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New trends of gyrotron development at KIT: An overview on recent investigations
摘要： Since many years KIT is strongly involved in the development of high power gyrotrons for use in ECRH. KIT is pursuing two development lines: (i) the conventional, hollow cavity gyrotron and (ii) the coaxial cavity gyrotron. KIT is pushing conventional cavity gyrotrons from 1 MW to 1.5 MW in a common project with IPP Greifswald. Coaxial cavity technology having the advantage of higher power capability, in particular at higher frequency, is used for the 2 MW 170 GHz short-pulse prototype. This gyrotron is currently being upgraded to allow pulse extension up to approximately 100 ms and up to 1 s in a second step. For a future DEMOnstration fusion power plant two challenging trends with respect to gyrotron features are recognized: (a) the operating frequency will be above 200 GHz and (b) the requested total efficiency of the gyrotron should be higher than 60%. KIT is addressing these requirements by investigating both gyrotron technologies for their performance at a frequency well above 200 GHz. We started careful analysis of multi-staged-depressed collectors.
关键词： Electron-cyclotron-resonance heating and current drive,Gyrotron,Coaxial cavity,Magnetron injection gun
更新于2025-09-23 15:23:52
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Recent experiments with the European 1MW, 170GHz industrial CW and short-pulse gyrotrons for ITER
摘要： The European Gyrotron Consortium (EGYC) is developing the European 1 MW, 170 GHz Continuous Wave (CW) industrial prototype gyrotron for ITER in cooperation with Thales Electron Devices (TED) and Fusion for Energy (F4E). This conventional, hollow-cavity gyrotron, is based on the 1 MW, 170 GHz Short-Pulse (SP) modular gyrotron that has been designed and manufactured by the Karlsruhe Institute of Technology (KIT) in collaboration with TED. Both gyrotrons have been tested successfully in multiple experiments. In this work we briefly report on the results with the CW gyrotron at KIT and we focus at the experiments at the Swiss Plasma Center (SPC). In addition, we present preliminary results from various upgrades of the SP tube that are currently tested at KIT.
关键词： Gyrotron,ITER,ECRH
更新于2025-09-23 15:23:52
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Gain and bandwidth of the TM-mode gyrotron amplifiers
摘要： This work discusses the feasibility of gyrotron amplifiers using TM modes by investigating their dispersion relations starting with the relativistic Vlasov equation. For an input signal carrying a real frequency x, the complex wave number kz solved from the dispersion relation tells us the growth rate and the bandwidth of an amplifier. Three modes (TE01, TM11, and TM01) operating at the fundamental cyclotron harmonic (s ? 1) with the same cutoff frequency will be discussed. The results show that the TM11- and TM01-mode gyrotrons require much higher beam current than the TE01-mode gyrotron traveling-wave tube (gyro-TWT) amplifier. The TM modes are unsuitable for the gyro-TWT amplifier as discovered by other authors. The gyrotron backward-wave (gyro-BW) amplifier is also examined. The dispersion relations indicate that the TM modes are as good as the TE modes. The gain and bandwidth of the TM11-mode gyrotron backward-wave amplifier (gyro-BWA) are studied by changing either the magnet field or the beam voltage. The TM11 mode is suitable and has a decent bandwidth for the operation of the gyro-BW amplifier.
关键词： relativistic Vlasov equation,TE01 mode,TM modes,gyro-BW amplifier,TM11 mode,gyrotron amplifiers,gyro-TWT amplifier,TM01 mode,dispersion relations
更新于2025-09-23 15:21:21
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[IEEE 2018 11th UK-Europe-China Workshop on Millimeter Waves and Terahertz Technologies (UCMMT) - HangZhou, China (2018.9.5-2018.9.7)] 2018 11th UK-Europe-China Workshop on Millimeter Waves and Terahertz Technologies (UCMMT) - Measurement of W-band gyro-TWA with wide bandwidth input signal
摘要： A W-band gyro-TWA has been developed to provide high output power and wide bandwidth. This letter presents the upgrade of the input signal generation of the W-band gyro-TWA, and the experiment results with frequency-swept input signals. The results show a 30 dB gain was achieved at a 1 GHz bandwidth input signal when the gyro-TWA was driven by a 40kV, 1.5 A electron beam.
关键词： gyrotron,frequency-swept,helically corrugated waveguide,traveling wave amplifier
更新于2025-09-23 15:21:01
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Vacuum Arc Plasma Heated by Sub-Terahertz Radiation as a Source of Extreme Ultraviolet Light
摘要： This paper presents the results of the ?rst experimental studies of the interaction of a powerful sub-terahertz radiation with expanding highly inhomogeneous plasma of vacuum arc discharge. The tantalum plasma of a vacuum arc discharge additionally heated by the focused sub-terahertz radiation of a gyrotron, the radiation power is up to 250 kW, and the wavelength is 1.2 mm. Characteristics of the light emission in the extreme ultraviolet range are presented.
关键词： gyrotron,vacuum arc plasma,Extreme ultraviolet light,sub-terahertz radiation
更新于2025-09-23 15:21:01
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Nonlinear Cyclotron Resonance Absorber for a Microwave Subnanosecond Pulse Generator Powered by a Helical-Waveguide Gyrotron Traveling-Wave Tube
摘要： A well-known principle for periodical production of high-power ultrashort optical pulses is related to passive mode locking realized when a saturable absorber is incorporated into the laser resonator. A similar effect can be implemented in two-section electronic oscillators comprising an amplifier and a saturable absorber, which should be applicable in the microwave frequency band and suitable for high-power operation. In this paper, we analyze in detail the possibility of realizing a saturable absorber based on cyclotron resonance interaction in the regular waveguide with initially rectilinear electron beam, when saturation is caused by the relativistic dependence of the gyrofrequency on electron energy. Maximum contrast between the absorption of a high-power signal and of a weak signal is achieved in the group synchronism regime when the particle velocity is close to the wave’s group velocity. Within the frame of a time-domain self-consistent model, we demonstrate that when such an absorber is installed in the feedback loop of an electron generator powered by existing Ka-band helical-waveguide gyrotron traveling-wave tube, periodical generation of subnanosecond pulses can be provided with peak power up to several hundred kW and sub-GHz repetition frequency. We discuss the influence of deviation from the group synchronism regime on the parameters of generated pulses. Experimental feasibility of the considered scheme is verified based on three-dimensional particle-in-cell simulations.
关键词： gyrotron traveling-wave tube,cyclotron resonance,subnanosecond pulse,saturable absorber,microwave
更新于2025-09-23 15:19:57
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Studies of a Gyrotron Traveling-Wave Tube with Helically Corrugated Waveguides at IAP Ras: Results and Prospects
摘要： The gyrotron traveling-wave tube (gyro-TWT) is a wideband version of gyrotron amplifiers, which produce pulsed or continuous-wave radiation in the millimeter-wavelength band at a power level that exceeds the powers produced by conventional TWTs with slow-wave structures and rectilinear beams by 1–2 orders of magnitude. Since 1996, researchers at the Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS) have been developing the concept of the gyro-TWT based on the use of a waveguide with a helically corrugated surface, which changes the dispersion of one of the eigenmodes in a circular waveguide radically. In this paper, we discuss several problems that arise in implementation of such devices, which many years of experimental studies have revealed, present the parameters of gyro-TWTs developed with allowance for specific applications of their end users, and discuss lines of further perfection of such amplifiers.
关键词： gyrotron traveling-wave tube,helically corrugated waveguide,high-power amplifiers,gyro-TWT,millimeter-wavelength band
更新于2025-09-19 17:13:59
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Selectivity Properties of Cylindrical Waveguides with Longitudinal Wall Corrugations for Second-Harmonic Gyrotrons
摘要： Spatial harmonic method is applied to investigate selectivity properties of longitudinally corrugated waveguides for potential application in second-harmonic gyrotrons. The effect of corrugations on frequencies, ohmic losses, and mode conversion of guiding TE modes is studied in details. Numerical results are presented for operating second-harmonic and competing first-harmonic modes of a 0.4-THz gyrotron with corrugated RF structure. It is shown that longitudinal wall corrugations of proper dimensions can ensure increase in ohmic losses and decrease in beam-wave coupling strength for the first-harmonic modes, while their effect on the operating mode is only slight. This demonstrates improved selectivity properties of corrugated waveguides for second-harmonic gyrotrons.
关键词： Ohmic losses,Gyrotron,Mode conversion,Cyclotron harmonic,Corrugated waveguide,Eigenvalue
更新于2025-09-11 14:15:04
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Long-Pulse Uncooled Copper Magnet for Gyrotron
摘要： The operation of a gyrotron requires a strong, stable magnetic ?eld over time. Working in the CW mode requires complex/cryogen solenoid cooling systems. Working in the pulse mode is possible with a simple solenoid, but only for short pulses, typically up to 50 μs. In this article, an intermediate working point for the gyrotron is presented: a pulsed gyrotron with a simple uncooled solenoid, which is capable of producing relatively long pulses of ～10 ms. To power a longer pulse with a simple solenoid, a super-capacitor (SC)-based system has been designed, which enables the extension of the operation of pulsed gyrotrons to tens of milliseconds, while keeping the system simplicity, without a cooling system for the solenoid. The setup was realized and a 27-ms current pulse of 1.1 kA was obtained through a gyrotron with a simple copper solenoid with a stability of ～0.3%. A 5-kW/10-ms radiation pulse at 28 GHz was measured from the gyrotron. This setup enables the use of a rather simple solenoid and a gyrotron and still obtains a rather long radiation pulse. This concept may open a new regime for pulsed gyrotrons.
关键词： Gyrotron,long pulse,magnetic ?eld,solenoid,millimeter wave
更新于2025-09-11 14:15:04
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A Novel Approach for Computation of High-Order Axial Modes in a Gyrotron Resonator
摘要： This paper presents a novel approach for computation of high-order axial modes (HOAMs) in a conventional and uptapered gyrotron resonator. A code has been developed which computes the eigenfrequency, Q-factor and axial ?eld pro?le of HOAMs in the absence of electron beam in the resonator. Cyclic coordinate search method has been used for the optimization of complex eigenfrequencies, which obviates the computation of gradients of radiation boundary conditions and, hence, reduces computational complexity. HOAMs have been computed for resonators operating at 10, 132, 203, and 424 GHz, and the results obtained have been found to be in good quantitative agreement with the experimental and numerical data available in the published literature. Broadband continuous frequency tuning bandwidth found for subterahertz resonators also agrees well with the published results. HOAMs computed for 1-THz gyrotron resonator designed at CSIR-CEERI have also been presented.
关键词： Broadband continuous frequency tuning (CFT),subterahertz,optimization,open resonator,terahertz,high-order axial modes (HOAMs),gyrotron
更新于2025-09-11 14:15:04