Elucidation of Discharge Mechanisms in He- and Ar-flexible Μ-Tube Plasmas by Temporally and Spatially Resolved Plasma Optical Emission Phoresis Spectroscopy

A Helium- and Argon-flexible μ-tube plasma (FμTP) driven by a square wave high voltage were investigated by means of temporally and spatially resolved spectroscopy to characterize the discharge mechanisms. These two discharge gases show different discharge behavior in the same FμTP-configuration. The mixtures of different concentration of propane in Ar were used as discharge gases to confirm the role of Ar+ in an Ar-FμTP by tuning the discharge behavior. It was demonstrated that, N2+ are mainly responsible for the excitation and ionization and only small amount of He+ are produced in a He-FμTP, whereas Ar-FμTP lives from Ar+. These ions as well as excited species do not propagate beyond the capillary during the negative half cycle, resulting in a negligible contribution for protonation in this half cycle. The present study proposes a new method to data analysis, Plasma Optical Emission Phoresis Spectroscopy, which allows to distinguish noble gas ions from excited noble gas species.