Development of divertor simulation research in the GAMMA 10/PDX tandem mirror

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

Development of multi-purpose MW gyrotrons for fusion devices

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

https://doi.org/10.1088/0029-5515/53/6/063003

Observation of ion cyclotron emission owing to DD fusion product H ions in JT-60U

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

https://doi.org/10.1585/pfr.5.S2067

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)".

Plasma generation at atmospheric pressure using a high-power microwave beam and its application to rocket propulsion

Oda, Yasuhisa*; Komurasaki, Kimiya*; Takahashi, Koji; Kasugai, Atsushi; Imai, Tsuyoshi*; Sakamoto, Keishi

Electrical Engineering in Japan, 161(2), p.1 - 7, 2007/11

https://doi.org/10.1002/eej.20573

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.

Upgrade program of ECRH system for GAMMA10

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

https://doi.org/10.13182/FST07-A1352

no abstracts in English

Characteristics of 28 GHz gyrotron for ECRH on GAMMA10

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

https://doi.org/10.13182/FST07-A1419

no abstracts in English

Suppression of fast electron leakage from large openings in a plasma neutralizer for N-NB systems

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

https://doi.org/10.1016/j.fusengdes.2006.07.067

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.

Overview of the national centralized tokamak programme

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

https://doi.org/10.1088/0029-5515/46/3/S05

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.

Design study of national centralized tokamak facility for the demonstration of steady state high- plasma operation

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

https://doi.org/10.1088/0029-5515/45/12/023

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.

Development of reliable diamond window for EC launcher on fusion reactors

Takahashi, Koji; Illy, S.*; Heidinger, R.*; Kasugai, Atsushi; Minami, Ryutaro; Sakamoto, Keishi; Thumm, M.*; Imai, Tsuyoshi

Fusion Engineering and Design, 74(1-4), p.305 - 310, 2005/11

https://doi.org/10.1016/j.fusengdes.2005.06.234

A new diamond window with the copper-coated edge for an EC launcher is developed. The diamond window is designed to cool its disk edge. Since Cu is coated at the entire edge, ingress of cooling water into a transmission line in case of failure on the edge is negligible. In addition, corrosion of Al blaze between the edge and the Inconel cuffs can be avoided. A 170GHz, RF transmission experiment equivalent to a MW-level transmission was carried out to investigate the capability of the edge cooling. The transmission power and pulse are 55kW and 3sec, respectively. Temperature increase was 45C and alomost became constant. Thermal calculation with tan of 4.410 and thermal conductivity of 1.9kW/m/K agrees with the experiment. Since tan of the diamond is much higher than the actual one (tan=210), the temperature increase corresponds to that of 1MW transmission. It concludes that the Cu coating dose not degrade the edge cooling capability and improves the reliability of the diamond window.