscillators with a non-linear saturable absorber installed in the feedback loop. This method of pulse formation resembles the passive mode-locking widely used in laser physics. Nevertheless, there is a specific feature in the mechanism of pulse amplification when consecutive energy extraction from different fractions of a stationary electron beam takes place due to pulse slippage over the beam caused by the difference between the wave group velocity and the electron axial velocity. As a result, the peak power of generated “gigantic” pulses can exceed not only the level of steady-state generation but also, in the optimal case, the power of the driving electron beam.
28 citations
TL;DR: In this article, the locking of the oscillation frequency of the operating TE28,12 mode by an external monochromatic signal in a multimode gyrotron operated at a frequency of 170 GHz in the switch-on regime close to the real one was studied.
Abstract: We study locking of the oscillation frequency of the operating TE28,12 mode by an external monochromatic signal in a multimode gyrotron operated at a frequency of 170 GHz in the switch-on regime close to the real one. Locking zones, i.e., regions of single-mode generation at the external-signal frequency are found on the “current—detuning” plane of parameters. It is shown that as the number of competing modes increases, the maximum achievable current decreases, and the locking zones contract at sufficiently high currents.
26 citations
TL;DR: In this article, a nonstationary self-consistent model was used to analyze the frequency locking and stabilization regimes arising in gyrotrons with low-Q resonators under the action of an external signal or when reflections from a remote nonresonant load are introduced.
Abstract: Using a nonstationary self-consistent model, we analyze the frequency locking and stabilization regimes arising in gyrotrons with low-Q resonators under the action of an external signal or when reflections from a remote nonresonant load are introduced. In the simulations, we used the parameters of high-power gyrotrons designed for controlled thermonuclear fusion with optimized resonator profile. This approach makes it possible to determine output characteristics of the gyrotrons operated in considered regimes taking into account the effect of the incident wave (external or reflected) on the longitudinal field structure with greater precision compared with the earlier results based on the fixed RF-field structure approximation, while qualitative results of the two approaches coincide. Analysis of the effect of reflections from a remote load has demonstrated a substantial dependence of the efficiency of the gyrotron frequency stabilization on the ratio between the characteristic time scale of the synchronism detuning fluctuations and the signal delay time.
24 citations
TL;DR: In this paper, the possibility of reducing the radiation frequency fluctuations by a factor of 3-5 using a nonresonant or highly resonant weakly reflecting load for the gyrotrons employed in controlled-fusion facilities is shown.
Abstract: The possibility of reducing the radiation frequency fluctuations by a factor of 3–5 using a nonresonant or highly resonant weakly reflecting load for the gyrotrons employed in controlled-fusion facilities is shown. The ranges of system parameters where the frequency stabilization is most effective were identified both analytically and numerically.
18 citations
TL;DR: In this paper, the authors considered the microwave radiation produced by an elecrovacuum amplifier through the same barrier window, which was proposed earlier, in the context of its application in a traveling-wave tube based on a waveguide with a helically corrugated surface.
Abstract: We consider in detail the method allowing one to input and output the microwave radiation produced by an elecrovacuum amplifier through the same barrier window, which was proposed earlier, in the context of its application in a traveling-wave tube based on a waveguide with a helically corrugated surface. Special attention is given to the splitter of differently polarized radiation, and the results of studying this splitter at wavelengths of about 6 and 1 mm theoretically and experimentally are presented.
12 citations
TL;DR: In this article, the authors study experimentally the automated microwave complex for microwave spectroscopy and diagnostics of various media, which was developed at the Institute of Applied Physics of the Russian Academy of Sciences in cooperation with GYCOM Ltd. on the basis of a gyrotron with a frequency of 263 GHz and operated at the first gyrofrequency harmonic.
Abstract: We study experimentally the automated microwave complex for microwave spectroscopy and diagnostics of various media, which was developed at the Institute of Applied Physics of the Russian Academy of Sciences in cooperation with GYCOM Ltd. on the basis of a gyrotron with a frequency of 263 GHz and operated at the first gyrofrequency harmonic. In the process of the experiments, a controllable output power of 0.1–1 kW was achieved with an efficiency of up to 17% in the continuous-wave generation regime. The measured radiation spectrum with a relative width of about 10
−6 and the frequency values measured at various parameters of the device are presented. The results of measuring the parameters of the wave beam, which was formed by a built-in quasioptical converter, as well as the data obtained by measuring the heat loss in the cavity and the vacuum output window are analyzed.
11 citations
TL;DR: In this paper, a high-power transmission line from the broadband pulsed Ka-band gyro-TWT to the phased antenna array was designed to operate in a pulse-periodic regime with a pulse width of up to 250 μs, a duty factor of 8, and an average output power of 15 kW.
Abstract: We present experimental results on a high-power transmission line from the broadband pulsed Ka-band gyro-TWT to the phased antenna array. The transmission line is designed to operate in a pulse-periodic regime with a pulse width of up to 250 μs, a duty factor of 8, and an average output power of up to 15 kW. Amplitude–frequency and phase–frequency characteristics of the transmission line were measured at a low power level. It is shown that the nonlinearity of the phase–frequency characteristic does not exceed ±10° in the 34 ± 0.5 GHz frequency band.
9 citations
TL;DR: In this article, the main units of a gyrotron operated in the continuous-wave regime with a generation frequency of 0.26 THz were developed for the use of a cryomagnet with a maximum magnetic field of 10 T.
Abstract: We present the results of developing the main units of a gyrotron operated in the continuous-wave regime with a generation frequency of 0.26 THz. To improve selection of the operating mode in a oversized electrodynamic system, the gyrotron works at the fundamental cyclotron harmonic, which anticipates the use of a cryomagnet with a maximum magnetic field of 10 T, which does not require filling with liquid helium. The results of optimizing the electron-optical system, the cavity, and the quasi-optical converter of the output radiation are presented, and the control system, which is developed for the gyrotron setup, is described.
6 citations
TL;DR: In this article, the authors demonstrate the possibility of forming a periodic series of ultra-short pulses, which has a peak power exceeding significantly the radiation power in stationary regimes, in a gyroresonance traveling-wave tube (gyro-TWT) with a bleachable cyclotron absorber in the feedback circuit.
Abstract: We demonstrate the possibility of forming a periodic series of ultra-short pulses, which has a peak power exceeding significantly the radiation power in stationary regimes, in a gyroresonance traveling-wave tube (gyro-TWT) with a bleachable cyclotron absorber in the feedback circuit. The mechanism of pulsed generation is similar to the method of passive mode locking, which is used widely in laser physics.
01 Sep 2016
TL;DR: In this paper, the authors present research activity on development of gyrotron travelling-wave tubes (gyro-TWTs) at the Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), where a helically corrugated waveguide is used as a principal part of their microwave circuits.
Abstract: Research activity on development of gyrotron travelling-wave tubes (gyro-TWTs) at the Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS) is presented. In the gyro-TWTs under discussion a helically corrugated waveguide is used as a principal part of their microwave circuits which ensures a number of advantages over other configurations of the gyro-TWTs.
01 Sep 2016
TL;DR: The main purpose of the System modification is an enhancement of the system reliability and implementation of all gyrotron systems into ITER machine and its control and safety system.
Abstract: Development of the gyrotron system for ITER is based on solution of many very difficult scientific and engineering problems. At present the main purpose of the system modification is an enhancement of the system reliability and implementation of all gyrotron systems into ITER machine and its control and safety system. Recently development of ITER gyrotron system in Russia came into completion phase.
19 Jun 2016
TL;DR: In this paper, a gyrotron-based setup developed by Gycom Ltd. jointly with IAP RAS and intended for use in superconducting ECR ion source FECRAL (a Fourth generation ECR Ion source with Advanced design in Lanzhou, China) is described.
Abstract: This paper describes gyrotron-based setup developed by Gycom Ltd. jointly with IAP RAS and intended for use in superconducting ECR ion source FECRAL (a Fourth generation ECR ion source with Advanced design in Lanzhou, China) [1]. The setup is capable to provide output power up to 20 kW in both CW and pulse (5–200 ms duration with less than 10 μs fall time and up to 5 Hz repetition rate) modes with 45 GHz frequency.
01 Sep 2016
TL;DR: A multi-megawatt Electron Cyclotron Resonance Heating (ECRH) system is in routine operation at the ASDEX Upgrade (AUG) tokamak.
Abstract: A multi-megawatt Electron Cyclotron Resonance Heating (ECRH) system is in routine operation at the ASDEX Upgrade (AUG) tokamak. It applies four step-tunable gyrotrons at 105 and 140 GHz with 10 s pulse length and output powers close to 1 MW. An upgrade with four more gyrotrons is underway which will double the installed power. The first two-frequency gyrotron of the new series has recently been installed. The final goal is to have around 6.5–7 MW at 140 GHz (or 5.5 MW at 105 GHz) from 8 units available in the plasma during the whole AUG discharge (10 s).
01 Sep 2016
TL;DR: Research activity on development of various types of gyro-devices at the Institute of Applied Physics of Russian Academy of Sciences (IAP RAS) and at industrial company GYCOM Ltd is presented in this paper.
Abstract: Research activity on development of various types of gyro-devices at the Institute of Applied Physics of Russian Academy of Sciences (IAP RAS) and at industrial company GYCOM Ltd is presented. Recent results of the development are illustrated by a number of examples of fabricated and tested gyrotrons-oscillators and gyro-amplifiers operating at very different frequencies.
01 Sep 2016
TL;DR: In this paper, a quasi-optical waveguide device based on the Talbot's effect effectively separates power flows of input and output radiation in the required frequency range for a sub-millimeter wave (260 GHz) broadband gyro-TWT's radiation input/output system is presented.
Abstract: In this paper the result of experimental investigation of one of the key elements of a sub-millimeter wave (260 GHz) broadband gyro-TWT's radiation input/output system is presented. A quasi-optical waveguide device based on the Talbot's effect effectively separates power flows of input and output radiation in the required frequency range.
01 Sep 2016
TL;DR: In this paper, a waveguide system for input/output radiation to and from a low-magnetic-field-operating W-band gyro-TWT was presented.
Abstract: We present a waveguide system which makes it possible to input/output radiation to and from a low-magnetic-field-operating W-band gyro-TWT being currently under development. The system makes it possible to use one barrier window at the collector's end both for radiation inputting and outputting.
TL;DR: In this article, the authors considered the problem of summing the power produced by several coherent sources of microwaves and proposed to use the Talbot effect in an oversized rectangular waveguide to solve it.
Abstract: We consider the problem of summing the power produced by several coherent sources of microwaves and propose to use the Talbot effect in an oversized rectangular waveguide to solve it. The operating frequency of the summator is 94.4 GHz. The calculated coefficient of summation of individual signals is equal to 2.8 dB in the 800 MHz frequency range with allowance for the ohmic loss. Computer simulation of the summator has been performed, and its characteristics have been studied at a low power level.