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Re: Tube snakeing

Posted By: JD Hill
Date: Thursday, 26 June 2008, at 4:08 p.m.

In Response To: Re: Tube snakeing (SVP Neon Equipment)

> 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

Thanks Mark.

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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