Understanding core tungsten (W) transport and control in an improved high-performance fully non-inductive discharge on EAST. (1st June 2022)

• Record Type: Journal Article
• Authors: Shi, Shengyu; Chen, Jiale; Bourdelle, Clarisse; Jian, Xiang; Odstrčil, Tomáš; Garofalo, Andrea M.; Cheng, Yunxin; Chao, Yan; Zhang, Ling; Duan, Yanmin; Wu, Muquan; Ding, Fang; Li, Yingying; Huang, Juan; Qian, Jinping; Gao, Xiang; Wan, Yuanxi
• Is Part Of: Nuclear fusion. Volume 62:Number 6(2022)
• Publication Date: 2022-06-01
• Subjects: EAST -- fully non-inductive discharge -- heavy/high-Z impurity W transport -- neoclassical and turbulent transport -- W control; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/ac3e3c
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: The behavior of heavy/high- Z impurity tungsten (W) in an improved high-performance fully non-inductive discharge on EAST with ITER-like divertor (ILD) is analyzed. It is found that W could be well controlled. The causes of no W accumulation are clarified by analyzing the background plasma parameters and modeling the W transport. It turns out that the electron temperature ( T e ) and its gradient are usually high while the toroidal rotation and density peaking of the bulk plasma are small. In this condition, the modeled W turbulent diffusion coefficient is big enough to offset the total turbulent and neoclassical pinch, so that W density profile for zero particle flux will not be very peaked. Combining NEO and TGLF for the W transport coefficient and the impurity transport code STRAHL, not only the core W density profile is predicted but also the radiated information mainly produced by W in the experiment can be closely reconstructed. At last, the physics of controlling W accumulation by electron cyclotron resonance heating (ECRH) is illustrated considering the effects of changed T e by ECRH on ionization balance and transport of W. It shows that the change of ionization and recombination balance by changed T e is not enough to explain the experimental observation of W behavior, which should be attributed to the changed W transport. By comparing the W transport coefficients in two kinds of plasmas with different T e profiles, it is shown that high T e and its gradient play a key role to generate large turbulent diffusion through increasing the growth rate of linear instability so that W accumulation is prevented.