 |
 |
 |
M. Fujiwara, H. Yamada, A. Ejiri, M. Emoto,
H. Funaba, M. Goto, K. Ida, H. Idei,
S. Inagaki, S. Kado, O. Kaneko, K. Kawahata,
A. Komori, S. Kubo, R. Kumazawa, S. Masuzaki,
T. Minami, J. Miyazawa, T. Morisaki, S. Morita,
S. Murakami, S. Muto, T. Mutoh, Y. Nagayama,
Y. Nakamura, H. Nakanishi, K. Narihara,
K. Nishimura, N. Noda, T. Kobuchi, S. Ohdachi,
N. Ohyabu, Y. Oka, M. Osakabe, T. Ozaki,
B. J. Peterson, A. Sagara, S. Sakakibara,
R. Sakamoto, H. Sasao, M. Sasao, K. Sato,
M. Sato, T. Seki, T. Shimozuma, M. Shoji,
H. Suzuki, Y. Takeiri, K. Tanaka, K. Toi,
T. Tokuzawa, K. Tsumori, K. Tsuzuki, I. Yamada,
S. Yamaguchi, M. Yokoyama, K. Y. Watanabe,
T. Watari, R. Akiyama, H. Chikaraishi, K. Haba,
S. Hamaguchi, M. Iima, S. Imagawa, N. Inoue,
K. Iwamoto, S. Kitagawa, Y. Kubota, J. Kodaira,
R. Maekawa, T. Mito, T. Nagasaka, A. Nishimura,
Y. Takita, C. Takahashi, K. Takahata, K. Yamauchi,
H. Tamura, T. Tsuzuki, S. Yamada, N. Yanagi,
H. Yonezu, Y. Hamada, K. Matsuoka, K. Murai,
K. Ohkubo, I. Ohtake, M. Okamoto, S. Satoh,
T. Satow, S. Sudo, S. Tanahashi, K. Yamazaki,
O. Motojima, A. Iiyoshi
National Institute for Fusion Science, Toki, Gifu, Japan
Abstract. The initial experiments of the Large Helical Device (LHD) have
extended confinement studies on currentless plasmas to a large scale (R =
3.9 m, a = 0.6 m). Heating by NBI of 3 MW has produced plasmas with a
fusion triple product of
8×1018keVm- 3s at a magnetic
field of 1.5T. An electron temperature of 1.5 keV and an ion temperature of
1.1 keV have been achieved simultaneously at the line-averaged electron
density of
1.5×1019m- 3. The maximum stored energy has
reached 0.22 MJ with neither unexpected confinement deterioration nor
visible MHD instabilities, which corresponds to
= 0.7%. Energy confinement times, reaching 0.17 s at the maximum, have shown
a similar manner to the present scaling law derived from the existing medium
sized helical devices, but improve on it by 50%. A distinguishing feature
of a favorable dependence of energy confinement time on density remains in
the present power density (
40kW/m3) and the electron density
(
3×1019m- 3) regimes unlike L-mode in tokamaks. High edge
temperatures of both electrons and ions as high as 200 eV have been observed
at the outermost flux surface, which indicate a qualitative jump in
performance from the helical devices to date. Spontaneously generated
toroidal currents agree with the physical picture of neoclassical bootstrap
currents. Change of magnetic configuration due to finite- effect has
been well described by the 3-D MHD equilibrium analysis. An escape of
particles from the core region leading to a hollow density profile has been
observed in hydrogen plasmas, which is mitigated through core fueling with a
pellet injection or in helium discharges.
IAEA 2001
