Excitation frequency dependent mode manipulation in radio-frequency atmospheric argon glow discharges

An experimental investigation is presented to characterize the dependence of discharge operation modes (α and γ modes) and their transition on excitation frequency in radio-frequency atmospheric argon glow discharges. The current-voltage characteristics are used to distinguish the α and γ modes at an excitation frequency range of 5–24 MHz. The operation regime of α mode with stable and uniform discharge in large volume is found to expand at higher excitation frequency. It is shown that, when excitation frequency is below 10 MHz, the discharge evolves directly into γ mode after gas breakdown and, when excitation frequency is above 10 MHz, the discharge operates in the coexistence mode of α and γ after mode transition.