
Vacuum
System
PlasmaQuant MS Series
92
Figure 7-4 - Visible skimmer cone with sampler cone removed
A Leybold SV40 BI rotary pump (RP) maintains a pressure of approximately 4 Torr
(5.33 mbar) in VC1 while the plasma is on and the gate valve is open.
This chamber interfaces with the plasma by the sampler cone orifice of approximately
1 mm diameter.
During normal operation, the RP operates all the time.
NOTE
The ICP- MS Aspect MS diagnostic software allows independent on/off control of
the RP.
The pressure in VC1 is not monitored during normal operation.
VC2 interfaces with VC1 by the skimmer cone orifice of approximately 0.5 mm
diameter. The gate valve can isolate VC1 from VC2. A PFEIFFER turbo-molecular
pump, referred to as Turbo1, evacuates VC2.
VC2 houses most of the mass spectrometer ion lenses. The typical operating pressure
(when the gate valve is open and the plasma on) is <4x10
-4
Torr. The base pressure
achievable after 24 hours of pump-down time is typically 1x10
-6
Torr (this pressure
can be monitored only if the penning vacuum gauge is installed).
The quadrupole entrance plate aperture, of approximately 4 mm diameter, couples
VC3 to VC2. Another PFEIFFER turbo-molecular pump, referred to as Turbo2,
evacuates this chamber.
The high vacuum system, VC2 and VC3, are both roughed through turbo-molecular
pumps Turbo1 and Turbo2 by the SV40 BI rotary pump. The pressure is monitored by
a thermocouple gauge (G1) fitted to the fore line tube at the inlet to RP and a Thermo
VAC gauge (GMain) fitted to the top of VC2.
A port fitted to the side of VC3 aids in troubleshooting. You can fit a Penning Gauge
(G2) to this port. A spare connection to the system control PCB, labeled penning, is
provided to connect an additional penning gauge into VC3. The typical base pressure
for VC3 is 1x10
-7
Torr and 1x10
-5
Torr during analysis.