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Re: [TCML] Arc intensity variations

Do you have an image or video showing this?

I don't think I have seen what you have talked about before. Here's example
of spark discharges from my small coil forming streamers in parallel from
what Jim mentioned. I don't see any of what you mentioned in photos from my
other coils of various sizes. See:


On Tue, May 19, 2015 at 10:15 AM, Carl Noggle <cn8@xxxxxxx> wrote:

> 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.
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