Large-volume and low-frequency atmospheric glow discharges without dielectric barrier

It is widely believed that, at low frequencies of 1–100 kHz, the generation of atmospheric pressure glow discharges (APGD) requires a dielectric barrier added to at least one electrode. This letter reports the experimental observation of a uniform and stable APGD generated between two bare electrodes without a dielectric barrier over a wide frequency range from 20 kHz to 260 kHz. Below 70 kHz, it is shown that preionization in the rising phase of the applied voltage is important and plasma generation occurs in the voltage-falling phase. Mechanism of barrier-free APGD is found to be different from both atmospheric dielectric-barrier discharges and radio-frequency APGD.