Aperture Centering

  1. In TEM center, put down the phosphor screen (Screen retract, right hand panel). The large screen camera will display the image in the TEM center.
  1. Minimize the beam using the “brightness dial” (left hand panel) and center the beam using the “Shift X&Y dials” (both hand panels, Figure 9). Note: If you do not see the circle scale on the image, right click in the Large Screen Camera window and select “Show Circle Scale”)
Figure 9: Condensed beam on large phosphor screen
  1. Insert Focus Screen “FScreen retract” (right hand panel) and correct the astigmatism on the “Focus Screen Camera” Window by clicking on “CL Stig” (left hand panel) and using “Def/Stig X&Y” dials (both hand panel) to make the beam round. Once finished click again on “CL Stig” to remove it from the assigned button.
Figure 10: Small beam on small focus screen
  1. Remove the focus Screen Camera by clicking “FScreen retract” (right hand panel).
  1. Spread the beam on the large phosphor screen with the “brightness dial” (left hand panel) until the inner circle is filled. If the beam did not spread evenly, recenter the CL aperture by hovering on the “microscope scheme” over the number displayed next to CL. Use the arrows the center the CL aperture (Figure 11).
Figure 11: Adjustment of physical CL aperture position
  1. Go in Diffraction mode “Diff button” (right hand panel).
  1. Center the OL aperture by hovering over the number next to “OL” (microscope scheme, TEM center). Use the arrows to center the OL aperture (Figure 12). The aperture is centered if you have the black circle (aperture) centered around the diffraction spot.
Figure 12: Adjustment of physical OL aperture position.
  1. Go back into Magnification mode by clicking the “Mag button” (right hand panel).