从 L 模式到 L-H 过渡,ASDEX 升级实验及相关陀螺动力学模拟

N. Bonanomi, C. Angioni, G. D. Conway, T. Happel, U. Plank, P. Schneider, G. Staebler
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引用次数: 0

摘要

这项工作将 ASDEX 升级型托卡马克的实验观测结果与湍流从 L 模式向 L-H 过渡和超越 L-H 过渡的相关陀螺动力学模拟相结合。专门的实验是在电子回旋加速器加热功率缓慢增加的情况下进行的。这些等离子体边缘湍流的陀螺动力学模拟突出了非线性电磁效应和外部流剪切(E × B 剪切)的关键作用,两者都与等离子体压力剖面随加热功率增加而演变有关。等离子体 βe 的增加会破坏低环模数湍流的稳定性,而湍流又会受到外部流剪切的强烈抑制。这使得等离子体压力剖面在湍流通量没有急剧上升的情况下发生演变。当所有实验测量到的等离子体参数都作为局部陀螺动能模拟的输入时,实验中的电子和离子热通量在所选放电的整个 L 模式阶段都得到了定量再现。利用不含 ELM 的 H 模式相的边缘参数进行的模拟仍然显示了前面讨论的机制的重要性,同时也说明了局部方法可能存在的局限性。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
From L-mode to the L–H transition, experiments on ASDEX upgrade and related gyrokinetic simulations
This work combines experimental observations from the ASDEX Upgrade tokamak with related gyrokinetic simulations of the turbulence moving from L-mode toward, and beyond, the L–H transition. Dedicated experiments have been performed with slow steps of increasing electron cyclotron heating power. Gyrokinetic simulations of the edge turbulence of these plasmas highlight the key roles of the non-linear electromagnetic effects and the external flow shear (E × B shear), both related to the evolution of the plasma pressure profile with increasing heating power. The increase in the plasma βe destabilizes turbulence at low toroidal mode numbers, that, in turn, is strongly suppressed by the external flow shear. This allows the plasma pressure profiles to evolve without a sharp rise in the turbulent fluxes. When all the experimentally measured plasma parameters are consistently included as inputs of the local gyrokinetic simulations, both the experimental electron and ion heat fluxes are quantitatively reproduced on the whole L-mode phase of the selected discharge. Simulations carried out with edge parameters of an ELM-free H-mode phase still show the importance of the mechanisms discussed earlier while also indicating possible limitations of the local approach.
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