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Tobita, Kenji; Nishio, Satoshi*; Enoeda, Mikio; Nakamura, Hirofumi; Hayashi, Takumi; Asakura, Nobuyuki; Uto, Hiroyasu; Tanigawa, Hiroyasu; Nishitani, Takeo; Isono, Takaaki; et al.
JAEA-Research 2010-019, 194 Pages, 2010/08
JAEA-Research-2010-019-01.pdf:48.47MBJAEA-Research-2010-019-02.pdf:19.4MB
This report describes the results of the conceptual design study of the SlimCS fusion DEMO reactor aiming at demonstrating fusion power production in a plant scale and allowing to assess the economic prospects of a fusion power plant. The design study has focused on a compact and low aspect ratio tokamak reactor concept with a reduced-sized central solenoid, which is novel compared with previous tokamak reactor concept such as SSTR (Steady State Tokamak Reactor). The reactor has the main parameters of a major radius of 5.5 m, aspect ratio of 2.6, elongation of 2.0, normalized beta of 4.3, fusion out put of 2.95 GW and average neutron wall load of 3 MW/m
. This report covers various aspects of design study including systemic design, physics design, torus configuration, blanket, superconducting magnet, maintenance and building, which were carried out increase the engineering feasibility of the concept.
Oshima, Takayuki; Fujita, Takaaki; Seki, Masami; Kawashima, Hisato; Hoshino, Katsumichi; Shibanuma, Kiyoshi; Verrecchia, M.*; Teuchner, B.*
Journal of Plasma and Fusion Research SERIES, Vol.9, p.620 - 624, 2010/08
For interface control and assembly, the CAD data will be exchanged and integrated in a new Data Base server installed at Naka for JT-60SA, where a common computer network efficiently connected between the Naka site for JAEA and the Garching site for F4E is needed to be established. To ensure the design environments, a VPN (Virtual Private Network) was introduced with CAD LAN on computer network physically-separated from JAEA intranet area and firewall. In July 2009, a new VPN connection between the Naka and Garching sites has been successfully demonstrated using IPSec-VPN technology with a commercial and cost-effective firewall/router for security. The VPN technology would provide a common platform for the development of remote experimentation techniques on JT-60SA between Rokkasho and Naka in collaboration with activities of the ITER Remote Experimentation Centre for the IFERC Project at Rokkasho.
Tobita, Kenji; Nishio, Satoshi; Enoeda, Mikio; Kawashima, Hisato; Kurita, Genichi; Tanigawa, Hiroyasu; Nakamura, Hirofumi; Honda, Mitsuru; Saito, Ai*; Sato, Satoshi; et al.
Nuclear Fusion, 49(7), p.075029_1 - 075029_10, 2009/07
Times Cited Count：137 Percentile：97.72(Physics, Fluids & Plasmas)Recent design study on SlimCS focused mainly on the torus configuration including blanket, divertor, materials and maintenance scheme. For vertical stability of elongated plasma and high beta access, a sector-wide conducting shell is arranged in between replaceable and permanent blanket. The reactor adopts pressurized-water-cooled solid breeding blanket. Compared with the previous advanced concept with supercritical water, the design options satisfying tritium self-sufficiency are relatively scarce. Considered divertor technology and materials, an allowable heat load to the divertor plate should be 8 MW/m or lower, which can be a critical constraint for determining a handling power of DEMO (a combination of alpha heating power and external input power for current drive).
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：21 Percentile：61.72(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.
TiO
pebble bed for a test blanket module in JAEATanigawa, Hisashi; Hoshino, Tsuyoshi; Kawamura, Yoshinori; Nakamichi, Masaru; Ochiai, Kentaro; Akiba, Masato; Ando, Masami; Enoeda, Mikio; Ezato, Koichiro; Hayashi, Kimio; et al.
Nuclear Fusion, 49(5), p.055021_1 - 055021_6, 2009/05
Times Cited Count：23 Percentile：64.51(Physics, Fluids & Plasmas)This paper presents recent achievements of the research activities for the TBM being developed in JAEA, focusing on the pebble bed of the tritium breeder materials and tritium behaviour. For the breeder material, the chemical stability of LiTiO has been improved by LiO additives. In order to analyze the pebble bed behaviour, thermo-mechanical properties of the LiTiO pebble bed has been experimentally obtained. In order to verify nuclear properties of the pebble bed, the activation foil method has been proposed and a preliminary experiment has been conducted. For the tritium behaviour, the chemical densified coating method has been well developed and tritium recovery system has been modified taking account of the design change of the TBM.
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.
Suzuki, Takahiro; Ide, Shunsuke; Oikawa, Toshihiro; Fujita, Takaaki; Ishikawa, Masao; Seki, Masami; Matsunaga, Go; Hatae, Takaki; Naito, Osamu; Hamamatsu, Kiyotaka; et al.
Nuclear Fusion, 48(4), p.045002_1 - 045002_9, 2008/04
Times Cited Count：39 Percentile：80.89(Physics, Fluids & Plasmas)Aiming at optimization of current profile in high-b plasmas for higher confinement and stability, a real-time control system of the minimum of the safety factor (
) using the off-axis current drive has been developed. The off-axis current drive can raise safety factor in the center and help to avoid instability that limits performance of the plasma. The system controls injection power of lower-hybrid (LH) waves, and hence, its off-axis driven current in order to control 
. The real-time control of is demonstrated in a high-
plasma, where follows the temporally changing reference 
from 1.3 to 1.7. Applying the control to another high- discharge (
=1.7, 
=1.5) with 
=2/1 neo-classical tearing mode (NTM), was raised above 2 and the NTM was suppressed. The stored energy increased by 16% with the NTM suppressed, since the resonant rational surface was eliminated. For the future use for current profile control, current density profile for off-axis neutral beam current drive (NBCD) is for the first time measured, using motional Stark effect (MSE) diagnostic. Spatially localized NBCD profile was clearly observed at the normalized 
of about 0.6-0.8. The location was also confirmed by multi-chordal neutron emission profile measurement. The total amount of the measured beam driven current was consistent with the theoretical calculation using the ACCOME code. The CD location in the calculation was inward-shifted than the measurement.
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.
Isayama, Akihiko; Suzuki, Takahiro; Hayashi, Nobuhiko; Ide, Shunsuke; Hamamatsu, Kiyotaka; Fujita, Takaaki; Hosoyama, Hiroki; Kamada, Yutaka; Nagasaki, Kazunobu*; Oyama, Naoyuki; et al.
AIP Conference Proceedings 933, p.229 - 236, 2007/10
no abstracts in English
Moriyama, Shinichi; Seki, Masami; Fujii, Tsuneyuki
Fusion Engineering and Design, 82(5-14), p.785 - 790, 2007/10
Times Cited Count：8 Percentile：51.22(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.
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.
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.
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 
10 sec injection was successfully injected to plasmas. Moreover it was demonstrated that it had comparably high plasma current drive capability (about 1.6 10
A/W/m), required as a current drive LH antenna.
Suzuki, Takahiro; Ide, Shunsuke; Oikawa, Toshihiro; Fujita, Takaaki; Ishikawa, Masao*; Seki, Masami; Matsunaga, Go; Takechi, Manabu; Naito, Osamu; Hamamatsu, Kiyotaka; et al.
Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03
For the first time, we have measured the current density profile for off-axis neutral beam current drive (NBCD), using motional Stark effect (MSE) diagnostic. A spatially localized NBCD profile was clearly observed at 
. The location was also confirmed by neutron emission profile measurement. The total amount of the driven current (0.15MA) was consistent with the decrease in the surface loop voltage. The off-axis current drive can raise safety factor (q) in the center and help to avoid instability that limits performance of the plasma. We have developed a real-time control system of the minimum q (qmin), using the off-axis current drive. Injection power of lower hybrid (LH) waves, and hence, its off-axis driven current controls qmin. In a high plasma (
, 
), the system was adopted to control qmin. With the control, qmin was raised and MHD fluctuations were suppressed. The stored energy increased by 16% with the MHD fluctuations suppressed.
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：24.22(Nuclear Science & Technology)no abstracts in English
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：44.9(Nuclear Science & Technology)no abstracts in English
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：6 Percentile：33.46(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 0.54 m 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.
Suzuki, Takahiro; Isayama, Akihiko; Ide, Shunsuke; Fujita, Takaaki; Oikawa, Toshihiro; Sakata, Shinya; Sueoka, Michiharu; Hosoyama, Hiroki*; Seki, Masami; JT-60 Team
AIP Conference Proceedings 787, p.279 - 286, 2005/09
A real-time control system of safety factor (q) profile was developed in JT-60. This system, for the first time, enables 1) real time evaluation of q profile using local magnetic pitch angle measurement by motional Stark effect (MSE) diagnostic and 2) control of current drive (CD) location (rhoCD) by adjusting the parallel refractive index 
of lower-hybrid (LH) waves through the change of phase difference (dphi) of LH waves between multi-junction launcher modules. The method for q profile evaluation was newly developed, without time-consuming reconstruction of equilibrium, so that the method requires less computational time. The system evaluates q profile within every 10ms, which is much faster than current relaxation time, typically order of 1s. Safety factor profile by the real-time calculation agreed well with that by equilibrium reconstruction with MSE. From temporal evolution of q (or current) profile, we evaluate CD location in real-time, too. The control system controls rhoCD through (or directly dphi) in such a way to minimize difference between the real-time evaluated q profile and its reference profile. The real-time control system was applied to positive shear plasmas (
), having plasma current of 0.6MA, toroidal field of 2.3T, and electron density of 
. In order to keep good coupling of LH waves to the plasma, gap between the launcher and the plasma surface was controlled to about 0.1m. The reference q profile was set to q(0)=1.3. The real-time q profile approached to the reference after application of real-time control; the controlled q profile was sustained for 3s, which was limited by injected LH power. RF experiments in JT-60U, such as stabilization of neo-classical tearing modes, plasma startup experiments, etc., are also presented.
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：60 Percentile：85.79(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.
Maebara, Sunao; Goniche, M.*; Kazarian, F.*; Seki, Masami; Ikeda, Yoshitaka; Imai, Tsuyoshi*; Beaumont, B.*
Review of Scientific Instruments, 76(5), p.053501_1 - 053501_7, 2005/05
Times Cited Count：1 Percentile：10.13(Instruments & Instrumentation)Development of a plasma facing module using Cold Isostatic Pressing Graphite (CIPG) had been done for a heat-resistant LHCD antenna. A thin stainless film (10
m), molybdenum film (10m) and copper film (50m) are laid to overlap each other on the CIPG materials, the CIPG surfaces were successfully coated with copper layer by diffusion bonding method. This module has four waveguides and a water cooling channel, the length is 206 mm. High power long pulse operation was successfully achieved up to 250 kW (125 MW/m)/700s. The module has been successfully tested at a RF power density which is equivalent, in terms of RF electric field (5kV/cm), to the one proposed for the LHCD antenna of ITER-FEAT. The outgassing rate of the copper-coated CIPG is estimated to be 3.2-5.110
Pa.m
/s.m at 100
C, it is assessed that a pumping system is not required to evacuate the pressure in the LHCD antenna.
