| AVS 59th Annual International Symposium and Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS1-WeA |
| Session: | Plasma Diagnostics, Sensors and Control 2 |
| Presenter: | J.M. Palomares Linares, Eindhoven University of Technology, the Netherlands |
| Authors: | J.M. Palomares Linares, Eindhoven University of Technology, the Netherlands E.A.D. Carbone, Eindhoven University of Technology, the Netherlands S. Hübner, Eindhoven University of Technology, the Netherlands W.A.A.D. Graef, Eindhoven University of Technology, the Netherlands J.J.A.M. van der Mullen, Eindhoven University of Technology, the Netherlands |
| Correspondent: | Click to Email |
In this contribution we report a series of experiments based on time resolved laser induced fluorescence (tr-LIF) on low temperature discharges. This technique is used, in combination with Thomson scattering (TS) measurements, to get insight in the excitation kinetics of the discharge.
This method is used to pump different levels within the 4p and 5p groups of the Ar excitation space, from the Ar metastable level 1s5. Measuring the tr-LIF decay times in combination with the TS measurements of electron density provides simultaneously total destruction rates by electron and heavy particle collision of the pumped levels. These effective excitation rates are of great importance for the development of models, and are scarce in the case of high excited argon levels.
Similarly, the time response of the collisional induced fluorescence signals (tr-LCIF) emitted by other excited levels is used to study the interaction between levels. In the particular case of Ar this method is used to obtain the “depopulation rates” of metastable 4s levels. When other gasses are introduced in the discharge tr-LCIF signals are obtained from the emission of different excited species of those gasses. These experiments enable us to probe in details the excitation exchange between different species. The use of a high rep-rate system is fundamental for the LCIF measurements, where the low intensity of the signals demands measurement times up to 30 minutes.
The experiments are done in a range of intermediate pressures (0.65 mbar – 40 mbar), on a surfatron microwave induced plasma, working with pure Ar, and mixtures of Ar with H2, O2, and N2. The tr-LIF diagnostic is performed with a 5KHz high rep-rate Nd:YAG laser in combination with a Dye laser system. This setup allows to record tr-LIF signals 500 times more intense than with the common 10 Hz systems. Two equivalent systems are used to pump different wavelengths, a tripled frequency Nd:YAG (@355 nm) in combination with a Coumarine-2 Dye laser (430 nm - 460 nm), and a doubled frequency Nd:YAG (@532 nm) with a Pyridine-1 Dye laser (670 nm – 720 nm). The Thomson scattering measurements are performed with an independent Nd:YAG (532 nm) system and a triple grating spectrograph for the detection of the scattered photons.