[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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



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

_________________________________________________________________ See
how Windows connects the people, information, and fun that are part
of your life. http://clk.atdmt.com/MRT/go/msnnkwxp1020093175mrt/direct/01/_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla



_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla