Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.
Nuclear Fusion, 51(8), p.083049_1 - 083049_8, 2011/08
Times Cited Count：51 Percentile：88.28(Physics, Fluids & Plasmas)Hydrogen negative ion beams of 490 keV, 3 A and 510 keV, 1 A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 2 m
for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60SA and ITER.
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
Hydrogen negative ion beams of 490keV, 3A and 510 keV, 1A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 
2 m for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60 SA and ITER.
Ikeda, Yoshitaka; Hanada, Masaya; Kamada, Masaki; Kobayashi, Kaoru; Umeda, Naotaka; Akino, Noboru; Ebisawa, Noboru; Inoue, Takashi; Honda, Atsushi; Kawai, Mikito; et al.
IEEE Transactions on Plasma Science, 36(4), p.1519 - 1529, 2008/08
Times Cited Count：12 Percentile：43.9(Physics, Fluids & Plasmas)The JT-60SA N-NBI system is required to inject 10 MW for 100 s at 500 keV. Three key issues should be solved for the JT-60SA N-NBI ion source. One is to improve the voltage holding capability. Recent R&D tests suggested that the accelerator with a large area of grids may need a high margin in the design of electric field and a long time for conditioning. The second issue is to reduce the grid power loading. It was found that some beamlets were strongly deflected due to beamlet-beamlet interaction and strike on the grounded grid. The grids are to be designed by taking account of beamlet-beamlet interaction in three-dimensional simulation. Third is to maintain the D- production for 100 s. A simple cooling structure is proposed for the active cooled plasma grid, where a key is the temperature gradient on the plasma grid for uniform D- production. The modified N-NBI ion source will start on JT-60SA in 2015.
Ikeda, Shugo; Matsuda, Tatsuma; Haga, Yoshinori; Yamamoto, Etsuji; Nakashima, Miho*; Kirita, Shingo*; Kobayashi, Tatsuo*; Hedo, Masato*; Uwatoko, Yoshiya*; Yamagami, Hiroshi*; et al.
Journal of the Physical Society of Japan, 74(8), p.2277 - 2281, 2005/08
Times Cited Count：10 Percentile：53.4(Physics, Multidisciplinary)We have succeeded in growing a high-quality single crystal of an antiferromagnet UPdGa by the Ga-flux method with the off-stoichiometric composition of U : Pd : Ga = 1 : 2 : 7.3. The electronic state has been investigated by the de Haas-van Alphen experiment, indicating the similar cylindrical Fermi surfaces as in an antiferromagnet UPtGa. We have also studied the pressure effect by measuring the electrical resistivity. The N
el temperature decreases with increasing pressure and becomes zero at 3.1 GPa. The antiferromagnetic state is changed into the paramagnetic state above 3.1 GPa.
Nojiri, Naoki; Shimakawa, Satoshi; Takamatsu, Kuniyoshi; Ishii, Yoshiki; Kawano, Shuichi; Kobayashi, Shoichi; Kawamoto, Taiki; Iyoku, Tatsuo
JAERI-Tech 2003-086, 136 Pages, 2003/11
JAERI-Tech-2003-086.pdf:8.67MB
To provide a basis for determination of the actual core power distribution, The power distribution experiments by measuring gross gamma ray emitted from fission products in the fuel assemblies were performed. The fuel assemblies were not spent condition but in-service condition. The averaged burn up was about 4,400 MWD/t. The gamma ray of a fuel assembly was measured with a GM counter under a temporary fuel withdrawing situation from the core during shutdown state. Uncertainties of the determination were from 3 to 6 percent in axial distribution per one fuel compact and within about 4 percent in radial and axial distribution of the core per one fuel assembly. It was concluded that the power distribution of the HTTR is almost equivalent to the expected power-profile shaping. Calculation of gamma ray distribution was performed by ORIGEN-2 code based the power distribution obtained by the Monte Carlo MVP code. The calculation results show good agreement with the experimental ones. The method, procedure, analysis, correction, determination and comparison are described in this report.
Saito, Shinzo; Tanaka, Toshiyuki; Sudo, Yukio; Baba, Osamu; Shindo, Masami; Shiozawa, Shusaku; Mogi, Haruyoshi; Okubo, Minoru; Ito, Noboru; Shindo, Ryuichi; et al.
JAERI 1332, 247 Pages, 1994/09
no abstracts in English
Tm Gamma-Ray Source; ; ; *; *
Hihakai Kensa, 20(3), p.121 - 126, 1970/00
no abstracts in English
Kojima, Atsushi; Tanaka, Yutaka*; Nakano, Shusuke*; Shimizu, Tatsuo; Akino, Noboru; Hanada, Masaya; Yamano, Yasushi*; Kobayashi, Shinichi*
no journal, ,
JT-60 negative ion source suffered from a low voltage holding capability for long time. Recently, the voltage holding was much improved by tuning the gap lengths and minimum lengths between the acceleration grids of the ion source. This improvement is attributed to voltage holding tests of the accelerator. However, in order to design the next ion sources such as ITER and JT-60SA, further understandings and databases of vacuum insulation are required. As for the effect of the electric field, a small electrodes with small aperture which has the locally strong electric field were tested in this time. We found that the maimum electric field did not affect on the breakdown voltage, and large area of the electric filed profile decreased the breakdown voltage.
Kojima, Atsushi; Shimizu, Tatsuo; Akino, Noboru; Hanada, Masaya; Yamano, Yasushi*; Kobayashi, Shinichi*; JT-60NBI Group
no journal, ,
Production of 500 keV, 3 A beams has been successfully achieved in the JT-60 negative by overcoming the low voltage holding of the accelerator. Toward the design of next ion source, we need to have database for the voltage holding capability based on experimental results. Up to now, voltage holding tests were carried out in terms of local electric field and surface area on large acceleration grids. This time, because outgas from FRP insulators has a possibility to affect the voltage holding of the acceleration grids, insulators made of low outgas epoxy was tested. As a result, because low outgas epoxy has small deviation of breakdown voltages, stable sustainment with 1.6 times higher voltage was attained than general epoxy insulators.
