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10-15 May 2021
Nice, France
Europe/Vienna timezone
The Conference will be held virtually from 10-15 May 2021

Investigation of intrinsic torque for L-mode and H-mode plasmas using balanced beam injection on EAST

11 May 2021, 14:00
4h 45m
Nice, France

Nice, France

Regular Poster Magnetic Fusion Experiments P2 Posters 2

Speaker

Bo Lyu (Institute of Plasma Physics, Chinese Academy of Sciences)

Description

Stable operation of future fusion reactors might largely rely on the attainable rotation levels for suppressing instabilities and turbulence transport 1. For reliable prediction of possible intrinsic torque, characteristics of intrinsic torque in current tokamak plasmas can provide valuable reference 2. Direct measurements of the intrinsic torque profile in L-mode and H-mode plasmas on the EAST tokamak have been performed using the available balanced neutral beam injection (NBI) 3. Co- and Counter-current neutral beams are modulated to balance the intrinsic and externally injected torque, which result in the rotation close to zero profile. The experimental results show that the intrinsic torque derived from momentum balance equations is found to be in the co-current direction, peaked in the plasma edge and negligibly small in the core. The results were compared with those obtained on the DIII-D tokamak and it was found to follow the same scaling law against the edge pressure gradient derived on the DIII-D tokamak 2. Newly measured intrinsic torque results for extended plasma parameters are reported.
Layout of EAST’s NBI systems for balanced injection
Figure 1 shows the neutral beam injection system of EAST, which consists two nearly identical neutral beam injectors designed to tangentially injecting high-energy beams up to 80keV/4MW. Both co- and ctr- NBI systes have two positive ion sources, which can be combined to inject various beam power and torques for obtain nearly zero rotation profile to measure intrinsic torque. The residual unbalanced external torque balances in intrinsic torque, which can be determined from momentum balance equation [4].
Figure 2 plots an experiment showing that slowly modulated co- and ctr- NBI power are added to the plasma so as to vary the plasma rotation in such a fashion that both the core rotation and rotation profiles reverse and keep a flat profile. Electron temperature and density profiles are shown to remain unchanged during the beam modulation. Also noted that, the normalized plasma pressure is also unchanged to minimize the effect of confinement change on the plasma rotation, since the confinement is closely related to plasma rotation as suggested by Rice scaling.
Modulated NBI  and variation of plasma rotation
Figure 3 (a) shows the obtained rotation profile during the beam modulation, in which the rotation profiles were modulated to transiently reverses the direction and relatively flat to suggest the momentum flux contribution can be ignored to use Eq. (1) for calculating the intrinsic torque. As shown in Figure 3(b), using the NBI deposited torque computed by NUBEAM, intrinsic torque is determined. The results show that the intrinsic torque is co-current and peaked towards the plasma edge, which is consistent with the theory that the edge pressure gradient is a major driving force. The shape of intrinsic torque profile measured on EAST is very similar to the intrinsic torque profile on DIII-D 1 . The intrinsic torque profiles of these two devices are both in the co-current direction, peaked towards the edge and relatively small in the core, and of an order of magnitude different. The edge torque is strongly correlated with the edge pressure gradient as seen on both devices, which can assist the prediction of rotation level on future deviced like ITER or CFETR [5].
Rotation profiles and intrinsic torque profiles
References: 1. Y. Liu et al Nucl. Fusion 44 (2004) 232; 2. W.M. Solomon et al, Nucl Fusion 51 (2011) 073010; 3. C.D. Hu et al, Plasma Sci. Technol. 17 (2015) 817; [4]. W.M. Solomon et al, Phys. Plasma 17 (2010) 056108; [5]. C. Chrystal et al., Phys. Plasma 24 (2017) 056113.

Affiliation Institute of Plasma Physics, Chinese Academy of Sciences
Country or International Organization China

Primary authors

Bo Lyu (Institute of Plasma Physics, Chinese Academy of Sciences) Mr Xunyu Wang (School of Nuclear Science and Technology, University of South China) Dr Yingying Li (ASIPP) Wayne M. Solomon (General Atomics) Dr Baolong Hao (Institute of Plasma Physics, Chinese Academy of Sciences) Mr Jun Chen (Department of Engineering and Applied Physics, University of Science and Technology of China) Dr Fudi Wang (Institute of Plasma Physics, Chinese Academy of Sciences) Dr Jia Fu (Institute of Plasma Physics, Chinese Academy of Sciences) Dr Xianghui Yin (School of Electric Engineering, University of South China) Dr Xingqiang Lu (School of Nuclear Science and Technology, University of South China) Sang Gon Lee (National Fusion Research Institute) Minyou Ye (School of Nuclear Science and Technology, University of Science and Technology of China) Baonian Wan (Institute of Plasma Physics, Chinese Academy of Sciences)

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