Study on Modes of the Pulsed Dielectric Barrier Discharges at Atmospheric Pressure in Helium

For the dielectric barrier discharge (DBD) at atmospheric pressure in helium excited by repetitive voltage pulses (called the pulsed DBD), two discharge modes, atmospheric pressure glow DBD (APGD), and atmospheric pressure Townsend DBD (APTD), have been numerically investigated by means of a 1-D fluid model. The influences of several important operation parameters, i.e., voltage growth rate r(vg), gap width d(g), dielectric thickness d(s), and dielectric constant epsilon(r), on the discharge modes have been explored. Especially, the parameter regions in which each discharge mode located have been presented, in an effort to indicate the effects of the interaction of r(vg), d(g), and d(s) on the discharge modes. This paper shows that there are two discharge modes in the pulsed DBD, relying on the used discharge parameters, and the obtained significant results are as follows. Based on the axial distributions of electric field, electron density, and ion density in the gap at the time point where the first discharge occurs, the discharge in APGD is of the following evident characteristics: 1) there are both cathode fall and quasi-neutral plasma bulk and 2) the electron density is evident large, when compared with those for the discharge in APTD. The increase of voltage growth rate or the increase of the capacitance of dielectrics by decreasing d(s) or by increasing epsilon(r) can induce the transition of the discharge mode from APTD to APGD. With the use of efficient large gap width, APGD is easier to be driven. In particular, to what extent can the discharge be affected by a discharge parameter? This is still governed by other parameters and is shown using the regions of the parameters in which each discharge mode located.