Re: How do I make a plasma cleaner ?

Dear David:
Your purpose is to graft amino molecules to a polymer surface.  This can be 
done in a plasma cleaner using ammonia gas.  For this process the plasma 
must be in a vacuum-tight chamber, operating at a pressure of about 1.0 
torr.  I recommend you think of a small piece of polymer so your chamber 
can be small-e.g. 3 inches diameter and 6 inches long.  The chamber can be 
made of pyrex glass or it can be metal, like aluminum, but it must be able 
to hold a vacuum.   The easiest kind of chamber to use is a small bell-jar 
designed for vacuum work.  

You will need a pipe connection going from a tank of ammonia (which is 
toxic and hazardous and 
which you must not work with without an adult guiding you).  A lecture bottle of 
ammonia is fine (This is a very small tank holding a small amount of gas under 
pressure).  The lecture bottle has a valve which opens to allow the gas to flow 
out.  There is a pipe connection on the bottle where you connect the pipe which 
runs from the lecture bottle to the plasma chamber.  The valve on the tank 
allows you to control the flow of ammonia into the chamber.  You must have a 
vacuumn pump connected to the chamber, which is used to pump the air out of the 
chamber and also to pump the ammonia out ot the chamber.  You will also need a 
vacuum gauge to measure the pressure in the chamber (Range 0-10 torr is 
good).  To make the plasma will require an electrode in the chamber, 
mounted on an insulator, to which you can make electrical contact through a 
vacuum feed through which has a wire sealed into a tube which is attached to 
the chamber wall. The wire passes into the vacuum chamber but the seal 
keeps the air out.  

Finally you will need a controllable power source to make the plasma.  The 
best choice will be a small RF generator capable of generating several 
thousand volts of radiofrequency power. (13.56 Megahertz is typical; 0-300 
watts range is enough power.) All of these parts can be obtained for 
perhaps $1,000, especially if you can find used ones.  It is difficult for 
me to give you more detailed information because I do not know your age, 
your grade, or your level of knowledge about this subject.  You should have 
a teacher who can work with you to assemble this apparatus.

It is possible to use a microwave oven to make this plasma but that will 
require special knowledge and I do not recommend it.  I would be very happy 
to give you more detailed information if you gave me more information about 
your knowledge and experience.  What grade are you in?

Sincerely,

R. Bersin
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