Details

Autor(en) / Beteiligte

• Wormeester, G
• Pancheshnyi, S
• Luque, A
• Nijdam, S
• Ebert, U

Titel

Probing photo-ionization: simulations of positive streamers in varying N2 : O2-mixtures

Ist Teil von

• Journal of physics. D, Applied physics, 2010-12, Vol.43 (50), p.505201-505201

Ort / Verlag

Bristol: IOP Publishing

Erscheinungsjahr

2010

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Photo-ionization is the accepted mechanism for the propagation of positive streamers in air though the parameters are not very well known; the efficiency of this mechanism largely depends on the presence of both nitrogen and oxygen. But experiments show that streamer propagation is amazingly robust against changes of the gas composition; even for pure nitrogen with impurity levels below 1 ppm streamers propagate essentially with the same velocity as in air, but their minimal diameter is smaller, and they branch more frequently. Additionally, they move more in a zigzag fashion and sometimes exhibit a feathery structure. In our simulations, we test the relative importance of photo-ionization and of the background ionization from pulsed repetitive discharges, in air as well as in nitrogen with 1 ppm O2. We also test reasonable parameter changes of the photo-ionization model. We find that photo-ionization dominates streamer propagation in air for repetition frequencies of at least 1 kHz, while in nitrogen with 1 ppm O2 the effect of the repetition frequency has to be included above 1 Hz. Finally, we explain the feather-like structures around streamer channels that are observed in experiments in high purity nitrogen, but not in air.