Agilent Technologies 5975C TAD VL MSD, Troubleshooting And Maintenance Manual

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200 5975 Series MSD Troubleshooting and Maintenance Manual
7
Analyzer
EI Ion Source
The EI ion source ( Figure 44 ) operates by electron ionization. The sample
enters the ion source from the GC/MSD interface. Electrons emitted by a
filament enter the ionization chamber, guided by a magnetic field. The
high-energy electrons interact with the sample molecules, ionizing and
fragmenting them. The positive voltage on the repeller pushes the positive ions
into the lens stack, where they pass through several electrostatic lenses. These
lenses concentrate the ions into a tight beam, which is directed into the mass
filter.
Ion source body
The ion source body ( Figure 44 ) is a cylinder.It holds the other parts of the ion
source, including the lens stack. With the repeller and the drawout plate, it
forms the ionization chamber. The ionization chamber is the space where the
ions are formed. Slots in the source body help the vacuum system to pump
away carrier gas and un-ionized sample molecules or fragments.