Ed,
The ion pump pumps stray gases not Cesium.
The waste Cesium is absorbed into getter materiel coating the inside
walls of the tube.
On the older HP tubes there is a small square of carbonized bamboo where
the waste beam strikes in addition to the gettering on the tube walls.
On a tube that has not operated for a while the stray gases love to dive
into the ionizer filament and oven filament.
So even though you might have zero ion pump current in Cs off, when you
go to operate and the filaments come on they boil off a big puff of gas
and peg the current. The filaments turn off and the pump pumps the gas
down till the filaments come on again. This process repeats until the
filaments are warmed up and have stopped releasing gas. Then the ovens
will stay on!
Cheers,
Corby
Ed,
The ion pump pumps stray gases not Cesium.
The waste Cesium is absorbed into getter materiel coating the inside
walls of the tube.
On the older HP tubes there is a small square of carbonized bamboo where
the waste beam strikes in addition to the gettering on the tube walls.
On a tube that has not operated for a while the stray gases love to dive
into the ionizer filament and oven filament.
So even though you might have zero ion pump current in Cs off, when you
go to operate and the filaments come on they boil off a big puff of gas
and peg the current. The filaments turn off and the pump pumps the gas
down till the filaments come on again. This process repeats until the
filaments are warmed up and have stopped releasing gas. Then the ovens
will stay on!
Cheers,
Corby
