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Tsuzuki, Kazuhiro; Kamiya, Kensaku; Shinohara, Koji; Bakhtiari, M.*; Ogawa, Hiroaki; Kurita, Genichi; Takechi, Manabu; Kasai, Satoshi; Sato, Masayasu; Kawashima, Hisato; et al.
Nuclear Fusion, 46(11), p.966 - 971, 2006/11
Times Cited Count:16 Percentile:47.35(Physics, Fluids & Plasmas)no abstracts in English
Kamiya, Kensaku; Oyama, Naoyuki; Ido, Takeshi*; Bakhtiari, M.*; JFT-2M Group
Physics of Plasmas, 13(3), p.032507_1 - 032507_9, 2006/03
Times Cited Count:15 Percentile:45.10(Physics, Fluids & Plasmas)Accompanying the HRS H-mode transition, the coherent magnetic fluctuations in the frequency range of the order of 10-100 kHz with significant variation are seen on the magnetic probes at the vessel wall. Above all, two types of edge MHD activities, which have associated toroidal mode number of n=1 and n7, respectively, seem to be more important for the HRS H-mode plasmas. To investigate their interaction, bi-spectral analysis is applied for the magnetic probe data. It is found to be a powerful tool, exhibiting the phase-coupled oscillations between two types of edge MHD activities having n=1 and n
7.
Kikuchi, Mitsuru; Nishio, Satoshi; Kurita, Genichi; Tsuzuki, Kazuhiro; Bakhtiari, M.*; Kawashima, Hisato; Takenaga, Hidenobu; Kusama, Yoshinori; Tobita, Kenji
Fusion Engineering and Design, 81(8-14), p.1589 - 1598, 2006/02
Times Cited Count:4 Percentile:30.06(Nuclear Science & Technology)Blanket-plasma interaction is important for plasma performance enhancement and reliability of first-wall/ blanket. Typical examples are harminization of wall stabilization and reduction of EM force during current quench, error field effect by ferritic steel, neutral-wall interaction under wall saturation, etc. JAERI reactor studies, JT-60U and JFT-2M results on this topics will be described.
Tsuzuki, Kazuhiro*; Kimura, Haruyuki; Kusama, Yoshinori; Sato, Masayasu; Kawashima, Hisato; Kamiya, Kensaku; Shinohara, Koji; Ogawa, Hiroaki; Uehara, Kazuya; Kurita, Genichi; et al.
Fusion Science and Technology, 49(2), p.197 - 208, 2006/02
Times Cited Count:11 Percentile:59.42(Nuclear Science & Technology)no abstracts in English
Kamiya, Kensaku; Kawashima, Hisato; Ido, Takeshi*; Oyama, Naoyuki; Bakhtiari, M.*; Kasai, Satoshi; Kusama, Yoshinori; Miura, Yukitoshi; Ogawa, Hiroaki; Tsuzuki, Kazuhiro; et al.
Nuclear Fusion, 46(2), p.272 - 276, 2006/02
Times Cited Count:3 Percentile:10.47(Physics, Fluids & Plasmas)An attractive operational regime without any large ELMs, namely High Recycling Steady (HRS) H-mode, was found on JFT-2M during Y2000 campaign after boronization. Recent experiments have concentrated on the studies of the access conditions for the HRS regime, in terms of the pedestal parameters. The HRS regime was more likely at higher edge density and lower edge temperature, which corresponds to the normalized electron collisionality of 1 in the plasma edge region.
Kawano, Yasunori; Nakano, Tomohide; Isayama, Akihiko; Asakura, Nobuyuki; Tamai, Hiroshi; Kubo, Hirotaka; Takenaga, Hidenobu; Bakhtiari, M.; Ide, Shunsuke; Kondoh, Takashi; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 81(8), p.593 - 601, 2005/08
An experiment to investigate mitigation effects of impurity pellet injection on disruption generated runaway electrons was carried out in the JT-60U tokamak device. Deposition of impurity neon pellets into a post-disruption runaway plasma was observed with increment of bulk electron density. At the impurity pellet injection, decay time of runaway current became shorter as factor of 2. There was an approximately linear relationship between changes in decay rate of runaway current and a photo-neutron signal which indicated loss of runaway electrons from the plasma. Consequently, enhanced loss of runaway electrons from a tokamak plasma, hence mitigation effect on them, by injection of impurity neon pellets was found.
Bakhtiari, M.; Kramer, G. J.*; Takechi, Manabu; Tamai, Hiroshi; Miura, Yukitoshi; Kusama, Yoshinori; Kamada, Yutaka
Physical Review Letters, 94(21), p.215003_1 - 215003_4, 2005/06
Times Cited Count:49 Percentile:83.70(Physics, Multidisciplinary)Bremsstrahlung radiation of runaway electrons is found to be an energy limit for runaway electrons in tokamaks. The minimum and maximum energy of runaway electron beams is shown to be limited by collisions and Bremsstrahlung radiation, respectively. It is also found that a massive injection of a high-Z gas such as Xenon can terminate a disruption-generated runaway current before the runaway electrons hit the walls.
Bakhtiari, M.; Tamai, Hiroshi; Kawano, Yasunori; Kramer, G. J.*; Isayama, Akihiko; Nakano, Tomohide; Kamiya, Kensaku; Yoshino, Ryuji; Miura, Yukitoshi; Kusama, Yoshinori; et al.
Nuclear Fusion, 45(5), p.318 - 325, 2005/05
Times Cited Count:46 Percentile:79.12(Physics, Fluids & Plasmas)In the previous works we had shown that injecting a mixture of large amounts of hydrogen and small amounts of argon can terminate a tokamak discharge quickly with avoiding runaway electron generation. In this work we have done the same experiments but with different gases in addition to argon. In fact we compared the effect of the puffing of argon, krypton, and xenon gases with and without simultaneous hydrogen gas puffing on disruption mitigation. We observed that injecting all impurities in the form of an admixture in hydrogen lead to faster plasma shutdowns with less runaway electron generation. We also found that injecting krypton gas (with or without hydrogen) seems to be a good candidate for plasma shutdown purposes since it induces low heat flux to divertor plates and avoids runaway electron generation more effectively.
Kawashima, Hisato; Uehara, Kazuya; Nishino, Nobuhiro*; Kamiya, Kensaku; Tsuzuki, Kazuhiro; Bakhtiari, M.; Nagashima, Yoshihiko*; Ogawa, Hiroaki; Hoshino, Katsumichi; Suzuki, Sadaaki; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 80(11), p.907 - 908, 2004/11
A comparison of divertor heat load between ELMy and "High Recycling Steady" (HRS) H-mode was carried out by fast measurements of the two dimensional emission, and the divertor electron temperature and ion saturation current on JFT-2M. They brought an attractive feature of HRS H-mode that the heat load was reduced to the level on time average that for ELMy H-mode, being able to avoid the severe heat load during pulsed ELM event. It was also indicated that the HRS H-mode was dominated by an enhancement of particle transport, whereas both heat and particle transport increased abruptly at ELM event.
Tsuzuki, Kazuhiro; Shinohara, Koji; Kamiya, Kensaku; Kawashima, Hisato; Sato, Masayasu; Kurita, Genichi; Bakhtiari, M.; Ogawa, Hiroaki; Hoshino, Katsumichi; Kasai, Satoshi; et al.
Journal of Nuclear Materials, 329-333(1), p.721 - 725, 2004/08
Times Cited Count:7 Percentile:44.45(Materials Science, Multidisciplinary)no abstracts in English
Kamiya, Kensaku; Bakhtiari, M.; Kasai, Satoshi; Kawashima, Hisato; Kusama, Yoshinori; Miura, Yukitoshi; Ogawa, Hiroaki; Oyama, Naoyuki; Sato, Masayasu; Shinohara, Koji; et al.
Plasma Physics and Controlled Fusion, 46(5A), p.A157 - A163, 2004/05
Times Cited Count:23 Percentile:58.54(Physics, Fluids & Plasmas)A new operating regime, High Recycling Steady (HRS) H-mode regime, has been discovered on JFT-2M, which is easily reproduced under the wall fueling from the boronized first wall. Accompanying the HRS H-mode transition, the coherent magnetic and floating potential fluctuations are seen on magnetic probes at vessel wall and Langmuir probe in SOL, respectively. These coherent fluctuations have a frequency of the order of 10-100 kHz with significant variation, which is recognized to be important to enhance the particle transport. The HRS can be seen even at 3 with
/
0.4 for the fixed delta
0.4 in the standard single-null divertor configuration. Recent experimental results from JFT-2M show that the plasma shape also seems to play an important role in determining the type of ELMs. The HRS regime can be extended up to delta
0.75 and
2.6 in the double-null configuration, while lower delta boundary exists at delta
0.3 with moderate
4 even at high recycling and/or density condition of
/
0.4.
Hoshino, Katsumichi; Nagashima, Yoshihiko*; Ido, Takeshi*; Tsuzuki, Kazuhiro; Kawashima, Hisato; Ogawa, Hiroaki; Bakhtiari, M.; Shinohara, Koji; Uehara, Kazuya; Oasa, Kazumi; et al.
Journal of Plasma and Fusion Research SERIES, Vol.6, p.345 - 348, 2004/00
no abstracts in English
Tsuzuki, Kazuhiro; Kimura, Haruyuki; Kawashima, Hisato; Sato, Masayasu; Kamiya, Kensaku; Shinohara, Koji; Ogawa, Hiroaki; Hoshino, Katsumichi; Bakhtiari, M.; Kasai, Satoshi; et al.
Nuclear Fusion, 43(10), p.1288 - 1293, 2003/10
Times Cited Count:39 Percentile:73.33(Physics, Fluids & Plasmas)no abstracts in English
Bakhtiari, M.; Azumi, Masafumi; Tsuzuki, Kazuhiro; Kamiya, Kensaku; Kawashima, Hisato; Kusama, Yoshinori; Sato, Masayasu; Hoshino, Katsumichi; JFT-2M Group
Physics of Plasmas, 10(8), p.3212 - 3216, 2003/08
Times Cited Count:15 Percentile:43.50(Physics, Fluids & Plasmas)The Tearing mode equation is solved in presence of a ferromagnetic resistive wall to study the effect of the ferromagnetism on the Tearing mode stability. It is shown that a ferromagnetic wall has a weak effect on the surface Tearing modes depending on the curent profile.
Bakhtiari, M.; Kawano, Yasunori; Tamai, Hiroshi; Miura, Yushi; Yoshino, Ryuji; Nishida, Yasushi*
Nuclear Fusion, 42(10), p.1197 - 1204, 2002/10
Times Cited Count:51 Percentile:81.09(Physics, Fluids & Plasmas)no abstracts in English
Bakhtiari, M.; Yoshino, Ryuji; Nishida, Yasushi*
Fusion Science and Technology, 41(2), p.77 - 87, 2002/03
Times Cited Count:6 Percentile:38.99(Nuclear Science & Technology)no abstracts in English
Tamai, Hiroshi; Yoshino, Ryuji; Tokuda, Shinji; Kurita, Genichi; Neyatani, Yuzuru; Bakhtiari, M.; Khayratdinov, R. R.*; Lukash, V.*; Rosenbluth, M. N.*; JT-60 Team
Nuclear Fusion, 42(3), p.290 - 294, 2002/03
Times Cited Count:36 Percentile:70.92(Physics, Fluids & Plasmas)no abstracts in English