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608 results on '"Ohyabu, N."'

1. Theoretical studies of equilibrium beta limit in heliotron plasmas

Author

Suzuki, Y., Watanabe, K. Y., Sakakibara, S., Nakajima, N., and Ohyabu, N.

Subjects
Physics - Plasma Physics
Abstract

In this study, the MHD equilibrium limit of LHD plasmas is studied using a 3D MHD equilibrium calculation code, HINT, which is an initial value solver based on the relaxation method without the assumption of nested flux surfaces. For finite beta equilibria, flux surfaces become stochastic in the peripheral region. However, though the axis shifts until the conventional limit, the separatrix to limit the equilibrium does not appear. For high beta equilibria, the force balance starts breaking in the stochastic region. To keep the force balance, the pressure gradient in the stochastic region decreases and the fixed profile is reduced. As the result, the volume averaged beta saturates. The beta value, where the force balance starts breaking inside the stochastic region, is proposed as an index of equilibrium beta limit in heliotron plasmas., Comment: 11 pages, 7 figures

Published
2020
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2. Spatial Distribution Measurement of High Energy Particle using Time-Of-Flight Neutral Particle Energy Analyzer in Large Helical Device

Author

G1/G2 Group, Ozaki, T., Goncharov, P., Murakami, S., Sudo, S., Shoji, M., Emoto, M., Funaba, H., Goto, M., Ida, K., Idei, H., Ikeda, K., Kanko, O., Kawahata, K., Kobuchi, T., Kubo, S., Kumazawa, R., Morita, S., Motojima, O., Muto, S., Mutoh, T., Nagayama, Y., Nakamura, Y., Nakanishi, H., Narihara, K., Noda, N., Ohdachi, S., Ohyabu, N., Oka, Y., Osakabe, M., Peterson, B., Saito, K., Sakakibara, S., Sasao, M., Sato, K., Seki, T., Shimozuma, T., Takeiri, Y., Tanaka, K., Torii, H., Tsumori, K., Watanabe, T., Watari, T., Zanza, V., Bracco, G., Sibio, A., Tilia, B., Stott, Peter E., editor, Wootton, Alan, editor, Gorini, Giuseppe, editor, Sindoni, Elio, editor, and Batani, Dimitri, editor

Published
2002
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6. 10 years of engineering and physics achievements by the Large Helical Device project

Author

Yamada, H., Imagawa, S., Takeiri, Y., Kaneko, O., Mutoh, T., Mito, T., Chikaraishi, H., Hamaguchi, S., Ida, K., Igami, H., Ikeda, K., Kasahara, H., Kobayashi, M., Kubo, S., Kumazawa, R., Maekawa, R., Masuzaki, S., Miyazawa, J., Morisaki, T., Morita, S., Nagaoka, K., Nakamura, Y., Narushima, Y., Osakabe, M., Saito, K., Sakakibara, S., Sakamoto, R., Seki, T., Shimozuma, T., Shoji, M., Suzuki, Y., Takahata, K., Tamura, H., Tsumori, K., Watanabe, K.Y., Yamada, S., Yanagi, N., Yoshimura, Y., Kawahata, K., Ohyabu, N., Komori, A., and Motojima, O.

Published
2009
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19. Conceptual design activities and key issues on LHD-type reactor FFHR

Author

Sagara, A., Mitarai, O., Imagawa, S., Morisaki, T., Tanaka, T., Mizuguchi, N., Dolan, T., Miyazawa, J., Takahata, K., Chikaraishi, H., Yamada, S., Seo, K., Sakamoto, R., Masuzaki, S., Muroga, T., Yamada, H., Fukada, S., Hashizume, H., Yamazaki, K., Mito, T., Kaneko, O., Mutoh, T., Ohyabu, N., Noda, N., Komori, A., Sudo, S., and Motojima, O.

Published
2006
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23. Nb interaction with hydrogen plasma

Author

Nakamura, Y., Livshits, A., Busnyuk, A., Suzuki, H., Nakahara, Y., and Ohyabu, N.

Subjects
Plasma (Ionized gases) -- Atomic properties, Plasma (Ionized gases) -- Electric properties, Niobium -- Electric properties, Niobium -- Atomic properties, Physics
Abstract

Energy dependence of the effects of ion bombardment on PDP, hydrogen retention, and the kinetics of boundary process is investigated in plasma experiment with an Nb membrane. Bombardment by ions of energy higher than 50 eV resulted in sharp decrease of the plasma driven permeation/retention and in acceleration of boundary processes are nonmonotonic in ion energy.

Published
2001

25. Local island divertor experiments on LHD

Author

Morisaki, T., Masuzaki, S., Komori, A., Ohyabu, N., Kobayashi, M., Feng, Y., Sardei, F., Narihara, K., Tanaka, K., Ida, K., Peterson, B.J., Yoshinuma, M., Ashikawa, N., Emoto, M., Funaba, H., Goto, M., Ikeda, K., Inagaki, S., Kaneko, O., Kawahata, K., Kubo, S., Miyazawa, J., Morita, S., Nagaoka, K., Nagayama, Y., Nakanishi, H., Ohkubo, K., Oka, Y., Osakabe, M., Shimozuma, T., Shoji, M., Takeiri, Y., Sakakibara, S., Sakamoto, R., Sato, K., Toi, K., Tsumori, K., Watababe, K.Y., Yamada, H., Yamada, I., Yoshimura, Y., and Motojima, O.

Published
2005
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29. Large Helical Device (LHD) program

Author

Fujiwara, M., Yamazaki, K., Okamoto, M., Todoroki, J., Amano, T., Watanabe, T., Hayashi, T., Sanuki, H., Nakajima, N., Itoh, K., Sugama, H., Ichiguchi, K., Murakami, S., Motojima, O., Yamamoto, J., Satow, T., Yanagi, N., Imagawa, S., Takahata, K., Tamura, H., Nishimura, A., Komori, A., Inoue, N., Noda, N., Sagara, A., Kubota, Y., Akaishi, N., Satoh, S., Tanahashi, S., Chikaraishi, H., Mito, T., Yamada, S., Yamaguchi, S., Sudo, S., Sato, K. N., Watari, T., Kuroda, T., Kaneko, O., Ohkubo, K., Kitagawa, S., Ando, A., Idei, H., Tsumori, K., Kubo, S., Kumazawa, R., Mutoh, T., Oka, Y., Sato, M., Seki, T., Shimozuma, T., Takeiri, Y., Hamada, Y., Narihara, K., Kawahata, K., Fujisawa, S., Hidekuma, S., Minami, T., Yamada, I., Ejiri, A., Tanaka, K., Sasao, M., Iguchi, H., Watanabe, K. Y., Yamada, H., Ohyabu, N., Suzuki, H., and Iiyoshi, A.

Published
1996
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30. Confinement physics of H-mode discharges in DIII-D

Author

Burrell, KH, Allen, SL, Bramson, G, Brooks, NH, Callis, RW, Carlstrom, TN, Chu, MS, Colleraine, AP, Content, D, DeBoo, JC, Dominguez, RR, Ferron, JR, Freeman, RL, Gohil, P, Greenfield, CM, Groebner, RJ, Haas, G, Heidbrink, WW, Hill, DN, Hinton, FL, Hong, R-M, Howl, W, Hsieh, CL, Jackson, GL, Jahns, GL, James, RA, Kellman, AG, Kim, J, Lao, LL, Lazarus, EA, Lehecka, T, Lister, J, Lohr, J, Luce, TC, Luxon, JL, Mahdavi, MA, Matsumoto, H, Mayberry, M, Moeller, CP, Neyatani, Y, Ohkawa, T, Ohyabu, N, Okazaki, T, Osborne, TH, Overskei, DO, Ozeki, T, Peebles, A, Perkins, S, Perry, M, Petersen, PI, Petrie, TW, Philipona, R, Phillips, JC, Pinsker, R, Politzer, PA, Porter, GD, Prater, R, Rensink, ME, Schaffer, MJ, Schissel, DP, Scoville, JT, Seraydarian, RP, Shimada, M, Simonen, TC, Snider, RT, Staebler, GM, Stallard, BW, Stambaugh, RD, Stav, RD, St John, H, Stockdale, RE, Strait, EJ, Taylor, PL, Taylor, TS, Trost, PK, Stroth, U, Waltz, RE, Wolfe, SM, Wood, RD, and Wroblewski, D

Subjects
Atomic, Molecular, Nuclear, Particle and Plasma Physics, Other Physical Sciences, Fluids & Plasmas
Abstract

The authors' data indicate that the L-mode to H-mode transition in the DIII-D tokamak is associated with the sudden reduction in anomalous, fluctuation-connected transport across the outer midplane of the plasma. In addition to the reduction in edge density and magnetic fluctuations observed at the transition, the edge radial electric field becomes more negative after the transition. They have determined the scaling of the H-mode power threshold with various plasma parameters; the roughly linear increase with plasma density and toroidal field are particularly significant. Control of the ELM frequency and duration by adjusting neutral beam input power has allowed us to produce H-mode plasmas with constant impurity levels and durations up to 5 s. Energy confinement time in ohmic H-mode plasmas and in deuterium H-mode plasmas with deuterium beam injection can exceed saturated ohmic confinement times by at least a factor of two. Energy confinement times above 0.3 s have been achieved in these beam-heated plasmas with plasma currents in the range of 2.0 to 2.5 MA. Local transport studies have shown that electron and ion thermal diffusivities and angular momentum diffusivity are comparable in magnitude and all decrease with increasing plasma current.

Published
1989

31. Characteristics of low-q disruptions in PBX

Author

Kaye, SM, Jahns, GL, Morris, AW, Sesnic, S, Bol, K, Chance, MS, Couture, P, Fonck, RJ, Gammel, G, Heidbrink, WW, Kaita, R, Kugel, HW, LeBlanc, B, Manickam, J, Ohyabu, N, Okabayashi, M, Reusch, MF, and Takahashi, H

Subjects
Atomic, Molecular, Nuclear, Particle and Plasma Physics, Fluids & Plasmas
Abstract

At low qψ (2.3 ≤ qψ ≤ 4.5), in the Princeton Beta Experiment, the discharges are limited by a hard disruption following the growth and sawtooth-like 'crash' of a ≤25 kHz precursor oscillation. The disruption, which occurs even in discharges with ⟨t⟨ well below the first stability regime boundary (2.5 μ0IpaBt), follows the crash of this precursor mode either immediately or with a delay of several milliseconds, with the immediate disruptions primarily occurring in the discharges with ⟨t⟩ close to the first regime limit. The highest ⟨t⟩ discharges also exhibit the fastest growth times and the highest level of edge MHD activity. Associated with the precursor mode crash is a loss of up to 30% of the plasma energy; thus, for non-zero delay shots, it is the crash and not the actual disruption that is the ⟨t⟩ limiting process. The delay period is interpreted as a period during which a locked mode, consisting of several toroidal components of comparable amplitude, grows. Because of the energy loss associated with the crash, the plasma goes vertically unstable during the delay period. The results of this study indicate that even within the relatively narrow low-qψ operating space, there is a continuum in the characteristics of the low-q^ disruptions with a primary dependence on the value of ⟨t⟩. While the ideal external kink instability may give rise to the growing oscillations that lead up to the ultimate disruption, the instabilities are weighted towards the edge only at the lowest qψ (≤3) and highest ⟨t⟩. The results of this study indicate that effects outside the scope of ideal MHD theory may play a significant role in low-qψ disruptions. © 1988 IOP Publishing Ltd.

Published
1988

32. Cooling and excitation tests of an inner vertical coil for the Large Helical Device

Author

Satow, T., Mito, T., Takahata, K., Yamamoto, J., Satoh, S., Nishimura, A., Yamada, S., Yanagi, N., Chikaraishi, H., Iwamoto, A., Tanahashi, S., Imagawa, S., Tamura, H., Yamazaki, K., Yamaguchi, S., Watanabe, K., Yamada, H., Noda, N., Sagara, A., Akaishi, K., Kubota, Y., Inoue, N., Suzuki, H., Morisaki, T., Kitagawa, S., Ohyabu, N., Komori, A., Baba, T., Moriuchi, S., Ohba, K., Iima, M., Yonezu, H., Hayashi, H., Taniguchi, Y., Ogawa, H., Tamura, S., Ohtake, I., Motojima, O., Morimoto, S., Takeo, M., Sato, S., Ninomiya, A., Ioka, S., Nakamoto, K., Uede, T., and Hoshi, Y.

Subjects
Solenoids -- Testing, Superconducting magnets -- Testing, Fusion reactors -- Equipment and supplies, Business, Electronics, Electronics and electrical industries
Abstract

The Large Helical Device (LHD) under construction at NIFS is a nuclear fusion experimental device consisting of two superconducting helical coils and three pairs of poloidal coils. A pair of inner vertical (IV) coils with a combined stored energy of 161 MJ have been delivered to NIFS. They were the 4 m outside diameter coils wound from cable-in-conduit conductors composed of 486 strands with a copper matrix. We conducted supercritical helium cooling and excitation tests to confirm the cooling and superconducting characteristics of one of the IV coils before its assembly into the LHD cryostat in 1997. It has been assembled into the SHe test facility at the Toki site of NIFS, and was cooled down and energized to 2.2 kA in February and March 1995. The test facility will be repaired in part, and the coil will be tested to confirm the characteristics at the rated current of 20.8 kA within the year.

Published
1996

41. DESIGN STUDY ON DIVERTOR PLATES OF LARGE HELICAL DEVICE (LHD)

Author

Noda, N., primary, Kubota, Y., additional, Sagara, A., additional, Ohyabu, N., additional, Akaishi, K., additional, Ji, Hantao, additional, Motojima, O., additional, Hashiba, M., additional, Fujita, I., additional, Hino, T., additional, Yamashina, T., additional, Matsuda, T., additional, Sogabe, T., additional, Matsumoto, T., additional, Kuroda, K., additional, Yamazaki, S., additional, Ise, H., additional, Adachi, J., additional, and Suzuki, T., additional

Published
1993
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42. DESIGN STUDY ON VACUUM VESSEL FOR LARGE HELICAL DEVICE

Author

Ioki, K., primary, Yamada, M., additional, Suzuki, Y., additional, Fujita, J., additional, Shimizu, K., additional, Iimura, M., additional, Okada, K., additional, Tado, S., additional, Motojima, O., additional, Ohyabu, N., additional, Yamazaki, K., additional, and Noda, N., additional

Published
1991
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43. DESIGN STUDY OF THE SUPERCONDUCTING LARGE HELICAL DEVICE

Author

MORIMOTO, S., primary, MOTOJIMA, O., additional, YAMAMOTO, J., additional, OHYABU, N., additional, YAMAZAKI, K., additional, AKAISHI, K., additional, NODA, N., additional, TANAHASHI, S., additional, KITAGAWA, S., additional, MITO, T., additional, SATOW, T., additional, OGAWA, Y., additional, KANEKO, H., additional, NISHIMURA, K., additional, TAKAHATA, K., additional, YANAGI, N., additional, SAGARA, A., additional, KUBOTA, Y., additional, TSUZUKI, T., additional, OHTAKE, I., additional, YAMADA, S., additional, YONEZU, H., additional, ASAO, M., additional, FUJII, K., additional, FUJIWARA, M., additional, and IIYOSHI, A., additional

Published
1991
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46. Review of initial experimental results of the PSI studies in the large helical device

Author

Masuzaki, S, Akaishi, K, Funaba, H, Goto, M, Ida, K, Inagaki, S, Inoue, N, Kawahata, K, Komori, A, Kubota, Y, Morisaki, T, Morita, S, Nakamura, Y, Narihara, K, Nishimura, K, Noda, N, Ohyabu, N, Peterson, B.J, Sagara, A, Sakamoto, R, Sato, K, Shoji, M, Suzuki, H, Takeiri, Y, Tanaka, K, Tokuzawa, T, Watanabe, T, Tsuzuki, K, Hino, T, Matsumoto, Y, Kado, S, and Motojima, O

Published
2001
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48. The effect of divertor tile material on radiation profiles in LHD

Author

Peterson, B.J., Masuzaki, S., Sakamoto, R., Sato, K., Inagaki, S., Sagara, A., Ohdachi, S., Nakamura, Y., Noda, N., Xu, Y., Rice, J.E., Ashikawa, N., Yamamoto, S., Takechi, M., Toi, K., Morita, S., Goto, M., Narihara, K., Inoue, N., Takeiri, Y., Sato, M., Osakabe, M., Tanaka, K., Tokuzawa, T., Sakakibara, S., Shoji, M., Kawahata, K., Kaneko, O., Ohyabu, N., Yamada, H., Komori, A., Yamazaki, K., Sudo, S., and Motojima, O.

Published
2001
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