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JAEA Reports

Upgrade of DC power supply system in ITER CS Model Coil Test Facility

Shimono, Mitsugu; Uno, Yasuhiro; Yamazaki, Keita; Kawano, Katsumi; Isono, Takaaki

JAEA-Testing 2014-004, 62 Pages, 2015/03

JAEA-Testing-2014-004.pdf:16.03MB

The ITER CS Model Coil Test Facility is composed of a helium refrigerator / liquefier system, a DC power supply system, a vacuum system and a data acquisition system. The DC power supply system supplies currents to two superconducting coils, the CS Model Coil and an insert coil. A 50-kA DC power supply is installed for the CS Model Coil and two 30 kA DC power supplies are installed for an insert coil. In order to evaluate superconducting performance of a conductor used for ITER Toroidal Field (TF) coils whose operating current is 68 kA, the line for an insert coil is upgraded. A 10-kA DC power supply was added, DC circuit breakers were upgraded, bus bars and current measuring instrument were replaced. In accordance to the upgrade, operation manual was revised.

Journal Articles

Recent results from the development of the electron cyclotron heating system for JT-60SA toward high-power long-pulse operations

Isayama, Akihiko; Kobayashi, Takayuki; Yokokura, Kenji; Shimono, Mitsugu; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Wada, Kenji; Hinata, Jun; et al.

Plasma and Fusion Research (Internet), 7(Sp.1), p.2405029_1 - 2405029_5, 2012/05

no abstracts in English

Journal Articles

Progress in ECRF antenna development for JT-60SA

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

Fusion Engineering and Design, 86(6-8), p.763 - 767, 2011/10

 Times Cited Count:5 Percentile:50.9(Nuclear Science & Technology)

Progress of antenna development of the Electron Cyclotron Range of Frequency system for JT-60 SA is presented. Capability of pulse length of 100 s, which requires active cooling for mirrors, and flexibility of beam injection angles in both poloidal and toroidal directions are required for the antenna with high reliability. Mechanical and structural design works of the launcher (antenna and its support with steering structure) based on a linear motion antenna concept are in progress. The key component is a long-stroke bellows which enables to alter poloidal injection angle and a bellows which enables to alter toroidal injection angle. Using a newly fabricated mock-up of the steering structure, it was confirmed that the antenna was mechanically realized for poloidal and toroidal injection angle ranges of -10 to +45$$^{circ}$$ and -15 to +15$$^{circ}$$, respectively. Those angles are consistent with angles required in JT-60SA. The results of thermal and structural analyses are also presented.

Journal Articles

Progress of high-power and long-pulse ECRF system development in JT-60

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

Nuclear Fusion, 51(10), p.103037_1 - 103037_10, 2011/10

 Times Cited Count:14 Percentile:35.31(Physics, Fluids & Plasmas)

A new gyrotron operation technique to increase oscillation efficiency was developed on the JT 60 ECRF system. The electron pitch factor was optimized by controlling anode voltage within 0.1 s after the start of the operation. By applying this technique, the gyrotron output power of 1.5 MW for 4 s was recorded, for the first time. The reduced collector heat load at 1.5 MW operations was reduced by 20% and it will be acceptable for longer pulse operation. A new gyrotron with an improved mode converter was developed in order to demonstrate reduction of the stray radiation which had limited the pulse length. The stray radiation was reduced to 1/3 of that of the original gyrotron. A conditioning operation of the improved gyrotron is proceeding up to 31 s at 1 MW. These progresses significantly contribute to enhancing the high power and long pulse capability of the ECRF system toward JT 60SA.

Journal Articles

Development of the long-pulse ECRF system for JT-60SA

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

Journal of Plasma and Fusion Research SERIES, Vol.9, p.363 - 368, 2010/08

Improvements are required for expanding the pulse length of the JT-60 ECRF system (5s) for JT-60SA (100s). Newly developed power supplies will be fabricated and installed by EU. The conditioning operation of an improved gyrotron equipping a newly designed mode convertor has been started. The mode convertor will reduce heat flux on the internal components and therefore expected to enable long pulse operation at 1 MW. Pre-programmed and/or feedback control of the heater current and anode voltage, which was successfully demonstrated in JT-60U, will be key techniques because the beam current decreases during a shot. The evacuated transmission lines have a capability of 1 MW per line. Since maintenance of the components in the vacuum vessel is difficult, a linear motion antenna concept was proposed to reduce risks of water leakage and fault of the driving mechanism in the vacuum vessel. The detailed design and the low power test of a mock-up antenna have been started.

Journal Articles

Developments of high power gyrotron and power modulation technique using the JT-60U ECRF system

Kobayashi, Takayuki; Terakado, Masayuki; Sato, Fumiaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Hiranai, Shinichi; Igarashi, Koichi; et al.

Plasma and Fusion Research (Internet), 4, p.037_1 - 037_10, 2009/08

Electron cyclotron (EC) heating and current drive (CD) are key tools to control fusion plasma especially for effective electron heating and for suppression of neoclassical tearing mode (NTM). Recently, developments of a high power gyrotron and a power modulation technique have been successfully achieved on JT-60U ECRF system in order to enhance the system performance. Stable gyrotron oscillation with oscillation power of 1.5 MW for 1 s was demonstrated in 2007, for the first time. Then temperature rise of cavity and collector has been investigated. It has been shown that the longer pulse operation with 1.5 MW by an improved 110 GHz gyrotron is possible. In addition, modulated ECCD in synchronized with NTM rotation has been performed with the oscillation power of 0.8 MW and the frequency around 5 kHz. The synchronizing system has worked very well and it has played an essential role in NTM suppression experiments on JT-60U.

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.

JAEA Reports

Study on disassembly work of the radio frequency heating system in the amplifier rooms and heating power supply building

Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Igarashi, Koichi; Sato, Fumiaki; Wada, Kenji; et al.

JAEA-Technology 2008-065, 98 Pages, 2008/10

JAEA-Technology-2008-065.pdf:38.83MB

Construction of the JT-60SA (super advanced) is planned as an upgrade of JT-60U as the satellite tokamak in ITER broader approach and as the national centralized tokamak facility program in Japan. The present JT-60U will be disassembled and the JT-60SA will be constructed at the same location in the JT-60 tours hall. The disassembly work will be planned in the period from 2009 to 2011. In this report, disassembly of the radio frequency heating system of JT-60U in the amplifier rooms and heating power supply building is studied on (1) object for disassembly, (2) work plan, (3) estimation of materials amount, (4) procedure.

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.

JAEA Reports

Study on disassembly work of the radio frequency heating system in the JT-60 torus hall

Yokokura, Kenji; Shimono, Mitsugu; Suzuki, Sadaaki; Sawahata, Masayuki; Igarashi, Koichi; Wada, Kenji; Moriyama, Shinichi

JAEA-Technology 2008-058, 103 Pages, 2008/08

JAEA-Technology-2008-058.pdf:33.88MB

This report summarized the studies on the disassemble work of radio frequency heating system in the torus hall as a preparation for the construction of JT-60SA (super advanced) which is the upgrade of the present large tokamak, JT-60U. The studies of the disassembly work were done with emphasis on the safety management because the work requires treatment of contaminated material with tritium and radiated material by neutron, and (1) object for disassemble, (2) work plan, (3) estimation of materials amount, and (4) procedure were summarized.

JAEA Reports

Development of the power modulation technique in JT-60U ECH system

Terakado, Masayuki; Shimono, Mitsugu; Sawahata, Masayuki; Shinozaki, Shinichi; Igarashi, Koichi; Sato, Fumiaki; Wada, Kenji; Seki, Masami; Moriyama, Shinichi

JAEA-Technology 2007-053, 28 Pages, 2007/09

JAEA-Technology-2007-053.pdf:4.3MB

The electron cyclotron heating (ECH) system at 110 GHz are injected to JT-60U plasmas with pulse modulation at dozens to hundreds of Hz in order to measure heat conductivity of the plasma to investigate plasma confinement. The JT-60U ECH system has a unique feature to realize the pulse modulation by controlling the anode voltage of the triode gyrotron without chopping the main acceleration voltage. The typical depth of the modulation is 80 % at the modulation frequency range of 12.2 Hz to 500 Hz. However in the JT-60SA, higher modulation frequency of some kHz will be required to stabilize neoclassical tearing mode (NTM). The modulation techniques have been investigated and the modulation frequency of 3.5 kHz with the modulation depth of 84 % has been achieved. The modulation frequency up to 3 kHz is available in the pulse widths of the practical operation. As a next step, replacement of the parts in the anode voltage divider circuit is planned to achieve higher modulation frequency.

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:72.02(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:48.84(Nuclear Science & Technology)

no abstracts in English

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.

JAEA Reports

Performance and experience of a 110 GHz gyrotron operation on the JT-60U ECH system

Takahashi, Masami*; Seki, Masami; Shimono, Mitsugu; Terakado, Masayuki; Igarashi, Koichi*; Ishii, Kazuhiro*; Kasugai, Atsushi

JAERI-Tech 2003-080, 27 Pages, 2003/11

JAERI-Tech-2003-080.pdf:3.11MB

The JT-60U electron cyclotron heating (ECH) system has been introduced to suppress MHD instabilities via a current profile control by local heating or current drive. The ECH system consists of four 1MW-110GHz gyrotrons, four 60m transmission lines composed of a corrugated waveguide with a diameter of 31.75mm and two steerable type mirror antennas. Recently, a gyrotron developed for ITER has realized high power in an extremely high frequency range of millimeter waves although there was no high power source around 110GHz ten years ago. Therefore, it requires many techniques to operate the gyrotoron. The oscillation conditions had to be found at output power 1MW by adjusting the magnetic field parameters and anode voltage after heater aging. Then conditioning of the gyrotoron was done, where the pulse length is gradually extended in order to operate for 1sec level of pulse length. Consequently, 1MW-5sec of the designed value was achieved and the ECH system with four gyrotrons successfully injected the millimeter wave energy of 10MJ into plasmas, which is the world record.

JAEA Reports

Measures against the damage of the antenna mouth of JT-60U LHRF system

Ishii, Kazuhiro*; Seki, Masami; Shimono, Mitsugu; Terakado, Masayuki; Igarashi, Koichi*; Takahashi, Masami*

JAERI-Tech 2003-079, 22 Pages, 2003/10

JAERI-Tech-2003-079.pdf:3.01MB

In JT-60U, the study of current drive by radio-frequency (RF) waves in lower hybrid range of frequency (LHRF) has been done as one of research and development works aiming at steady state operation of tokamaks. The main subject of hardware and technology development in this study is to develop a high power LHRF antenna, the main component of the system. The LHRF antenna is set closely to plasma to efficiently inject RF power into it. The LHRF antenna normally receives heat loads from the plasma, and it is required to inject high RF power. Then, it has become a problem that the antenna mouth was melted by excessive heat loads from plasma or it was melted and deformed by RF discharges. As a counter measurement against this, the LHRF antenna has been conditioned to improve its stand-off voltage capability. Furthermore, by monitoring the temperature of the LHRF antenna, adjusting its position, developing a injection method of power modulation even for current drive, and setting an arc sensor which picks up the RF discharge, the damage of the antenna mouth has been suppressed.

JAEA Reports

Low-power and long-pulse test of a klystron of the JT-60U LHRF heating system

Shimono, Mitsugu; Seki, Masami; Terakado, Masayuki; Igarashi, Koichi*; Ishii, Kazuhiro*; Takahashi, Masami*; Shinozaki, Shinichi; Hiranai, Shinichi; Sato, Fumiaki*; Anno, Katsuto

JAERI-Tech 2003-075, 29 Pages, 2003/09

JAERI-Tech-2003-075.pdf:4.62MB

no abstracts in English

JAEA Reports

Power modulation by changing anode voltage of the 110GHz-gyrotron on JT-60U ECH system

Terakado, Masayuki; Seki, Masami; Shimono, Mitsugu; Igarashi, Koichi*; Mitsunaka, Yoshika*; Isayama, Akihiko; Anno, Katsuto; Ikeda, Yoshitaka

JAERI-Tech 2003-053, 25 Pages, 2003/06

JAERI-Tech-2003-053.pdf:3.23MB

The Electron Cyclotron Range of Frequencies (ECRF) system having four 110 GHz-gyrotrons has been successfully operated on JT-60U to locally heat a plasma (ECH) and drive a plasma current (ECCD) for high plasma performance owing to suppressing MHD activities. For investigation of plasma confinement the ECRF power is intermittently injected into plasmas to evaluate thermal conductivity. We have successfully performed power modulation by changing the anode voltage. The power modulation ratio of 80 % is attained changing the anode voltage by only about 10%. Modulation frequency is from 12 Hz to 500 Hz. The mode converter is heated when oscillation efficiency of the main mode decreases in changing the anode voltage. This seems to be due to the parasitic oscillation at the entrance of the converter. The gyrotron will be able to be protected by monitoring the temperature rise in the converter.

JAEA Reports

Operational experiences of the super conducting magnet for a gyrotron of the JT-60U ECH system

Igarashi, Koichi*; Seki, Masami; Shimono, Mitsugu; Terakado, Masayuki; Ishii, Kazuhiro*; Takahashi, Masami*

JAERI-Tech 2003-030, 40 Pages, 2003/03

JAERI-Tech-2003-030.pdf:5.83MB

The JT-60U electron cyclotron heating (ECH) system can heat plasmas locally and drive a plasma current with four 1 MW-5 sec gyrotrons. The super conducting magnets (SCM) are required for oscillation of the gyrotron at a working frequency of 110 GHz. The SCM provides a high magnetic field of 4.5T at the cavity inside the gyrotron. This SCM system is characterized by (1) operation without liquid Helium owing to a 4 K-refrigerator applied to the magnetic coils, (2) easy maintenance. Operational experiences about the SCM system through a long term experiment for a high power gyrotron are very valuable. According to those operational experiences, it is clarified the 4 K-refrigerator should be renewed in oder to keep low temperature of the SCM. It is also found that 200 hours or less are required for the super conducting condition ($$<$$5K) after long stopping time of the refrigerator up to 150 hours. This is useful information for making a plan about ECH experiments.

Journal Articles

Power control by changing anode voltage of a 1MW-gyrotron

Terakado, Masayuki; Shimono, Mitsugu; Igarashi, Koichi*; Takahashi, Masami*; Ishii, Kazuhiro*; Seki, Masami

Heisei-14-Nendo Tokyo Daigaku Sogo Gijutsu Kenkyukai Gijutsu Hokokushu, 3 Pages, 2003/03

no abstracts in English

61 (Records 1-20 displayed on this page)