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Transpector MPH Operating Manual
The sensor consists of three main parts: (See Figure 3-1.)
ion source (ionizer)
quadrupole mass filter
ion detector
These parts are mounted on an electrical feedthrough flange, bolted to the vacuum
space where the gas analysis measurements are made.
Figure 3-1 Transpector MPH sensor
The sensor works only in a high-vacuum environment because the ions, once
created, must not collide with neutral gas species or the walls of the ion source.
Otherwise, they cannot be detected. At low pressure, the total flight path of the ions
is long enough to pass through the quadrupole without collisions.
3.3 The Ion Source
The ion source of Transpector MPH is optimized for detecting residual gases in a
vacuum system. The sensor has an open construction that facilitates the flow of
gas species into the ionization region. Figure 3-2 on page 3-3 shows the open ion
source in more detail.
Inside the ion source, a large current is put through a filament. This current heats
the filament and causes it to emit electrons, which collide with the gas species
forming ions. Once a gas specie is ionized, electric fields can be used to
manipulate it.
The ions formed in the ion source result from the loss of electrons and thus are
positive in charge.
Ion Source Quadrupole Detector
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