Nanosecond pulsed atmospheric pressure argon microplasmas

This study details the generation and characterisation of a 3 nanosecond pulsed atmospheric pressure Argon discharge, and provides a comparison with a comparable DC discharge. There is a growing interest in short pulsed excitation of microplasmas as a gateway to access highly non-equilibrium discharge chemistry that is inaccessible using other excitation mechanisms. By combining time-resolved electrical and optical diagnostics the repetitive 3 nanosecond pulses considered in this study are shown to produce highly transient discharges with electron densities in excess of 10$^{17}$cm$^{-3}$. During the afterglow period electrons rapidly cool below the excitation threshold suggesting emission from excited Argon neutrals should also diminish rapidly. However, Argon emissions are observed for several microseconds after each applied pulse, far in excess of their radiative lifetimes. Potential repopulation mechanisms are considered and it is concluded that electron-ion recombination is the most likely recombination process.