Thermo Scientific Prima PRO, Руководство пользователя

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Technical Description: System
Ion Source
B-6 Prima PRO & Sentinel PRO Mass Spectrometers User Guide Thermo Fisher Scientific
Figure B
–3.
Ion source
Figure B–3 illustrates the ion source. The electrons are drawn to the
source by a positive potential and then pass through the source via
apertures on either side. They are collected on an electrode, referred
to as the electron trap, on the opposite side of the source. The ribbon
of electrons interacts with some of the molecules of the sample
stream and forms a cloud of ions in the source cavity.
A single exit slit from the source is positioned close to the path of the
electron beam, and therefore the ionisation region. By creating a
negative potential difference between the source block and an
additional electrode, the source slit, positive ions are drawn out of
the ion source. The ion source is held at a potential above ground
termed the ion energy: for the Prima PRO this is 1 kV.
Ions leaving the source through the exit slit pass between two half
plates which focus and steer the beam. The potential difference
between the two plates is varied to steer the beam on to the source
slit. The voltage difference between the mean half plate voltage and
the ion source block is varied to focus the ion beam. The ion beam
leaves the source assembly via the alpha slit, which trims the beam
height prior to injection into the sector.
Inside the ion source an additional electrode, referred to as the
repeller, is positioned directly opposite the ion exit slit. Operating at
Filament
assembly
Source magnets
Electron
beam
Sample inlet