Open AccessTemporal evolution of electron density and temperature in low pressure transient Ar/N2 plasmas estimated by optical emission spectroscopy
Author(s) -
J. Kaupe,
P. Riedl,
D Coenen,
Slobodan Mitic
Publication year - 2019
Publication title -
plasma sources science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 108
eISSN - 1361-6595
pISSN - 0963-0252
DOI - 10.1088/1361-6595/ab252d
Subject(s) - argon , atomic physics , electron density , electron temperature , electron , plasma , chemistry , emission spectrum , radiative transfer , quenching (fluorescence) , plasma diagnostics , analytical chemistry (journal) , spectral line , physics , fluorescence , optics , quantum mechanics , astronomy , chromatography
A recently published method for the analysis of phase-resolved optical emission spectra was extended in order to permit estimation of time-resolved electron density profiles. The previously presented method combined collisional-radiative modelling with a self-absorption method to estimate the evolution of T e with sub-cycle time-resolution. However, it was not capable to give similar profiles for n e as the model was insensitive to its variations. The extensions proposed in this work describe a way to also estimate the electron density with sub-cycle time resolution from the changing rates of the argon Paschen 1s states. The method was applied to a low-pressure DBD-jet operated with argon and several argon–nitrogen mixtures with up to 4% N 2 . Good agreement among evaluation of n e from changing rates of individual 1s states was observed during the collisional phase and the full-cycle temporal profile could be calculated from relative changes in light emission. Electron densities exhibited a drop for larger admixtures of nitrogen and ranged from 10 17 m −3 to 10 18 m −3 . As assumed in a previous work, the electron temperature model worked without explicit consideration of additional processes even when N 2 affected the plasma. However, presumably due to collisional quenching by nitrogen, two argon Paschen 2p levels were found to be inappropriate for T e estimation and had to be removed. Values for electron temperature from the remaining levels remained at a similar value as for pure argon.