John T. M. Lyles wrote:
>We have two 2 liter/sec Ion pumps mounted on each tube. When connected to a
>4 kV DC supply, they will attract the gas molecules and clean up the tube
>during operation. As higher power is reached, the grid, plate heat up more,
>and outgassing continues, beyond what the manufacturer can deal with in
>bakeout. Its interesting to watch the spikes of ion pump current, as gas
>burps are released in the tube. If it gets above a certain amount, we trip
>off the plate voltage with an interlock, to minimize arcing inside.
Thanks, John, very interesting - especially bit about the gas burps.
(In a vacuum, no-one can you hear you burp...?)
Someone was telling me about a way to test tubes for gas by running them
in "ion-gauge mode". The control grid is biased positive so that it
collects electron current from the filament, while the anode/screen is
biased negative and collects any current due to positive ions. Do you
know anything about that technique, John or anybody else?
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
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