(EX/P1-14) Steady-State Operation of ICRF Heated Plasma in the Large Helical Device
T. Mutoh1),
R. Kumazawa1),
T. Seki1),
K. Saito1),
H. Kasahara1),
Y. Nakamura1),
S. Masuzaki1),
S. Kubo1),
Y. Takeiri1),
T. Shimozuma1),
Y. Yoshimura1),
H. Igami1),
T. Watanabe1),
H. Ogawa2),
J. Miyazawa1),
M. Shoji1),
N. Ashikawa1),
K. Nishimura1),
M. Osakabe1),
K. Tsumori1),
K. Ikeda1),
K. Nagaoka1),
Y. Oka1),
H. Chikaraishi1),
H. Funaba1),
S. Morita1),
M. Goto1),
S. Inagaki1),
K. Narihara1),
T. Tokuzawa1),
R. Sakamoto1),
T. Morisaki1),
B. J. Peterson1),
K. Tanaka1),
H. Nakanishi1),
M. Nishiura1),
T. Ozaki1),
F. Shimpo1),
G. Nomura1),
C. Takahashi1),
M. Yokota1),
Y. P. Zhao3),
J. G. Kwak4),
S. Murakami5),
H. Okada5),
H. Yamada1),
K. Kawahata1),
N. Ohyabu1),
O. Kaneko1),
K. Ida1),
Y. Nagayama1),
K. Y. Watanabe1),
N. Noda1),
A. Komori1),
S. Sudo1),
O. Motojima1)
1) National Institute for Fusion Science, Toki, Japan
2) Graduate University for Advanced Studies, Hayama, 240-0163 Japan
3) Institute of Plasma Physics, Academia Sinica, Hefei, 230031, P.R.China
4) Korea Atomic Energy Institute, Daejeon,305-600, Korea
5) Kyoto University, Kyoto 606-8501, Japan
Abstract. Achieving steady-state plasma operation at high plasma
temperatures is one of the important goals of worldwide magnetic fusion
research. High temperatures of approximately 1-2 keV, and steady-state
plasma-sustainment operations have been reported. After the last IAEA
conference, the steady state operation regime was greatly extended in the
Large Helical Device (LHD). A high-temperature plasma was created and
maintained for more than 30 min with a world record injected heating energy of
1.3 GJ in 2004FY, and recently for 54 min with 1.6 GJ in the 2005FY
experimental program. The three-dimensional heat-deposition profile of the LHD
helical divertor was modified, and during long-pulse discharges it effectively
dispersed the heat load using a magnetic-axis swing technique developed at the
LHD. A sweep of only 3 cm in the major radius of the magnetic axis position
(less than 1% of the major radius of the LHD) was enough to disperse the
divertor heat load. The steady-state plasma was heated and sustained mainly by
hydrogen minority ion heating using ion cyclotron range of frequencies
(ICRF). By accumulating the small flux of charge-exchanged neutral particles
during the long pulse operation, a high energy ion tail which extended up to
1.6 MeV was observed. The long pulse operations lasted until a sudden increase
of radiation loss occurred, presumably because of metal wall flakes dropping
into the plasma. The sustained line-averaged electron density and temperature
were approximately
0.8×1019m-3 and 2 keV, respectively, at a 1.3GJ
discharge (#53776) and
0.4×1019m-3 and 1 keV at a 1.6GJ discharge
(#66053). The average input power was 680 kW and 490 kW, and the plasma
duration was 32 min and 54 min, respectively. These successful long operations
show that the heliotron configuration has a high potential as a steady-state
fusion reactor.
Full paper available (PDF)
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