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3.4.3 Column Alignment Operation
For the best performance of the instrument, alignment of the electron optical column axis is
necessary. Generally, an electromagnetic alignment is sufficient, while a mechanical alignment
may be needed for more critical applications.
Perform the following alignment when you change the accelerating voltage, Probe Current mode,
or setting of Cond Lens1. If you notice the image moving while focusing or correcting
astigmatism, only perform an Aperture Alignment or Stigma Alignment, respectively.
The S-4800 allows alignment conditions to be saved for each combination of accelerating voltage
and Probe Current mode.
If an alignment operation has been made at a particular
combination of settings, only a slight adjustment (usually
Aperture Alignment) is necessary when you return to that
condition.
For all electromagnetic alignments, either drag the mouse in
the grid area of the Alignment dialog window or adjust the
STIGMA/ALIGNMENT X and Y knobs on the control panel.
NOTICE: 1. For normal microscopy, use electro-magnetic column alignment. Do not
manipulate the objective aperture. Mechanical alignment of the electron optical
system including the objective aperture and beam monitor aperture is done at an
accelerating voltage of 1 kV (See the alignment procedures 3.12.). If you do
mechanical alignment at other voltages, you may end up with inability of
performing complete electro-magnetic alignment at some other accelerating
voltages.
2. Before performing mechanical alignment, wait for more than two hours after
starting the heating of the objective lens aperture. If mechanical alignment is
made immediately after the start of heating the objective lens aperture, the
alignment condition will be affected by thermal expansion of the objective lens
aperture.
3. To save operating conditions effectively, it is recommended to perform a Degauss
operation after focusing and before column alignment.