用于三维全电磁粒子模拟的电荷守恒共形发射技术北大核心CSCD

给出了满足电荷守恒的共形发射技术。首先阴极表面由三角网格共形描述,发射带电粒子时,根据电荷和电流线性分配方式和离散高斯定律,带电粒子的初始位置设置在与三角面元处于同一个网格元胞内,离三角面元最近且处于金属内部的网格点上。带电粒子的初始运动由两部分组成:一是由三角面上的法向场推进所产生的运动;二是使发射粒子在阴极面上分布呈随机性而设定的随机运动。运动产生的电流按照电荷守恒定律分配到离散网格中,并且由于粒子的初始位置设置在整网格点上,带电粒子的共形发射不会产生非物理的静电累加。最后通过同轴二极管模型来验证共形发射模型的正确性。

Charge conserving emission technique for three-dimensional conformal particle-in-cell simulations

The charge conserving emission technique is presented in this paper. Based on the relationship between the charge and current distributions and Gauss law preservation, the emitting surface is triangulated, and the charged particle is initially located at the nearest conductor node to the conformal emission triangle. The motion trajectory of the charged particle is decided by two components: the normal component and the transversal component. The normal component is the displacement under the normal electric field of the emission triangle within one step; the transversal component is a random displacement parallel to the emission triangle, whose step size is constrained by the shape of the emission triangle. Currents generated by the movement of charged particles are distributed to the discrete grid according to the charge conserving law. As the charged particle starts from the conductor node, the conformal emission is free of nonphysical electrostatic accumulation. Finally a cylindrical diode is simulated to validate the technique.