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Recent progress on the development of a high power 170 GHz gyrotron obtained in Japan Atomic Energy Agency (JAEA) is presented. Firstly, the repetitive operation of 800 kW/600 s with an interval of 20-30 min was performed. The electrical efficiency was 52-57% with the depressed collector. The 72 shots of 88 shots was very stable 600 s oscillation. No damage was found on the gyrotron by this test....
The high power gyrotron and the power coupling efficiency with the corrugated waveguide are discussed. The 170 GHz transmission lines(TLs) for electron cyclotron heating and current drive (EC H&CD) system in the International Thermonuclear Experimental Reactor (ITER) require higher purity of HEιι mode to minimize a transmission loss. In addition, higher order modes will generate a stray RF in...
This paper reviews the design and functionality of the 24 MW 170 GHz electron cyclotron heating and current drive system being planned for the ITER Tokamak. The sub-systems (power supplies, gyrotrons, transmission lines and launcher antennas) are described based on present day technologies, while on-going R&D provides component and sub-system testing with the possibility of increasing the reliability...
Recent progress on a high power 170 GHz gyrotron development in JAEA is presented. After the demonstration of ITER basic performance, the gyrotron has been operated for 3 years, and recorded ~200 GJ of total output energy. As a next activity, a study of a CW-power modulation of the gyrotron for NTM (Neo classical Tearing Mode) stabilization has started. Up to now, power modulation of 5 kHz for short...
The ITER Electron Cyclotron Heating and Current Drive (ECH&CD) transmission line components will need to be suitable for 1-2 MW CW operation. The high heat loads compared to existing transmission lines will require enhanced cooling and, for some components, new or modified designs. Testing at representative ITER conditions of key components has been carried out at the JAEA 170 GHz gyrotron test...
The performance requirement of 1 (possibly 2) MW cw at 170 GHz for ITER Electron Cyclotron Heating and Current Drive transmission line components is much more demanding than the performance that has been demonstrated on present devices. The high ITER heat loads will require enhanced cooling and, for some components, new or modified designs. In addition to thermal management issues, the components...
Recent progresses in gyrotron development and related technologies are presented. The gyrotron demonstrated ITER relevant parameters at 170 GHz (1 MW, 800 s, 55 %), and proved a reliability with long operation period. Recently, one hour operation was obtained at 0.8 MW with the efficiency of 57 %, and total output energy of 190 GJ was recorded with 2 years operation. On the other hand, a power increase...
An ITER torus window prototype with CVD diamond disks and corrugated waveguides are being investigated by using IR imaging and temperature measuring technique during high power RF microwave loading up to 1 MW at a frequency of 170 GHz at the JAEA gyrotron facility. To evaluate the cooling efficiency of the window design the temperature distribution over the diamond disk area is measured and compared...
This paper investigates the development of the atmospheric breakdown on the high power Gaussian beam observed using a high speed video camera. The movie with 5-1 mus frame interval time was taken. A high power millimeter wave beam generated by 170 GHz gyrotron was used. First the breakdown at the focal point was observed. The beam was focused using an offset parabolic mirror. A separated ionization...
A 1 MW 170 GHz long pulse gyrotron is required for a power source of the electron cyclotron heating and current drive (EC H&CD) system on ITER (International Thermonuclear Experimental Reactor). In the ITER gyrotron development of JAEA (Japan Atomic Energy Agency), a stable 1 MW 170 GHz oscillation has been achieved at CW-relevant pulse duration (800 s), which is a twice of burning time of ITER...
A 170 GHz, high power and long pulse RF experiments of the ITER relevant transmission line consisting of 63.5 mm circular corrugated waveguides, bends, an in-line switch and etc... was, for the first time, carried out. The transmission efficiency of 92% from the inlet of the transmission line to the end, which is comparable to the specification value was successfully obtained. The anomalous incremental...
A steady-state operation of 1 MW/800 s with the efficiency of 55%, which exceeded 1 MW/400 s of the performance required in ITER, was demonstrated in 170 GHz gyrotron. The oscillation characteristics in the long pulse operation was clarified, and the advanced operation scenario of the gyrotron to the high efficiency oscillation was newly established by controlling a pitch factor of the electron beam...
A 1MW 170GHz long pulse gyrotron is required for a power source of an electron cyclotron heating and current drive (EC H&CD) system on ITER (International Thermonuclear Experimental Reactor). After the R&D works of 15 years in Engineering Design Activities (EDA) of ITER a stable 1MW 170GHz oscillation has been attained at CW- relevant pulse duration (800s). The efficiency was 55 % with the...
On the development of 170 GHz gyrotron for the ITER, stable output power of 0.6 MW with the efficiency of ~45% was obtained for 1000 s, which corresponds to a discharge time of steady state experiment of the ITER.
A high power millimeter-wave beam generated by a 170 GHz gyrotron was injected into a cylindrical tube and atmospheric plasma was generated. The ionization front and a shock wave were propagated in the tube during the millimeter-wave pulse. From the pressure history measurement and plasma emission imaging in the tube, the propagation velocity of the shock wave was found identical to that of the ionization...
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