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Nakashima, Yosuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Oki, Kensuke*; Sakamoto, Mizuki*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; Imai, Tsuyoshi*; et al.
Journal of Nuclear Materials, 463, p.537 - 540, 2015/08
Times Cited Count:22 Percentile:85.16(Materials Science, Multidisciplinary)Nakashima, Yosuke*; Sakamoto, Mizuki*; Yoshikawa, Masayuki*; Oki, Kensuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; et al.
Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10
Kariya, Tsuyoshi*; Minami, Ryutaro*; Imai, Tsuyoshi*; Eguchi, Taku*; Sakamoto, Keishi; Mitsunaka, Yoshika*; Numakura, Tomoharu*; Endo, Yoichi*
Plasma and Fusion Research (Internet), 8, p.1205107_1 - 1205107_2, 2013/10
Minami, Ryutaro*; Kariya, Tsuyoshi*; Imai, Tsuyoshi*; Numakura, Tomoharu*; Endo, Yoichi*; Nakabayashi, Hidetaka*; Eguchi, Taku*; Shimozuma, Takashi*; Kubo, Shin*; Yoshimura, Yasuo*; et al.
Nuclear Fusion, 53(6), p.063003_1 - 063003_7, 2013/06
Times Cited Count:12 Percentile:45.06(Physics, Fluids & Plasmas)Minami, Ryutaro*; Kariya, Tsuyoshi*; Imai, Tsuyoshi*; Numakura, Tomoharu*; Endo, Yoichi*; Nakabayashi, Hidetaka*; Eguchi, Taku*; Shimozuma, Takashi*; Kubo, Shin*; Yoshimura, Yasuo*; et al.
Nuclear Fusion, 53(6), p.063003_1 - 063003_7, 2013/06
Sato, Shoichi*; Ichimura, Makoto*; Yamaguchi, Yusuke*; Katano, Makoto*; Imai, Yasutaka*; Murakami, Tatsuya*; Miyake, Yuichiro*; Yokoyama, Takuro*; Moriyama, Shinichi; Kobayashi, Takayuki; et al.
Plasma and Fusion Research (Internet), 5, p.S2067_1 - S2067_4, 2010/12
Ion cyclotron emissions (ICEs) due to deuterium-deuterium fusion-product (FP) ions on JT-60U are studied. ICE due to H-ions is identified from the difference of the toroidal wave number of 2nd ICE(D). The parameter dependence for the appearance of ICE(H) is investigated from the experimental conditions and also is studied by using "Escape Particle Orbit analysis Code (EPOC)".
Kariya, Tsuyoshi*; Minami, Ryutaro*; Imai, Tsuyoshi*; Sakamoto, Keishi; Kubo, Shin*; Shimozuma, Takashi*; Takahashi, Hiromi*; Ito, Satoshi*; Muto, Takashi*; Mitsunaka, Yoshika*; et al.
Fusion Science and Technology, 55(2T), p.91 - 94, 2009/02
Times Cited Count:11 Percentile:58.37(Nuclear Science & Technology)Oda, Yasuhisa*; Komurasaki, Kimiya*; Takahashi, Koji; Kasugai, Atsushi; Imai, Tsuyoshi*; Sakamoto, Keishi
Electrical Engineering in Japan, 161(2), p.1 - 7, 2007/11
Times Cited Count:1 Percentile:11.73(Engineering, Electrical & Electronic)Experiments on microwave plasma generation and its application to microwave beamed energy propulsion were conducted using a 1 MW-class, 170 GHz gyrotron. The microwave beam was focused using a parabola reflector and plasma was initiated near the focal point in the ambient air. Plasma propagated upstream in the microwave beam channel while absorbing microwaves. Its propagation velocity was supersonic when the microwave power density was greater than 75 kW/cm. The propulsive impulse was measured using a cone-cylinder shaped thruster model. As a result, the maximum momentum coupling coefficient was obtained at a certain plasma propagation distance. In addition, a larger momentum coupling coefficient was obtained when plasma was propagated at a supersonic velocity. This is because supersonic plasma propagation forms a strong shock wave, resulting in an efficient pressure increase.
Imai, Tsuyoshi*; Kasugai, Atsushi; Higaki, Hiroyuki*
Heisei-19-Nen Denki Gakkai Zenkoku Taikai Koen Rombunshu, 7, p.S9(24) - S9(26), 2007/03
no abstracts in English
Imai, Tsuyoshi*; Tatematsu, Yoshinori*; Numakura, Tomoharu*; Sakamoto, Keishi; Minami, Ryutaro*; Watanabe, Osamu*; Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Kamata, Yasuhiro*; Machida, Norihito*; et al.
Fusion Science and Technology, 51(2T), p.208 - 212, 2007/02
Times Cited Count:9 Percentile:53.64(Nuclear Science & Technology)no abstracts in English
Kamata, Yasuhiro*; Imai, Tsuyoshi*; Tatematsu, Yoshinori*; Watanabe, Osamu*; Minami, Ryutaro*; Saito, Teruo*; Sakamoto, Keishi; Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Machida, Norihito*; et al.
Fusion Science and Technology, 51(2T), p.412 - 414, 2007/02
Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)no abstracts in English
Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Imai, Tsuyoshi*; Saito, Teruo*; Tatematsu, Yoshinori*; Sakamoto, Keishi; Minami, Ryutaro*; Watanabe, Osamu*; Numakura, Tomoharu*; Endo, Yoichi*
Fusion Science and Technology, 51(2T), p.397 - 399, 2007/02
Times Cited Count:11 Percentile:60.02(Nuclear Science & Technology)no abstracts in English
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.
Kashiwagi, Mieko; Hanada, Masaya; Yamana, Takashi*; Inoue, Takashi; Imai, Tsuyoshi*; Taniguchi, Masaki; Watanabe, Kazuhiro
Fusion Engineering and Design, 81(23-24), p.2863 - 2869, 2006/11
Times Cited Count:4 Percentile:29.92(Nuclear Science & Technology)Plasma neutralizer is one of key components to achieve the required system efficiency ( 50 %) for a negative-ion based neutral beam (N-NB) system in a fusion power plant. In the plasma neutralizer, highly ionized plasma is required at lower pressure, e.g., ionization degrees of
30 % at
0.08 Pa for 1 MeV negative ions. In such low pressure, mean free path of fast electron that contributes to ionizations becomes longer than the neutralizer's dimensions. Therefore, suppression of fast electron leakage from large openings that are beam entrance and exit is a crucial issue to realize plasma neutralizers. To suppress the fast electron leakage from the openings, authors propose a shield field, which is a weak transverse magnetic field of only 30 Gauss applied locally around the opening. The shield field are numerically examined and designed by using a three dimensional particle orbit code. In the experimental studies, this weak shield field is applied at the openings (diam. = 20 cm) of an arc discharge driven plasma neutralizer (length = 200 cm, diam. = 60 cm). The plasma parameters inside and outside of the opening were measured by a Langmuir probe. The electron energy distribution function (EEDF) showed that considerable fast electrons, which were leaked from the opening, were suppressed successfully by the weak shield field of 30 Gauss. Thus the leaking fast electrons were repelled into the neutralizer to deposit their energy for the plasma production. At a result, the plasma production efficiency (plasma density / arc power) was improved by a factor of 1.5 at
0.08 Pa.
Oda, Yasuhisa*; Komurasaki, Kimiya*; Takahashi, Koji; Kasugai, Atsushi; Imai, Tsuyoshi*; Sakamoto, Keishi
Denki Gakkai Rombunshi, A, 126(8), p.807 - 812, 2006/08
Experiments on microwave plasma generation and its application to microwave beamed energy propulsion were conducted using a 1MW-class, 170GHz gyrotron. The microwave beam was focused using a parabola reflector and plasma was initiated near the focal point in the ambient air. Plasma propagated upstream in the microwave beam channel while absorbing microwave. Its propagation velocity was supersonic when the microwave power density was larger than 75kW/cm. The propulsive impulse was measured using a cone-cylinder shaped thruster model. As a result, maximum momentum coupling coefficient was obtained at a certain plasma propagation distance. In addition, large momentum coupling coefficient was obtained when plasma was propagated at a supersonic velocity. It would be because supersonic plasma propagation forms a strong shock wave, resulting in an efficient pressure increase.
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:40.72(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.
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:9.69(Nuclear Science & Technology)no abstracts in English
Tamai, Hiroshi; Akiba, Masato; Azechi, Hiroshi*; Fujita, Takaaki; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; Hosogane, Nobuyuki; Ichimura, Makoto*; et al.
Nuclear Fusion, 45(12), p.1676 - 1683, 2005/12
Times Cited Count:15 Percentile:44.69(Physics, Fluids & Plasmas)Design studies are shown on the National Centralized Tokamak facility. The machine design is carried out to investigate the capability for the flexibility in aspect ratio and shape controllability for the demonstration of the high-beta steady state operation with nation-wide collaboration, in parallel with ITER towards DEMO. Two designs are proposed and assessed with respect to the physics requirements such as confinement, stability, current drive, divertor, and energetic particle confinement. The operation range in the aspect ratio and the plasma shape is widely enhanced in consistent with the sufficient divertor pumping. Evaluations of the plasma performance towards the determination of machine design are presented.
Maebara, Sunao; Moriyama, Shinichi; Saigusa, Mikio*; Sugimoto, Masayoshi; Imai, Tsuyoshi; Takeuchi, Hiroshi
Fusion Engineering and Design, 75-79, p.823 - 827, 2005/11
Times Cited Count:2 Percentile:17.20(Nuclear Science & Technology)An RF-Input coupler with a multi-loop antenna using co-axial waveguides has been developed for the RFQ linac on IFMIF. In case of using a loop antenna, the loop antenna structure will affected phase difference and power balance in each cavity. A mock-up loop antenna using the pipe diameter of 10mm was fabricated, phase differences and power balances were measured by a low power test. It is found that it is necessary to shorten the installed depth up to 3 cm to make the phase differences and power balance small. But, from a withstanding voltage, it is difficult to couple multi-MW with the single coupler. The coupling with multi-loop antennas using two or four loops is better than one loop antenna from the point views of both withstanding voltage and power balance. The phase difference and power balance were also measured in both cases. A good average phase-difference of 179. and a good RF power balance within 8% error for each cavity were obtained. These results showed one of feasibility for an RF-Input coupler with a multi-loop antenna in the IFMIF 175 MHz RFQ.
Hanada, Masaya; Seki, Takayoshi*; Takado, Naoyuki*; Inoue, Takashi; Morishita, Takatoshi; Mizuno, Takatoshi*; Hatayama, Akiyoshi*; Imai, Tsuyoshi*; Kashiwagi, Mieko; Sakamoto, Keishi; et al.
Fusion Engineering and Design, 74(1-4), p.311 - 317, 2005/11
Times Cited Count:7 Percentile:44.05(Nuclear Science & Technology)no abstracts in English