[Amps] power vacuum tube hi-pot and "conditioning"

[Traian]

Hello Peter,

and thank you for answer.
During my search on the web, I have reached some similar info as yours,
but it seemed to be applied to very large power microwave tubes only
and the vacuum ion pump you describe is used for improving the
vacuum for these very high voltage tubes.

The post below:

http://lists.contesting.com/archives/html/Amps/2001-09/msg00232.html

was the most interesting and useful for explaining what was hapening.
Reading it again, carefully, I realised that what I found is an already
known method aplied for improving vacuum for some power tubes
when manufactured.
Indeed, it seems that some sort of "gettering" was produced that way.


Thanks,
73 and all the best,
Traian


peter.chadwick at Zarlink.Com wrote:

> Traian,
>
> is the effect you're seeing the same as the 'vac ion pump' that some big
> tubes have? As I understand it, the ionisation attracts the gas ions to the
> electrode and keeps the vacuum up.
>
> I first saw it back in 1966 ( I do feel old at times!) on a Siemens YH1045
> travelling wave tube. 10 watts in, 10kW out at 5.4GHz or so.  18kV on the
> collector at 3 amps, and 1 amp at 22kV on the helix. The vac ion pump ran
> at 2kV: we had to get the current below a few microamps, and it was
> interesting with 1960's technolgy sensing the low currents and getting
> temperature stability - the few integrated op amps around had too much bias
> current. Anyhow, we ran the vac ion pump all the time and it kept the tube
> hard. I ssupect Traian is seeing a similar effect that cleans up the
> vacuum.
>
> 73
>
> Peter G3RZP