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Subject: Glow Discharge cleaning

Date: 11/29/01 at 12:48 AM
Posted by: Ken Hunter
E-mail: kb7h@onemain.com
Message Posted:

Hi...

I am attempting to build a chamber to evaporate aluminum onto a glass telescope mirror and have heard of "glow discharge cleaning" but have not found any good description of how it is done.

I imagine that once the chamber is closed, a preliminary pumpdown is started and at some point a high voltage is fed into the tank via a high voltage feedthru. Once the vacuum reaches a certain point a "glow" would be observed (assuming a transparent tank). At some higher vacuum, the glow would disappear. I hope that so far I am correct.

I have obtained an ignition transformer (10,000V w/center tap grounded). Using 2 high voltage diode stacks, I can come up with 5KV DC for the discharge to the tank.

Will this be enough voltage for the glow discharge?
Do I really need DC voltage?
What is the typical glow discharge current?
Is there a preferred configuration for the probe or conductor inside the tank for the HV discharge?
Should I put the glow discharge close to the glass or at the other end of the tank?
At what vacuum levels will the glow start and quench?
Will this loss of the discharge tell me that I have enough vacuum to begin the evaporation?
I do have gauges but wonder if the glow is a usable barometer of good/high vacuum?

Any help would be appreciated.

Thanks,

Ken Hunter
http://www.geocities.com/atm_ken_hunter


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