R wrote:
A great deal, but I don't have time to trade the same old one-liners
with him, yet again.
However, the following are genuine questions so I'll try to answer them.
>> This is a deposit of chemically active metal,... ... In larger
>>transmitting tubes the
>> getter is usually something like zirconium, which needs a higher
>> temperature to function correctly.
>
>Does zirconium gettering take place at room temperature?
The gettering (adsorption) reaction that traps the gas goes faster at
higher temperatures. Gettering by zirconium does take place at room
temperature, but at a very slow rate.
To complete the story, there is also an opposite de-sorption reaction
that releases the gas. At normal anode operating temperatures,
adsorption goes much faster than desorption so there is a net gettering
effect. But at very high temperatures the desorption reaction overtakes
the adsorption, so there is then a net release of gas. That is how the
tube structure is de-gassed during manufacture, by heating it to a much
higher temperature than normal.
>Do 3-500Zs utilize a zirconium getter?
As far as I'm aware, 3-500Zs do have a zirconium getter on the plate, so
it works well when the plate is hot. In answer to Vic's question, that
does seem to imply that those tubes need to be run with some plate
dissipation if there is a need to clean up the vacuum... but I'd defer
to anyone with more practical experience.
--
73 from Ian G/GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek
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