Effect of Pulse Rise Time on OH Generation of a 10-NS Pulsed Helium Plasma Jet

Plasma-produced reactive oxygen species (ROS), such as hydroxyl radicals (OH), have a wide variety of applications, including sterilization of surfaces, food processing and even optimization of plasma ignition efficiency for combustion. Generation of these species is heavily dependent on the pulse parameters, including pulse width, pulse rise time and the energy per pulse. It has been reported that the majority of OH is generated during the rising and falling time of the pulse [1]. When using longer pulse durations (>200-ns), these events can be seen as separate OH generation events. But when a much shorter pulse duration is used (~ 10-ns), these events happen so close together that they overlap, affecting the plasma chemistry and energy deposition [2]. It is currently unknown if the pulse rise time has an effect on the production of OH at shorter pulse durations. Using a single needle electrode, a helium plasma jet was generated in air using a 10-ns pulse width and a rise time of either 3-ns or 9-ns. The spatially and temporally resolved OH production by 10-ns pulse helium plasma jets in ambient air were measured using laser induced fluorescence. The effect of the pulse rise time on OH production is discussed.