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EU is presently developing 170 GHz, 1 MW, CW, gyrotrons for the electron cyclotron heating and current drive (ECH&CD) system of the ITER tokamak. The EU gyrotron development program and the present status of the main contracts are described in this paper.
The effect of cathode emission nonuniformities on electron beam quality in gyrotrons and a method for suppressing this effect by optimization of the electric field distribution in the gun region are studied experimentally and using computer modelling.
We present a novel method for calculating the linearly polarized mode contents in an overmoded corrugated waveguide. The proposed method is based on calculating the low order irradiance moments of the measured radiated intensity profiles at several distances from the waveguide aperture. The method is validated by the data measured from a 63.5 mm diameter corrugated waveguide at 170 GHz and a 19 mm...
Future controlled fusion reactors require the development of MW-class gyrotrons at higher frequencies. To withstand the ohmic heating in the resonator walls, such gyrotrons should operate in higher order modes than the present-day tubes. This is why the analysis of stability of operation in such modes is of vital importance for future gyrotrons. In this paper, the stability of gyrotron operation is...
The new gyrotron simulation code TWANG-PIC, a Particle-In-Cell (PIC)-version of the code will be presented, which solves the slow-timescale self-consistent wave-particle interaction equations for a single transverse mode. This code represents a considerable improvement with respect to the previous trajectory-code by relaxing the approximation of a time-frozen electromagnetic (EM)-field during the...
The electron cyclotron heating and current drive (ECH/ECCD) gyrotron complex on the DIII-D tokamak is being upgraded with the addition of new gyrotrons. The transmitted power monitoring in the high power millimeter wave transmission system will be upgraded with new rf power monitors sensitive to the wave polarization and mode content. The speed of the real time steering antenna is being increased...
An innovative compact normal room temperature magnet has been developed for use with millimeter-wave gyrotrons. An example of an electropermagnet has been made and tested to 2.0 T, has a 30 mm ID bore and a 25 mm flat field cavity region, suitable for efficient fundamental and 2nd harmonic mode high power pulse and CW gyrotrons to at least 110 GHz, and is only ∼22 kg. Gyrotron design with this magnet...
A 527 GHz gyrotron has been designed and built for an 800 MHz DNP-NMR spectrometer. The gyrotron is designed at the second harmonic (ω=2 ωc) of the electron cyclotron frequency to produce 20 W continuous microwave power at 527 GHz frequency using a diode type electron gun (Vk ∼ 13.0 kV, Ib=150 mA). An internal dimpled wall helical cut launcher is designed along with two mirrors and an internal periscope...
To provide stable output power of a gyrotron during long operation time the power stabilization was achieved by two schemes with PID feedback control of heater current and anode voltage. It was based on the dependence of the output power on both the anode voltage and the beam current and also on the dependence of the beam current on the gun heater current. Both schemes provided decrease of the power...
Backward wave oscillation modes in a TE01 Gyro-TWT are researched by a nonlinear theory with consideration of electrons misalign. The results show the output power of most oscillation modes decreases with the increment of misaligns distance.
A 0.42 THz fourth-harmonic large orbit gyrotron (LOG) operating with TE4,2 mode is designed and studied. Unlike the widely used TEm, 1 mode in previous high harmonic (harmonic number s>=4) LOGs, the increase of radial index from 1 to 2 and even larger values bears the potential to enhance the beam-wave interaction efficiency as well as to decrease the cavity wall loss. 3D PIC simulation has shown...
Gyrotron FU CW GV has been developed as a multiple-frequency gyrotron. The main mode is TE10, 6 and corresponding frequency is 265 GHz. More than ten modes oscillated and Gaussian beams were radiated for these modes. A double-disk window was adopted to maintain the transmittance through the window in high level for a wide range of frequency.
Two megawatt-class gyrotrons at frequencies of 117.5 GHz and 170 GHz have recently been fabricated and tested at CPI. The 117.5 GHz gyrotron was designed to produce up to 1.8 MW, for 10-second pulses. The 170 GHz gyrotron is specified as a 500 kW CW system, but has been designed with the goal of generating up to 1 MW CW. Thus far both gyrotrons have achieved the peak power goals in initial testing...
Sub-THz gyrotrons with the functions of frequency control are useful for application to high power sub-THz spectroscopy including a DNP enhanced high-sensitive NMR spectroscopy. Continuous frequency tunability, frequency modulation and frequency step-changing will be achieved for our Gyrotron FU CW Series and such special functions of frequency control are applied for additional enhancement of NMR...
The upgraded Electron Cyclotron Resonance Heating (ECRH) system at ASDEX Upgrade (AUG) has been routinely used in the last experimental campaign. A further upgrade will replace an existing system of four short-pulse (140 GHz, 2s, 500 kW) gyrotrons. 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).
Recent progress of JAEA high power long pulse gyrotrons is reported. Multi-frequency oscillation and the high efficiency long distance power transmission were demonstrated at three frequencies, 170 GHz, 137 GHz and 104 GHz. The output power of 1 MW was obtained at three frequencies. The transmission efficiency from the gyrotron window to the end of the 40 m transmission line is 91 %, 89 % and 84 %,...
Beyond ITER, a future nuclear fusion demonstration power plant (DEMO) demands gyrotron frequencies above 200 GHz and gyrotron efficiencies of higher than 60 %. The unit power must well exceed 1 MW. Fast frequency tunability in steps of 2–3 GHz (in a few seconds) using broadband or tunable CVD-diamond windows is required. Beside these fundamental requirements, slow frequency tunability (in a few minutes)...
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