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Re: Streamer growth and filming it all

Hi Jeff, Jim, Terry, John, all,

A few comments in general first.  What I would like to
see is how exactly streamers (and/or arcs) are formed.
A few questions that pop up right away are:

a.) How exactly do they form. Do they form nm for nm or
     does the initial streamer "lash out" a few inches and grow
     the rest of the length?

b.) Why do they stop growing. Is it really *just* a matter of
     temperature. In other words, does the ion channel simply
     cool off too fast?

c.) Using two coils, how are streamers attracted to each other?
     The point where these two connect must get pretty hot. Why
     donīt (or do they?) branch out from here?

d.) What is it with the Banjo effect? Is it really just a matter of
     the surrounding, heated air, which drives the sparks into
     this form. If so, why do they go up and down (i.e. the banjo
     form). I would expect, sooner or later the air is hot enough
     to just move the streamers upward, similar to a Jacobīs
     Ladder, until the rip off.

e.) How (if it) does the ion channel change, once the streamer
     hits something grounded (i.e. turns into an arc)? I think an
     infrared film would help as one could analyze the spark
     and ion channel temperature.

f. ) Following d & e: I would think the banjo effect would be more
     pronounced once an arc forms (more current=> higher flame
     temperature), yet my coil seems to form more "banjos" when
     it is simply "streaming" into thin air.

g.) Why and how do streamers branch out. Is it really the same
     streamer or is it just an optical illusion, (i.e. not really the
     same streamer), because our eyes arenīt fast enough to
     detect this.

h.) High speed filming of the RSG, might also tell us something.

I am sure there are many more questions, which could be asked
about the how and why of TC sparks. More comments interspersed
below.

> Original Poster: "Jeff W. Parisse" <jparisse-at-teslacoil-dot-com>
> Well... I've got a bunch of industry contacts that I could call about
> such a project. I'll see what I can do...

Great. Keep us updated on any results you discover.

Original Poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
>They're not hideously expensive to rent (several hundred
>$/day), but the film stock costs eat you alive..  Figure $1
>/foot for rawstock and processing, and at 12 frames per
>foot, it adds up fast.

Over here, you CANīT get your hands on such a camera,
unless you are a professional. Iīm sure there are
companies who would rent you a camera AND a crew for
bags of money.... ;o( Of course, I hadnīt thought of the
film costs. This really would a reason to use an electronic
camera.

>As you can imagine synchronizing with the spark
>development might be a challenge.

Do you really mean *synchronizing* the two or do you
mean *starting* the camera at the right moment. Clearly
you will need to start the camera just a "nanosecond"
before you start the TC,  but why would you need to
*phase* camera and spark?


Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>Hi,
>The new Olympus video system (the fastest) can do
>8000 frames/sec.
>What I must wonder is if 8000 FPS is fast enough?
> My coil fires every 8333uS and has a burst duration
>of 334uS (~82kHz). In that time, there are about 50
>High voltage peaks in the burst each lasting about 6uS.
>A frame rate of 8000 with 1/80000 shutter speed will
>capture a 12.6uS bit every 126uS with a frame
>resolution of about 100x100 pixels.  So it would be a
> fuzzy fleeting view at best.  Of course the hot streamers
>channels should be much more visible

One reason AGAINST the electronic camera: Itīs
electronic ;o). You would have to be sure that it is
within a well shielded enclosure to prevent EMF, AM/FM
noise from false triggering the camera and "knocking
out" the CCD. Also, you would need to protect it from
getting hit from any sparks. A mechanical camera is
pretty much immune to these things. Also a big coil
(more power and lower FRes) would help out as it
gives off more light and the lower Fres is, the more
time you have to take the pictures. Also as Jim pointed
out, 8000fps might not catch the SAME streamer. Maybe
a single shot or a very low bpsīd setup would help during
filming. While I am an amateur photograph, who knows
more than just how to click the "fire" button on a camera,
but this is getting into realms probably best left to the
pros of HSP, which (I am sure) could answer these kind
of questions with ease. After all thatīs what they get paid
for ;o)). Guys like Jeff P. and Bill W. have a wide range
of coils (and operating possibilities). One of these coils
should be able (I hope) to "fill the bill" successfully.

>but I wonder if they would differ much from a regular
>video camera or simply obscure much of the neat stuff?

See above for ideas, which canīt be caught with a normal
film camera. Of course the whole thing will probably *look*
less spectacular, but then calculating Medhurst and
disproving the 1/4 wave theory is also less exciting than
actually watching sparks fly, but it does give us better
insight into what is going on in a TC ;o)


Original Poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
>Bazelyan and Raizer, "Spark Discharge", has a number
>of streak camera photos of developing HV sparks (1
>MV+). They might have used an image intensifier (i.e.
>night vision goggles), or an electronic streak camera
>(fastest of fast).

Hmm, the idea of using an image intensifier hasnīt crossed
my mind. Wouldnīt it blur a fast acting subject, like a
spark discharge is?

Original Poster: John Williams <jwilliams-at-edm-dot-net>
>I think the real problem you would run into using a high
>speed camera with a tesla coil is the sensitivity of the
>film or CCD, depending on if it's film or electronic.
>Those half a million frame per second film cameras are
>very light thirsty critters. So you'd need not only a fast
>camera, but one that has a really good film speed, or
>the equivalent.
>The high speed photography set ups I've seen are
>either in broad daylight or under enough tungsten light
>to soften a lead block.
>Tesla coil streamers aren't very bright.

True, but sparks are self illuminating. Most HSP objects
donīt give off there own light, which results in the need
for bright lights. A bullet shot from a gun, needs to
encounter so much light, that it reflects enough for the
camera to catch it. Not something your average flashlight
will accomplish. If you use a "film" camera (no electronics)
you can actually adjust the speed of the film AFTER you
have taken the pictures (special developing process). This
will increase the graininess of the film, but as we are not
taking pictures of a *complex* subject (like a person), this
is of little importance.

Coiler greets from Germany,
Reinhard