Continuum gyrokinetic simulations of electrostatic ion scale turbulence are presented for the case of a diverted (single-null) tokamak geometry. The simulation model, implemented in the finite-volume code COGENT, solves the long-wavelength limit of the full-F gyrokinetic equation for ion species coupled to a vorticity equation for electrostatic potential variations, where a fluid model is used for an electron response. The model describes the ion scale ion temperature gradient (ITG) and resistive drift modes as well as neoclassical ion physics effects. Different turbulence regimes are observed depending on the plasma profiles, and the roles of a self-consistent background electric field and an X-point geometry are explored. In particular, increasing the pedestal density gradient and the corresponding radial electric field is demonstrated to suppress the ITG turbulence, whereas the same edge plasma background can still be destabilized by the resistive modes when the plasma resistivity is increased. The effects of X-point geometry are assessed by comparing cross-separatrix simulations with counterpart calculations performed for a toroidal annulus geometry. For the simulation parameters considered, similar global behaviour is observed in both cases, whereas strong local suppression of turbulence fluctuations is demonstrated near the X-point for the case of a single-null geometry.

中文翻译：

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使用旋动代码 COGENT 模拟偏滤器托卡马克中的静电离子尺度湍流

针对转向（单零）托卡马克几何结构的情况，提出了静电离子尺度湍流的连续回转动力学模拟。在有限体积代码 COGENT 中实施的仿真模型解决了离子物质的全 F 陀螺动力学方程的长波长限制，该方程与静电势变化的涡量方程耦合，其中流体模型用于电子响应。该模型描述了离子尺度离子温度梯度 (ITG) 和电阻漂移模式以及新古典离子物理效应。根据等离子体剖面观察到不同的湍流状态，并探索了自洽背景电场和 X 点几何形状的作用。尤其是，增加基座密度梯度和相应的径向电场被证明可以抑制 ITG 湍流，而当等离子体电阻率增加时，相同的边缘等离子体背景仍然会因电阻模式而变得不稳定。X 点几何的影响是通过比较交叉分离模拟与对环形环形几何进行的对应计算来评估的。对于所考虑的模拟参数，在两种情况下都观察到类似的全局行为，而对于单零几何的情况，在 X 点附近证明了湍流波动的强烈局部抑制。X 点几何的影响是通过比较交叉分离模拟与对环形环形几何进行的对应计算来评估的。对于所考虑的模拟参数，在两种情况下都观察到类似的全局行为，而对于单零几何的情况，在 X 点附近证明了湍流波动的强烈局部抑制。X 点几何的影响是通过比较交叉分离模拟与对环形环形几何进行的对应计算来评估的。对于所考虑的模拟参数，在两种情况下都观察到类似的全局行为，而对于单零几何的情况，在 X 点附近证明了湍流波动的强烈局部抑制。