TECHNICAL INFORMATION
VACION PLUS PUMP INSTALLATION
Inspection procedure
VacIon
Plus
pumps are evacuated, baked out,
sealed and leak-checked at below 1x10
-10
Torr
(mbar) or below prior to shipping. The following
information and procedures can be used to estab-
lish the vacuum integrity of a VacIon
Plus
pump
before installation.
Visual inspection
Inspect the pump and magnet for physical damage
which may have occurred during shipment. Inspect
the pinch-off seal. If it is open, the pump is at at-
mospheric pressure.
,
WARNING!
The pinch-off seal is extremely sharp. Be careful.
A VacIon
Plus
pump that has been exposed to at-
mosphere during shipment, or while in storage, will
operate properly if it has otherwise not been dam-
aged.
The pump is not harmed by such exposure, al-
though it is good practice to keep it under vacuum
when not in use to exclude dust and the accumula-
tion of water vapor from the environment.
Vacuum evaluation
The ion pump is shipped in an evacuated condi-
tion. Before removing the shipping flange for in-
stallation on a vacuum system, it is recommended
that the pump be started briefly to verify vacuum
integrity and proper operation.
To verify the vacuum integrity of the new pump be-
fore venting:
1. Connect the pump to the control unit as di-
rected in the instruction manual of the control
unit.
,
WARNING!
The high voltage which is present in the ion pump
from the control unit can cause severe injury or
death.
2. With the main power switch in the OFF posi-
tion, plug the control unit into a suitable power
source.
3. Turn the power to ON.
4. Observe the reading for an indication of one of
the following conditions:
−
If the pump is free of leaks and is at a low
pressure, the pressure indication shall within
10 minutes fall to or below the 10
-8
Torr
(mbar) range as the volume of gas is
pumped.
−
If the pressure inside the pump is at or near
atmospheric level, an arc may strike inside
the high voltage feedthrough giving a pop-
ping sound and the pump current will fluctu-
ate. If this occurs, turn the power OFF
immediately.
5. If the vacuum integrity has been lost, the pump
should be leak-checked with a mass spec-
trometer leak detector before installation on the
system.
Short circuits
If there is a short circuit between the anode and
cathodes in the pump (or cathode to pump body),
the short-circuit current of the control unit will be
drawn and low voltage will be indicated. If a short
circuit exists in the control unit or high voltage ca-
ble and connector, low voltage will also be ob-
served when the high voltage connector is
disconnected from the pump (refer to the control
unit manuals). An ohm meter reading on the pump
feedthrough may not be effective in finding a short.
Short circuits may be caused by mechanical shock
to the pump. If the pump is shorted, contact Var-
ian.
TYPICAL INSTALLATION
A typical installation is shown in Fig. 16 and con-
sists of:
1. VacIon Plus pump.
2. A Valve to seal off the pump from the rest of
the system (if required).
3. The control unit.
4. A clean roughing pump (i.e. turbo).
5. A thermocouple gauge capable of indicating
pressure from atmosphere to 10
-3
Torr/mbar
range.
6. A valve to seal off the roughing pump from the
vacuum chamber. Roughing lines, are usually
made of stainless steel or copper tubing, or
other low vapour pressure material.
7. High voltage cable.
8. Backing pump (diaphragm or scroll).
14
87-900-106-01(B)