Re: A Puzzle
From: Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: bert.hickman-at-aquila-dot-com
Sent: Sunday, September 07, 1997 2:45 AM
To: Tesla List
Subject: Re: A Puzzle
Tesla List wrote:
> From: Richard Wayne Wall[SMTP:rwall-at-ix-dot-netcom-dot-com]
> Sent: Friday, September 05, 1997 3:56 PM
> To: Tesla List
> Subject: Re: A Puzzle
> Bert wrote:
> "A TC at its's first voltage peak may have NO current flowing into the
> toroid from the resonator."
> Excellent! Now, a little progress is being made. Parenthetically, NO
> current flows with subsequent voltage peaks either. The top
> termination is charged only with electrostatic energy by these peak
> voltages. These quarter wave resonate coils are hybrid electrical
> translators. They convert EM energy to ES energy. And, only
> electrostatic electrical energy charges the top termination. It is
> repetitive intense electrostatic fields that successively ionize gases
> in the spark channel. Contrary to popular opinion, "current levels
> required to support streamer growth are in the multi-ampere range" are
> not required to form the ionization channel. In fact, current, per se,
> does not cause ionization. This is an outmoded EM concept. Ionization
> of ambient gases around a TC is due to electrostatic energy.
I think we have a semantic problem here. Even initial avalanche
processes require current "flow" from the HV terminal to the surrounding
air, first in microamps (ala Trichel pulses perhaps), then milliamps
(multiple/cascading avalanches), and then amperes/multiple amperes as
spark breakdown <rapidly> progresses. The driving force for initial
avalanche multiplication is unquestionably electrostatic (at least for
the frequencies used in Tesla Coils). You are correct - current, per
se, does not cause initial ionization - movement/collisions of free
electrons with gas molecules under the influence of high electrostatic
However, increasing higher levels of current must be supplied from the
HV terminal in order to progress from initial corona, streamer
propagation, and (if the path is completed) power arc. If we stop the
process just short of a power arc, we've "limited" the current to a
lower value than for a power arc, but it's still very substantial. It
takes a lot of energy to blast a highly ionized conductive channel into
the air. DURING this process electrostatic energy is very rapidly
converted to ionized particles, excited/metastble particles, heat light,
EM radiation, and acoustic energy in the newly formed streamer. The
vehicle for this energy transfer process is a high current pulse flowing
from the terminal to the streamer root. The snap you hear is the shock
wave of the new path's creation or extension. And the resulting current
pulse is not very much different than that seen during a critically
damped capacitor discharge.
> As others on the list have pointed out, there are environmental factors
> outside and adjacent to the TC which influence spark formation. These
> factors regulate formation of the ion channel. Electrostatic
> ionization of air molecules produces energetic charged particles and
> electrons which constitute the ion cloud. Once formed, these charged
> particles may move under the influence of electrostatic fields.
> Current is produced only by movement of charged mass particles. This
> is a very important EM concept. These currents are usually local and
> are in response to movement of charged masses due to local
> electrostatic gradients.
I completely agree.
> It's a mistake to believe these ion induced
> currents are constantly moving back and forth and exchanged with the
If I've got a streamer discharge, current IS flowing between the top
terminal and the surrouding air, and represents a path of energy loss
from the resonator-toroid pair. While the current flow can be either
way, the energy flow (at least due to streamer current) is only one way
- out of the resonator:toroid system and to the surrounding air.
> Nor, do these secondary currents in the spark channel beget
> ionization and formation of the discharge channel.
I strongly disagree. Once we've formed a streamer, we've created a
fairly conductive path which extends and locally distorts the electric
field of the HV terminal, in effect projecting it out into the space
charge region surrounding the terminal. Recombination, diffusion,
convective cooling, and radiation are all conspiring to eliminate this
channel. There's ample empirical evidence that it takes a heavy spike of
current to initiate a streamer or extend it. In the case of TC's, it
takes high current to reignite an old channel in subsequent bangs. The
light bulb experiment gives strong evidence for high current levels.
There's also indirect evidence in the improved performance when using
larger toroids (larger lumped C), and larger resonators (larger
distribued C): hotter and longer streamers.
I will agree that the distorted high voltage fields created between the
streamer tips and space charge do the "dirty work" of ionizing the air
in advance of the streamer. However, in order to extend a streamer, we
must also supply a large enough "slug" of current through the conductive
portion to ohmically reheat the existing channel, re-ionizing it
thermally. If we can supply enough current, some energy is left over to
ionize an additional path length, extending the streamer. It takes
voltage AND current to do it this. Reduce the current, and you slow
down/stop streamer growth. Collapse the driving voltage and you stop the
There's over 50+ years of experimental evidence confirming both initial
Townsend AND Streamer propagation mechanisms in long spark formation.
Are you saying that this is an outmoded EM concept?
-- Bert --