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Re:streamer capacitance effects (was re: How to rise the seco (fwd)) (fwd)



---------- Forwarded message ----------
Date: Thu, 16 Jul 1998 08:06:43 -0700
From: Jim Lux <James.P.Lux-at-jpl.nasa.gov>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re:streamer capacitance effects (was re: How to rise the seco (fwd))

Tesla List wrote:
> 
> ---------- Forwarded message ----------
> Date: 15 Jul 1998 13:47:47 -0700
> From: Dale Hall <Dale.Hall-at-trw-dot-com>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: RE>Re: How to rise the seco
> 
> RE>Re: How to rise the secondary? (fwd)
> 
> Terry, List,
> 
> Regarding streamer capacitance loading affect on PRI/SEC frequency;
> It would seem that Fo would be unaffected by streamer capacitance due
> to the fact that by the time the streamer emits/grows all the charge
> deposited on the Cs possible is there and the streamer subsequently
> emits and grows from that charge. The streamer suspected of enlarging
> Cs is there connected for only ~10-100 nanoS's each<<1/Fo  Is it possible
> that as 100's of streamers are producing more ozone that the dielectric
> constant is changing around the coil - could that account for the lower Fo
> required to maintain long discharges ?
> 
> 
I don't think ozone (or any gas) has an appreciably different dielectric
constant than air. It's just not dense enough.  FWIW, ozone probably has
a higher breakdown voltage than nitrogen.

But, what about the capacitance increase due to lots of little streamers
(most of which you can't see), and the "fuzz" coming out of the big
streamer you can see. This could significantly increase the capacitance
increment, over that from the simple "piece of wire" model.

We should be able to look at a coil's waveforms with and without
streamers (i.e. by changing the voltage) and determine the change in
L,C, and R. The dimensions are all small (relative to wavelength) so a
lumped model should work. however, the time varying nature of the
streamer, and the nonlinear R might throw this off. However, postulate a
simple model, and try to fit it to the observed data. 

We might also want to drive the coil with a high power pulse source
(rather than a spark gap, which puts its own characteristics into the
question), more like a single shot capacitive discharge approach. Maybe
an SCR (with a reverse flywheel diode around it) might work for this
test, since what you want is a switch that turns on and stays on, but
doesn't have an unpredictable closing behavior. An impact switch might
also do the trick. Discharge the cap and let the thing ring all the way
down.