Study of atmospheric radio-frequency Ar/02 plasma used for PTFE surface treatment

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Optical diagnostics and mass spectrometry on the afterglow of an atmospheric pressure Ar/O2 radiofrequency plasma used for polymer surface treatment

International audienceIn the context of polymer surface treatment, the afterglow of an atmospheric pressure Ar/O2 radiofrequency plasma is characterized by optical emission spectroscopy, laser induced fluorescence and mass spectrometry. The influence of the O2 gas flow rate and the source power on the plasma properties (gas temperature, Ar excitation temperature, relative concentrations of O atoms and OH radicals) are evaluated. We show that for plasma torch-to-substrate distances lower than 6 mm, the afterglow creates a protective atmosphere, thus the plasma gas composition interacting with the substrate is well controlled. For higher distances, the influence of ambient air can no longer be neglected and gradients in Ar, O2 and N2 concentrations are measured as a function of axial and vertical position

Investigation of N(4S) kinetics during the transients of a strongly emissive pulsed ECR plasma using ns-TALIF

International audienceNanosecond-two-photon absorption laser induced fluorescence (ns-TALIF) technique was employed to investigate the transients of a strongly emissive pulsed microwave discharge. We analysed the conditions that have to be fulfilled in order to use the TALIF intensities measured with the laser central frequency tuned to the absorption peak instead of the fully integrated laser excitation spectrum absorption for measuring N-atom densities. We demonstrate the validity of the method in our conditions and applied it for the straight forward monitoring of N-atom densities during the transients of a pulsed ECR plasma. We especially demonstrated the existence of an unexpected increase in N(4S) atom density of about 10% at the early stage of the transition from high- to low-power phase. Using a self-consistent quasi-homogenous plasma model encompassing a detailed state-to-state kinetics, a thorough analysis of the N-atom and N2(B) kinetics was carried out and enabled attributing this enhancement to surface de-excitation of N(2D) and N(2P) atoms. The rise of the N(4S) atom density can serve as an indicator of the concentration of N(2D) and N(2P) atoms in the discharge

Investigation of picosecond laser pulse properties using a streak camera and their utilization for TALIF studies in a microwave plasma torch

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