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arXiv 2203.15909physics.plasm-ph
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草状ELMs的特性及其对偏滤器热通量宽度的影响

Characteristics of grassy ELMs and its impact on the divertor heat flux width

Nami Li, X. Q. Xu, N. Yan, Y. F. Wang, J. Y. Zhang, J. P. Qian, J. Z. Sun, D. Z. Wang

摘要:

用BOUT++湍流数值模拟方法研究了60 s稳态长脉冲高β p EAST草状ELM放电. BOUT++线性模拟表明,不稳定模谱覆盖了从低n(n=10~15)剥离-气球模(P-B)到高n(n=40~80)漂移-阿尔文不稳定性的环形模数范围。非线性模拟结果表明,ELM碰撞过程中,尽管漂移-阿尔文不稳定性在线性增长阶段占主导地位,但低n剥离模态仍会引起ELM碰撞,在压力梯度峰值位置产生脉动,并径向向外扩散到刮削层(SOL).然而,漂移-阿尔文湍流延迟了草状ELM的开始,并随着波动延伸到基座顶部区域而增加了能量损失。仿真结果进一步表明,如果剥离驱动器被删除,波动幅度下降了一个数量级,ELM崩溃消失。偏滤器热通量宽度比基于HD模型和ITPA多托卡马克标度(或经验Eich标度)的估计值大约2倍,这是由于强径向湍流输运。

英文摘要:

BOUT++ turbulence simulations are conducted for a 60s steady-state long pulse high \{beta}p EAST grassy ELM discharge. BOUT++ linear simulations show that the unstable mode spectrum covers a range of toroidal mode numbers from low-n (n=10~15) peeling-ballooning modes (P-B) to high-n (n=40~80) drift-Alfvén instabilities. Nonlinear simulations show that the ELM crash is trigged by low-n peeling modes and fluctuation is generated at the peak pressure gradient position and radially spread outward into the Scrape-Off-Layer (SOL), even though the drift-Alfvén instabilities dominate the linear growth phase. However, drift-Alfvén turbulence delays the onset of the grassy ELM and enhances the energy loss with the fluctuation extending to pedestal top region. Simulations further show that if the peeling drive is removed, the fluctuation amplitude drops by an order of magnitude and the ELM crashes disappear. The divertor heat flux width is ~2 times larger than the estimates based on the HD model and the ITPA multi-tokamak scaling (or empirical Eich scaling) due to the strong radial turbulence transport.

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