Two-dimensional simulation of discharge characteristics of argon plasma in microhollow cathode

Argon plasma was numerically simulated to describe the discharge characteristics of microhollow cathode discharge (MHCD) using a two-dimensional fluid computational model. Results indicate that the MHCD operates in a normal glow discharge mode in the pressure (2�10⁴~4�10⁴ Pa), current (1.0~2.5 mA) operating regime. Most predictions presented in this paper, such as I-U characteristics and all species number densities, are in qualitative and quantitative agreement with the referred experimental results. Under the typical conditions, the electron temperatures in the ring-shaped cathode sheath region reach 20 eV. The discharge is characterized by significant gas heating since the peak gas temperatures are several hundreds of Kelvin above the room temperature for all cases. It is found that the production of ions is dominated by different processes in different regions by chemical-kinetic process analysis. In the cathode sheath region, electron-impact ground-state atom ionization is the predominant production mechanism, while electron-impact excited-state atom ionization in the center of the discharge dominates inside the hollow. At the center line of the discharge outside the hollow, the production rate of ions is mainly determined by kinetic processes involving electron-impact excited-state atom ionization, Penning ionization and electron-impact ground-state atom ionization.