Ion millers are a pain in the neck! They are designed to remove material from the sample. This means: a) that they always remove material from other places too and b) that the material gets deposited somewhere else. The result of this is that ion millers are inevitably high-maintenance instruments.

Therefore it is important to make the most of them when they are in operation. To aid in this quest, two things can be helpful: to get the beam well aligned and to know the milling rate.

An ion gun, however powerful the beam it produces, is of no use if the beam misses the sample. A means of checking the alignment is therefore of great importance.