Functional Description
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___________________________________________________________________ MS Detector
_______________________ Finnigan LTQ Hardware Manual _____________________
2-13
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heater from turning on continuously above a preset temperature. The
undertemperature feature identifies faults in the platinum probe sensor that
would otherwise cause the heater to turn full on.
Ions from the ion transfer capillary enter the tube lens. The tube lens has a
mass dependent potential applied to it to focus the ions towards the opening of
the skimmer. When you tune the LTQ, you adjust the tube lens offset voltage
to maximize sensitivity by balancing desolvation with fragmentation.
Ions from the tube lens pass through the skimmer and move toward the Q00
quadrupole. The skimmer acts as a vacuum baffle between the higher pressure
ion source interface region (at 1 Torr) and the lower pressure Q00 ion guide
region (at 50 mTorr) of the vacuum manifold.
The ion source interface is enclosed in a vacuum chamber that is evacuated by
the rotary-vane pump to a pressure of approximately 1 Torr.
Figure 2-8. Cross sectional view of the ion source interface and Q00
ion guide
Ion Transfer
Capillary
Skimmer
Lens L0
Tube Lens
Quadrupole
Heater Block
Heater Cartridge
Vent Prevent
Ball
Ion Sweep
Cone
Vacuum
Manifold
Q00