Re: Lower secondary cself => better performance?

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>

Hi Boris,

My comments are interspersed below...

Tesla list wrote:
> 
> Original poster: "boris petkovic by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <petkovic7-at-yahoo-dot-com>
<SNIP>
> > (BTW, for those who
> > are very seriously interested in gaining a better
> > understanding of
> > streamer formation and propagation, undoubtedly one
> > of the most valuable
> > in-print publications on this topic is "Spark
> > Discharge" by E. M.
> > Bazelyan and Y. P Raizer (CRC Press, 1998, 320pp,
> > ISBN 0-8493-2868-3 -
> > $105 from Borders On-Line - cheap it is not...
> > superb it is...).
> ---
> Surely,this is a good book.
> But,most of the content deals with monopolar pulses
> (If this were ,for example, Marx bank list ..- no
> better literature at the moment-OK.)
> However,due to its' much complex voltage output
> waveform ,TCs' arcs formation and propagation
> phenomena are somewhat different  to be completely
> analized the same way  like in that book.
> ----

I fully agree, but unfortunately I've not been able to locate any recent
books that cover high voltage RF discharges in the context of what is
presently known for monopolar pulses or line frequency AC discharges.
While there are lots of books that cover RF and microwave discharges for
plasma processing, fusion research, etc., I have been unable to find any
that cover propagation of _long_ RF discharges. This may be because,
unlike lightning protection or power utility work, there's not much of a
practical "need" to understand long RF discharges. This could be an area
ripe for some true scientific research! 

You are also quite correct that TC's present a MUCH different
environment for streamer and leader propagation. The summary that I
presented really only covered a simple sequence of discharges as the
voltage climbed between initial breakout and the voltage peak upon
completion of the first primary-secondary energy transfer. I didn't
mention other interesting things, such as channel heating due to voltage
(and current) reversals - where charge can be pulled back OUT of the
surrounding region, and back through the arc channel, re-heating it and
keeping it "active", even if the negative-polarity streamer doesn't
actually propagate. Nor the effects of 2nd or 3rd notch quenching, where
there's some evidence that 2nd notch quenching may result in longer
sparks than first notch quenching. Nor the effects of channel reignition
and streamer lengthening as a function of BPS rate. It looks like
there's LOTS of work left for this century of coiling as well...  :^)  
> 
> > Under the right conditions, an initial streamer
> > transforms itself into a
> > high current channel, called a leader, which very
> > rapidly propagates to
> > a distance which is governed by the amount of charge
> > that is
> > _immediately_ available from the top terminal.
> ---
> Actually,a state of discharge called streamer
> propagates much faster than the state called leader.
> Bursts of corona streamers recorded in Mhz scope
> frames,show that their importance for TC is of as
> great significance as the formation of the leader
> itself.
> -----

I agree. Again there was a limit to the detail I could try to cover in a
reasonably sized post. There's no doubt that streamers are instrumental
in helping redistribute charge in relatively large regions around the
toroid, and they are (usually) the precursor to true leader formation.
However, unlike leaders, streamers leave the air cold and mostly
non-conductive. But they do help "pave the way" for subsequent leaders.
And, during propagation, the leader's remote head is literally
surrounded by streamers that help feed and redistribute charge into (or
out of) the region around the leader tip. Be it a step of the leader or
a streamer "flash", the effects are similar - bursts of charge that tend
to reduce toroid potential, eventually choking off further propagation.

> 
>  The
> > leader provides a
> > conductive path for charge to be injected from the
> > top terminal
> > into surrounding regions of lower potential in a
> > sudden surge of
> > [ampere-level] displacement current. Charge residing
> > in the internal
> > capacitance of the resonator does not significantly
> > impact the
> > length of this step. Even though the more correct
> > term for the streamers
> > we see is probably "leaders",
> ---
> Very short living  leaders ,yes.
> I assume that becouse of TC + - output shape these are
> the form of degenerated leaders.

I'm not sure. I've sometimes envisioned TC streamers as being similar in
appearance to arrested leaders (a leader that's made it partially across
the gap, and then the voltage is removed by externally short circuiting
the gap). Voltage reversals on the TC might be likened to a sequence of
arrested leaders (of both polarities) in rapid succession. A MUCH more
interesting situation than the "simple" monopolar case... :^)

> 
> A Leader moving to and fro with respect to the coil
> terminal.
> ---
<SNIP>
> 
>  Both conditions can be met (at least
> > for a while) in a
> > Tesla Coil with a properly sized topload.
> ----
> There,must  be somewhere  balans between 2 things for
> squzing out an optimum (the longest spark):
> between Size of the electrode,and the most apropriate
> output voltage for bottling the longest spark up.
> It wouldn't be suprising,for me, to get more than just
> one optimal solution for given power input.
> ---

There's certainly a possibility that there may be _many_ different ways
achieve "optimal" performance. The major challenge may simply be in
determining WHEN we have actually reached an optimal condition! Present
state of the art in TC theory appears to require that we compare spark
length versus input power for large numbers of coils and coil
configurations, looking for the attributes of the "best" performers.
TSSP may ultimately provide some insight to this over time... :^) 

<SNIP>

>  Recovery of top voltage and its further rise during
> ring up ,for TC case,depends on the moment in a chain
> of succesive
> discharges (high BPS rate),when potential is
> considered.Througout succesive bangs ,TC arcs
> propagate,thus adding more and more influence
> (additional capacity for example) by their presence
> and they are really "part of the system" as someone
> said before.
> These are the most complex phenomena in examining TC
> operation.
> It is better,and more interesting if you ask me to
> speak in terms of El. field and electrode surface and
> space El.field gradients.
> 
> Regards,
> Boris
<SNIP>

I fully agree.. and isn't that part of what makes the study of TC's so
fascinating! Thanks for the comments and the additional insights, Boris! 

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com