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Oct 13 – 18, 2014
Hotel Park Inn Pribaltiyskaya
Europe/Moscow timezone

Plasma Structure Change and Intermittent Fluctuation near Magnetic Island X-Point under Detached Plasma Condition in LHD

Oct 16, 2014, 2:00 PM
4h 45m
Green 8-9 (Hotel Park Inn Pribaltiyskaya)

Green 8-9

Hotel Park Inn Pribaltiyskaya

Saint Petersburg, Russian Federation
Poster Poster 6

Speaker

Prof. Noriyasu Ohno (Nagoya University)

Description

Recent study in the Large Helical Device (LHD) indicated that applying resonant magnetic perturbation (RMP) field is able to keep highly-radiating zone near the magnetic island X-point inside the ergodic region and particle flux onto the divertor plate is reduced accompanied by stable plasma detachment [1]. However, it is not clear yet where the particle flux starts to decrease in the RMP assisted plasma detachment experimentally. In addition, recent studies in several magnetic confinement devices implied that intermittent cross-field transport would be enhanced in the detached divertor [2-4]. We have investigated plasma structure change and plasma fluctuation property near helical divertor X-point and on divertor plate by using a fast scanning Langmuir probe and a probe array embedded on a divertor plate in the RMP assisted detached plasmas in LHD. When the RMP induced magnetic island X-point (n/m = 1/1) is located near the helical divertor X-point, the reduction of particle flux accompanied by the plasma detachment occurred near the helical divertor X-point (n/m = 2/10), which leads to the reduction of the particle flux at the strike point on the divertor plate. We also found that when the divetor plasma turned to be the detached condition, the enhanced plasma fluctuations were confirmed between the helical divertor X-point and ergodic region, which exhibited a dynamic behavior having a large amount of positive-spike components with highly intermittent property. [1] M. Kobayashi et al., Nucl. Fusion 53 (2013) 093032. [2] B.L. Stansfield et al., J. Nucl. Mater. 241-243 (1997) 739. [3] N. Ohno et al., J. Plasma Fusion Res. 80 (2004) 275. [4] H. Tanaka et al., Phys. Plasmas 17 (2010) 102509.
Country or International Organisation Japan
Paper Number EX/P6-26

Primary author

Prof. Noriyasu Ohno (Nagoya University)

Co-authors

Dr Gen Motojima (National Institute for Fusion Science) Dr Hirohiko Tanaka (National Institute for Fusion Science) Dr Masahiro Kobayashi (National Institute for Fusion Science) Prof. Suguru Masuzaki (National Institute for Fusion Science) Prof. Tomohiro Morisaki (National Institute for Fusion Science) Dr Tsuyoshi Akiyama (National Institute for Fusion Science) Dr Yoshiro NARUSHIMA (National Institute for Fusion Science) Prof. Yoshiyuki Tsuji (Nagoya University)

Presentation materials