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Journal Articles

JT-60SA assembly and metrology

Suzuki, Sadaaki; Yagyu, Junichi; Masaki, Kei; Nishiyama, Tomokazu; Nakamura, Shigetoshi; Saeki, Hisashi; Hoshi, Ryo; Sawai, Hiroaki; Hasegawa, Koichi; Arai, Takashi; et al.

NIFS-MEMO-67, p.266 - 271, 2014/02

no abstracts in English

JAEA Reports

Assembly work and transport of JT-60SA cryostat base

Okano, Fuminori; Masaki, Kei; Yagyu, Junichi; Shibama, Yusuke; Sakasai, Akira; Miyo, Yasuhiko; Kaminaga, Atsushi; Nishiyama, Tomokazu; Suzuki, Sadaaki; Nakamura, Shigetoshi; et al.

JAEA-Technology 2013-032, 32 Pages, 2013/11

JAEA-Technology-2013-032.pdf:8.86MB

Japan Atomic Energy Agency started to construct a fully superconducting tokamak experiment device, JT-60SA, to support the ITER since January, 2013 at the Fusion Research and Development Directorate in Naka, Japan. The JT-60SA will be constructed with enhancing the previous JT-60 infrastructures, in the JT-60 torus hall, where the ex-JT-60 machine was disassembled. The JT-60SA Cryostat Base, for base of the entire tokamak structure, were assembly as first step of this construction. The Cryostat Base (CB, 250 tons) is consists of 7 main made of stainless steel, 12m diameter and 3m height. It was built in the Spain and transported to the Naka site with the seven major parts split, via Hitachi port. The assembly work of these steps, preliminary measurements, sole plate adjustments of its height and flatness, and assembly of the CB. Introduces the concrete result of assembly work and transport of JT-60SA cryostat base.

Journal Articles

Development of a linear motion antenna for the JT-60SA ECRF system

Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Hoshino, Katsumichi; Suzuki, Sadaaki; Hiranai, Shinichi; Yokokura, Kenji; Sawahata, Masayuki; Terakado, Masayuki; Hinata, Jun; et al.

Fusion Engineering and Design, 88(6-8), p.935 - 939, 2013/10

 Times Cited Count:3 Percentile:62.81(Nuclear Science & Technology)

An antenna having a first mirror driven in the linear motion (LM) and a fixed second mirror was proposed for electron cyclotron range of frequency (ECRF) heating and current drive system, to minimize the risk of cooling-water-leakage. Basic mechanical feasibilities of the bellows covering the movable structures of the antenna were previously investigated using a mock-up. This time, a support structure of the shaft has been designed using a metallic sliding bearing with solid lubricant. The sliding bearing can support combination of linear and rotational motions while a ball bearing supports either linear or rotational motion. We have newly installed the sliding bearing into the mock-up. A vacuum pumping test has been carried out paying attention to the influence of the solid lubricant by mass analysis. To design the LM antenna for JT-60SA in detail, heating and current drive characteristics for typical experimental scenarios of JT-60SA has been investigated by calculation.

Journal Articles

Dual frequency ECRF system development for JT-60SA

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

Fusion Science and Technology, 63(1T), p.160 - 163, 2013/05

 Times Cited Count:6 Percentile:39.84(Nuclear Science & Technology)

A dual frequency electron cyclotron range of frequency system has been developed for JT-60SA, by which a second frequency (135 $$sim$$ 140 GHz) is generated in addition to the first frequency of 110 GHz. A development of a dual frequency gyrotron is a key to realize the dual frequency system. The second frequency was chosen to be 138 GHz from the above frequency range from the viewpoint of gyrotron design. In order to realize high-power ($$>$$ 1 MW) and long-pulse operation for both frequencies, we designed main components of the gyrotron (the diamond window, cavity resonator and quasi-optical mode converter). We found the optimum parameter set from the parameters of these components, which has discrete characteristics. It was confirmed that the output power higher than 1 MW is obtained for both frequencies as a result of numerical design. Based on the above design, a dual frequency gyrotron was newly fabricated. In the conditioning operation, an output power was obtained as we expected.

Journal Articles

Dual frequency gyrotron development for JT-60SA

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

Proceedings of 37th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2012) (USB Flash Drive), 2 Pages, 2012/09

A new dual frequency (110 GHz and 138 GHz) gyrotron development began for JT-60SA. An output power and efficiency higher than 1 MW and 30% with a peak heat load lower than 1.4 kW/cm$$^{2}$$ were obtained for both frequencies in calculation. High mode conversion efficiencies of the quasioptical mode converter (96.8% for 110 GHz and 98.3% for 138 GHz), which is higher than the previously developed 110 GHz long pulse gyrotron (96.5%), was obtained. The new gyrotron was fabricated and conditioning operation has been started from the middle of June 2012. The gyrotron output power of approximately 200 kW was obtained, so far, as we expected in the design of the gyrotron at low beam current of 10 A and low beam voltage of 75 kV.

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.

JAEA Reports

Measures of the trouble on the long pulse in JT-60U electron cyclotron heating system

Hiranai, Shinichi; Suzuki, Sadaaki; Sato, Fumiaki; Kobayashi, Takayuki; Hasegawa, Koichi; Yokokura, Kenji; Moriyama, Shinichi

JAEA-Technology 2010-031, 24 Pages, 2010/09

JAEA-Technology-2010-031.pdf:1.71MB

The JT-60U electron cyclotron heating (ECH) system injects a millimeter wave at 110 GHz into the JT-60U plasma, and heats the plasma or drives a current locally to enhance the confinement performance of the JT-60U plasma. The ECH system of high power gyrotrons, transmission lines and antenna that launch millimeter wave beams toward the plasma. On the long pulse injection, one of the most important purposes is to prevent arcing in the transmission lines and to transmit millimeter wave beams efficiently. This report describes the problems occurred in a long pulse injection test (0.5 MW, 30 s), e.g., increase in released gas, temperature rise of the transmission line and an arcing at the vacuum window during the conditioning process. It also describes measures for the problems, e.g., improvements in vacuum pumping system, cooling system, and arc detector and introduction of the new dummy road system.

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

Improvement of the protection devices for JT-60U LHRF antenna system

Suzuki, Sadaaki; Seki, Masami; Shinozaki, Shinichi; Sato, Fumiaki; Hiranai, Shinichi; Ishii, Kazuhiro*; Hasegawa, Koichi; Moriyama, Shinichi

JAEA-Technology 2007-055, 27 Pages, 2007/09

JAEA-Technology-2007-055.pdf:4.18MB

In the experiments featuring lower hybrid range of frequency (LHRF) system in JT-60U, carbon grills were attached to the plasma-facing part of the antenna in order to avoid the damage by the excessive heat load from the plasma. However some electric discharge traces were found there in the observation after the experiments. To avoid such discharges, improvements of the arc detector and the protection interlock by visible picture detection were tackled. In the arc detector, the amplification circuit was improved in order to obtain shorter response time and higher resolution of optical detection. Moreover, in visible picture detection, a new function of RF-on/off control utilizing PC image processing was added to distinguish the light of the arc from one of the plasma. This report summarizes improvement of the protection interlock device in a LHRF heating system.

JAEA Reports

Development of power measuring device of transmission type with dielectric for high power millimeter wave

Yokokura, Kenji; Moriyama, Shinichi; Hasegawa, Koichi; Suzuki, Sadaaki; Hiranai, Shinichi; Ishii, Kazuhiro*; Sato, Fumiaki

JAEA-Technology 2007-045, 22 Pages, 2007/07

JAEA-Technology-2007-045.pdf:6.1MB

A power measuring device using a dielectric disk for a high power millimeter waves is investigated. In the device, a high power wave is transmitted in a waveguide and then heats a dielectric installed in the waveguide. The transmitted power is estimated from the temperature rise of the dielectric disk. It is a new type of power measurement device, which is not sensitive to higher modes or change of their polarization in time. It also can measure the wide power range of kW to MW levels flexibly by choosing dielectric material proper to the power level as a detector. In the report, materials that have small dielectric loss for millimeter wave are chosen, and their properties of temperature rise and millimeter wave power capacity are estimated. On the basis of these results, design of the power measurement device and fabrication of its prototype are described for practical use in the electron cyclotron heating systems for the JT-60U and JT-60SA.

JAEA Reports

Power injection performance of the LH antenna tipped with carbon grills in JT-60U

Ishii, Kazuhiro; Seki, Masami; Shinozaki, Shinichi; Hasegawa, Koichi; Hiranai, Shinichi; Suzuki, Sadaaki; Sato, Fumiaki; Moriyama, Shinichi; Yokokura, Kenji

JAEA-Technology 2007-036, 30 Pages, 2007/07

JAEA-Technology-2007-036.pdf:17.06MB

The lower hybrid (LH) antenna in JT-60U has interaction with plasmas because it should be close to them in order to inject effectively radio frequency (RF) power into them. As a result, it has been a serious problem that the antenna mouth made of stainless steels was damaged due to excessive heat loads of plasmas and RF breakdowns. To solve the problem, a heat-resistant LH antenna was developed tipping carbon grills with fairly high heat resistance on the antenna mouth, and therefore reduction in damages on the mouth was expected. Power injection into plasmas was firstly performed with the heat-resistant antenna. RF conditioning was done carefully in the initial phase because RF breakdown due to outgassing from the grills might be occurred. After sufficient degassing was done through RF conditioning, RF power of about 1.6 MW $$times$$ 10 sec injection was successfully injected to plasmas. Moreover it was demonstrated that it had comparably high plasma current drive capability (about 1.6 $$times$$ 10$$^{19}$$ A/W/m$$^{2}$$), required as a current drive LH antenna.

Journal Articles

Compact toroid injection system for JFT-2M

Fukumoto, Naoyuki*; Ogawa, Hiroaki; Nagata, Masayoshi*; Uyama, Tadao*; Shibata, Takatoshi; Kashiwa, Yoshitoshi; Suzuki, Sadaaki; Kusama, Yoshinori; JFT-2M Group

Fusion Engineering and Design, 81(23-24), p.2849 - 2857, 2006/11

 Times Cited Count:5 Percentile:57.7(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Ripple reduction with ferritic insert in JFT-2M

Shinohara, Koji; Sato, Masayasu; Kawashima, Hisato; Tsuzuki, Kazuhiro; Suzuki, Sadaaki; Urata, Kazuhiro*; Isei, Nobuaki; Tani, Takashi; Kikuchi, Kazuo; Shibata, Takatoshi; et al.

Fusion Science and Technology, 49(2), p.187 - 196, 2006/02

 Times Cited Count:7 Percentile:48.06(Nuclear Science & Technology)

In JFT-2M, the toroidal field ripple was reduced by ferritic insert. Two kinds of ripple reduction were carried out. In the first case, ferritic steel was installed between toroidal field coil and vacuum vessel, just under toroidal field coil, outside vacuum vessel. In the second one, ferritic steel was installed inside vacuum vessel covering almost whole inside wall. The ripple was successfully reduced in the both cases. The temperature increment on the first wall measured by infrared TV was also reduced. A new version of OFMC code was also developed to analyze fast ion behavior in the complex structure of the toroidal field. The TF ripple reduction with ferritic insert in JFT-2M is summarized in this article.

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