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Journal Articles

Evaluation of plasma current profile on a low-aspect-ratio tokamak reactor

Sengoku, Seio

Denki Gakkai Rombunshi, A, 129(9), p.585 - 588, 2009/09

To evaluate a bootstrap-current-profile quickly, a simple method has been developed with a novel approximation. This results in that all of the neoclassical diffusion coefficients for the gradient become the polynominals only in variables of inverse aspect-ratio, $$varepsilon$$, effective charge, Z$$_{eff}$$ and collisionality, $$nu$$$$^{*}$$, in the whole range of variables. The resultant current profile is well reproduced from ITER benchmark with transport code including the case with internal-transport-barrier. This method is applied to a commercial reactor, VECTOR, low-aspect-ratio tokamak reactor. The fraction of bootstrap-current, I$$_{BS}$$/I$$_{p}$$, are evaluated as: $$sim$$ 55%, $$sim$$ 60% and $$sim$$ 100% for the normal-shear, weakly-reversed-shear and strongly-reversed-shear (with current-hole) plasmas, respectively.

Journal Articles

Study of SOL/divertor plasmas in JFT-2M

Kawashima, Hisato; Sengoku, Seio; Uehara, Kazuya; Tamai, Hiroshi; Shoji, Teruaki*; Ogawa, Hiroaki; Shibata, Takatoshi; Yamamoto, Masahiro*; Miura, Yukitoshi; Kusama, Yoshinori; et al.

Fusion Science and Technology, 49(2), p.168 - 186, 2006/02

 Times Cited Count:2 Percentile:81.25(Nuclear Science & Technology)

Experimental efforts on JFT-2M have been devoted to understand SOL/Divertor plasmas and to investigate power and particle controllability. Open divertor configuration was used for the first decade of JFT-2M started in 1984. We found out the SOL/Divertor plasma properties such as in/out asymmetry, heat and particle diffusivities, and SOL current at ELMs. Handling of power and particle was demonstrated by active control methods such as local pumping, edge ergodization, divertor biasing, and edge heating. For improvement of power and particle control capability of divertor, it was modified to closed configuration in 1995, which demonstrated the baffling effects with narrower divertor throat. Dense and cold divertor state (n$$_{e}$$$$^{div}$$ = 4$$times$$10$$^{19}$$ m$$^{-3}$$ and T$$_{e}$$$$^{div}$$ = 4 eV), compatible with the improved confinement modes (e.g. H-mode), was realized by strong gas puffing. Being related with the core confinement at H-mode, the edge plasma fluctuations were identified by an electrostatic probe. These are reviewed in this paper.

Journal Articles

Steady-state operation of high-beta/low aspect ratio tokamak reactor with bootstrap current

Sengoku, Seio

Purazuma, Kaku Yugo Gakkai-Shi, 80(11), p.940 - 943, 2004/11

Recent spherical tokamak (ST) experiments exhibit many advantageous results including plasma start-up without center solenoid, higher fraction of non-inductive current, formation of internal thermal-barrier as seen on conventional tokamak. In order to reflect these efforts on the design of so called "non-inductive steady-state (SS) operation scenario" and "current ramp-up scenario" of low-aspect reactor, fractions of bootstrap current and neutral-beam-driven current on VECTOR-OPT reactor are estimated. The operation with this SS scenario is shown to be feasible if the normalized beta, $$beta$$n, is raised to grater than 5 typical in ST.

Journal Articles

Performance of ITER as a burning plasma experiment

Shimada, Michiya; Mukhovatov, V.*; Federici, G.*; Gribov, Y.*; Kukushkin, A.*; Murakami, Yoshiki*; Polevoi, A. R.*; Pustovitov, V. D.*; Sengoku, Seio; Sugihara, Masayoshi

Nuclear Fusion, 44(2), p.350 - 356, 2004/02

Recent performance analysis has improved confidence in achieving Q $$>$$ 10 in inductive operation in ITER. Performance analysis based on empirical scaling shows the feasibility of achieving Q $$>$$ 10 in inductive operation with a sufficient margin. Theory-based core modeling indicates the need of high pedestal temperature (2-4 keV) to achieve Q $$>$$ 10, which is in the range of projection with pedestal scaling. The heat load of type-I ELM could be made tolerable by high density operation and further tilting the target plate (if necessary). Pellet injection from High-Field Side would be useful in enhancing Q and reducing ELM heat load. Steady state operation scenarios have been developed with modest requirement on confinement improvement and beta (HH98(y,2) $$>$$ 1.3 and betaN $$>$$ 2.6). Stabilisation of RWM, required in such regimes, is feasible with the present saddle coils and power supplies with double-wall structure taken into account.

Journal Articles

Performance of ITER as a burning plasma experiment

Shimada, Michiya; Mukhovatov, V.*; Federici, G.*; Gribov, Y.*; Kukushkin, A. S.*; Murakami, Yoshiki*; Polevoi, A. R.*; Pustovitov, V. D.*; Sengoku, Seio; Sugihara, Masayoshi

Nuclear Fusion, 44(2), p.350 - 356, 2004/02

 Times Cited Count:39 Percentile:20.43(Physics, Fluids & Plasmas)

Performance analysis based on empirical scaling shows the feasibility of achieving Q $$geq$$ 10 in inductive operation. Analysis has also elucidated a possibility that ITER can potentially demonstrate Q $$sim$$ 50, enabling studies of self-heated plasmas. Theory-based core modeling indicates the need of high pedestal temperature (3.2 - 5.3 keV) to achieve Q $$geq$$10, which is in the range of projection with presently available pedestal scalings. Pellet injection from high-field side would be useful in enhancing Q and reducing ELM heat load in high plasma current operation. If the ELM heat load is not acceptable, it could be made tolerable by further tilting the target plate. Steady state operation scenarios at Q = 5 have been developed with modest requirement on confinement improvement and beta (HH98(y,2) $$geq$$ 1.3 and betaN $$geq$$ 2.6). Stabilisation of RWM, required in such regimes, is feasible with the present saddle coils and power supplies with double-wall structure taken into account.

Journal Articles

Evaluation of plasma current profile on a low-aspect-ratio tokamak reactor

Sengoku, Seio

Denki Gakkai Purazuma Kenkyukai Shiryo (PST-03-41), p.23 - 26, 2003/09

no abstracts in English

Journal Articles

Suppression of hydrogen absorption to V-4Cr-4Ti alloy by TiO$$_{2}$$/TiC coating

Hirohata, Yuko*; Motojima, Dai*; Hino, Tomoaki*; Sengoku, Seio

Journal of Nuclear Materials, 313-316(1-3), p.172 - 176, 2003/03

 Times Cited Count:11 Percentile:37.8(Materials Science, Multidisciplinary)

Titanium oxide film was coated on entire surface of a V-4Cr-4Ti alloy to reduce hydrogen absorption at low temperature region. The film consisted with a mixture of TiO2 and TiC. The content of TiO$$_{2}$$ was approximately 80%. The hydrogen absorption rate of Ti-oxide coated V-alloy largely decreased with increase of the film thickness. In the case of the film with a thickness of 0.5 micron, the absorption rate was fifty times smaller than that of non-coated V-alloy at the absorption temperature of 573 K.

Journal Articles

Characteristics of boundary plasmas after the removal of divertor baffle plates and boronization on JFT-2M

Kawashima, Hisato; Sengoku, Seio; Tsuzuki, Kazuhiro; Ogawa, Hiroaki; Kimura, Haruyuki

Journal of Nuclear Materials, 313-316, p.1338 - 1342, 2003/03

 Times Cited Count:3 Percentile:72.76(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Deuterium retention of V-4Cr-4Ti alloy exposed to the JFT-2M tokamak environment

Hirohata, Yuko*; Oda, Tomomasa*; Hino, Tomoaki*; Sengoku, Seio

Journal of Nuclear Materials, 290-293, p.196 - 200, 2001/03

 Times Cited Count:12 Percentile:32.76(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Low activated materials as plasma facing components

Hino, Tomoaki*; Hirohata, Yuko*; Yamauchi, Yuji*; Sengoku, Seio

Proceedings of IAEA 18th Fusion Energy Conference (CD-ROM), 5 Pages, 2001/00

no abstracts in English

Journal Articles

Performance of V-4Cr-4Ti alloy exposed to the JFT-2M tokamak environment

Johnson, W. R.*; Trester, P. W.*; Sengoku, Seio; Ishiyama, Shintaro; Fukaya, Kiyoshi; Eto, Motokuni; Oda, Tomomasa*; Hirohata, Yuko*; Hino, Tomoaki*; Tsai, H.*

Journal of Nuclear Materials, 283-287(Part1), p.622 - 627, 2000/12

 Times Cited Count:2 Percentile:79.55(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Deuterium pumping experiment with superpermeable Nb membrane in JFT-2M tokamak

Nakamura, Yukio*; Sengoku, Seio; Nakahara, Yukio*; Suzuki, Naoyuki*; Suzuki, Hajime*; Oyabu, Nobuyoshi*; Busnyuk, A.*; Notkin, M.*; Livshits, A.*

Journal of Nuclear Materials, 278(2-3), p.312 - 319, 2000/04

 Times Cited Count:9 Percentile:43.49(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Hydrogen retention of V-alloy under plasma irradiation of JFT-2M

Oda, Tomomasa*; Hirohata, Yuko*; Hino, Tomoaki*; Sengoku, Seio

Shinku, 43(3), p.325 - 328, 2000/03

no abstracts in English

Journal Articles

Compact toroid injection experiment in JFT-2M

Ogawa, Toshihide; Fukumoto, Naoyuki*; Nagata, Masayoshi*; Ogawa, Hiroaki; Maeno, Masaki; Hasegawa, Koichi; Shibata, Takatoshi; Uyama, Tadao*; Miyazawa, Junichi*; Kasai, Satoshi; et al.

Nuclear Fusion, 39(11Y), p.1911 - 1915, 1999/11

 Times Cited Count:29 Percentile:31.48(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Advanced material tokamak experiment (AMTEX) program with ferritic steel for JFT-2M

Sato, Masayasu; Miura, Yukitoshi; Kimura, Haruyuki; Kawashima, Hisato; Sengoku, Seio; Yamamoto, Masahiro; ; Shibata, Takatoshi; Akiyama, Takashi*; Abe, Mitsushi*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 75(6), p.741 - 749, 1999/06

no abstracts in English

Journal Articles

Reports of ITER physics R&D expert meeting

Hosogane, Nobuyuki; Asakura, Nobuyuki; Sugie, Tatsuo; Yoshino, Ryuji; Fukuda, Takeshi; Kusama, Yoshinori; Tobita, Kenji; Ide, Shunsuke; Shimada, Michiya; Sengoku, Seio; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 75(2), p.156 - 161, 1999/02

no abstracts in English

Journal Articles

Studies of boundary plasmas and fueling on the JFT-2M

Ogawa, Hiroaki; Miura, Yukitoshi; Fukumoto, Naoyuki*; Hasegawa, Koichi; Kawashima, Hisato; Maeno, Masaki; Nagata, Masayoshi*; Sengoku, Seio; Shibata, Takatoshi; Kasai, Satoshi; et al.

Journal of Nuclear Materials, 266-269, p.623 - 628, 1999/00

 Times Cited Count:12 Percentile:31.81(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Study of a closed divertor with strong gas puffing on JFT-2M

Kawashima, Hisato; Sengoku, Seio; Ogawa, Toshihide; Ogawa, Hiroaki; Uehara, Kazuya; Miura, Yukitoshi; Kimura, Haruyuki; JFT-2M Group

Nuclear Fusion, 39(11Y), p.1679 - 1686, 1999/00

 Times Cited Count:13 Percentile:55.38(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Report from ITER physics R&D expert meeting

Fukuda, Takeshi; Wakatani, Masahiro*; Toi, Kazuo*; Takizuka, Tomonori; Miura, Yukitoshi; Ogawa, Yuichi*; Takamura, Shuichi*; Oyabu, Nobuyoshi*; Hosogane, Nobuyuki; Sengoku, Seio; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 74(8), p.885 - 887, 1998/08

no abstracts in English

Journal Articles

Evaluation of magnetic field due to ferromagnetic vacuum vessel in tokamak

*; Abe, Mitsushi*; Tadokoro, Takahiro*; Miura, Yukitoshi; Suzuki, Norio; Sato, Masayasu; Sengoku, Seio

Purazuma, Kaku Yugo Gakkai-Shi, 74(3), p.274 - 283, 1998/03

no abstracts in English

103 (Records 1-20 displayed on this page)