Re: Hi Power Discharge "Disruptive"

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

Original poster: FIFTYGUY-at-aol-dot-com 

In a message dated 11/9/04 10:29:07 AM Eastern Standard Time,
tesla-at-pupman-dot-com writes:

 > A high turns ratio between the primary provides a high
 >  voltage step up of around  100:1 with the added resonant boost to provide
 >  some where around a Mega volt with 20 Kv input.

     I've heard some folks on this List disavow the turns ratio voltage
multiplication. IIRC, if the primary-secondary were a tightly-coupled 
transformer,
with the same geometry for both coils, then this would be valid. But they
aren't.
     I personally think that we aren't seeing a even MegaVolt off the top of
typical coils. I think a 5' streamer is the propagation of a high-frequency
spark of much lower voltage through a pre-ionized channel.
     My proof: fire a static SGTC coil with one pulse (or even at a very low
pulse rate - via a variac/slide choke and resonant charging for a SGTC). How
long are the streamers? Pretty short. You know the primary cap voltage at 
firing
was the same as at full-power operation - that's the only way the spark gap
could fire. We've had other experimental and anecdotal evidence here that
maximum spark length requires perhaps 100-150 bps (even though 300 bps is 
supposed
to be aesthetically pleasing). CW coils give a shorter, fatter "flame".
There's a lot of talk about streamer "growth".
     If all the energy in the coil has dissipated in a very short burst, long
before the next pulse, then there must be a time-dependent effect due to the
previous streamer. If the thing produced a MegaVolt every pulse, then we'd get
3' streamers every time, no matter how slow the pulse rate. Instead, we need
to run at a minimum burst rate to ensure full streamer "growth". How lucky for
us that it's around 120bps...
     There's a lot of streamer modeling being tossed around, especially by the
SSTC folks. But does the little 1-50pF of capacitance adequately provide for
this minimum bps for long streamers?
     If we want a top-down design of "I want spark length of x inches", it
seems to me we ought to know more about streamers, and how to grow them.

-Phil LaBudde