Re: theory(?) for long sparks

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Re: theory(?) for long sparks
From: Tesla List <tesla-at-stic-dot-net>
Date: Wed, 26 Nov 1997 19:30:11 -0600
Approved: tesla-at-stic-dot-net

From: 	D.C. Cox[SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent: 	Thursday, November 27, 1997 3:30 PM
To: 	Tesla List
Subject: 	Re: theory(?) for long sparks

to: Jim Lux

I still find it very hard to believe a resonance transformer operating at 5
MEV could produce a spark 300+ feet long.  We have operated a dual unit at
8 MEV and under optimal tuning at 150 kw only produced a spark 80 feet long
(max).  300 ft. would imply a tremendous amount of additional energy would
need to be added to the spark channel to achieve a heated streamer that
long, ie, similar to a jacob's ladder climbing arc effect.  

DR.RESONANCE-at-next-wave-dot-net

> 
> From: 	Jim Lux[SMTP:jimlux-at-earthlink-dot-net]
> Sent: 	Tuesday, November 25, 1997 8:27 AM
> To: 	Tesla List
> Subject: 	theory(?) for long sparks
> 
> I have just gotten my copy of "spark discharge" by Bazelyan and Raizer
(CRC
> press). I have been inspired by the picture of the 100 meter+ spark
> produced by only 5 MV, and have given some thought to what it takes to
make
> long sparks.
> 
> It appears that a spark propagates at around 2-3 cm per microsecond. If
the
> voltage pulse producing the spark only lasts 10 microseconds, the maximum
> spark length that can be developed will be in the area of 20-30 cm. 
> 
> What is necessary for the spark to start is that the field at the
starting
> point be greater than the breakdown for air (i.e. around 30 kV/cm). Then,
> for the spark to propagate, the voltage has to increase enough to cover
the
> drop along the spark, and, the source has to supply sufficent current to
> "fill" the spark channel with charge. (I am doing horrible injustice to
the
> pretty complex physics here, sorry).
> 
> So, then, if you want to produce a 100 meter spark, (i.e. 1E4 cm), the
> voltage has to be there for at least 5000 microseconds, and probably
> longer. Further, the voltage has to be high enough to overcome the drop
in
> a 100 meter long spark channel, i.e. several MV.
> 
> A tesla coil running at 100 kHz (for example), has a half period of only
5
> microseconds, well short of the desirable 5 milliseconds. It is possible
> that the fine structure (i.e. the 100 kHz carrier) isn't the significant
> thing, but rather the overall envelope (i.e. the time til the first
> "notch"), which would be more consistent with the observed 1-3 meter
length
> sparks from a medium sized tesla coil.
> 
> Ideas anyone?
> 
>