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.