RE: Measuring Streamer characteristics

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 

At 07:47 AM 10/4/2004 -0600, you wrote:
>Original poster: "Steve Conner" <steve.conner-at-optosci-dot-com>
> >This is
> >how we came up with the 220K +1pF per foot of capacitance model for a
> >streamer load.
>
>Terry (and others)
>
>Could you explain this further please? It never seemed right to me. Richie
>Burnett and I have seen a lot of weird things in our SSTC work, and the best
>explanation we can think of is: As a streamer gets longer, its equivalent
>shunt resistance to ground must go down, not up. So I don't see how a model
>that says "X ohms per foot" can be correct.
>
>I'm trying to do some experiments similar to Terry's and see what comes up
>
>http://scopeboy-dot-com/tesla/experiment/
>
>Steve C.


I think that Terry just adjusted the values in the model until the waveform 
in Spice looked like the waveform on the real device.

In this model, the resistance is the resistance of the plasma tube along 
the leader.  In "real life", the resistance would be inversely proportional 
to the current, along with a time varying term as the air heats up and cools.

The capacitance (which is the dominant load) is proportional to streamer 
length, and, of course, would vary as the streamer grows.  1pF/ft is a sort 
of empirical number that seems to work.  Bazelyan and Raizer also use 
numbers of this general magnitude, with several pages of justification, 
based on calculations of the diameter of the leader, etc.


One can literally spend a PhD dissertation worth of work trying to come up 
with a model of a growing spark, but given all the other variables, it 
might not change the overall results much.