Re: Florescent Foolishness

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Re: Florescent Foolishness
From: Tesla List <tesla-at-stic-dot-net>
Date: Fri, 28 Nov 1997 22:34:55 -0600
Approved: tesla-at-stic-dot-net

From: 	Thomas McGahee[SMTP:tom_mcgahee-at-sigmais-dot-com]
Sent: 	Thursday, November 27, 1997 2:31 PM
To: 	Tesla List
Cc: 	ghunter-at-mail.enterprise-dot-net
Subject: 	Re: Florescent Foolishness


> From: 	ghunter-at-mail.enterprise-dot-net[SMTP:ghunter-at-mail.enterprise-dot-net]
> Sent: 	Wednesday, November 26, 1997 4:48 PM
> To: 	Tesla List
> Subject: 	Florescent Foolishness
> 
> I've been probing the secrets of the universe with a burned out 
> florescent tube and a Tesla coil.  Actually, I've just been showing 
> off for the kids.  My latest plaything is a "soft white" tube about 
> 4' long and about 1" in diameter.  I've taped it to the end of a wooden 
> yardstick.
> 
> -The Dark Spot-
> 
> When the tube is within 5 or 6 feet of my TC, it glows like mad. 
> When I allow a spark to actually jump to it, it glows even brighter. 
> Big deal.  But when I have the tube near the secondary but just out
> of reach of sparks, I've noticed a dark spot.  The dark spot is
> about 4" long and coresponds to the point on the tube that is
> closest to the secondary.  The rest of the tube, before and after
> the dark spot, glows brightly.  As I move the tube away from the
> secondary, the dark spot becomes less distinct.  Hmmm...
> 

Interesting. I do know that objects in the way can distort the
field. Perhaps the metal end cap and internal electrodes are
influencing the light . Can you get the dark spot to be anywhere
other than near the end? 

Recall that it is UV that is exciting the phosphors, and this
UV comes from the plasma inside the tube. Anything that distorts
the plasma will affect light intensity also. Perhaps the internal
electrodes are producing streamers that reach out a ways before
striking the phosphors. Areas located before the place where
the streamers settle down would appear dark. Just a conjecture.

> -The Orange Spot-
> 
> Whether in direct contact with a spark or not, the TC excited tube
> glows the same color as it once did in a light fixture--daylight
> white. However, if I allow a spark to jump to the glass envelope of
> the tube instead of the AC prongs, It glows bright orange at the
> point where the spark touches it.  The orange spot is about 4" long. 
> The rest of the tube glows the normal blue-white color.  How does it
> make orange light around the site of spark contact?
> 

What you are seeing is sodium glow. When you hit the glass some of
the sodium in the glass (or perhaps some other element also) is
brought to life in the form of a small streamer. Do this for more
than a few seconds and the glass wall will develop a pinhole.
There is a LOT of heat involved here!

> -Field Shape-
> 
> I can roughly trace the RF field shape around the secondary with
> the tube by moving it around like a wand.  With a toroid terminal on
> top, the brightest glow occurs when the tube is on either side of
> the secondary.  Straight out from the middle of the secondary
> winding is most intense of all.  Directly above the toroid is the
> weakest glow (nearly dark).  The excitation field seems to be toroidal,
> surrounding the secondary like a fat donut.  With a sphere top
> terminal, the RF field seems much more isotropic, with respectable
> glow even directly above the secondary.  I was vaguely aware of the
> shielding properties of toroids, but I didn't expect to
> see such a drastic difference in RF field shape.
> 

Excellent experiment. Being able to visualize the e-field shape
will help you gain a new appreciation for how different shaped
toploads affect e-field shape.


> Having way too much TC fun in cold, muddy East Anglia,
> 
> Greg
> 

Hope these reflections help.
Fr. Tom McGahee
>