AI 中文总结
研究DIII-D托卡马克中从ITG到TEM主导湍流转变时的湍流核心动量传输，应用特定框架经傅里叶分析分离相关贡献，通过多种计算证实转变，发现残余应力在低扭矩等离子体核心旋转预测中起重要作用，应纳入预测模型。
AI 中文摘要
准确预测环形等离子体旋转对于优化未来聚变装置的约束和稳定性至关重要。本研究调查了DIII-D托卡马克中从离子温度梯度（ITG）主导湍流到捕获电子模（TEM）主导湍流转变过程中的湍流核心动量传输。将先前为ASDEX升级开发的动量传输框架应用于调制中性束注入实验，通过对旋转响应的傅里叶分析分离扩散、对流和残余应力贡献。数据集涵盖低旋转条件、主导电子加热以及背景ExB剪切率低于湍流增长率的情况，更接近反应堆相关条件。回旋动理论CGYRO和回旋流体TGLF计算证实扫描涵盖了ITG到TEM的转变。分析得出普朗特数接近1。箍缩数对转变无明确依赖性，而是大致与对数密度梯度相关。归一化残余应力在转变过程中呈现非单调的V形依赖性：在深ITG和深TEM区域为共流，在中间混合模式区域接近零或为逆流。这种趋势在与电子动能分布梯度的关系上近似为线性依赖性，表明由分布剪切效应产生残余应力。较弱的背景ExB剪切进一步使残余应力向逆流值偏移。对代表性ITG和TEM放电进行的线性CGYRO模拟得出的普朗特数和箍缩数与实验结果吻合良好，支持了在TEM主导区域的回旋动理论动量传输预测。这些结果表明残余应力在低扭矩等离子体的核心旋转预测中起重要作用，应纳入未来反应堆情景的预测模型中。
英文摘要
Accurate prediction of toroidal plasma rotation is essential for optimizing confinement and stability in future fusion devices. This work investigates turbulent core momentum transport in the DIII-D tokamak across a transition from ion-temperature-gradient (ITG)- to trapped-electron-mode (TEM)-dominated turbulence. A momentum transport framework previously developed for ASDEX Upgrade is applied to modulated neutral beam injection experiments, separating diffusive, convective, and residual-stress contributions via Fourier analysis of the rotation response. The dataset spans low-rotation conditions, dominant electron heating, and background ExB shearing rates below turbulence growth rates, accessing more reactor-relevant conditions. Gyrokinetic CGYRO and gyrofluid TGLF calculations confirm the scan covers an ITG-to-TEM transition. The analysis yields Prandtl numbers near unity. The pinch number shows no explicit dependence on the transition, instead ordering roughly with the logarithmic density gradient. The normalized residual stress, in contrast, exhibits a non-monotonic, V-shaped dependence across the transition: co-current in deep ITG and deep TEM regimes, near-zero or counter-current in the intermediate mixed-mode regime. This trend collapses onto an approximately linear dependence against electron kinetic profile gradients, suggesting residual stress generation by profile-shearing effects. Weaker background ExB shearing further shifts residual stress toward counter-current values. Linear CGYRO simulations for representative ITG and TEM discharges yield Prandtl and pinch numbers in good agreement with experiment, supporting gyrokinetic momentum-transport predictions in TEM-dominated regimes. These results indicate residual stress plays an important role in core rotation prediction for low-torque plasmas and should be included in predictive models of future reactor scenarios.
