Dust poses a serious threat to tokamak operation and safety. It is important to study the behaviour of dust grains under tokamak's discharge conditions, which depends heavily on their size and charge. Existing simulations mainly address issues on dust grains with radii larger than 1 μm, in which case, the drift effect due to electromagnetic fields can be safely ignored. For nanometer scale dust grains, however, the drift effect becomes significant and a new model based on guiding‐centre system needs to be established. In this work, the NDS has been done under BOUT++ framework. The simulation contains two parts. Part one, NDS evaluates the charging and ablation processes of the dust grains. In the second part, the guiding‐centre orbits of dust particles are tracked in tokamak plasmas, whose parameters are obtained from BOUT++, a highly desirable C++ code package for performing parallel plasma fluid simulations with an arbitrary number of equations in 3D curvilinear coordinates. The orbit of nanodust dynamics is described by guiding centre equations for simplicity, and these equations are numerically solved by conventional fourth‐order Runge Kutta method. Simulations provide results such as trajectories and evolutions of dust particles with different sizes and velocities for different tokamak geometries. Results show tungsten dust grains with a radius of a few nanometers launched from outer midplane will oscillate before totally ablated in C‐Mod. The oscillation in this case is driven by the ion drag force. Larger Nanodust with a radius of 100 nm, on the contrary, cannot be completely constrained by the electromagnetic field. The high plasma temperature and density in the seperatrix region causes severe dust ablation, resulting in total ablation within several ms.

中文翻译：

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托卡马克中纳米级尘埃颗粒的建模

灰尘对托卡马克的运行和安全构成了严重威胁。研究在托卡马克排放条件下尘埃颗粒的行为非常重要，这在很大程度上取决于尘埃颗粒的大小和电荷。现有的模拟主要解决半径大于1μm的尘埃颗粒的问题，在这种情况下，可以安全地忽略由于电磁场引起的漂移效应。但是，对于纳米级的尘埃颗粒，漂移效应变得显着，因此需要建立基于引导中心系统的新模型。在这项工作中，NDS已在BOUT ++框架下完成。仿真包含两个部分。第一部分，NDS评估了粉尘颗粒的充电和烧蚀过程。在第二部分中，在托卡马克等离子体中追踪尘埃粒子的引导中心轨道，其参数是从BOUT ++获得的，一个非常理想的C ++代码包，用于在3D曲线坐标系中使用任意数量的方程式执行并行等离子体流体模拟。为了简化起见，通过指导中心方程来描述纳米尘埃动力学的轨道，并且这些方程通过常规的四阶Runge Kutta方法进行数值求解。对于不同的托卡马克几何形状，模拟提供了诸如轨迹和不同大小和速度的尘埃颗粒演变的结果。结果显示，从外中平面发射的半径为几纳米的钨尘颗粒会先振荡，然后在C-Mod中完全烧蚀。在这种情况下，振荡是由离子拖曳力驱动的。相反，半径为100 nm的较大的纳米粉尘无法完全受到电磁场的约束。