Probing photo-ionization : experiments on positive streamers in pure gases and mixtures
| Autor: | F M J H van de Wetering, E.M. van Veldhuizen, Ute Ebert, R Blanc, S Sander Nijdam |
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| Přispěvatelé: | Elementary Processes in Gas Discharges, Multiscale Dynamics |
| Jazyk: | angličtina |
| Rok vydání: | 2010 |
| Předmět: |
010302 applied physics
Photo ionization Range (particle radiation) Argon Materials science Acoustics and Ultrasonics Analytical chemistry chemistry.chemical_element FOS: Physical sciences 02 engineering and technology 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Nitrogen Oxygen Physics - Plasma Physics Surfaces Coatings and Films Electronic Optical and Magnetic Materials Plasma Physics (physics.plasm-ph) chemistry Orders of magnitude (specific energy) Free electron density 0103 physical sciences Limiting oxygen concentration 0210 nano-technology |
| Zdroj: | Journal of Physics D: Applied Physics, 43(14), 145204-1/16. Institute of Physics Journal of Physics D: Applied Physics, 43, 1-16 |
| ISSN: | 0022-3727 |
| Popis: | Positive streamers are thought to propagate by photo-ionization whose parameters depend on the nitrogen:oxygen ratio. Therefore we study streamers in nitrogen with 20%, 0.2% and 0.01% oxygen and in pure nitrogen, as well as in pure oxygen and argon. Our new experimental set-up guarantees contamination of the pure gases to be well below 1 ppm. Streamers in oxygen are difficult to measure as they emit considerably less light in the sensitivity range of our fast ICCD camera than the other gasses. Streamers in pure nitrogen and in all nitrogen/oxygen mixtures look generally similar, but become somewhat thinner and branch more with decreasing oxygen content. In pure nitrogen the streamers can branch so much that they resemble feathers. This feature is even more pronounced in pure argon, with approximately 10^2 hair tips/cm^3 in the feathers at 200 mbar; this density could be interpreted as the free electron density creating avalanches towards the streamer stem. It is remarkable that the streamer velocity is essentially the same for similar voltage and pressure in all nitrogen/oxygen mixtures as well as in pure nitrogen, while the oxygen concentration and therefore the photo-ionization lengths vary by more than five orders of magnitude. Streamers in argon have essentially the same velocity as well. The physical similarity of streamers at different pressures is confirmed in all gases; the minimal diameters are smaller than in earlier measurements. Comment: 28 pages, 14 figures. Major differences with v1: - appendix and spectra removed - subsection regarding effects of repetition frequency added - many more smaller changes |
| Databáze: | OpenAIRE |
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