Comparison of particle-in-cell and electron-Boltzmann hybrid simulations for the collisional sheath of an argon DC discharge

Summary form only given. The collisional sheath of an argon dc discharge is investigated by using a full particle-in-cell (PIC) model and a hybrid model which treats electrons with the Boltzmann relation. The simulated parameters are based on the experimental parameters used in a laser optogalvanic spectroscopy measurement. From the PIC simulation, it was observed that the electrons follow the Boltzmann relation in wide range with a slight discrepancy in the sheath, but the electron temperature is not constant in the sheath region. Even with these effects, the electric field and the potential profiles obtained by the two models agree well with only small discrepancy at the steady state, and the ion collision frequency can be represented as a function of the average ion velocity. With the relation between the collision frequency and the average ion velocity, dimensionless fluid equations are established for the ion dynamics in the steady state in order to study the nonlinear dynamics of ions in the collisional sheath. In addition, a two-dimensional PIC simulation provides wide information about the ion dynamics in the collisional sheath, such as ion acoustic waves and solitons, which are compared with analytic theory for a collisionless case.