Effect of preionization on forming atmosphere glow discharges in air

There are some obstacles in obtaining atmosphere glow discharge plasma although the technology of low-pressure glow discharge plasma has been highly developed. Discharge stability decreases greatly as pressure increases, especially in air. As a way to produce high electron densities and lower the electric field for discharges, a preionization method is used to prevent the transition from glow to steamer-like discharge in air. It is found that the preionization can assist the starting of discharges and lower the electric field for discharging in air effectively. Under normal atmosphere conditions, the electric fields employed in the reactor decrease by about 25% when the preionization method is adopted. Some experimental conditions which effect the preionization are studied to test the validity and stability of the preionization method. Experimental results show that the preionization plays an important role in the atmosphere glow discharge in air and its effect varies with some factors such as gas flow and frequency of the power supply.