Recent Progress of Nano-Seconds Pulsed Discharge and its Applications

Non-thermal plasma has been widely used for various applications. The observation of discharge plasmas is an essential aspect for understanding the plasma physics of this growing field. Generally, a pulsed discharge having time duration of 100s nanoseconds consists of streamer head propagation, glow-like discharge and arc discharge phases. It is well known that the propagation phenomenon of the streamer head between electrodes is strongly influenced by the polarity of the applied voltage. Typically, both of the positive and negative streamer heads propagate with the acceleration, and the propagation velocity of the positive streamer head is faster than that of the negative one. In the present study, a nano-seconds pulsed power generator which can generate a pulsed voltage with 5 ns of duration and 2.5 ns of rise and fall times was developed, and the propagation of the positive and negative streamer heads were observed using this generator. The results show that the discharge phenomena are totally different from the general pulsed discharge. The average propagation velocity of the nano-seconds streamer heads was 6.1 mm/ns for 67 kV applied voltage, which is five times faster than that of the general one (100 ns of pulse duration). Furthermore, no significant difference of the propagation velocities was observed between the positive and negative applied voltages. The reason for the faster propagation velocity resulted in the nano-seconds pulsed discharge is the faster voltage rise time in comparison with the general pulsed discharge. Furthermore, the application using nano-seconds pulsed discharge for ozone generation showed highest energy efficiency than other discharge methods.