Atmospheric pressure radio frequency glow discharges in argon: effects of external matching circuit parameters

Numerical simulations of radio frequency atmospheric pressure argon glow discharges were performed using a one-dimensional hybrid model. The discharge simulations were carried out for a parallel plate electrode configuration with an inter-electrode gap of 1.0 mm together with an external matching circuit. The external matching circuit parameters were found to have significant effect on the discharge characteristics. The results indicate that the discharge can operate at either the alpha or gamma mode depending on the matching circuit parameters. The two modes of operation were found to be distinctly different. The predicted Ar* density was considered to provide qualitatively the visual appearance of the alpha or gamma mode discharge. The alpha mode was found to have a luminous region in the center of the discharge. On the other hand, the gamma mode had luminous regions very close to the electrodes which were followed by alternating dark and bright regions. The appearance of the simulated gamma mode was found to resemble that of an atmospheric pressure direct current glow discharge. The predicted gas temperature indicated the gamma mode to have higher gas temperature compared with the a mode.