23P132-B
Transition of Heat and Momentum Transports
熱と運動量の輸送遷移現象
K. Nagaoka, K. Ida, M. Yoshinuma, Y. Takeiri, M. Yokoyama, S. Morita, K. Tanaka, T. Ido, A.
Shimizu, N. Tamura, H. Funaba, S. Murakami1, M. Goto, H. Takahashi, C. Suzuki, Y. Suzuki, K.
Ikeda, M. Osakabe, K. Tsumori, H. Nakano, O. Kaneko, H. Yamada and LHD Experiment Group
永岡賢一，居田克巳，吉沼幹朗，竹入康彦，横山雅之，森田繁，田中謙治，井戸毅，清水昭博，田村直樹，舟場芳久，村上定義1，後藤基志，高橋裕巳，鈴木千尋，池田勝則，長壁正樹，津守克嘉，中野治久，金子修，山田弘司，ＬＨＤ実験グループ
National Institute for Fusion Science, 322-6 Oroshi-Cho Toki-City, 509-5292, Japan
核融合科学研究所 〒509-5292 土岐市下石町322-6
1
Department of Nuclear Engineering, Kyoto University, Kyoto, 606-8501, Japan
京都大学大学院工学研究科原子核工学専攻、〒606-8501京都市左京区吉田本町
Different toroidal rotation profiles were observed between co- and ctr-rotating plasmas with ion ITB inLHD. Transport analysis reveals the existence of spontaneous rotation which become large with increase ofion temperature gradient (growth of ion ITB). The differences of heat transport characteristics such as
threshold heating power and saturation of temperature gradient, are observed, which seems to be
attributable to rotation shear effect.

1. Introduction
Recently
Non-local
phenomena
andoff-diagonal term effects in transport matrix
attract much attention in transport study ofmagnetically confined fusion plasmas. Because
they often dominate the transport properties andare useful to control magnetohydrodynamics(MHD) stabilities. In particular, spontaneousrotation has been strongly studied in tokamak
plasmas, and the empirical scaling law of
spontaneous rotation was obtained for H-mode
plasma [1]. However, the physical mechanism ofspontaneous rotation and the effects on heattransport property are still open questions.
In this paper, heat and momentum transportobserved in ion internal transport barrier (ionITB) formation in the Large Helical Device(LHD) plasmas are presented. The spontaneous
toroidal rotation and effects of rotation shear on
the heat transport are discussed.
2. Ion ITB Plasmas in LHD
An ion ITB forms in LHD plasma heated byneutral beam injection (NBI) and has extended
high-ion-temperature regime of helical plasma
beyond 7 keV. The electrostatic potential
measurement using a heavy ion beam probe (HIBP)
showed a negative radial electric field (Er) in thecore region and no significant electric field sear wasobserved [2]. Numerical simulation studies suggest
a zonal flow excitation in the core of ion ITB as aphysical mechanism of ion ITB formation in helicalplasmas [3]. The impurity transport in the ion ITB

core in LHD is quite different from tokamak ITB
plasmas and a significant outward convection ofimpurities forms a hollowed profile of impurities(Impurity Hole formation). The heavier impurities
form the steeper hollowed profiles. The
simultaneous realization of good heat confinement
and poor impurity confinement is preferable forsteady state operation of fusion burning plasmas[4-5].

Fig. 1 Ion temperature and toroidal rotation
profiles in the case of co-rotating (Pnb_Co=7.4MW,Pnb_Ctr=2.6MW, Pnb_perp=3.3MW and ne_bar=1.5 x1019 m-3) and ctr-rotation plasmas (Pnb_Co=3.5MW,Pnb_Ctr=9.0MW, Pnb_perp=3.6MW and ne_bar=1.6 x1019 m).

3. Dependence on the direction of rotation
Figure 1 shows the profiles of ion temperatureand toroidal rotation with ion ITB in the case of coand ctr-rotating plasmas. The direction of toroidal
rotation in the ion ITB core is consistent withexternal torque (tangential NBI). But the rotation
profiles are significantly different between co- andctr-rotations. The rotation shear of co-rotatingplasma is larger than that of ctr-one. The ion
temperature is slightly different between them, andthe temperature gradient in co-rotating plasma islarger, implying that the even weak rotation shear
may affects the heat transport.
In order to investigate the transportcharacteristics, the heat and momentum deposition
profiles of tangential and perpendicular NBIs areevaluated by FIT code, and the heat and momentum
flux at the normalized minor radius of (reff/a99)~0.3
was estimated. Figure 2 shows the flux v.s gradientrelation of momentum transport in the transition
phase from L-mode to ion ITB. The shear of
co-rotating plasma increases in the ion ITB phase,
while it of ctr-rotating one is suppressed. This
indicates that the spontaneous rotation with thegrowth of ion temperature gradient (formation ofion ITB) is driven in the co-direction.

Fig. 2 Momentum transport flux as a function ofgradient of momentum at the normalized minor
radius of 0.3. The momentum flux and thegradient of momentum in the ctr-rotating plasma
are negative values. For the comparison, theabsolute values of them are plotted in this figure.

Figure 3 shows the normalized heat flux as afunction of temperature gradient. The temperature
gradient increases with heating power with similarslope between co- and ctr-rotating plasmas.
However the threshold power for ion ITB transition
seems to be different and higher heating power isrequired in the ctr-rotating plasma. The larger
temperature gradient is obtained in the co-rotatingplasmas with lower heating power.

Fig. 3 Flux-gradient relation of ion heat transport
at normalized minor radius of 0.3

4. Discussions and Conclusions
Non-linear flux-gradient relations are clearlyfound in momentum and heat transport of ion ITB
plasmas. The comparison between co- andctr-rotating plasmas reveals the existence of
spontaneous rotation driven in the co-direction withincrease of ion temperature gradient (growth of ionITB) and better heat confinement characteristics(larger ion temperature gradient and lower thresholdpower) in the co-rotating plasmas. It is interestingfrom viewpoint of comparison with transport
suppression by rotation shear discussed as atokamak ITB mechanism [6]. In order to understandthe mechanism of ion ITB in helical plasmas,
further investigations and detailed analyses arenecessary in both experimental and theoreticalfields.
Acknowledgments
We thank Profs. K. Itoh and S.-I Itoh for fruitfulcomments and LHD team for their excellent
operations. This research was supported by NIFS
(NIFS10ULRR702).
References[1] J. Rice, et al.,: Nucl. Fusion 47 (2007) 1618.
[2] K. Nagaoka, et al.,: Nucl. Fusion 51 (2011) 083022.
[3] M. Nunami, et al: Plasma Fusion Res. 6 (2011)
1403001.
[4] M. Yoshinuma, el al.,: Nucl. Fusion 49 (2009)
062002.
[5] K. Ida, el al.,: Phys. Plasmas 16 (2009) 056111.
[6] H. Jhang,: 1st Asia Pacific Transport Working Group,
PLI-3, Toki, Japan, 2011.