Supermagnet physics demos
Microwave oven experiments
THE SECRET TO MAKING
(Originally discovered by Ed Harris, 1995, 'usa-tesla' discussion group)
In the above videos, I used a Handheld Tesla Coil, "violet ray" style, $100 - $200
[ ONE MORE VIDEO TOO, SEE BELOW ]
If you can build an argon-filled discharge chamber, it allows you
to get many times the arc length of a standard air-discharge tesla coil.
In some high pressure plasma experiments, people have in the past
sometimes added helium gas to raise the working pressure of a plasma
discharge -even up to and beyond 15psi.
I have tested this idea recently with a homemade plasma sphere run
from a small 15kHz flyback supply. I can obtain 15psi discharges in
helium with some small partial pressure of air(or other gas) with rather
small input from the flyback (est~5Kv).
So yes! You can run a plasma sphere at atmospheric pressure with
helium + small dopant gas.
Now if I can only find some reasonably non-toxic gas which produces nice
Well- some guy remarked previously about using a plastic bag or the like
as a atmospheric pressure plasma sphere. So I accepted the challenge :)
I was able to make a plasma sphere using a rubber balloon which was very well
purged of air (air partial pressure approximately 1/1000 atmospheric
pressure) and filled with helium. Powered by a 10kV flyback circuit, the
arcs inside the balloon could be seen to extend from the central electrode
all the way out to the rubber (about 5 inches).
Hope some others try this
It's rather neat!
Date: Sat, 12 Aug 1995 11:51:29 -0700 (PDT)
From: William Beaty <>
To: list physics teaching
Subject: Rubber ballon plasma sphere
Wow, at one atmosphere!!! How about sealing a rubber glove to a largish
balloon, stick a hand inside, and let plasma play on your fingers? Got a
good camera? Should be good for an Omni magazine cover!
And how about an entire room with a Helium or Argon atmosphere? Such
things must exist somewhere. If a *glassless* plasma globe unit was taken
into one, wouldn't the plasma filaments extend right out into the air?
And what would happen to colors and plasma-filament structure when small
bags of various 1-atm gases were released in such a room? Or if a
handheld unit was moved through various gas layers in a glovebox chamber?
Or hold your breath, go inside, touch a larger tesla coil terminal, and
see if humans can serve as plasma globe electrodes.
If the leads to a neon-sign transformer were connected across a large
volume of Helium, would a "beam" of red plasma leap between them? If so,
what would happen if you poked at the plasma beam with a glass rod, or
tried to cut it with a glass sheet? Could a plasma-globe power supply and
a UV laser be used to create a *real* Star-Wars movie lightsaber effect
inside a large He-filled chamber? Mind boggling.
The physics demonstrators sure are going to have fun with this one!
- Bill Beaty,
Shoot arcs from fingertips!
MPEG 1.5M bill b. 9/2005
MORE STUFF from billb
Ed Harris discovered that pure Argon works even better than Helium, giving
bright white snakelike discharges like those seen in various Plasma
I experimented with this and found that Nitrogen contamination (air)
wrecks the effect. Therefor, if you try an Argon-Balloon Plasma Globe,
you need to flush all the air out first. Do this by squeezing out the
balloon, filling it part way with Argon, allowing the argon to all
'squeal' out, then fill the balloon with Argon all the way. The argon in
the balloon can generate long white discharges, but if you wait for a few
hours, the nitrogen will get in through the rubber walls and spoil the
If a metal rod or coathanger wire is pushed up into the balloon
and the balloon neck is sealed with cable ties, you've got yourself a
quick and dirty non-glass plasma globe! It only lasts a few hours
before air diffuses through the rubber and poisons the effect again.
I messed with the argon gas in a large plexiglas cube. Argon is a bit
heavier than air. If you fill a box slowly with argon from the bottom, and
provide an exit hole at the top, the box will fill up slowly, and you can
obtain long, snakelike discharges near the bottom of the box as the
slightly-heavy argon drives the air upwards. The argon hose MUST have a
diffuser such as an aquarium air-stone, or just tie a piece of paper towel
around the end of the hose. The same tesla coil terminal that only gives
inch-long discharges in air will give foot-long discharges in Argon.
Pretty cool to move the tesla coil terminal wire to different places in
the box and watch the discharge grow from a dim, purple air corona to
blazing white argon snakes many inches long.
What would happen if we had a box with layers of helium, neon, argon, etc.
inside? As the electrode was pushed through various layers, the plasma
filaments would take on totally different color and length.
Trap a layer of argon between nitrogen above, and something heavy (maybe
CO2 or sulfur hexaflouride) below. Then a wire could connect to that
argon layer, and a blazing disk of plasma would flow out into the narrow
argon layer. (or does SF4 gas make long plasma streamers too?)
If you build a plexiglas box, be aware that the fumes from plexiglas
solvent or from silicone caulk will pollute your argon. Let your box dry
for a couple of days before working with the argon, maybe attach a tiny
fan to holes in the box to drive out the outgassing glue fumes.
Oh, the industrial grade argon obtainable in welding tanks (about 70$
recharge) works just great. An Argon+CO2 mix didn't work, CO2 apparently
also poisons the long-sparks effect.
Plasma Globe links, magazine articles, etc.
I used a Handheld Tesla Coil, $130, #HS-10 from Edu. Inno. catalog, SEE
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