Effects of discharge voltage waveform on the discharge characteristics in a helium atmospheric plasma jet

We present here an analysis of the discharge characteristics of a He plasma jet operating under three different types of applied voltage waveform: (a) a mu s-pulse voltage waveform with a slow voltage rise time, (b) ns-pulse, and (c) rectangular voltage waveforms with fast voltage rise time. Optical emission measurements show that the application of a voltage with a fast voltage rise time induces rapid discharge growth and, consequently, produces an abundance of energetic electrons, which in turn leads to high optical emission from the O atoms. We also estimate the optical emission efficiency of the O atom (eta(o)), which corresponds roughly to the production efficiency of the reactive O species. eta(o) increases with increasing applied voltage, and the highest value of eta(o) is obtained in the shortest pulse discharge, which was ignited by a ns-pulse voltage waveform with a fast voltage rise time and short pulse width. (C) 2015 AIP Publishing LLC.