Version 2017-01-19 for GI use
Although diffraction can be useful, diffraction of electron waves around the aperture
openings can interfere with the initial wave front. The results are an unclear or out-of-
focused image. It is important to create a balance between reduction of spherical
aberration and diffraction by selecting an appropriate sized aperture.
How to align the TEM? [For assistants only!!]
Insert a holy grid in the TEM like described here above.
Go to Mag1 (lower diaphragm handle f to the left) , Magnification minimal to LOW
(switch 4 to the left). 800x
Do not forget to spread the bundle with the brightness knob.
Alignment procedure step A:
Switch handle f of the lower diaphragm to the right
Close the beam as much as possible and use the shift knobs left end right to center
the spot right on the small dot on the phosphor plate.
Spread the bundle with the brightness knob
Center the position of the spread bundle using the lateral and front knobs of the upper
diaphragm this time. (Note, upper handle is directed to the left)
Repeat above four steps if necessary (iteration) Additional tip Geert-Jan: adapt the
magnification so that the edge of the bundle respect to the opening on the phosphor
plate is optimal to view the centering.
When ready, switch back the lower handle f to the left.
Press the Diff (diffraction) button on the right panel.
Make a bright narrow pin spot and center the surrounding halo using the leftand right
DEF knobs
When ready, spread bundle and press Mag1 again. Dif goes out.
Click on COND STIG in the left panel. Turn the brightness knob left and right. The
shape of the bundle should remain round. If it is elliptical, correct for this with the Def
knobs left and right. When ready, press COND STIG again.