发表机构
Princeton Plasma Physics Laboratory, Princeton University; Gridfire Inc（普林斯顿等离子体物理实验室，普林斯顿大学; Gridfire公司）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过局域回旋动理学分析，考察了MAST-U中L模和H模等离子体对电子温度梯度和ExB剪切的ETG模输运敏感性，发现ETG湍流在L模外芯区可主导电子热输运，但在H模中作用有限。
AI 中文摘要
对兆安球形托卡马克升级装置（MAST-U）的综合模拟表明，在一系列运行区间内，湍流电子热输运可主导离子输运。能够产生这种行为的失稳模式有限，主要候选者为微撕裂模（MTMs）和电子温度梯度（ETG）驱动模。本工作利用局域回旋动理学分析，研究了MAST-U上两个L模等离子体和一个H模等离子体中的电子尺度芯部输运。考察了ETG模的线性和非线性敏感性，特别关注其对电子温度梯度和ExB剪切率的依赖。在L模放电中，ETG模在较宽的径向区域上呈线性不稳定，并可驱动达到实验相关水平的电子热输运，尤其是在外芯区域。输运对电子温度梯度和ExB剪切均高度敏感，非线性模拟显示输运具有刚性，并在不确定度范围内与实验估计吻合良好。然而，在靠近芯部区域，ETG驱动的输运减弱，不足以完全解释观测到的反常热通量。相比之下，在H模等离子体中，ETG模在芯部稳定或仅弱不稳定，导致电子尺度输运可忽略。这归因于更高的平衡压力梯度和降低的电子温度梯度，两者均对ETG湍流起稳定作用。在芯部旋转剖面坍塌后，ETG模可在靠近外芯区域变得不稳定，但通常仍不足以解释全部输运水平。总体而言，ETG湍流在设定L模等离子体（尤其是较大半径处）的电子热输运方面可发挥重要作用，但在高性能H模条件下不太可能占主导地位。
英文摘要
Integrated modelling of the Mega Ampere Spherical Tokamak Upgrade (MAST-U) indicates that turbulent electron heat transport can dominate over ion transport across a range of operating regimes. Only a limited set of instabilities are able to produce this behaviour, with the primary candidates being microtearing modes (MTMs) and electron temperature gradient (ETG) driven modes. This work investigates electron-scale core transport in two L-mode plasmas and one H-mode plasma on MAST-U using local gyrokinetic analysis. The linear and nonlinear sensitivities of ETG modes are examined, with particular focus on their dependence on electron temperature gradients and ExB shearing rates. In L-mode discharges, ETG modes are found to be linearly unstable over a broad radial region and can drive experimentally relevant levels of electron heat transport, particularly towards the outer core. The transport is strongly sensitive to both the electron temperature gradient and the ExB shear, with nonlinear simulations showing stiff transport and good agreement with experimental estimates within uncertainty. Towards the core, however, ETG-driven transport is reduced and is insufficient to fully explain the observed anomalous heat flux. In contrast, in the H-mode plasma ETG modes are found to be stable or only weakly unstable in the core, resulting in negligible electron-scale transport. This is attributed to higher equilibrium pressure gradients and reduced electron temperature gradients, both of which stabilise ETG turbulence. Following the collapse of the core rotation profile, ETG modes can become unstable towards the outer core, but typically remain insufficient to account for the full level of transport. Overall, ETG turbulence can play a significant role in setting electron heat transport in L-mode plasmas, particularly at larger radii, but is unlikely to dominate in high-performance H-mode conditions.
