Functional Description
MS Detector
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______________________ Finnigan LTQ Hardware Manual _______________________
The ion gauge control circuit controls the ion gauge and reads back the
pressure signal. (The ion gauge measures the pressure in the analyzer region
of the vacuum manifold.)
The Convectron gauge control circuit controls the Convectron gauge and
reads back the pressure signal. (The Convectron gauge measures the pressure
in the foreline and the ion transfer capillary-skimmer region of the vacuum
manifold.)
The vacuum protection circuitry monitors the pressure in the ion transfer
capillary-skimmer region of the vacuum manifold, as measured by the
Convectron gauge, and in the analyzer region of the vacuum manifold, as
measured by the ion gauge. The vacuum protection circuitry turns off power
to the ion optics and mass analyzer RF and waveform generation circuitry,
8 kV power supply (for the API source), electron multiplier and conversion
dynode power supply, APCI vaporizer heater, and dc voltages to the ion
transfer capillary heater, tube lens, ion optics, and mass analyzer if one or
more of the following conditions arise:
•
The pressure in the ion transfer capillary-skimmer region is above 3 Torr
•
The pressure in the analyzer region is above 5
×
10
-4
Torr
•
The high-voltage safety interlock switch on the API source is open (that
is, the door to the Ion Max ion source is open)
The LED labeled Vacuum on the front panel of the LTQ is illuminated green
whenever the vacuum protection circuitry indicates that the vacuum is OK
(and the safety interlock switch on the API source is closed).
The RF voltage control circuitry controls and monitors the PCBs that are
responsible for RF voltage generation.
The temperature monitoring circuitry monitors the temperatures at several
PCBs in the MS detector.
The diagnostic circuitry monitors the outputs of various components and
circuits on the LTQ. Information on voltages, currents, temperatures, flow
rates, logic, etc. is sent to the data system, where it can be accessed via
diagnostics views of Tune Plus.
RF / Waveform Voltage Generation Electronic
Assemblies
The RF/waveform voltage generation electronic assemblies produce the RF
voltages for the mass analyzer, Q00 and Q0 quadrupoles, and Q1 octapole.
They also produce the ion isolation waveform voltage, resonance excitation
RF voltage, and resonance ejection RF voltage that are applied to the exit rods
of the mass analyzer.
