MDS from Scratch

• Set up Search mode
  • Start MDS, click Search
  • Load "Basic" -- a good alignment of the microscope
  • Mag mode 1 (NOT SADIFF)
  • Set mag to 10K, and fully expand beam
  • Go to SADIFF mode
  • Choose combination of camera length and Diff Focus to get correct mag and brightness (should just be short of covering CCD)
  • Move Free Lens Control slider all the way right to get dim beam (beam will move a little). Remember to hit "All Off" when going to Focus.
  • Recommended camera length 150-200 cm
  • Adjust position of beam with PLA (NOT Image shift!!) to put beam over Fastscan camera
  • If things are funny/messed up, go back to mag mode and fix
• Set up Focus mode
  • Got to Focus in MDS
  • Load "Basic" alignment
  • Set up mag/beam to desired level (200 K, spot 1, 10 pA/cm2 is usual). Use Mag 1 or Mag 2, not SA Mag.
  • Adjust position of beam to be different from Photo-set position using image shift/beam shift as follows:
    • Using Beam shift, move beam to very top of large screen
    • Using Image shift, bring back down to center of screen
    • Repeat. Repeat again if it seems too close for you.
  • Beam is now centred over 2K camera. To set position of beam over Fastscan camera:
    • a) approximate - use beam shift to move to correct position. Since position is not exactly centred, cannot be used reliably for stigmatism correction
    • b) more exact: Use the "Off axis" macro in EMMenu3 to move beam using PLA. Remember to use "On axis" before taking picture, as PLA shift is applied to PhotoSet as well
• Set up PhotoSet mode:
  • Go to PhotoSet in MDS
  • Load "Basic" Alignment
  • Set up mag/beam as desired. Use Mag 1 or Mag 2, not SA Mag. Use 9-10 pA/cm2 for a 1-second exposure.
• Alignment of Search and PhotoSet
  • Go to Search mode
  • Find a clean area of ice to burn
  • Go to Focus, then PhotoSet. Burn a nice hole using a long exposure with the screen down
  • Go back to Search. Centre burn hole using PLA shift (NOT image shift)

Deflectors used in MDS

• Mag Mode = Image Shift 1
• Diff Mode = PL Align

Other notes

• MDS remembers last mag set used, though this is not saved anywhere accessable
• If the last user messed things up by using non-standard settings or pushing the wrong button, MDS will have to be reprogrammed as described above.
• If you lose beam in Focus, remember to turn Free Lens Control to "All Off".
• Never use SA Mag, as the lens/delfector settings are different from Mag1/Mag2
• Monitor Lens/deflector levels. Remember that neutral is 8000 8000. Should be no image shift in PhotoSet mode, PLA should be neutral unless off-axis.

subsub level topic

• Set ALLOWTOPICVIEW =

-- BillRice - 12 Mar 2007