See DAVE'S RESEARCH LAB,
http://lynx.neu.edu/home/httpd/d/dlima/davelab.htm

Date: Sun, 13 Jul 1996
From: "Lima, David" <dlima@analogic.com>
Reply to: usa-tesla@usa.net
Subject: Plasma Junky


1. Globes require either rarefied atmosphere (air) or any noble gas or
combination thereof. i.e Helium, Argon, Krypton.... Different
combinations produce different colours. Eye of the Storm is rumoured
to use Helium and Neon.

2. A source of Helium is your local party store. They sell disposable
canisters for filling party balloons.  However the quality of this helium
may not be suitable for globes. Experimentation is required. 

2.5 Carbon Dioxide seems to work too (color is white)

3. A source of globes is your local lighting store. I have ordered 14 inch
clear globes from my local dealer.  I can get an 18 incher too. Your local
Home Depot will have some globes up to about 9 inches. 

4. The globes need to be evacuated to about 1-2 torr. However the rumour
persists that commercial globes (Eye of the Storm)  are at low vacuum and
a secret mixture of noble gases allows this. I have created plasma at 15
inches of mercury in rarefied helium. Helium seems to increase the
pressure at which plasma will happen. 

5. There is a 'Plasma God' out there somewhere named Bill Parker who has   
all the answers.

6. Don't bother using a hand vacuum pump unless you want carpal-tunnel
syndrome and a nifty wrist sling. It takes a few thousand pumps to get the
globe down to the right vacuum. The mechanical action of this pump makes
it very hard to go below 5 torrs. An oil based vacuum pump does the job in
seconds. You'll have to make a few calls to vacuum engineering companies
in your area to find one. Play the 'starving student' and you'll get one
for about $200-250. These pumps retain their value. 


7. I am fortunate enough to have an Eye of the Storm to experiment with. 
In my quest to recreate quality plasma, I have found that power supply is
not the critical factor in plasma quality. Connecting my common 'flyback'
(you know, the one with the two 3055's) supply to the Eye of the Storm,
the plasma was identical to the 'Storms own supply.  BTW, the 'Storm uses
an astable configured 555 timer driving a flyback.  The HV output is
considerably small, a 1/4 inch arc can be drawn. 

8. You may notice that most professional globes have their center terminal
encased in glass. This is to prevent electrical migration.  I have
experimented with this in the lab, hollowing out small round GE vanity
bulbs and carefully stuffing a Chore-Boy copper scrub pad inside. I coated
the inside of the bulb with a conductive silver paint beforehand. It
looked really nice but I think an uncoated bulb with the Chore-Boy inside
looks even better. Performance wasn't effected either way. The inside of
this assembly in professional globes is not evacuated. This makes it a
chore, boy, to seal everything airtight (bulb to standoff, standoff to
base with HV lead inside) 

1. Safety glasses must be worn ALWAYS.

2. Do not use Propane or Hydrogen unless you dislike your face.

3. Implosion is a consideration, a globe used must be able to withstand   
   the vacuum applied. Even though my globes are thick wall, I still keep
   a plexi-glass barrier between me and the experiment.

4. See rule 1

My nagging questions are:

1. Is purity an issue? i.e. Is my pump favouring certain molecules when
   evacuating thus leaving 'junk' in the globe -effecting plasma?

2. Do I need a diffusion pump and cryo-trap to create a hard vacuum
   before backfilling?

2. Is outgassing an issue? Do my vinyl tubes hinder me?

3. Where does one get neon? Is it expensive?

I appreciate your comments, criticisms, knowledge. I have collected
several mag articles containing plasma-plans, I can post the names
and dates if there is interest.

Dave
dlima@analogic.com

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