Ametek Dycor Dymaxion Mass Spectrometer, Руководство пользователя

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Overview
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1-3
ion volume and create ions.
Once the positive ions are formed, they are extracted from the ion region and
focused towards the quadrupole mass filter by a difference in potential. Lens 1
has an applied negative voltage that, due to a difference in electrostatic potential,
attracts the newly formed positive ions, passing them through Lens 2. Lens 2, in
turn, focuses the electrons into the quadrupole.
EI Ionization
The energy of the bombarding electrons is much greater than the bonds that hold
the molecule together. When a single electron is removed, a positive ion is cre-
ated - this is referred to as a molecular ion. When the bombarding electrons cause
the molecular bonds to break, fragment ions form. This ionization process is
known as electron impact ionization (EI).
Operation of the mass spectrometer depends on maintaining low vacuum pres-
sures. These pressures take into account not only the operational pressures of the
mass spectrometer, but also the pressures of the sampling system environments.
Figure 1-1a.
Closed source
components.
Repeller
Filament Source Grid
Focus Plate
. .
. .
. .
. .
. .
Filament
Repeller
Source Grid
Focus Plate
Top Alumina
Collar
M ass Filter
Figure 1-1b.
Open source components.