Bakeout Operation - Agilent Technologies VacIon Plus 800 Manual Del Usuario

Technical Information

Bakeout Operation

For every ultra-high vacuum (UHV) application, it is necessary to bake the whole
vacuum system in order to reach the ultimate pressure. This is done by heating the
pump and all the components in the system and is generally required to quickly
achieve base pressure less than 1E-8 mbar.
Do not exceed the temperature limits reported in Table 1.
CAUTION
Note that it is possible to perform the bakeout in two ways, that is to say with the
ion pump on or off. In the first case (bakeout with the ion pump on).
1 Heat the pump body and the vacuum system to temperatures between 150 °C
and 220 °C (220 °C is the maximum allowable for most bakeable high voltage
cables). This temperature is high enough to degas the pump surfaces of water
vapor without damaging the magnet and high voltage connector. Note that the
system components must be compatible with the bakeout temperature. The
heating must be approximately even on all surfaces or evaporated water will
condense on the colder surfaces resulting in an incomplete bakeout and
preventing achievement of UHV vacuum pressure.
2 Monitor the pump current on the control unit. Agilent recommends that current
during the bakeout should not exceed 25 mA; if this value is exceeded, turn the
bakeout off and then on again when low current is restored. An automatically
controlled relay may be used to control the heaters and to monitor the current
limit during the bakeout in automatic mode.
3 Bake the VacIon Plus pump for at least 24 hours. Longer bakeout periods are
recommended when the pump has been used with heavy gas loads or when
UHV pressure (1E-9 mbar or less) is desired.
4 As the pump and the system cool down to room temperature, a drop in
pressure should be observed.
Agilent VacIon Plus 800 User Manual 223