Re: Coiling Waveforms.

From: 	Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: 	bert.hickman-at-aquila-dot-com
Sent: 	Saturday, August 09, 1997 2:09 AM
To: 	Tesla List
Subject: 	Re: Coiling Waveforms.

Tesla List wrote:
> >>
> >John,
> >
> >I can back up Malcolm's measurements. I've done numerous measurements on
> >my 10" coil under various operating conditions in order to characterize
> >its operational behavior. The longest ring-down time on the secondary
> >only occured when the secondary did not break out, and after the primary
> >gap quenches, since under these conditions the resonator is losing
> >energy at the slowest rate. These measurements were performed in order
> >to estimate effective secondary "Q" during various output streamer
> >loading conditions.
> >
> >The bottom line:
> >Even under the "best-case", no-breakout, condition, the resonator fully
> >"rings down" prior to the NEXT gap firing. Each secondary energy "event"
> >is essentially independent of the previous one. On my system, full
> >ringdown occurred in about 1000 uSec when breakout was inhibited.
> >Secondary ring-down dropped to about 100 uSec when streamers were
> >present. [This translated to a non-breakout Q of about 188 going down to
> >about 19 under breakout conditions].
> >
> >The time between successive gap firings (about 320 BPS) was of the order
> >of 3X the longest ring-down period with no breakout, and about 30X the
> >ring-down period when streamers were present. Since the rate of
> >secondary energy loss significantly worsens when streamers are present,
> >any proposal that secondary energy could somehow be building up on
> >sucessive "bangs" is inconsistent with empirical measurements on
> >operating 2-coil systems.
> >
> >-- Bert H --
> ------------------------------------------------------------
>    Bert H. -
>    In studying your test waveforms did you notice anything that would
> indicate a difference in waveform for the extra long spark?  How do you
> think the long spark is created? Do you think the long spark has more energy
> than the short sparks? Where do you think the extra energy comes from?
>    How do you think the input watts should be split up between the long and
> the short sparks for a standard watts per foot of spark rating?   Is this
> important enough to pursue?
>     John Couture


Because of the complexity of the processes, all I can offer is some
educated speculations:

I'm personally convinced that extra-long sparks are ultimately due to
the how successive streamer discharges form and grow, and is virtually
independent of the coil once you've set up the appropriate initial
conditions. I run off a static/vacuum gap system. My primary energy per
bang is very consistent (within 5% for gap firing voltage, or about 10%
in Joules/bang). Numerous scope measurements have also convinced me
that, from a secondary:toroid energy standpoint, each "bang" is
virtually independent of the previous one. I also observe those rare
long sparks. However, I don't believe that these occurences have
anything to do with extra energy being somehow available at the output

Under the appropriate conditions, the path and length of a given
streamer is strongly influenced by the streamer(s) which preceded it. If
you repetitively hammer away at the surrounding air with successive
bangs at a fast enough rate, thermal cooldown and ionic recombination
don't completely remove all traces of the previous streamer path. This
is particularly true at the "root" of the streamer since the current and
thermal heating effects tend to be greates at this point. In effect, the
next bang is "assisted" from the weakenned path of left over hot and
partially ionized air left over from the previous streamer. This lets
the next bang reignite a portion of the previous "weakenned" channel.
Slow the bang-to-bang rate down too much, and you merely get a series of
single  short, sparks. Increase the break rate sufficiently, and barring
too much disruption of the path, each successive streamer will "build"
upon the path of it's predecessor, until energy balance has been

Lots of things can thwart this process before steamer growth extends to
completion (i.e., hitting maximum length for a given coil running at a
given power level). A slight breeze, a dash or turbulence, whatever...
we're dealing with chaotic processes after all. Because conditions have
to be "just right", MOST of the time it doesn't happen! Since we're
dealing with statistical processes, the only way to comparatively
measure relative performance is probably the one that Greg suggested
earlier - look at sparklength achieved for a commonly accepted % of the
time. Or maybe measuring the applause is truly a better measure after
all! :^)

Is a sparklength vs power metric worth pursuing? Probably - since it's
an approach to getting a commonly accepted figure of merit which can be
used to compare coil performance, and "wallplug" input power IS
something that can be measured. 

Gaseous coiling to you!

-- Bert H --