Varian 990 dCLD II, Operation Manual

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Model 990 dCLD II Component Leak Detector
2-5
2.2.2 Dual Mechanical Pump Configuration
Figure 2-2 Dual Mechanical Pump Configuration
Note: Foreline and Cal Leak valves are under the control of the 990 dCLD II.
Table 2-4 Dual Mechanical Pump System Valve Sequence
State Vent
Valve
Rough
Valve
Test
Valve
Remarks
Pre-Vented Closed Closed Closed The Pre-Vented state allows time to ensure that all valves
are closed before any open. The time spent in the
pre-vented state depends on valve actuation time.
Vented Opened Closed Closed The Vented state places the fixture at atmosphere. The
backing primary pump keeps the turbo backed.
Pre-Roughing Closed Closed Closed The Pre-Roughing state allows time to ensure that all
valves are closed before any open. The time spent in the
pre-roughing state depends on valve actuation time.
Roughing Closed Opened Closed The Roughing state brings the fixture to vacuum.
Test Closed Closed Opened The Test Valve re-opens at the appropriate foreline
pressure, exposing the fixture to the foreline.
S
pec
Tu
rb
o
Cal Le
ak
Cal
Leak
Foreline
Turbo Spec Tube Assembly
Length is Proportional
Keep Distance as
Test Valve
Rough Valve
Vent Valve
Fixture
Backing
(in box)
Short as Possible
to Sensitivity
Primary
Pump
Roughing
Primary
Pump
Tu
be