Tokunaga, Tomoharu*; Kuno, Kohei*; Kawakami, Takumi*; Yamamoto, Takahisa*; Yoshigoe, Akitaka
International Journal of Hydrogen Energy, 45(28), p.14347 - 14353, 2020/05
To understand the catalytic behavior of graphite and carbon black with mainly 6-membered rings with sp bonds for H production by CH decomposition, fullerenes with 6-membered rings and also those comprising 5- and 7-membered rings with sp bonds was investigated using gas chromatography, XPS and TEM analysis. From these analysis, it is anticipated that the ring structures without 6-membered rings in carbon materials with sp bonding contribute to the catalytic behavior for CH decomposition at a low temperature of 400C.
Okudaira, Takuya; Shimizu, Hirohiko*; Kitaguchi, Masaaki*; Hirota, Katsuya*; Haddock, C. C.*; Ito, Ikuya*; Yamamoto, Tomoki*; Endo, Shunsuke*; Ishizaki, Kohei*; Sato, Takumi*; et al.
EPJ Web of Conferences, 219, p.09001_1 - 09001_6, 2019/12
Parity violating effects enhanced by up to 10 times have been observed in several neutron induced compound nuclei. There is a theoretical prediction that time reversal (T) violating effects can also be enhanced in these nuclei implying that T-violation can be searched for by making very sensitive measurements. However, the enhancement factor has not yet been measured in all nuclei. The angular distribution of the (n,) reaction was measured with La by using a germanium detector assembly at J-PARC, and the enhancement factor was obtained. From the result, the measurement time to achieve the most sensitive T-violation search was estimated as 1.4 days, and a 40% polarized La target and a 70% polarized He spin filter whose thickness is 70 atmcm are needed. Therefore high quality He spin filter is developed in JAEA. The measurement result of the (n,) reaction at J-PARC and the development status of the He spin filter will be presented.
Strasser, P.*; Abe, Mitsushi*; Aoki, Masaharu*; Choi, S.*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; et al.
EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01
Haruna, Takumi*; Yamamoto, Tatsuya*; Miyairi, Yoji*; Shibata, Toshio*; Taniguchi, Naoki; Sakamaki, Keiko; Tachikawa, Hirokazu*
Zairyo To Kankyo, 64(5), p.201 - 206, 2015/05
Diffusion coefficients of DO in the films was determined in order to estimate corrosion rate of carbon steel for the overpack in ground water. Fe plates were heated to form oxide films. The films were characterized with XRD and SEM. After that, the specimen was contacted with DO for 5184 ks, followed by subjected to TDS to obtain an amount of DO absorbing into the film. As a result, single-layered film of FeO was formed at 573 and 723 K, and double-layered film of FeO and FeO was formed at 873 K. It was found that an amount of DO in the film correlated linearly with a square root of the absorption period, and that the amount was steady for a long period. From the results and Fick's second law, diffusion coefficients of DO was determined as 9.710 cms for the FeO film, and 5.510 cms to 2.210 cms for FeO film.
Dairaku, Masayuki; Watanabe, Kazuhiro; Tobari, Hiroyuki; Kashiwagi, Mieko; Inoue, Takashi; Sakamoto, Keishi; Hanada, Masaya; Akino, Noboru; Ikeda, Yoshitaka; Yamamoto, Takumi*
JAEA-Technology 2008-091, 23 Pages, 2009/03
A plasma generator whose inner dimensions are 25 cm in width, 59 cm in length, and 31 cm in depth for a high power and long pulse ion source in neutral beam injector has been designed and fabricated. The plasma generator has a beam extraction area of 12 cm in width and 46 cm in length. A target of the output beam using the plasma generator is to produce deuterium positive ion beams up to 120 keV, 65 A for longer than 200 s pulses. Arrangement of the permanent magnets and filaments has been designed by using an electron trajectory simulation code to produce uniform and high density plasma with high proton yield. Cooling channels have been also designed to operate the long pulse plasma generation with a 100 kW arc discharge power.
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
no abstracts in English
Bae, Y. S.*; Na, Y. S.*; Oh, Y. K.*; Kwon, M.*; Bak, J. S.*; Lee, G. S.*; Jeong, J. H.*; Park, S. I.*; Cho, M. H.*; Namkung, W.*; et al.
Fusion Science and Technology, 52(2), p.321 - 333, 2007/08
An 84-GHz, 500-kW gyrotron system have been installed at KSTAR, and the initial test of the gyrotron has been carried out with 20 sec-pulse and an output RF power of 500 kW. The launcher system having with a highly flexible steering mirror was fabricated and would inject 500-kW rf power into the KSTAR plasma. KSTAR will employ 170-GHz EC current drive (CD) in ITER-relevant experiments such as the suppression of the neoclassical tearing modes and the creation of an electron internal transport barrier. A JAEA 170-GHz, 1-MW gyrotron on loan in accordance with a Korea-Japan fusion collaboration agreement, and it will be used for the 170-GHz, 1-MW ECCD system in 2010. This paper describes the current status of the installation and initial conditioning tests of the 84-GHz gyrotron system as well as the development plan of the 170-GHz ECH and CD system. Also, this paper discusses the CD efficiency and the steering range of the second-harmonic X-mode injection.
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.
Ikeda, Yoshitaka; Umeda, Naotaka; Akino, Noboru; Ebisawa, Noboru; Grisham, L. R.*; Hanada, Masaya; Honda, Atsushi; Inoue, Takashi; Kawai, Mikito; Kazawa, Minoru; et al.
Nuclear Fusion, 46(6), p.S211 - S219, 2006/06
Recently, the extension of the pulse duration up to 30 sec has been intended to study quasi-steady state plasma on JT-60U N-NBI system. The most serious issue is to reduce the heat load on the grids for long pulse operation. Two modifications have been proposed to reduce the heat load. One is to suppress the beam spread which may be caused by beamlet-beamlet interaction in the multi-aperture grid due to the space charge force. Thin plates were attached on the extraction grid to modify the local electric field. The plate thickness was optimized to steer the beamlet deflection. The other is to reduce the stripping loss, where the electron of the negative ion beam is stripped and accelerated in the ion source and then collides with the grids. The ion source was modified to reduce the pressure in the accelerator column to suppress the beam-ion stripping loss. Up to now, long pulse injection of 17 sec for 1.6 MW and 25 sec for 1 MW has been obtained by one ion source with these modifications.
Hirane, Nobuhiko; Ishikuro, Yasuhiro; Nagadomi, Hideki; Yokoo, Kenji; Horiguchi, Hironori; Nemoto, Takumi; Yamamoto, Kazuyoshi; Yagi, Masahiro; Arai, Nobuyoshi; Watanabe, Shukichi; et al.
JAEA-Technology 2006-028, 115 Pages, 2006/03
JRR-4, a light-water-moderated and cooled, swimming pool type research reactor using high-enriched uranium plate-type fuels had been operated from 1965 to 1996. In order to convert to low-enriched-uranium-silicied fuels, modification work had been carried out for 2 years, from 1996 to 1998. After the modification, start-up experiments were carried out to obtain characteristics of the low-enriched-uranium-silicied fuel core. The measured excess reactivity, reactor shutdown margin and the maximum reactivity addition rate satisfied the nuclear limitation of the safety report for licensing. It was confirmed that conversion to low-enriched-uranium-silicied fuels was carried out properly. Besides, the necessary data for reactor operation were obtained, such as nuclear, thermal hydraulic and reactor control characteristics. This report describes the results of start-up experiments and burnup experiments. The first criticality of low-enriched-uranium-silicied core was achieved on 14th July 1998, and the operation for joint-use has been carried out since 6th October 1998.
Hoshino, Katsumichi; Yamamoto, Takumi; Tamai, Hiroshi; Oasa, Kazumi; Kawashima, Hisato; Miura, Yukitoshi; Ogawa, Toshihide; Shoji, Teruaki*; Shibata, Takatoshi; Kikuchi, Kazuo; et al.
Fusion Science and Technology, 49(2), p.139 - 167, 2006/02
The main results obtained by the various heating and current drive systems, external coil system and divertor bias system are reviewed from the viewpoint of the advanced active control of the tokamak plasma. Also, the features of each system are described. The contribution of the JFT-2M in these areas are summarized.
Umeda, Naotaka; Yamamoto, Takumi; Hanada, Masaya; Grisham, L. R.*; Kawai, Mikito; Oga, Tokumichi; Akino, Noboru; Inoue, Takashi; Kazawa, Minoru; Kikuchi, Katsumi*; et al.
Fusion Engineering and Design, 74(1-4), p.385 - 390, 2005/11
In negative ion based neutral beam injector (N-NBI) for JT-60U, some modifications for extent pulse duration from 10 second, which is design value, to 30 second was conducted. Main limit to prevent pulse extension was heat loads onto grounded grid in an ion source and onto beam limiter placed at 22 m from the ion source. To reduce these heat loads, beam extraction area was optimized and the limiter was changed to one which had about twice thermal capacity. As a result of these modifications, the temperature rise of the water which was cooling grounded grid could be suppressed under 40 degree, which can operate in steady state condition. The temperature rise of the limiter could be restricted to 60%. Untill now the beam pulse extended to 17 second of 1.6MW power at 366keV energy, and injection of 30 seconds will be achieved in next experiment.
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
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
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-. 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.
Yamamoto, Takumi; Oga, Tokumichi; Kawai, Mikito; Akino, Noboru; Kazawa, Minoru; Umeda, Naotaka
Heisei-16-Nen Denki Gakkai Zenkoku Taikai Koen Rombunshu, 219 Pages, 2004/00
In JAERI, 10 MW and 500 keV negative-ion based neutral beam injection (N-NBI) system for JT-60U was constructed in 1996, in order to study a plasma heating and current drive in high-density plasma by high-energy beam injection. Thereafter, improvement of beam performance has been carried out while N-NBI system was available for experiments on JT-60U. The maximum beam energy of 418 keV and the maximum injection power of 6.2 MW have been achieved with a hydrogen beam, so far. In addition, 10 seconds of injection pulse duration, which is the designed value, was attained at the injection power of 2.6MW. Further improvement is required for the performance to reach to the final targets. It was made it clear that the performance was limited by the withstanding voltage of acceleration and heat load on acceleration grids in the ion source.
Inoue, Takashi; Hanada, Masaya; Iga, Takashi*; Imai, Tsuyoshi; Kashiwagi, Mieko; Kawai, Mikito; Morishita, Takatoshi; Taniguchi, Masaki; Umeda, Naotaka; Watanabe, Kazuhiro; et al.
Fusion Engineering and Design, 66-68, p.597 - 602, 2003/09
The neutral beam (NB) injection has been one of the most promising methods for plasma heating and current drive in tokamak fusion devices. JAERI has developed high energy electrostatic accelerators for the NB systems in JT-60U and ITER. Recent progress on this R&D are as follows: 1) In the JT-60U NB system, some of the beams has been deflected due to distorted electric field in the accelerator, resulting in an excess heat load on the NB port. By correcting the electric field, a continuous injection of H beam was succeeded for 10 s with the NB power of 2.6 MW at 355 keV. 2) To increase the beam energy, a metal structure called stress ring was designed. The ring reduces electric field concentration at the triple junction point (interface between metal and dielectric insulator inside vacuum). Initial test of the accelerators with the stress rings has shown higher voltage hold off performance in both accelerators for JT-60U and ITER R&D than that without rings.
Yamamoto, Takumi; JT-60 Team
Fusion Engineering and Design, 66-68, p.39 - 48, 2003/09
Development of technology on facilities for JT-60U and resultant progress of the plasma performance are reported. The main objectives of JT-60U are to demonstrate integrated high plasma performance that contributes to establishment of the physical and technological bases of ITER and a steady state tokamak fusion reactor. Recently, performance exploration in advanced tokamak regimes has been conducted intensively, by using 500 keV negative-ion based neutral beam injection (N-NBI) and 110GHz electron cyclotron (EC) systems for plasma heating and current drive, and a repetitive centrifugal pellet injector for efficient core particle fueling.
Kawai, Mikito; Akino, Noboru; Ebisawa, Noboru; Grisham, L. R.*; Hanada, Masaya; Honda, Atsushi; Inoue, Takashi; Kazawa, Minoru; Kikuchi, Katsumi*; Kuriyama, Masaaki; et al.
Fusion Science and Technology, 44(2), p.508 - 512, 2003/09
The negative ion source for negative ion based neutral beam injector(N-NBI) of JT-60U aims at generating a negative ion beam with 500 keV and 22A for 10s. The N-NBI system was completed in 1996, followed by starting the efforts to increase beam power and energy. (1)Spatial non-uniformity of the source plasma causes position-dependent divergence of a beamlet due to mis-matching of local beam perveance. A part of the divergent energetic beams is intercepted by the grids and resultantly produce the excessive heat load of the grids and/or induce the high voltage breakdown. So several techniques to take measures against and to correct the non-uniformity in these sources were implemented. (2)Correction of beamlet deflection by adjusting the electric field at the extraction grids. It improved the beam divergence and then decreased an excessive heat load of a beam limiter by more than 50 %. As a result, the maximum injection power 6.2MW and beam pulse duration 10 seconds were obtaind.
Kaneko, Osamu*; Yamamoto, Takumi; Akiba, Masato; Hanada, Masaya; Ikeda, Katsunori*; Inoue, Takashi; Nagaoka, Kenichi*; Oka, Yoshihide*; Osakabe, Masaki*; Takeiri, Yasuhiko*; et al.
Fusion Science and Technology, 44(2), p.503 - 507, 2003/09
High energy negative-ion-based neutral beam injection (N-NBI) is expected as an efficient and reliable tool of heating and current driving for reactor plasmas such as ITER. A world wide activity on developing technology of negative ion production and beam formation started in 1980's and the great progress has been achieved up to now. In particular, Japan has two large projects that planned adopting N-NBI for real plasma experiments; the JT-60U tokamak and the LHD heliotron, which further motivated the R&D activity. These R&D programs were carried out at JAERI and NIFS separately in Japan, and both were successfully done. The first beam injection experiment was made on the JT-60U in 1996, followed by the LHD in 1998. They were the first experiments on heating plasma by high energy beam in tokamaks and in stellerators, and the obtained results were very promising.
Umeda, Naotaka; Grisham, L. R.*; Yamamoto, Takumi; Kuriyama, Masaaki; Kawai, Mikito; Oga, Tokumichi; Mogaki, Kazuhiko; Akino, Noboru; Yamazaki, Haruyuki*; Usui, Katsutomi; et al.
Nuclear Fusion, 43(7), p.522 - 526, 2003/07
The Negative-ion based Neutral Beam Injection System (N-NBI) for JT-60U has been operating for plasma heating and non-inductive current drive since 1996. The target is inject of neutral beam into plasma with beam energy 500 keV, injection power 10 MW, for 10 seconds. Until now pulse duration time was restricted up to 5.3 seconds because of larger heat load of port limiter. Recently from the measurement of beam profile at 3.5m downstream from the ion source, it was found that the outermost beamlets in each segment were deflected outward. It was caused by non-uniform electric field by grooves. By improving this, outermost beamlet deflection angle was decreased from 14 mrad to 4 mrad. In this result, 10 seconds injection, which is target parameter, has achieved at 355 keV, 2.6MW, while pulse length was restricted up to 5.3 seconds by larger heat load of port limiter.