Ion Pumps are worthy of a wikipedia check. They are used in high vacuum
systems, once the vacuum is established with a roughing pump such as a
Roots blower style or mechanical chug-chug recipocating. They help
maintain the vacuum absorbing small qtys of free molecules. However,
they are mounted via a tabulation or tubing off the main vessel, so they
have limitations. Big tubes might have a 2 liter/sec 'appendage' pump.
They don't actually have any moving parts, using a voltage of 3000-7000
volts DC through a current limited power supply. In particle
accelerators, plasma sources, ion beam, or ion implantation sources,
they might be much larger, like the size of a keg. These require power
sources of 50 mA or so, while the little ones run off of 100 uA or less.
In vacuum tube manufacture they are used along with another more modern
devices called a cryo-pump. Like was said earlier, big tubes of over 100
kW dissipation often have appendage ion pumps mounted underneath. You
can tell the quality of the vacuum from the power supply current, and
when the tube is heated in operation and outgasses, the spikes in
current will indicate the event, can be used to even interlock the HV or
bias so that the tube won't run with trashed vacuum. This helps prevent
internal arcing from the outgassing from damaging the grids and cathode.
73
John
K5PRO
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