Instruction Manual IGM402 Hornet
InstruTech
Page 20
5.4
Degas
Degas is used to rid the gauge sensor of adsorbed gas. Degas is achieved by applying Electron Bombardment (EB)
to the grid. The intervals at which degas should be applied vary for each application. The low pressure
measurement performance of the transducer will normally improve after each degassing cycle.
Degas can only be applied while the filament is turned on and operating.
Ensure vacuum level is at or less than 5.00 x 10
-5
Torr before attempting to initiate degas.
Power during degas is about 3 watts higher than the normal operating power.
Degas will automatically turn off after 2 minutes when using factory default settings. Degas can be
programmed for duration of 2 to 10 minutes.
The IGM402 will continue to measure pressure while degas is in progress.
Degas will automatically turn off if the pressure exceeds 3.00 x 10
-4
Torr during the degas cycle.
Degas can be interrupted by turning the IGM402 filament off.
5.5
Filament Material Selection / Venting the Chamber
The choice of which filament to use in the IGM402 is primarily dependent upon the process and process gases
the ion gauge will be used with. For general vacuum applications, dual yttria coated filaments are offered for
use with air and inert gases such as N
2
, argon, etc. Optional dual tungsten filaments are available for use with
gases not compatible with yttria filaments.
1) Yttria coated iridium filament
In most general vacuum applications, the yttria coated iridium filament is the best choice.
Yttria filaments typically operate at a lower temperature than tungsten filaments and thus have a lower
outgassing rate at UHV and lower chemical reactivity with active gases.
Yttria filaments typically have a longer operating life than Tungsten filaments in clean applications.
The yttria coated filament can survive occasional accidental start attempts at atmosphere in air, but the overall
life of the filament may be shortened during each occurrence. Good vacuum practice is to use the CVG101
Worker Bee™
convection gauge (CG1) to know when to turn on the ion gauge filament.
2) Tungsten filament
Typically a bare tungsten filament is a better choice in those applications where an yttria coated filament is
quickly damaged due to the gas type in use. For example, processes such as ion implantation may use tungsten
filaments. Be aware that corrosive applications are hard on any filament and filament life will be
reduced when
operating in such environments. Tungsten filaments are easily damaged by exposure to air/oxygen during
