Modeling wall ion fluxes in an RF discharge: insights from 2D PIC simulation
Résumé
Global models of plasma discharges have been widely used to simulate plasma reactors in the fields of plasma processing and space propulsion. These models rely on accurate description of the ion current leaving the plasma: after undergoing a pre-sheath drop, the ions enter the sheath at Bohm velocity. The pre-sheath drop is characterized by an edge-to-center plasma density ratio and heuristic models were formerly derived to understand how this parameter varies with plasma temperatures and ion mean free path, based on one-dimensional (1D) transport theory, and validated by 1D simulation. A model of ICP discharges was implemented into a 2D benchmarked PIC code, running with various gases (Ar, He, Xe). These simulations show that the ion flux has a strong spatial dependency in agreement with former results and that it is affected by the aspect ratio of the discharge reactor. The influence of dielectric walls is also investigated.