Comparison of discharge mode transition of air plasma under pulsed and sinusoidal excitations

The transition from O-3 to NO (x) discharge mode is common for air plasma with an increase of discharge power density, which greatly changes the chemistry of the plasma as well as its application effect. Although this discharge mode transition has been intensively studied in recent years, differences between plasmas subject to pulsed or sinusoidal excitations have rarely been reported on. In this study, a surface dielectric barrier discharge is excited using either a microsecond pulsed voltage or a sinusoidal voltage. The discharge mode transition of these two excitations is then comparatively studied. The results indicate that pulsed excitation produces more O-3 in O-3 mode discharge; the O-3 concentration for pulsed excitation is 27.7% higher than that for sinusoidal excitation at the same power density of P = 0.08 W cm(-2). On the contrary, it produces less NO and NO2 in NO (x) mode discharge; the NO concentration for pulsed excitation is 13.2% lower than that for sinusoidal excitation at P = 0.32 W cm(-2). As a result, pulsed excitation delays the transition of the discharge mode when the discharge power density increases. This can be attributed to the higher electron and lower gas temperature of the pulse-excited plasma, which promotes O-3 and inhibits NO (x) production.