Re: Streamers

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

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

Note: copy also forwarded to the Tesla List...

Hi Gary,

Just a quick note before I head to work...
It's the average lifetime of _free electrons_ that's only about 11 nSec
- positive and negative ions can persist for many orders of magnitude
longer (milliseconds or longer). The point I was making was that it's
really only the free electrons that do the "dirty work" in the avalanche
breakdown, streamer, and leader processes, not any of the residual ions
that happen to be lingering around in the same vicinity. 

Re: ion cloud around the coil & capacitance:
In an operating coil, we're likely seeing the effect of displacement
currents via leaders and streamers into the region around the toroid.
This exchange of charge between the topload and surrounding region looks
and behaves like an additional capacitance (since charge can flow into,
and back out of, this region via the streamers and the main leader). The
additional "capacitance" lowers the secondary system's resonant
frequency. BTW, hot leaders aren't even necessary - once we start
getting streamers (the dim, diffuse precursor discharges), we'll start
getting significant charge exchanges to/from the surrounding regions and
begin seeing higher "effective" capacitance on the topload and frequency
shifting. 

If you very quickly powered down the system and instrumented it, you
would not see the additional capacitance since the output terminal
voltage would now be too low to support the streamer mechanisms behind
it... i.e., you would not see the added capacitance of the "ion cloud"
even though the ions were still there.

Best regards,

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



Tesla list wrote:
> 
> Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Gary.Lau-at-compaq-dot-com>
> 
> Hi Bert:
> 
> If the average lifetime of ions at STP is only 11 nsec, that calls into
> question the widely held belief that an "ion cloud" surrounding the top
> load will lower the resonant frequency to something less than its
> un-powered value.  If such a cloud exists, it would have to persist between
> bangs to alter the frequency.  Any further thoughts to reconcile this?
> 
> Regards, Gary Lau
> MA, USA
> 
> Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <bert.hickman-at-aquila-dot-net>
> 
> Dave and all,
> 
> I still suspect the main reason why leaders follow the previous channel
> from bang to bang is lower air density and not the presence of residual
> ions. The reason? Although longer lived positive and negative ions can
> indeed persist from one bang to the next, their presence does not
> directly contribute to the spark breakdown process on the next bang.
> 
> Avalanche breakdown initially requires free electrons, accelerated by an
> E-field, colliding with air molecules, to create an increasing cascading
> shower of free electrons. For the avalanche to proceed, the rate of free
> electron creation must exceed the rate of electron loss through
> attachment (to oxygen or water vapor molecules to form negative ions).
> Electron attachment occurs very quickly in air. Any free electrons
> created during the previous bang are long gone by the time of the next
> bang, having been captured by electronegative gases in the air since the
> average "free" electron life in air at STP is only about 11 nSec.
> 
> It is possible to "detach" some free electrons from negative ions via
> thermal collisions with other molecules. This process requires fairly
> high temperatures (>1,000 K), but is it possible that detachment
> provides some free electrons. It's likely more fundamentally that the
> spark channel used by the previous leader leaves behind a "tube" of
> significantly less dense (lower pressure) air which has not had the
> opportunity to dissipate into the cooler surrounding air. Within this
> lower density tube, the mean free path of new seed electrons (from
> cosmic ray, background radiation, or electron detachment) is longer,
> allowing the electrons to gain more kinetic energy from the E-Field
> between collisions, increasing the probability of ionizing collisions
> and avalanche multiplication. In this manner, the hotter "echo" of the
> previous spark channel most likely becomes the preferred region for
> avalanche breakdown during the NEXT bang.
> 
> The presence of residual ions in the region may be mostly of scientific
> interest, since these ions don't appear to have as much of a role in
> avalanche breakdown during a subsequent bang as the lower air
> pressure.
> 
> Best regards,
> 
> -- Bert --
> --
> Bert Hickman
> Stoneridge Engineering
> Email:    bert.hickman-at-aquila-dot-net
> Web Site: http://www.teslamania-dot-com