Thermo Scientific TSQ Quantum XLS, Руководство пользователя

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Functional Description
Mass Spectrometer
Thermo Scientific TSQ Quantum XLS Series User Guide 27
The ion source block holds the ion volume in its center. Samples are introduced from the
GC capillary column through an aperture on the side of the ion source block and then into
the ion volume. Gases for calibration or chemical ionization enter the ion volume through the
transfer line.
Figure 16. EI (left), closed EI (center), and CI (right) ion volumes and holders
Cartridge heaters heat the ion source block and lens assemblies to minimize the rate at which
deposits form on the ions source block, ion volume, and lens assemblies. The ion source block
is also heated to assist in the rapid temperature equilibration of the ion source block and ion
volume after the filament is turned on. In EI mode, the ion source is typically maintained at
150
o
C to 220
o
C. However, you can sometimes use lower or higher temperatures for certain
applications. In the CI mode, the ion source is typically maintained at 180
o
C to 200
o
C. The
ion source heater is feedback controlled.
The filament assembly, positioned in a recess at the top of the ions source block, contains the
filament, reflector, and electron lens. The filament is a rhenium wire that is electrically heated
to produce electrons by thermionic emission. The reflector repels electrons emitted by the
filament away from the filament toward the ion volume. The filament and its reflector are
maintained at a negative potential relative to the ion volume. The electron lens prevents
positive ions from traveling up the electron beam. In turn, this prevents positive ions from
leaving the ion volume through the electron entrance hole. The difference in potential
between the filament and the ion volume determines the electron energy.
Two permanent magnets are held in a magnet yoke in the proper position above and below
the ion source block. The permanent magnets collimate the electron beam and cause the
beam to spiral through the ion volume. This ensures optimum ionization of the sample.
The ion source of the TSQ Quantum XLS Series mass spectrometer has two ion source len
assemblies, called the L1, L2, and L3 lens assembly and the heated Q0 quadrupole assembly.
The lenses extract the ions formed in the ion source and transmit them to the ion optics. The
lens L1 voltage is mass dependent. The rods of the heated Q0 quadrupole contact the rods of
the Q0 quadrupole and share their rf and dc voltages.
Ion volume
holder
Electron
entrance
hole
Ion exit hole
(front)
Electron
exit hole
GC effluent, CI gas, calibration gas
entrance hole