This step is to align the beam to make it parallel to the axis of the column. The purpose of this step is to make beam to hit specimen perpendicularly. A coma is not a good thing, as it generates some phase error to the data.
The procedure is below.
Press button and select .
Select or from the same page.
Adjust the to let the wobbling be symmetrical around the center of the beam. The feature at very center of the large screen has minimum shift.
If you perform this with Obj aperture in, then re-check the certering of objective aperture.
The step size button on is used to control the amplitude of the beam wobbling.
The steps used here only give "roughly" parallel beam to the axis. If you need very acurate "0" tilt beam, a different alignment procedure - Coma-Free is needed.
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