A plasma loss to sidewall model for 1D PIC/MCC simulation for plasma transport estimation

Abstract

A plasma loss to sidewall model is used for one-dimensional (1D) particle-in-cell (PIC) with Monte Carlo collision (MCC) simulation to calculate plasma transport through a transverse magnetic field in a negative ion source chamber. The presented 1D model includes plasma radial loss treatment when calculating the plasma transport in the axial direction. It does not cost computation effort as much as a 2D or 3D model and can be used to estimate the plasma transport process quickly. The conventional 1D kinetic model calculates particle motion only in the ‘x’-direction. The sidewall loss in the ‘y’ ‘z’ direction is not included, leading to unusual plasma distribution. Especially when applying a transverse magnetic field, the motion and loss of electrons along the magnetic field line to the sidewall are ignored. Thus electrons are completely constrained by the magnetic field, resulting in abnormal plasma density accumulation. The sidewall loss estimation method uses Bohm velocity calculated from plasma parameters as radial loss velocity to obtain the plasma flux to the sidewall. And the sidewall loss rate can be obtained from the flux combined with chamber geometry. This method is integrated into a self-developed 1D PIC–MCC program to examine its effect. Several verification cases are performed separately for the PIC, MCC, and the sidewall loss treatment module, and the results exhibit good reliability. Simulations are then carried out to study plasma transport across the magnetic field under similar conditions to actual experiments. Simulation results agree with the experiment, which indicates that the 1D sidewall loss model is useful when dealing with plasma transport in the source chamber.