FEI Quanta FEG 250, User'S Operation Manual

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System Overview: System Layout of Quanta FEG
2-6
Final Lens Aperture Strip
The strip is made from a Mo coated Si. Either manual (numbered
click-stop mechanism positions) or Automatic Aperture System (AAS)
motorized software-control (option - see Chapter 9) enables to choose
the aperture most applicable to your imaging needs (see Chapter 5).
The left hand turn of the large ring moves the aperture holder
outwards towards the larger aperture. After the aperture change, it is
necessary to tune its position by using the inner knob and the one on
the right side, controlling horizontal plane fine movements (see
Chapter 6).
FIGURE 2-6 FINAL LENS APERTURE STRIP CONTROL KNOB
WA R N I N G !
Aligning the final lens aperture is a mechanical process. It is
possible to misalign the aperture strip and obscure the beam
from reaching the sample. Adjustment should only be done by
those with the understanding of how to proceed. The aperture
holes edges cleanness is also very important (see Chapter 8).
TABLE 2-1 APERTURE SIZES AND THEIR USE
No. Standard Option Option
Recommended use
(related to Standard sizes)
1 1000 µm 1000 µm 1000 µm Service Alignment (hole in frame)
2 - - -
3 50 µm 100 µm 30 µm High current applications
4 40 µm 50 µm 30 µm X-ray mapping of low-Z elements at low voltages
5 30 µm 40 µm 20 µm General imaging or X-ray analysis
6 30 µm 30 µm 15 µm Dynamic experiments
7 20 µm 30 µm 10 µm High resolution imaging