Last updated 10/29/2020
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F20 Alignments
●
F20 alignments should be done by EMG staff ONLY!!
●
Alignments can be done with room temperature (RT) holder or cryo holder. Alignments should
be done with a grid with carbon support, ideally a cross-grating replica grid.
●
Steps 1 - 4 should be done with no specimen in the path of the beam. You can use a ben to pull
the holder out partially. If you’re confident that gun alignments are good, skip steps 1 - 4.
●
Steps 5 - 11 should be done on specimen.
1.
Gun tilt (“Tune” → “Gun” → “Gun Tilt”)
a.
Focus beam (with intensity knob)
b.
Center beam (beam shift trackball on left knobset)
c.
Open beam (intensity knob) CW past crossover (past second circle) and use MF X and Y
to get the brightest beam (lowest
exposure time)
i.
Stay away from edge of FEG
d.
Condense and center the beam (trackball)
e.
Open beam up to the RIGHT so that it’s
just past second circle
f.
Center condenser 2
aperture (image →)
g.
Click next, repeat steps b-e
2.
Gun Shift (“Tune” → “Gun” → “Gun Shift”)
a.
Condense beam, then center beam using
MF X and Y
b.
Repeat for next step
3.
Spot size dependent gun shift (“Tune” → “Gun” → “Spot size
-
dependent Gun Shift”)
a.
Similar to step II, focus beam and center using MF X and Y for all spot sizes
4.
Condenser Astigmatism (“Tune” tab → “Stigmator” inset → “Condenser”)
a.
NOT tune → alignments → stigmator → condenser stigmator
b.
High mag, ~100kX
c.
Use MF X and Y to make sure beam opens and closes circularly and concentrically over
both sides of crossover
d.
Click “None” when done
5.
Eucentric height and focus
a.
Holder should now be placed back into the path of the beam.
b.
In leginon, “Z
-
focus” node → simulate target (or do this manually by following steps
b -
e below)
c.
Find a piece of dirt that is large (easily visible at low mag, ~5k)
d.
“Stage/beam” tab → “Stage2” flapout
→ “Wobbler”. Use “Z axis” +/
- (right knob-set) to
adjust stage z-height until feature on screen stops moving (about -180 um for RT holder;
-30 um for cryo holder).
e.
Rough focus by pressing “Eucentric focus” on right knob-set
Summary of Contents for TF20
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