Re: Useless questions

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

No need to do this... The question of the physical state of the streamers
has been answered at great length in the published literature on sparks and
arcs.

As for IR film, yes, it IS available, both black and white and false color,
but, be aware that this isn't really for thermal imaging (although the high
speed black and white IR film is slightly sensitive to thermal IR).

In any case, the gas in a spark is at a high enough temperature that the
blackbody emission peak is well up into the visible.

Now, if you had a high speed spectroscope, you might be able to measure the
temperature of the spark channel between leader propagation bursts (i.e. as
the RF changes polarity). You might be able to get useful data with a set
of fast detectors and some color filters that span a suitable range of
wavelengths, just considering the air as a big blackbody radiator.  The
detectors would need response times on the order of 10 nanoseconds (i.e.
1/100-1/1000 RF period), but that's not a real challenge these days.. Most
photodiodes are this fast.  You've got a pretty bright source to look at.
You'd take the intensity you record in each band, and fit a blackbody curve
to it, using temperature and overall intensity as the variables.  Two
sensors could theoretically do it, since you've got only two unknowns, but
I suspect that four or five would do a better job.  The filters wouldn't
have to be all that wonderful (wratten gels would work, as would standard
dichroics).  Calibration migh!
 t be a
challenge: Where are you going to find blackbody sources at a series of
temperatures.. unless you build them. You might be able to use things like
tungsten lamps at various filament temperatures (working against a standard
color temperature meter, for instance).


I'd have to think about how you could do that.. you might not need to do an
absolute calibration.

You'd be looking at the bulk of all the sparks at once (on the assumption
that they'll all be doing pretty much the same thing), so you don't need
fancy focussing.

If you want to get real fancy.. you need hi resolution spectroscopy, and
you look for the broadening of the spectral lines due to temperature.



Tesla list wrote:
> 
> Original poster: "Malcolm Watts by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
> 
> Hi John,
> 
> On 21 Feb 2002, at 8:11, Tesla list wrote:
> 
> > Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <Mildewhaus-at-aol-dot-com>
> >
> > Hi guys! OK a few questions,What state of being is  a streamer when it
comes
> > off a T.C.?Does it have a temperature,I mean we all know what heat an arc
> can
> > create when it connects with something,but does it have it's own temp.?
> >                                                              john in nyc
> 
> Yes. An infrared pic of some streamers would tell the story.Has
> anyone with suitable gear done this? Can one buy 35mm IR film?
> 
> Regards,
> Malcolm
>