Electronegative plasma diagnostic by laser photo-detachment combined with negatively biased Langmuir probe
| Autor: | Francesco Taccogna, Nishant Sirse, A. Bendib, Albert R. Ellingboe, N. Oudini |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
010302 applied physics
Physics Electron Plasma Condensed Matter Physics Laser 01 natural sciences 010305 fluids & plasmas Ion law.invention Electronegativity symbols.namesake Physics::Plasma Physics Saturation current law 0103 physical sciences symbols Langmuir probe Electron temperature Atomic physics |
| Zdroj: | Physics of Plasmas. 25:053510 |
| ISSN: | 1089-7674 1070-664X |
| DOI: | 10.1063/1.5024826 |
| Popis: | We propose a new technique for diagnosing negative ion properties using Langmuir probe assisted pulsed laser photo-detachment. While the classical technique uses a laser pulse to convert negative ions into electron-atom pairs and a positively biased Langmuir probe tracking the change of electron saturation current, the proposed method uses a negatively biased Langmuir probe to track the temporal evolution of positive ion current. The negative bias aims to avoid the parasitic electron current inherent to probe tip surface ablation. In this work, we show through analytical and numerical approaches that, by knowing electron temperature and performing photo-detachment at two different laser wavelengths, it is possible to deduce plasma electronegativity (ratio of negative ion to electron densities) α, and anisothermicity (ratio of electron to negative ion temperatures) γ−. We present an analytical model that links the change in the collected positive ion current to plasma electronegativity and anisothermicity. Particle-In-Cell simulation is used as a numerical experiment covering a wide range of α and γ− to test the new analysis technique. The new technique is sensitive to α in the range 0.5 1. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|