1 - Nuclear Sciences and Applications - IAEA

6. CONCLUSIONS
IAEA-CN-50/A-II-3 119
Studies of the locked mode, the periodic m = 1 burst mode, the high frequency
magnetic oscillations and the frequent ELMs are being carried out in JT-60. The
results are summarized as follows:
(1) Locked modes are a serious problem for high-Ip and low-q operation of the
present large tokamaks and the next step tokamaks. It is found that the locked
mode during the current ramp-up phase is stabilized by high power NB heating
and the stable Ip = 2.6-3.2 MA and q^ = 2.2-2.7 discharge has been
attained. The characteristics of this mode during the current ramp-up phase in
JT-60 suggest that the mode is kink-like.
(2) A periodic m = 1 burst mode similar to a fishbone has been observed. The
mode frequency increases with the toroidal rotation frequency. This result is
consistent with the theoretical prediction that the observed mode frequency is
enhanced by the toroidal rotation frequency over the toroidal precession
frequency, when toroidal rotation exists.
(3) In divertor discharges, magnetic oscillations with narrow bandwidth at high
frequency are excited by NB injection, and it is shown that the resistive
interchange mode is one candidate for exciting the oscillations.
(4) Frequent ELMs have been observed in lower X-point discharges, and it is found
that the frequent ELMs occur in the regime of /Sp/qeff > 0.25.
ACKNOWLEDGEMENTS
The authors wish to thank the members of JAERI who have contributed to the
JT-60 project throughout its progress. They also wish to express their gratitude to
Drs S. Mori, K. Tomabechi and M. Yoshikawa for continued encouragement and
support.
REFERENCES
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[2] NINOMIYA, H., et al., Nucl. Fusion 28 (1988) 1275.
[3] ISHIDA, S., et al., Nucl. Fusion 28 (1988) 2225.
[4] JT-60 TEAM, Bull. Am. Phys. Soc. 32 (1987) 1362.
[5] TSUJI, S., et al., Paper IAEA-CN-50/A-V-1, these Proceedings, Vol. 1.
[6] STAMBAUGH, R., et al., in Controlled Fusion and Plasma Heating (Proc. 15th Eur. Conf.
Dubrovnik, 1988), Vol. 12B, European Physical Society (1988).
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