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Superdense core mode in the Large Helical Device with an internal diffusion barrier
Author(s) -
T. Morisaki,
N. Ohyabu,
S. Masuzaki,
M. Kobayashi,
R. Sakamoto,
J. Miyazawa,
H. Funaba,
K. Ida,
K. Ikeda,
O. Kaneko,
S. Morita,
S. Mutoh,
K. Nagaoka,
Y. Nagayama,
N. Nakajima,
K. Narihara,
Y. Oka,
M. Osakabe,
B. J. Peterson,
S. Sakakibara,
M. Shoji,
Y. Suzuki,
Y. Takeiri,
N. Tamura,
K. Tanaka,
K. Tsumori,
K. Y. Watanabe,
I. Yamada,
H. Yamada,
A. Komori,
O. Motojima
Publication year - 2007
Publication title -
physics of plasmas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.75
H-Index - 160
eISSN - 1089-7674
pISSN - 1070-664X
DOI - 10.1063/1.2718530
Subject(s) - divertor , physics , plasma , large helical device , core (optical fiber) , magnetohydrodynamics , atomic physics , diffusion , pellets , impurity , particle (ecology) , density gradient , pressure gradient , tokamak , mechanics , nuclear physics , materials science , optics , thermodynamics , oceanography , quantum mechanics , composite material , geology
In reduced recycling discharges using a local island divertor in the Large Helical Device [O. Motojima, H. Yamada, A. Komori et al., Phys. Plasmas 6, 1843 (1999)], a stable high-density plasma develops in the core region when a series of pellets is injected. A core region with ~5×10^20 m^?3 and temperature of 0.85 keV is maintained by an internal diffusion barrier (IDB). The density gradient at the IDB (r/a~0.6) is very high, and the particle confinement time in the core region is ~0.4 s. Because of the increase in the central pressure, a large Shafranov shift up to ~0.3 m is observed. The critical ingredients for IDB formation are a strongly pumped divertor to reduce edge recycling, and multiple pellet injection to ensure efficient central fueling. No serious magnetohydrodynamics activity and impurity accumulation have been observed so far in this improved discharge

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