Experimental study on asymmetrical period-one discharge in dielectric barrier discharge in helium at atmospheric pressure

Dielectric barrier discharge at atmospheric pressure not only behaves as a symmetrical period-one (SP1) discharge, but can also manifest itself as an asymmetrical period-one (AP1) discharge in certain ranges of parameters. In our study, a parallel electrode configuration is adopted and a series of discharge experiments are carried out in atmospheric helium at gap widths of 1, 4, 7 and 10 mm, respectively. The effects of gap width and driving voltage frequency on the symmetry of period-one discharge are investigated. Experimental results show that: AP1 discharge can be readily observed in a large range of parameters for the gap width and driving voltage frequency. AP1 discharge is prone to occur for a larger gap width; the critical value of the driving voltage frequency, beyond which the initial discharge is AP1 discharge, decreases as the gap width is increased. Results presented in this paper preliminarily verify the numerical simulations and the analysis which were previously reported in those papers studying the effect of gap width on AP1 discharge. Thus it can be conjectured that the AP1 discharge is not caused only by parameter asymmetry of discharge configuration, it can be also an intrinsic instability in terms of high frequency under certain parameters combination of gap width and driving voltage frequency.