Probing photo-ionization: experiments on positive streamers in pure gases and mixtures
By S. Nijdam, van de F.M.J.H. Wetering, R. Blanc, Van Veldhuizen, Ute Ebert. 2009
185 citations recorded by the source corpus.
Positive streamers are thought to propagate by photo-ionization; the parameters of photo-ionization 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 gases. 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 102 hair tips cm−3 in the feathers at 200 mbar; this density can 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.
Subfields: Biomedical Engineering, Electrical and Electronic Engineering, Spectroscopy
View Paper: https://www.semanticscholar.org/paper/ba703460e491f183aa7056c4ad3b0122d4463481
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In Electrical and Electronic Engineering
Citations in the corpus
- Dynamics of a guided streamer (‘plasma bullet’) in a helium jet in air at atmospheric pressure (2013, background): “Recent measurements (Nijdam et al 2010) of (unguided) streamer velocities in N2/O2 mixtures and in argon have shown that the velocity depends linearly on the applied voltage but is independent of the mixture.”