Control of reactive species formation in atmospheric pressure plasmas using pulsed power deposition*

The success of atmospheric pressure plasmas in a wide range of applications relies on the production of a diverse array of reactive species. As a result, control of reactive species densities is fundamentally important for the development and optimisation of plasma-based processes. In addition, the rate of delivery of reactive species to targets and the energy efficiency of production are often of particular importance. Due to the non-linear nature of plasma-chemical processes, these parameters are often challenging to optimise on an empirical basis. Further, many application-relevant plasma systems operate using pulsed power deposition and utilise a wide variety of temporal power deposition schemes where the peak and average power deposition, temporal pulse width and pulse repetition frequency can vary over orders of magnitude. In order to effectively understand and optimise the operating conditions of such sources, experimentally validated simulations using plasma-chemical reaction schemes with sufficient detail as to capture the main reaction pathways both during the active plasma and afterglow phases are essential. In this contribution, the state of development and experimental validation of such reaction schemes for N₂, O₂ and H₂O-containing plasma sources is presented and discussed. These schemes are subsequently used together with zero-dimensional plasma-chemical kinetics simulations to systematically study the production of application-relevant reactive species such as NO and H₂O₂ as a function of the power deposition profile. As application-relevant model systems, dielectric barrier discharges and discharges formed in bubbles within liquids are chosen. Special attention is paid to the timescales for the formation and consumption of reactive species and their relationship to the temporal duration of the pulsed power deposition and the pulse repetition frequency.