Agilent Technologies VacIon Plus 800 Manual Del Usuario página 224

Technical Information
In the second case (bakeout with the ion pump off), an external turbo pump,
connected to the system through a bakeable isolation valve, is necessary.
The ion pump should be switched on when the system is still at the bakeout
temperature, then the turbo pump should be insulated and the system should be
kept at high temperature for the final part of the bakeout process, until the ion
current begins to decrease.
It is worth noticing that this second method gives the best vacuum performance,
since the outgassed species are not sorbed by the ion pump (inside which they will
remain), but they are removed from the vacuum system by the turbomolecular
pump. This helps to preserve the ion pump lifetime.
It is strongly recommended to degas filaments (e.g. in gauges or residual gas
NOTE
analyzers) when the system is at high temperature. If they are outgassed at room
temperature, this operation will compromise the effectiveness of the bakeout.
224 Agilent VacIon Plus 800 User Manual