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10-15 May 2021
Virtual Event
Europe/Vienna timezone
The Conference will be held virtually from 10-15 May 2021

High-$\beta_N$ Experiments and Corresponding MHD Activities in the HL-2A Tokamak

12 May 2021, 08:30
4h
Virtual Event

Virtual Event

Regular Poster Magnetic Fusion Experiments P3 Posters 3

Speaker

Wei Chen (Southwestern Institute of Physics)

Description

Achieving high-$\beta_N$ for current and future tokamaks is a challenging and important issue, where \beta_N is the normalized toroidal beta. High-$\beta_N$ is beneficial for the ignition and fusion reaction, as well as the ratio of bootstrap current is proportional to $\beta_N$. Recently, on HL-2A a high-performance region, combining edge and internal transport barriers (double transport barriers, dubbed as DTBs), had been obtained by high-power NBI and LHW heating, and shown in the Fig.1. Usually, the internal transport barrier (ITB) forms just after the NBI injection, and the ITB foot locates near q=1 surface where the magnetic shear is weak and the flow shear is significant to suppress effectively turbulence fluctuations. Subsequently, the center/edge ion temperature and toroidal rotation both decrease/increase, meanwhile, the plasma density increases, as a result that the pedestal creates and L-H transition occurs. The ELM-free H-mode sustains around 40 ms with DTBs. Accompany with the density ascending, the type-I ELM emerges and \beta_N reaches maximum at the moment. In this scenario, $\beta_N$ >3.0 is realized, and corresponding $H_{98}$~1.3, $f_{bs}$~30% and G~0.4. Meanwhile, the high-$\beta_N$ scenario has also been successfully modeled using integrated simulation codes, i.e. OMFIT and METIS. A steady-state high-$\beta_N$ (t~0.8s and $\beta_N$ >2.0) scenario is also obtained by the pure NBI.Typical high-$\beta_N$ experimental results with DTBs on HL-2A (left), and ion temperature profiles with DTBs (right).
In such high-$\beta_N$ plasmas, there are abundant MHD instabilities, including low-frequency MHD oscillation and high-frequency coherent mode in the edge, and neoclassical tearing mode (NTM) and Alfvén modes in the core (shown in the Fig.2), as well as complex MHD dynamics, e.g. nonlinear wave-wave and wave-particle interactions. Some new physics problems need yet to be resolved, namely how sustain and control MHD and transport barrier to achieve higher and steady-state high-$\beta_N$.MHD activities in high-$\beta_N$ plasmas. Low-frequency (10 kHz<f<50 kHz) NTMs and high-frequency (60 kHz<f<150 kHz) Alfvén modes.

References
[1] C. M. Greenfield, et al, Phys. Rev. Lett. 86 (2001) 4544.
[2] K. H. Burrell, et al, Phys. Rev. Lett. 102 (2009) 155003.
[3] E. R. Solano, et al, Phys. Rev. Lett. 104 (2010) 185003.
[4] W. Suttrop, et al, Plasma Phys. Control. Fusion 45 (2003) A151.

Country or International Organization China
Affiliation Southwestern Institute of Physics

Primary authors

Wei Chen (Southwestern Institute of Physics) Liming Yu (Southwestern Institute of Physics) Prof. Min Xu (Southwestern Institute of Physics) Xiaoquan JI (Southwestern Institute of Physics) Zhongbing Shi (Southwestern Institute of Physics) Jiquan Li (Southwestern Instotute of Physics) Xuantong Ding (Southwestern Institute of Physics) Dr Xiaoxue He (Southwestern Institute of Physics) Mr Yonggao Li (Southwestern Institute of Physics) Min Jiang (Southwestern Institute of Physics) Mr Shaopo Gong (Southwestern Institute of Physics) Dr Jie Wen (Southwestern Institute of Physics) Mr Zhengji Li (Southwestern Institute of Physics) Mr Yongfu Shi (Southwestern Institute of Physics) Dr Zengchen Yang (Southwestern Institute of Physics) Wulyu Zhong (Southwestern Instotute of Physics) Aiping Sun (Southwestern Institute of physics) Dr Jianyong Cao (Southwestern Institute of Physics) Dr Qingwei Yang (Southwestern Institute of Physics) yi liu (Southwestern Instotute of Physics) Longwen Yan (Southwestern Instotute of Physics) Xuru Duan (Southwestern Institute of Physics)

Presentation Materials