Zeiss AURIGA Compact Crossbeam, Instruction Manual

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EHT
The emitted electrons are accelerated by the acceleration voltage ( U
EHT
).
The beam booster ( U
B
, booster voltage), which is always at a high potential when the acceleration
voltage is at most 20 kV, is integrated directly after the anode. This guarantees that the energy of
the electrons in the entire beam path is always much higher than the set acceleration voltage. This
considerably reduces the sensitivity of the electron beam to magnetic stray fields and minimises
the beam broadening.
Apertures
The electron beam passes through the anode aperture ( 3 ) first, afterwards through the multihole
aperture ( 4 ). Standard aperture is the 30 µm aperture hole that is the central aperture. The aper-
ture size is decisive for the probe current. Other aperture sizes are selectable to meet the require-
ments of a wide range of applications.
Stigmator
The stigmator compensates for astigmatism, so that the electron beam becomes rotationally sym-
metrical. The electron beam is focused onto the specimen while being deflected in a point-by-point
scan over the specimen surface.
Before the electron beam exits the objective lens ( 7 ), the electrostatic lens creates an opposing
field which reduces the potential of the electrons by + 8 kV. The energy of the electrons reaching
the specimen surface (
9
) therefore corresponds to the set acceleration voltage (EHT).
Signal detec-
tion
When the primary electron beam hits the specimen, certain interaction products are released,
which can be recorded by specific detectors.