Re: Those rare, long sparks

From: 	Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: 	bert.hickman-at-aquila-dot-com
Sent: 	Sunday, July 27, 1997 12:40 AM
To: 	Tesla List
Subject: 	Re: Those rare, long sparks

Tesla List wrote:
> From:   richard hull[SMTP:rhull-at-richmond.infi-dot-net]
> Sent:   Wednesday, July 23, 1997 3:07 PM
> To:     tesla-at-pupman-dot-com
> Subject:        Those rare, long sparks
> All,
> Of the miriad of quantifiable and well understood non-linear processes, the
> many unquantifiable and little understood non-linear processes, the few
> unimagined and unkown non-linear processes involved in this cacophony of
> energy conversion and loss, we had a SINGULAR EVENT.  During this event a
> certain large number of non-linear processes involving, critical timings,
> phasings, magnetic collapses, electrostatic images, ionic bridging effects,
> etc., all summed at a single instant in time!  It is that simple.  It is
> un-repeatable outside of the laws of probabilty during another long run.
> Inspite of all these improbable events.  This singular result is what a plus
> ultra system is gauged by when old hands gather.
> We can certainly gauge coil performance by continuos drawn arcs, exactly as
> we gauge any commercial, for sale, product where real, continuous, stable,
> output is demanded.
> This reduces the system to a manufactured commodity.  Without magic moments.
> Data gathered with continous arc will let us engineer better continous arc
> systems, but will it engineer those magic moments?  No, I say.
>   Most of the magic comes from surroundings and mechanisms outside of the
> simple series resosant system. Any attempt to improve the continuous arcer
> might or might not result in better magic moments due to interactions beyond
> the closed continuous arcing system back upon that system when uncoupled
> from a drawn arc!
> How many of us use our coils as "ignition coil"-like demonstrators,
> mindlessly buzzing away with continuous drawn arcs?
> Richard Hull, TCBOR

Richard, John(s), and all,

And who says engineers aren't poets at heart? :^)

There's certainly a degree of randomness and chaotic processes going on
within the overall systems making up a classical Tesla Coil or Maggie.
However, I also suspect that the majority of the variability in
sparklength is more attributeable to breakdown, streamer path
reignition, and streamer propagation processes themselves. And much of
this is outside the direct control of the coiler, grizzled expert or
beginner alike. Turbulence, associated with the mixing of cooler
surrounding air and the very hot spark channel, can be clearly observed
in the writhing, almost lifelike appearance of the high-current streamer
root coming off the toroid. Contrast this with the almost unvarying
discharge that can often be observed off a spherical terminal, where the
upward heat flow results in reignition of most of the earlier vertical
channel path. 

There's little doubt that certain coils seem to perform much better than
others, whether the metric is spark length versus resonator length,
sparklength verus input power, or whatever. However, in most cases, the
key parameters is "sparklength". But sparklength to what...(?) and how
frequently? Fundamental to the idea of making quantitative measurement
is the concept that the ACT of measuring should MINIMALLY PERTURB that
which we wish to measure... Now repetitive high current strikes to
grounded objects clearly do NOT meet this criteria. 

Streamers dissipating into the air are a more natural mode of TC
operation, but these are tough to "measure" after the fact unless they
just barely connect to some object that can later be measured for
straight-line distance from the toroid. However, vertically-headed
streamers may tend to be artifically lengthenned by thermal heating from
the spark itself, and any external thermal sources may also tend to
artificially increase the length by introducing localized concentrations
of thermally-generated ions or conductive carbon particles - the lighted
candle for example in Bert Pool's excellent Maggie runs. 

So how could we arrive at a minimally-perturbing sparklength
measurement? Qualifying discharge lengths should probably be "nearly"
horizontal within, say, +/-30 degrees(?). The discharge should be to a
conductive object, but we may not necessarily want this object to be
connected to a "hard" ground. There should also be clear evidence that
the streamer has bridged the full distance - a brightenning of the spark
could be sufficient. 

A possible approach:
Suppose we use a small breakout bump on the toroid as a way to help
"steer" the streamers in a single direction. If the bump is properly
sized, the "root" of most streamers should originate here. Suppose we
make a group of targets, each consisting of a common 4 foot long
fluorescent light. We could wrap the top ends with a small "cap" of
aluminum foil, and leave the other end sitting in a couple of stacked 5
gallon LDPE buckets. If directly hit by a long streamer, a bulb should
brightly light from capacitively coupled current, but the discharge
current should be much less than if the bottom of the tube were hard
grounded. This would make for a group of inexpensive targets that would
allow for fairly accurate, minimally-perturbing measurements. With the
breakout bump, it would also allow us to measure the elusive extra-long
streamer that would, hopefully, connect to one of the fluorescents. Once
the key comparative measurements are made, the tubes can be put away,
the steering bump removed, and the awesome magic glory of an unfettered
coil again be appreciated.

A question:
To those running with synchronous gaps - Do you guys see occasional
extra-long streamers on your systems? Synchronous gap systems should be
much more consistent with respect to the BPS rate and energy per bang.
If you guys ALSO see rare long sparks, this would tend to lend more
credence that most of the randomness/chaos is actually coming from the
streamer generation process itself.

Safe coilin' to you!

-- Bert H --