Streamer propagation dynamics in a nanosecond pulsed surface dielectric barrier discharge in He/N₂ mixtures

An atmospheric pressure surface dielectric barrier discharge in helium–nitrogen mixtures is investigated experimentally using phase-resolved optical emission spectroscopy and computationally employing a two-dimensional simulation framework. A good qualitative agreement between experiments and simulations is found. It is shown that by applying microsecond or nanosecond driving voltage waveform pulses, the discharge exhibits filamentary or homogeneous structures. The time evolution/propagation of the homogeneous surface ionization wave for different nitrogen admixtures, pressures, and applied voltage is studied and analyzed. Both, simulations and experiments indicate that for the positive applied voltage pulse, a streamer possessing the typical dynamics of the positive streamer is ignited on the powered side of the electrode. At the same time, on the grounded sides, two streamers are formed: one possessing the dynamics of a negative streamer, which propagates towards the center of the cell of the electrode grid, and a positive one in the opposite direction. It is also shown that the positive streamers on the powered side are partly responsible for the velocity of the negative streamers on the grounded side. Simulations show a deceleration of the negative streamers as soon as two positive streamers collide and then close to the meeting point vanish due to the repulsive electrostatic interactions between them. Additionally, from the time-resolved measurements of the emission signal, the quenching rate constants of the He–I (3 s) 3 S 1 state by collisions with helium and nitrogen are determined to be 9 ( ± 4 ) × 10 − 12 cm 3 s −1 and 3 ( ± 1 ) × 10 − 10 cm 3 s −1 , respectively at T = 400 ± 50 K.