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Re: Tube snakeing

Posted By: SVP Neon Equipment
Date: Thursday, 26 June 2008, at 1:10 p.m.

In Response To: Re: Tube snakeing (JD Hill)

> Any thoughts on why it takes so long to show
> up??

Occluded contaminants that are not removed during processing are permanently sealed in the tube when it is filled with gas and sealed off from the manifold system. During tube operation, as the glass and electrodes begin to warm up and the ionization process "scrubs" the inside of the tube, these contaminants begin to desorb and are slowly released into the plasma stream. Inert gas (neon, argon, etc.) will not combine with any other kind of gas regardless of how much voltage and current is used. They also have a much different ionization potential. So when contaminant gases are present they ionize separately from the inert gas and want to take a separate path through the tube, thereby causing the snaking affect that you are seeing. When the tube is turned off and cooled the contaminant gases re-condense. When the tube is cold and then turned on again the process repeats itself. Eventually some of the contaminant gases are "cleaned up" through a chemical process with the electrode emission/getter coating. During this process, any free oxygen molecules in the tube will combine with the mercury vapor (assuming it is a mercury tube) and create mercury oxide and cause staining in one form or another. If the residue contaminant gas is too great it will not be completely cleaned up by the electrodes and the tube will progressively degrade. A properly processed tube should not exhibit any snaking. But if one does show minor signs of it, it should stop doing so within a few minutes. This is typically accomplished on the burn-in table before the mercury is inserted into the tube.

Mark

SVP Neon Equipment

Messages In This Thread

• Tube snakeing -- JD Hill -- Tuesday, 24 June 2008, at 11:46 p.m.
  • Re: Tube snakeing -- SVP Neon Equipment -- Wednesday, 25 June 2008, at 11:27 a.m.
    • Re: Tube snakeing -- JD Hill -- Wednesday, 25 June 2008, at 3:43 p.m.
      • Re: Tube snakeing -- SVP Neon Equipment -- Thursday, 26 June 2008, at 1:10 p.m.
        • Re: Tube snakeing -- JD Hill -- Thursday, 26 June 2008, at 4:08 p.m.

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