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

Abrupt Reversal of Convective Flow of Carbon Impurity during Impurity-Hole Formation on 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

Dr Mikirou Yoshinuma (National Institute for Fusion Science)

Description

An extremely hollow carbon impurity profile (impurity-hole) has been observed associated with increase of ion temperature gradient in the discharges with ion-ITB on LHD. Simultaneous achievement of the impurity-hole and ion-ITB is favorable feature in nuclear fusion plasma, where both good energy confinement and ash exhaust are required. The impurity-hole is characterized as small diffusion and large outward convection of impurities [1]. The outward convection observed in experiment contradicts to the prediction of neoclassical impurity transport and the convection velocity becomes larger as the magnetic axis shifted outward and the ion charge of Z is increased [2]. In this paper, the dynamic behaviors of the convection velocity of carbon impurity during the formation of impurity-hole are described. (1) The dynamic impurity transport analysis shows that the abrupt (time scale of 30 ms) reversal of turbulent-driven convection flow of carbon impurity from inward to outward takes place at the formation. (2) The reversal starts at the position where the ion temperature gradient becomes steep and propagates toward the core and edge in the time scale of 100 ms while the ion temperature increases in the time scale of 300 ms. [1] M.Yoshinuma, et al., Nucl.Fusion 49(2009)062002. [2] K.Ida, et al., Phys.Plasmas 16(2009)056111.
Country or International Organisation Japan
Paper Number EX/P6-30

Primary author

Dr Mikirou Yoshinuma (National Institute for Fusion Science)

Co-authors

Dr Haruhisa Nakano (National Institute for Fusion Science) Dr Hiromi Takahashi (National Institute for Fusion Science) Dr Katsumi Ida (National Institute for Fusion Science) Dr Kenichi Nagaoka (National Institute for Fusion Science) Dr Kenji Tanaka (National Institute for Fusion Science) Dr Masaki Osakabe (National Institute for Fusion Science)

Presentation materials