Temperate micro-plasmas for environmental purposes sources, properties, diagnostics & challenges
Résumé
Low temperature atmospheric pressure plasma sources are on significant interest in various environmental applications. The rich non-equilibrium chemistry enables one to develop original processes at room temperature making this an feature a very attractive solution to treat heat sensitive material such as biological matter. Non-equilibrium non thermal plasmas are mainly driven by elementary processes involving electrons and the electric field. Micro-plasmas are plasma sources with at least one of their physical dimension in the micrometer scale. This allows one to use lower excitation voltage to yield very high electric field. In this presentation one will review two different methods to investigate the electric field experimentally. One is based on the electro-optical probe based on the Pockel’s effect. The second method is known as the Stark split and shift polarization spectroscopy with the line profile analysis of the He line at 492.19nm. Both technique will be compared while using a reference source, an atmospheric pressure plasma jet device allowing for producing reproducible guided ionization waves. This talk will present experimental results obtained with both methods followed by a discussion on a comparative part of the study. The comparison will be supported by numerical simulation results of guided ionization waves available in the literature. Last but not least, the Stark polarization spectroscopy will be detailed and applied for the first time to real micro-hollow cathode discharges. Preliminary results will be shown to reveal the rather complex electric field distribution in this kind of micro-metric reactors. Extreme values up to 70kV/cm will be reported and discussed particularly in regards to the impact on the electron chemistry.