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Journal Articles

Development and achievements on the high power ECRF system in JT-60U

Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Hiranai, Shinichi; et al.

Nuclear Fusion, 49(8), p.085001_1 - 085001_7, 2009/07

 Times Cited Count:14 Percentile:42(Physics, Fluids & Plasmas)

In the gyrotron development in JT-60U ECRF system, output power of 1.5 MW for 1 s has been achieved at 110 GHz. It is the world highest power oscillation $$>$$ 1 s. In addition to the carefully designed cavity and collector in view of thermal stress, an RF shield for the adjustment bellows, and a low-dielectric-loss DC break enabled this achievement. Power modulation technique by anode voltage control was improved to obtain high modulation frequency and 5 kHz has been achieved for NTM stabilizing experiments. Long pulse demonstration of 0.4 MW, 30 s injection to the plasma has been achieved with real time control of anode/cathode-heater. It has been confirmed that the temperature of cooled components were saturated and no evidence of damage were found. An innovative antenna having wide range of beam steering capability with linearly-moving-mirror concept has been designed for long pulse. Beam profile and mechanical strength analyses shows the feasibility of the antenna.

Journal Articles

Design study of an ECRF antenna for JT-60SA

Kobayashi, Takayuki; Moriyama, Shinichi; Fujii, Tsuneyuki; Takahashi, Koji; Kajiwara, Ken; Sakamoto, Keishi

Fusion Engineering and Design, 84(2-6), p.1063 - 1067, 2009/06

 Times Cited Count:8 Percentile:41.28(Nuclear Science & Technology)

Design study of an ECRF antenna for JT-60SA is being carried out. An antenna concept which equips a linearly-driven flat mirror and a fixed-curved mirror was evaluated by using a numerical code. This antenna enables to alter millimeter-wave injection angle widely, only by a linear motion of the flat mirror. Therefore, the antenna eliminates a flexible tube for coolant supply and a link mechanism in vacuum vessel. In this work, it was clarified that the beam radius was expanded wider in poloidal direction compared with the expected one which was evaluated by the Gaussian optics. Then, the surface structures of the mirrors were modified in order to obtain the narrower beam radius on the resonance surface. It was found that the beam radius on the resonance surface became effectively narrower than that of the previous design by an increase in the curvature radius of the fixed-curved mirror or by a modification of the linearly-driven mirror as a diverging mirror.

Journal Articles

Status of JT-60SA tokamak under the EU-JA broader approach agreement

Matsukawa, Makoto; Kikuchi, Mitsuru; Fujii, Tsuneyuki; Fujita, Takaaki; Hayashi, Takao; Higashijima, Satoru; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Ide, Shunsuke; Ishida, Shinichi; et al.

Fusion Engineering and Design, 83(7-9), p.795 - 803, 2008/12

 Times Cited Count:13 Percentile:26.45(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Long pulse/high power ECRF system development in JT-60U

Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Hiranai, Shinichi; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

In the gyrotron development in JT-60U ECRF system, output power of 1.5 MW for 1 s has been achieved at 110 GHz. It is the world highest power oscillation $$>$$ 1 s. In addition to the carefully designed cavity and collector in view of thermal stress, an RF shield for the adjustment bellows, and a low-dielectric-loss DC break enabled this achievement. Power modulation technique by anode voltage control was improved to obtain high modulation frequency and 5 kHz has been achieved for NTM stabilizing experiments. Long pulse demonstration of 0.4 MW, 30 s injection to the plasma has been achieved with real time control of anode/cathode-heater. It has been confirmed that the temperature of cooled components were saturated and no evidence of damage were found. An innovative antenna having wide range of beam steering capability with linearly-moving-mirror concept has been designed for long pulse. Beam profile and mechanical strength analyses shows the feasibility of the antenna.

Journal Articles

Achievement of 1.5 MW, 1 s oscillation by the JT-60U gyrotron

Kobayashi, Takayuki; Moriyama, Shinichi; Seki, Masami; Sawahata, Masayuki; Terakado, Masayuki; Fujii, Tsuneyuki

Plasma and Fusion Research (Internet), 3, p.014_1 - 014_3, 2008/03

Gyrotrons are used for electron cyclotron heating (ECH) / current drive (ECCD) as high power millimeter wave sources in high performance plasma experiments. Pulse length from 0.1 to several seconds with high power is required in present tokamak experiments, such as JT-60U. However, 0.1 s oscillation had only been achieved in the power level of 1.5 MW. In JAEA, high power and long pulse oscillation experiments by using the latest JT-60U gyrotron have been tried to achieve power level of 1.5 MW and pulse length over 1 s. As a result, 1.5 MW/1 s oscillation has been successfully achieved by the fine optimization of operation parameters. In this paper, the first results of the oscillation experiment of 1.5 MW for 1 s and future plans of gyrotron improvements are described.

Journal Articles

Electron cyclotron heating applied to the JT-60U tokamak

Hoshino, Katsumichi; Suzuki, Takahiro; Isayama, Akihiko; Ide, Shunsuke; Takenaga, Hidenobu; Kubo, Hirotaka; Fujita, Takaaki; Kamada, Yutaka; Fujii, Tsuneyuki; Tsuda, Takashi; et al.

Fusion Science and Technology, 53(1), p.114 - 129, 2008/01

 Times Cited Count:2 Percentile:78.3(Nuclear Science & Technology)

We report on the applications of the ECH to the JT-60U tokamak. The ECH contributes to the advanced tokamak study in JT-60U in such respects as (1)NTM suppression, (2)Study on the internal transport barrier, (3)Impurity exhaust, (4)Tokamak start-up without center solenoid, (5)Current hole study, (6)Confinement and transport study, and (7)Start-up and shut-down assist. These contributions comes from the good local coupling of the ECH to the tokamak plasma.

Journal Articles

Design study of a new antenna system for steering microwave beam in electron cyclotron heating/current drive system

Moriyama, Shinichi; Seki, Masami; Fujii, Tsuneyuki

Fusion Engineering and Design, 82(5-14), p.785 - 790, 2007/10

 Times Cited Count:7 Percentile:45.74(Nuclear Science & Technology)

A power measurement method for an electron cyclotron heating (ECH) system using a ceramic disk was studied and tested. A model calculation showed that the disk edge temperature of the diamond vacuum window was sufficient to estimate the transmission power at 1 MW and 110 GHz with a response time of 0.2 s. The initial high power test with very thin thermocouple demonstrated successful power measurement with response time of $$<$$ 1.0 s. The concept of the linear motion ECH antenna suitable for reactor (like) environment is newly introduced and studied. A typical design would involve a mm-wave beam reflected at a flat mirror and a concave mirror. In the second reflection, the reflection angle can be changed by varying the point of reflection. The point of reflection is easily controlled by the linear movement of either the flat mirror or the concave mirror. It is notable that mirror rotation, which may require regular maintenance, is not required and backlash can be eliminated.

Journal Articles

Overview of national centralized tokamak program; Mission, design and strategy to contribute ITER and DEMO

Ninomiya, Hiromasa; Akiba, Masato; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hayashi, Nobuhiko; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Inoue, Nobuyuki; et al.

Journal of the Korean Physical Society, 49, p.S428 - S432, 2006/12

To contribute DEMO and ITER, the design to modify the present JT-60U into superconducting coil machine, named National Centralized Tokamak (NCT), is being progressed under nationwide collaborations in Japan. Mission, design and strategy of this NCT program is summarized.

Journal Articles

JT-60SA project for JA-EU broader approach satellite tokamak and national centralized tokamak

Kikuchi, Mitsuru; Matsuda, Shinzaburo; Yoshida, Naoaki*; Takase, Yuichi*; Miura, Yukitoshi; Fujita, Takaaki; Matsukawa, Makoto; Tamai, Hiroshi; Sakurai, Shinji; Ikeda, Yoshitaka; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 82(8), p.455 - 469, 2006/08

no abstracts in English

Journal Articles

Overview of the national centralized tokamak programme

Kikuchi, Mitsuru; Tamai, Hiroshi; Matsukawa, Makoto; Fujita, Takaaki; Takase, Yuichi*; Sakurai, Shinji; Kizu, Kaname; Tsuchiya, Katsuhiko; Kurita, Genichi; Morioka, Atsuhiko; et al.

Nuclear Fusion, 46(3), p.S29 - S38, 2006/03

 Times Cited Count:13 Percentile:51.64(Physics, Fluids & Plasmas)

The National Centralized Tokamak (NCT) facility program is a domestic research program for advanced tokamak research to succeed JT-60U incorporating Japanese university accomplishments. The mission of NCT is to establish high beta steady-state operation for DEMO and to contribute to ITER. The machine flexibility and mobility is pursued in aspect ratio and shape controllability, feedback control of resistive wall modes, wide current and pressure profile control capability for the demonstration of the high-b steady state.

Journal Articles

Engineering design and control scenario for steady-state high-beta operation in national centralized tokamak

Tsuchiya, Katsuhiko; Akiba, Masato; Azechi, Hiroshi*; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; et al.

Fusion Engineering and Design, 81(8-14), p.1599 - 1605, 2006/02

 Times Cited Count:1 Percentile:88.23(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Performance of the LH antenna with carbon grill in JT-60U

Seki, Masami; Moriyama, Shinichi; Shinozaki, Shinichi; Hasegawa, Koichi; Hiranai, Shinichi; Yokokura, Kenji; Shimono, Mitsugu; Terakado, Masayuki; Fujii, Tsuneyuki

Fusion Engineering and Design, 74(1-4), p.273 - 277, 2005/11

 Times Cited Count:3 Percentile:72.14(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Development and contribution of RF heating and current drive systems to long pulse, high performance experiments in JT-60U

Moriyama, Shinichi; Seki, Masami; Terakado, Masayuki; Shimono, Mitsugu; Ide, Shunsuke; Isayama, Akihiko; Suzuki, Takahiro; Fujii, Tsuneyuki; JT-60 Team

Fusion Engineering and Design, 74(1-4), p.343 - 349, 2005/11

 Times Cited Count:7 Percentile:49.09(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Compact antenna for two-dimensional beam scan in the JT-60U electron cyclotron heating/current drive system

Moriyama, Shinichi; Kajiwara, Ken*; Takahashi, Koji; Kasugai, Atsushi; Seki, Masami; Ikeda, Yoshitaka; Fujii, Tsuneyuki; JT-60 Team

Review of Scientific Instruments, 76(11), p.113504_1 - 113504_6, 2005/11

 Times Cited Count:3 Percentile:75.8(Instruments & Instrumentation)

A compact antenna has been designed and fabricated to enable millimeter wave beam scan in the toroidal and the poloidal directions of the JT-60U Tokamak, for electron cyclotron heating (ECH) and current drive (ECCD) experiments. It consists of fast movable flat mirror mounted on the Tokamak vacuum vessel, and rotary focusing mirror attached at the end of the waveguide supported from outside of the vacuum vessel. This separate support concept enables compact structure in the shallow port (0.68 m $$times$$ 0.54 m $$times$$ 0.2m) sharing with a sub-port for an independent diagnostic system. The flat mirror is driven during a shot by a servo-motor with a 3 m long drive shaft to refuse influence of the high magnetic field to the motor. The focusing mirror is rotated by a simple mechanism with a push rod and an air cylinder. The antenna has been operated reliably for 3 years after small improvement in the rotary mechanism. It has been contributing ECH and ECCD experiments especially current profile control, in JT-60U.

Journal Articles

Electron cyclotron heating assisted startup in JT-60U

Kajiwara, Ken*; Ikeda, Yoshitaka; Seki, Masami; Moriyama, Shinichi; Oikawa, Toshihiro; Fujii, Tsuneyuki; JT-60 Team

Nuclear Fusion, 45(7), p.694 - 705, 2005/07

 Times Cited Count:42 Percentile:16.13(Physics, Fluids & Plasmas)

Electron cyclotron heating (ECH) assisted start-up experiment was performed in JT-60U. The breakdown loop voltage, becoming the maximum value at the plasma start-up, successfully reduced from 30 V to 4 V (E = 0.26 V/m) by 200 kW ECH. This fulfills the value less than 0.3 V/m, which corresponds to the maximum electric field required in ITER. Moreover, in order to investigate properties of start-up plasmas, parameter scans of the ECH power, prefilled gas pressure, resonant position, polarization angle and injection position were carried out and the dependence on them were obtained. It was revealed that the properties have dependences on the injection position and polarization angle in large tokamaks although they seemed to have no dependence on them from the experiments in small and medium tokamaks. In addition, in experiments of the plasma start-up using second and third harmonic ECH, it was found that the plasma current was ramped by 800 kW second harmonic ECH and was not ramped by 1.6 MW third harmonic ECH even with 7 MW neutral beam injection heating.

Journal Articles

Operational progress of the 110GHz-4MW ECRF heating system in JT-60U

Fujii, Tsuneyuki; Seki, Masami; Moriyama, Shinichi; Terakado, Masayuki; Shinozaki, Shinichi; Hiranai, Shinichi; Shimono, Mitsugu; Hasegawa, Koichi; Yokokura, Kenji; JT-60 Team

Journal of Physics; Conference Series, 25, p.45 - 50, 2005/00

The JT-60U electron cyclotron range of frequency (ECRF) is utilized to realize high performance plasma. Its output power is 4 MW at 110 GHz. By controlling the anode voltage of the gyrotron used in the JT-60U ECRF heating system, the gyrotoron output can be controlled. Then, the anode voltage controller was developed to modulate the injected power into plasmas. This low cost controller achieved the modulation frequency 12 - 500 Hz at 0.7 MW. This controller also extended the pulse width from 5s to 16 s at 0.5 MW. For these long pulses, temperature rise of the DC break made of Alumina ceramics is estimated. Its maximum temperature becomes $$sim$$ 140 deg. From the analysis of this temperature rise, DC break materials should be changed to low loss materials for the objective pulse width of 30 s. The stabilization of neoclassical tearing mode (NTM) was demonstrated by ECRF heating using the real-time system in which the ECRF beams are injected to the NTM location predicted from ECE measurement every 10 ms.

Journal Articles

Steady state high $$beta_{rm N}$$ discharges and real-time control of current profile in JT-60U

Suzuki, Takahiro; Isayama, Akihiko; Sakamoto, Yoshiteru; Ide, Shunsuke; Fujita, Takaaki; Takenaga, Hidenobu; Luce, T. C.*; Wade, M. R.*; Oikawa, Toshihiro; Naito, Osamu; et al.

Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/11

no abstracts in English

Journal Articles

Progress in physics and technology developments for the modification of JT-60

Tamai, Hiroshi; Matsukawa, Makoto; Kurita, Genichi; Hayashi, Nobuhiko; Urata, Kazuhiro*; Miura, Yushi; Kizu, Kaname; Tsuchiya, Katsuhiko; Morioka, Atsuhiko; Kudo, Yusuke; et al.

Plasma Science and Technology, 6(1), p.2141 - 2150, 2004/02

 Times Cited Count:2 Percentile:92.17(Physics, Fluids & Plasmas)

The dominant issue for the the modification program of JT-60 (JT-60SC) is to demonstrate the steady state reactor relevant plasma operation. Physics design on plasma parameters, operation scenarios, and the plasma control method are investigated for the achievement of high-$$beta$$. Engineering design and the R&D on the superconducting magnet coils, radiation shield, and vacuum vessel are performed. Recent progress in such physics and technology developments is presented.

Journal Articles

Performance and development of heating and current drive systems in JT-60U

Fujii, Tsuneyuki; Kasugai, Atsushi; JT-60 Team

Proceedings of 20th IEEE/NPSS Symposium on Fusion Engineering (SOFE 2003), p.222 - 227, 2003/10

The key factors to realize highly integrated performance plasma performances are control of profiles of current, pressure, rotation and so on. Therefore, several types of heating and current drive systems, ECH, LH, ICH, negative and positive ion based NBI systems, have been introduced into JT-60U. The ECH system with output power 4MW at 110 GHz has been developed using four 1 MW gyrotrons. The gyrotron has achieved 1MW-5sec output of the designed value by suppressing the parasitic oscillation with SiC RF absorber built-in. This gyrotron may get higher output power because it can adjust the anode voltage and extend the range of oscillation parameters. The NBI system has been attained 5.8 MW at 400 kV of beam energy with the negative ion based one and 28 MW with the positive ion based one. In a development work of the negative ion based NBI system, a detailed study on beamlet steering for multi-beam focusing was done, including of the space charge effects among beamlets. Then, 2.6 MW for 10s has been achieved.

Journal Articles

Progress of electron cyclotron heating/current drive technology in JT-60U

Moriyama, Shinichi; Ikeda, Yoshitaka; Seki, Masami; Sakamoto, Keishi; Kasugai, Atsushi; Takahashi, Koji; Kajiwara, Ken*; Isayama, Akihiko; Suzuki, Takahiro; Fukuda, Takeshi*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 79(9), p.935 - 944, 2003/09

An optimization of current profile is a key issue for attaining higher plasma performance in Tokamak, such as stabilization of neo-classical tearing mode (NTM) and control of internal transport barrier (ITB). In JT-60U, a high power electron cyclotron heating (ECH) system at 110 GHz has been developed for local plasma heating and current drive. We have demonstrated the technical feasibility of the antenna which can scan EC beam in both toroidal and poloidal directions. The toroidal scan enabled co- and counter- current drive and also pure plasma heating. An automatic stabilization of the NTM was demonstrated by means of current drive at the location of magnetic island using a feedback control of poloidal beam angle. The total injected power has been extended to 2.8 MW for 3.6 sec and each gyrotron delivers ~ 1 MW for 5 sec. This world record of the injection energy was attained by an upgrade of the gyrotron using RF absorber in the beam tunnel to suppress the parasitic oscillation and improvement of the transmission efficiency of the waveguide system.

130 (Records 1-20 displayed on this page)