[TCML] Rectifying A Tesla Coil: Point-Plane Collector Experiments -works!

[Bert Hickman]

Hi Jeff and all,

It sounds like you may be seeing the fainter portions of "streamer 
corona" or "burst corona" discharges. These are countless microscopic 
filamentary low temperature streamer discharges that actually do the 
work of transferring charge into and from the surrounding air. Streamer 
corona discharges are the precursors to hot leader discharges. They also 
feed current into propagating positive and negative leaders to support 
growth and current for leader channel heating. Because they inject 
"space charges" into the surrounding air, they can cause interesting 
electrostatic effects at a significant distance from the HV terminal.

The brighter portions of corona streamers commonly appear as a bluish 
haze extending outward from leader tips. However, they can also appear 
directly on the surface of electrodes if leaders have not yet formed. To 
the dark-adapted eye their true (i.e., much longer) length can be 
observed. Because your eye can't see colors at low light levels, they'll 
look a ghostly white or gray color, but their actual color is 
bluish-purple (from excited nitrogen and oxygen molecules). This can be 
confirmed by taking longer camera exposures.

Anyone can see these as long as they can (safely!) operate their coil in 
a completely darkened room. Light from the spark gap must be completely 
shielded from view. The spark gap(s) should be closed down so that the 
coil is operating just below the point where leaders begin to form 
("breakout"). You'll need to allow your eyes to become fully 
dark-adapted. If you then fire up the coil, you should be able to see 
the topload surrounded by countless faint white discharges that 
continually change and pulsate in sync with changing coil voltage. They 
can often be seen best by looking at them indirectly. For others who 
have not seen these unique discharges, try it and you'll gain a new 
perspective about what's REALLY going on around your topload... :^)

Bert

Jeff Behary wrote:
> 
> Bert,
> 
> The information you posted below is wonderful!
> 
> A comment/question concerning this great paragraph:
> 
>> In a positive discharge (where the discharge begins propagating
>> from the more anode to the cathode), the leading edge of the
>> propagating positive leader, and the leader channel that connects
>> back to the anode, are bright and filamentary/spark-like. However,
>> the streamer region ahead of the leader tip is diffuse, dimmer
>> region that looks like a directed cone of corona pointing towards
>> the cathode. If the HV source does not have sufficient energy to
>> completely bridge the gap, or if the HV pulse is of very short
>> duration, you get a miniature Tesla Coil-like air discharge: a
>> bright length of spark that only goes part way across the gap, with
>> a diffuse glow between the sharply defined leader tip and the
>> cathode electrode.
>> 
> 
> First off, one thing you mentioned in that post hits the nail right
> on the head for what I'm seeing here most of the time, and "how" I'm
> seeing it.
> 
> Low power levels seem critical as you mention, and a spark gap with
> capacity (6" plates or even a normal spark gap with a .001 condenser
> in parallel with it...) - gap set just at the very maximum distance,
> the capacity seems to help this to happen - whether its mechanically 
> part of the gap or externally with a small cap in parallel - the
> discharges do speak volumes, but in my case I don't know what
> language they're speaking!  Luckily you are a good translator!
> 
> In the case of "Phantom Streamers", which closely resemble Negative
> discharges in Static Machines, I noticed a few things about them,
> maybe you can elaborate...
> 
> They seem to appear in some coils at the ends of sparks generated
> from the topload - I've seen as an example branching positive-like
> sparks a foot long where the conical diffusion will extend from the
> very tips of the branches outward - sometimes from a needle thin
> portion out to a cone 6" or 8" in diameter or more at the base.  Its
> a fascinating display to say the least.
> 
> (As an example, I think for 100 watts of power one tank circuit used
> a .2 mfd cap, a simple 6" diameter spark gap with 1.25" diameter
> tungsten faces, gap set to discharge once or twice a second, approx
> 1000 volt transformer, with a 5" diameter cylindrical Tesla Coil
> normally giving sparks 3-4 feet long at full power)
> 
> In the case of other coils though, I've seen them with nearly the
> opposite conditions - high voltage tank circuits charging small caps
> and discharging across gaps only the fraction of the maximum voltage
> - for example, a single Pancake Coil, 9" diameter, as little as 200
> turns of wire, 10kV OBIT, .01 mfd cap, 1/8" diameter 2 or 3 series
> spark gap (total gap less than .06")  In this case, the 2" ball
> terminal of the coil showed no "roots" or sparking to speak of, but
> phantoms nearly 12" long - the same "diffused" phenomenon of the
> above coil, but diffusing in all directions from the same sphere, 360
> degrees...it would produce a 2-3" spark if you brought a metal rod to
> the ball, but little to any brush or other sparking effects without
> some external influence approaching.  Even with a metal rod drawing
> sparks, the phantoms still persist in all directions regardless...
> 
> Now, in the later case changing the condenser capacity has little
> effect in the appearance of the "phantoms".  Likely because the cap
> value is small?  In the former case, changing the capacity would make
> the "phantoms" start to have some shape, maybe slight branching or
> wavy-ness, where before they were pretty much straight faint
> lines...?
> 
> Also, in both cases, the phantoms appear to strobe inward or outward.
> At first sight I thought they were stobing outward, but it seems to
> make more sense that they could be strobing inward toward the
> terminals from the outside air...the cathode representing the free
> space around, as opposed to an actual metal terminal?  Maybe its as
> if there was a positive spark barely visible at the terminal, or
> simply not discharging from the terminal, and the negative diffusion
> is the only thing seen, ocurring to a much greater extent,  maybe 85%
> of the visible discharge?
> 
> A further question, the length of the Phantom streamers seen, and the
> presence of them felt is much different.  If you can see a phantom
> streamer for 6 - 12", you may feel strong electro-static effects
> present by them at a distance of 12" to even 2 feet or more when the
> conditions are right.  The hair on your arm will vibrate up and down
> at a similar rate that you see them strobing...  the effect is much
> stronger when you place your hand directly in the visible portion,
> but there is definately a very real portion not visible, or maybe too
> faint to see...?  I live in high humidity, it would really curious to
> try this somewhere in a dry climate...
> 
> Jeff
> 
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