Larry,
Impurities in the metals can contribute by liberating more gas when heated to
the temperatures the tube operates at. It would be according to what the
impurity is. Hydrogen would be one that comes to mind where a lot of metals
during manufacture are mixed purposely to limit it. In a tube, hydrogen gas
ions that result from the hydrogen being struck by the electrons, can travel
lightning fast as compared to the other gases which are slow acting in speed.
They have a lot to do with the space charge, and the only time they're wanted
is in some types of thyratrons.
Best,
Will
*********** REPLY SEPARATOR ***********
On 7/28/06 at 8:23 AM Larry Carman wrote:
>Another thought. Could impurities introduced during manufacturing of the
>different metals used in tube construction be associated with tube arcing?
>
>Larry N5BIP
>
>
>
>-----Original Message-----
>
>From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
>Behalf Of Tom W8JI
>
>Sent: Friday, July 28, 2006 6:53 AM
>
>To: Amps Amps
>
>Subject: [Amps] Arc distance
>
>
>
>I wouldn't want people to walk away with the false idea that spacing is the
>only major parameter that determines arc distance in a given dielectric
>media. The shape is extremely important, as are any small sharp edges.
>
>
>
>A blunt smooth surface for a given spacing can have several times the
>voltage breakdown of a similar spacing with a sharp edge or even a very
>small sharp protrusion.
>
>
>
>People who think they can look at a complex structure and predict where it
>will break down based on spacing are kidding themselves and fooling anyone
>else who believes them.
>
>
>
>I suspect the incorrect bandswitch and capacitor breakdown voltages that
>are
>tossed out as "fact" come from looking at gaps or perhaps testing parts
>that
>are exceptionally smooth or testing under other best-case conditions, or
>maybe even just invented without any factual basis at all.
>
>
>
>73, Tom W8JI
>
>
>
>
>
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