Shorter pulse rising time of pulse DC voltage makes atmospheric pressure non-equilibrium plasma more reactive

Summary form only given. Recently, several groups worldwide have proposed that the APNP driven by short pulses have several advantages over the traditional discharge driven by kHz voltages, including higher energy efficiency for ozone synthesis and UV power output, relative easier to generate diffuse plasma, better power transfer efficiency to the plasma and so on^[1-2]. It is generally assumed that short pulses have a short rising time t_rise and this short rising time may result in the overvoltage breakdown. The overvoltage breakdown could further enhance the ionization and excitation processes because more high energy electrons may be generated under such conditions. But until now, no quantitative investigation has been reported on how the t_rise will affect the plasma characteristics. In this paper, the effect of pulse rising time variable from 4 μs to 100 ns on plasma characteristics is investigated. The experimental results show that, when the trise is reduced from 4 μs to 140 ns, the length of the plasma plume increases from less than 20 mm to about 70 mm, the peak value of the discharge current increases from about 0.2 A to 1.3 A. The corresponding breakdown voltage increase from less than 4 kV to about 6 kV and the electron temperature increase from 1.25 eV to 1.55 eV. These results confirm that the shorter the pulse rising time is, the more reactive the plasma is.