From: Bert Hickman
Date: Mon, 02 Jul 2001 23:55:19 -0500
Subject: Re: [TSSP] Toroid breakdown voltage indirect meas.
Paul Wrote: > Does anyone know anything about photo-ionisation? UV photons emitted by > relaxing ions in the streamer passing some distance through the air to > ionise an atom some way away, thus seeding a new electron avalanche from > that point? Does this phenomena play a role in TC discharges? > > Cheers, > -- > Paul Nicholson, > Manchester, UK. > -- Paul and all, Photoionization appears to play a secondary role in avalanche breakdown versus the primary one: electron impact ionization. Photoionization is considered a major contributor in the generation of seed electrons to support avalanches in streamer propagation. One hypothesis is that, once an initial avalanche begins, energetic photons are emitted by the excited atoms in the avalanche, which triggers the generation of secondary electrons. These then act as the seeds for additional avalanches. Since photons are emitted and absorbed in a random manner, so will the production of secondary electrons - Raizer offers this as one explanation for experimentally observed zigzag paths of streamers and spark channels. (Yuri P. Raizer, "Gas Discharge Physics", Springer-Verlag, 2nd corrected printing, 1997). Since streamers are always the precursers of leaders, and are always present at the tips of arrested leaders, they play a central role in TC discharges. And thus, so does photoionization. -- Bert -- -- Bert Hickman Stoneridge Engineering Email: bert.hickman@aquila.net Web Site: http://www.teslamania.com
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.