Operating Procedure - Agilent Technologies VacIon Plus 800 Manual Del Usuario

Instructions for Use

Operating Procedure

1 Check that the controller HV polarity is correct for the pump: positive polarity for
Diode pumps and negative for StarCell pumps. Refer to the relevant pump control
unit instruction manual and follow the procedure below when operating the pump:
establish a minimum starting pressure in the vacuum system, by means of a pre-
vacuum turbomolecular pump (supported by a primary pump). We recommend to
install an all-metal valve between the ion pump and the turbomolecular pump, in
order to be able to insulate it at a later stage.
2 Plug the control unit into a suitable power source and switch the power ON.
Follow the instructions in the manual of the control unit to feed the ion pump.
3 Observe the voltage, current and pressure on the display of the control unit. If
the ion pump has been started at too high pressure, typically the voltage will be
of some hundreds Volts. If the voltage remains constant at these values, in
order to avoid pump overheating we suggest to turn it off and start it again at a
lower pressure (see the paragraph "Use"). A current value near the short-circuit
current of the control unit could indicate that an unconfined glow discharge
exists in the pump and system. A temporary rise in roughing pressure will
usually be noticed during any starting procedure. If the ion pump has been
started to the recommended pressure, the voltage will quickly reach the pre-set
value (3, 5 or 7 kV). Once at the operating voltage, the current will start to
decrease. We recommend at this point to close the roughing valve, in order to
insulate the ion pump and the system from the turbomolecular pump. If the ion
pump voltage drops after closing the roughing valve, reopen the valve for
additional rough pumping.
As the pressure decreases, the voltage again will rise, and the roughing valve
may be closed.
4 When the voltage has reached the pre-set operating value, set the control unit in
the PROTECT condition, if the control unit has this predisposition. The system
is now automatically protected against pressure increases above the pre-set
limit. If such an increase should occur, the control unit will be turned off
automatically.
5 If the control unit allows you to set the pump type in use, the controller display
will show the pressure value obtained by the conversion of the current value, as
per the pressure versus current graph shown in the paragraph "Technical
Information" of this manual. If the controller does not have this predisposition,
please directly refer to this diagram. It is worth noticing that the pressure
indication could be not correct if, during its operation, the ion pump starts to be
affected by leakage current. In this case the pressure obtained by the current
conversion shown on the display will be higher than the real one.
Agilent VacIon Plus 800 User Manual 203