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I have worked my whole life in high voltage and pulse power and made
several TCs. Therefore, I am highly qualified to dispense wisdom in
such matters as this. I've seen this phenomenon many times, with TCs
and with Marx generators. Beginning of wisdom ---> I have no idea.
<--- end of wisdom. The brightness of an arc is proportional to the
current and to the gas pressure, which are both pretty constant along an
arc. I just looked at a whole bunch of TC arcs that terminate in the
air, and did not see any of these bright sections. I think they only
appear in arcs to ground or some other low impedance point. The bright
sections are usually more or less in the middle of the arc channels.
It might be enlightening to take a pix of this phenomenon with a plastic
diffraction grating. You could get an idea of the temperature of the
bright and dim regions from the relative brightness of different lines
and from the relative brightness of the lines vs the continuum. If you
photographed the arc in front of a black background such as flock paper,
maybe you would see dim discharges paralleling the dim section.
Another interesting question is, why are the transitions between the dim
and bright channel sections so abrupt? That's weird. Could it be some
kind of glow-arc transition? There must be some real physics here. I
think this is something worth investigation by the TC community. Let
the experiments be made.
---Carl
Reporter: "Mr. Roentgen, what did you think when you saw these
mysterious images?"
Roentgen: "I did not think, I investigated."
On 5/19/2015 5:14 AM, Jim Lux wrote:
On 5/19/15 3:09 AM, b alex pettit jr via Tesla wrote:
Hi All,
I have a low powered TC that can produce arcs in the 2" to 8"
range,secondary resonant freq 190 KHz.
On any power setting, if I use a conductive rod to attract arcs (
sparks ) and space itto get individual, non branching arcs, there is
surprisingly a consistent, repetitive pattern of brighter and darker
( fatter and thinner ) areas along its length.. Such as
-------=========----------===----------------------------------------
Anyone have any ideas why this may be so ? I would have expected
consistency,but there are arc segments with a brightness maybe 5
times the other portions.
What is the propagation velocity of an arc in air ?
This has been confirmed by others so it is not related to my 'visual
acuity'.
What you see as a single spark is actually a lot of sparks following
mostly the same paths. Not only is there a spark moving for each half
cycle of the RF (way faster than you can see), but there's also
multiple spark groups corresponding to the AC line voltage peaks.
When the sparks happen to align (or not) changes the apparent brightness.
If you see a picture of a TC operating in a small movement of air,
sometimes you see the different sparks (for AC line voltage cycles)
spread out in parallel.
the other thing affecting apparent brightness is whether the spark is
traveling exactly normal to the line of sight, or more aligned with
it. This is really obvious when you are looking at a spark coming
towards you: the spark segments that are exactly parallel to your
line of sight look like really bright dots. Most people who have been
in a "cage of death" faraday cage kind of situation have commented on
this. I've tried to take a picture of it, but not been very
successful: I think it's partly due to how the human visual system
works in real time.