Re: On sparks

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Terry,
          I'm following your project with considerable interest.

On 29 Mar 01, at 19:14, Tesla list wrote:

> Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
> 
> Hi,
> 
> It is interesting to note that with a solid state gap, one may have
> say a low BPS rate (higher voltage) at the beginning of the streamer
> formation and then have a higher BPS rate (higher current) once the
> streamer is formed and growing.  You could really vary the gap timing,
> dwell, BPS as you wanted with a little monitor to know what the coil
> is up to at that instant of time.  It is all just a matter of hooking
> up digital ICs (I suppose you could hook up a microprocessor too ;-)).
>  I guess you can kind of tweak the BPS rate and such to give the
> streamer just what it wants. Perhaps with a little more monitoring you
> could measure the streamer impedance and adjust the coil to feed it...

Actually you could control the entire thing from a precision pulse 
generator (not that I'd advocate using an expensive bit of gear 
around something as banal as high voltage high current sparks of 
course :)

     You will probably find yourself entangled in a Mobius Loop if 
you try adjusting the coil to streamer impedance. As anyone who has 
drawn out a foot arc from a standard arc welder (and has more than a 
passing interest in things electrical) knows, the impedance of that 
arc is vastly different from your 220k/ft figure ;)

>  An odd thought...
> 
> I also note that solid state gaps will have a "softer" turn on which
> will eliminate that large initial energy spike.  I wonder if that
> giant VHF, UHF, GHz... noise burst makes a difference in getting the
> streamer started?

I doubt it. The secondary is a high Q bandpass filter. I've never 
seen spiking in the secondary as I've observed in the primary e-field.
 
> An interesting idea Jim had about flash tubes to fire a solid state
> gap. My design is all complex digital but a flash tube may be a cheap
> and easy way to go for a simpler form of solid state gap trigger. 
> Have to be sure the tube does not eat too much energy.  Solid state
> gaps really are a study in not loosing energy to anything but the
> streamer...

I would imagine that running a tube well under a Joule would suffice 
but that's and interesting point about the energy (integrated over 
time anyway). 

> I wonder if Kennan's coil performance is hurt buy the MOSFET's VI
> curves. Maybe IGBTs would not waist as much energy as heat since they
> tend to have a much lower voltage drop at high currents?  I have not
> been following Kennan's experiments as much as I should have been...

With the amount of paralleling one wouldn't expect so but the heating 
would tell the true story. A few volts means a lot more if the feed 
voltage is a few hundred rather than a few thousand.

Regards,
malcolm