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Vacuum System
Vacuum Gauges
Thermo Scientific Orbitrap Fusion Series Hardware Manual 21
Vacuum Gauges
The Orbitrap Fusion Series MS contains three types of vacuum gauges that measure the
pressure in specific regions of the vacuum manifold. In the Tune application, you can observe
the readback values for the vacuum gauges on the By Function page in the Status pane (under
Source and FT Vacuum).
• Convection pressure gauge—Measures pressure down to a fraction of a milliTorr (mT).
The instrument uses two convection gauges:
– Source pressure gauge—Measures the pressure in the RF lens and API ion transfer
tube region in the vacuum manifold and the foreline, which connects the triple-inlet
turbomolecular pump and the forepump or forepumps.
– Collision pressure gauge—Measures the pressure in the IRM.
• Ion gauge—Measures the pressure in the multipole MP3 and LIT region of the vacuum
manifold.
The ion gauge produces energetic electrons that cause the ionization of molecules in the
ion gauge. A collector attracts positive ions formed in the ion gauge. The collector current
is related to the pressure in the vacuum manifold. The ion gauge is also involved in
vacuum protection.
• Ultra high vacuum (UHV) pressure gauge—A compact cold cathode (inverted
magnetron) gauge measures the pressure in the Orbitrap region of the vacuum manifold.
Vacuum Pumps
The Orbitrap Fusion Series MS requires one or two external forepumps and three internal
turbomolecular pumps to provide the vacuum pressures for the seven vacuum regions
(Figure 5).
The forepumps create the vacuum necessary for the proper operation of the turbomolecular
pumps. They also evacuate the ion transfer tube region of the vacuum manifold.
The forepumps’ detachable power supply cords plug into separate, single-phase 230 Vac wall
outlets and the relay control cable connects to the mass spectrometer’s SV65 Pump Enable
connector (Figure 3) so that the mass spectrometer can remotely turn the forepumps on and
off. The Main Power switch controls the SV65 Pump Enable connector, not the electronics
service switch.
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