Version 1.04, SPRING 2001

PRE-USE CHECKLIST :

1. Check log book for machine status.

2. Log in starting time.
3. Cover main viewing window and fill front cold trap with lN2.
4. Fill back cold trap.
5. Check FILAMENT knob at the full CCW setting.
6. Remove OBJECTIVE and SELECTED AREA apertures.
7. Microscope magnification at approx. 3-10kx.

SAMPLE INSERTION AND REMOVAL :

Removal -

1. Stand facing airlock.
2. Pull specimen rod from column about 1.5 cm to the stop.
3. Turn specimen rod about 10^O counterclockwise to the next stop.
4. Pull specimen rod from column 5.0 cm more, to the next stop.
5. Turn specimen rod about 170^O counterclockwise to next stop.
6. Set airlock switch to air; wait 10 sec.
7. Gently pull specimen rod from column

Insertion -

1. Insert specimen in holder of choice.
2. Insert specimen holder into the airlock (pin in the notch)
3. Press gently and set airlock switch to EVAC position.
4. Wait for red pumping-lamp to go out.
5. Turn specimen rod clockwise 170^o and ease into column.
6. Turn specimen rod clockwise 10^o to view specimen.
7. Allow vacuum to recover to 10^-6 range before continuing.

ALIGNMENT :

A. Saturation and gun tilt -

1. Check vacuum < 5 x ,10^-6 T (GUN,COL,CAMERA-green, SPEC-yellow)
2. Check mode selector button is SA.
3. Check HV 200 kV (for routine operation)
4. While watching screen, slowly turn FILAMENT knob until a beam is seen.
5. Using BRIGHTNESS (C2 lens), focus the beam to crossover.
6. Using the FILAMENT knob, bring the beam to an under-saturated condition (so that bright and dark regions can be seen in the crossover spot).
7. Using GUN TILT controls, make the undersaturated spot symmetrical (the CBS 'eye'). If necessary, the GUN HORIZ controls can be used to center the spot.
8. Using the FILAMENT knob, fully saturate the beam (bright and dark regions in the spot merge).
9. Check BEAM CURRENT =< 10 mA over dark current

B. Condenser aperture alignment -

1. Set magnification to 5 kx
2. Bring beam to cross-over with BRIGHTNESS (C2) control.
3. Center beam on screen with BRIGHTNESS CENTERING knobs.
4. Spread beam until illumination of the screen just touches the edges.
5. Center beam with the condenser aperture x-y controls.
6. Repeat steps 1-5 until the the spot center does not shift as the BRIGHTNESS knob is adjusted.

C. Gun horizontal and brightness centering -

1. Set SPOTSIZE to 5 mm
2. Bring beam to crossover with BRIGHTNESS (C2) control.
3. Center beam on screen with the GUN HORIZ knobs.
4. Set SPOTSIZE to 1 mm
5. Bring beam to crossover with BRIGHTNESS (C2) control.
6. Center beam with BRIGHTNESS CENTERING knobs.
7. Repeat steps 1-6 until there is no displacement
at crossover between SPOTSIZE 5 mm and 1 mm.

D. Condenser astigmatism -

1. Method 1:

1. Using the BRIGHTNESS (C2) control, bring the beam through crossover. Note the shape of the beam at either side of crossover. If the beam has the same shape in both conditions, stigmation is complete.
2. At one side of crossover, use the COND STIGM controls to make the beam shaped more like the beam at the other side of crossover.
3. Repeat steps a,b until stigmation is complete.

2. Method 2:

1. Bring beam to cross-over with BRIGHTNESS (C2) control.
2. Adjust COND STIGM to yield smallest spot size.
3. Check that the beam shape is the same at over and under focus.

E. Z-axis alignment -

1. Make sure sample is fully inserted.
2. Bring goniometer to 0^O.
3. Set magnification ca. 10kx
4. Center a reference point on the main screen.
5. Tilt goniometer ~10^O away from zero.
6. Using the z axis control, re-center the reference point. Refocus.
7. Repeat steps 1-5 at progressively higher tilts until there is no specimen translation on tilting.

F. Beam tilt adjustment -

1. Select a feature at screen center Mag ~50 kx.
2. Focus.
3. Press HV MODULULATION button
4. Adjust BEAM TILT until there is no lateral translation of the image.

OPERATION-TIME PROCEDURES :

Objective aperture insertion:

1. Select an electron lucent area of the specimen .
2. Insert some SA aperture.
3. switch to diffraction mode
4. Insert desired objective aperture.
5. Center aperture around main beam spot with translator controls.

Objective lens stigmation:

Method 1:

1. At desired magnification, find small, obviously astigmatic reference feature.

2. Using the FOCUS (OL) controls, observe the reference feature(s) at both sides of focus. Note the distortion of the feature at either side of crossover. If the unfocused image has the same at both over- and under-focus, than stigmation is complete.

3. At one side of focus, use the OBJ STIGM controls to reduce the distortion of the unfocused feature.

4. Repeat steps b,c until stigmation is complete.

Method 2: (Works best for holey carbon films.)

1. At high magnification, find a small hole in the thin area.
2. Remove any objective aperture.
3. Observe the Fresnel fringes slightly away from Gaussian focus.
4. Adjust OBJ STIGM controls so that the Fresnel fringes are the same
around the entire circumference of the hole.

Method 3:

1. At desired magnification, find reference feature.
2. Find best focus using the FOCUS (OL) controls.
3. Adjust OBJ STIGM controls to improve the image sharpness.
4. Check for astigmatism of the reference feature at over- and under-
focus.

CHANGING FILM :

1. Make sure the FILAMENT (heating current) knob is completely desaturated (fully CCW).
2. Turn off room lights, panel lights, and TV monitors.
3. Turn on safe lights (overhead and darkroom)
4. Press the camera system AIR button.
5. Vent the film desiccator using the toggle switch above the desiccator door handle.
6. Put on clean dust free gloves.
7. Open camera chamber and remove camera receiver box.
8. Pull out guide rail assembly to stop and remove supply box.
9. Insert full supply box from desiccator.
10. Place empty receiver box in front of guide rail assembly.
11. Shut camera chamber door, pressing firmly.
12. Press camera system EVAC button.
13. Immediately take receiver and supply boxes to darkroom for a film change.
14. Open lid from receiver and remove negatives to a light tight box
15. Refill film holder plates.
16. Slide refilled plates into the supply magazine.
17. Press down on THE METAL FRAME, NOT THE FILM to insert the next plate.
18. Insert magazine cover with the 'teeth' towards back of box.
19. Place loaded magazine and empty receiver in desiccator.
20. Close door, turn on toggle switch.
21. Hold door shut until vacuum draws it tight.
22. Reset film counter to 21.
23. Turn off safe light.

AFTER-USE CHECKLIST :

1. Set MAGNIFICATION to 5 kx.
2. Desaturate filament to the FILAMENT full CCW setting.
3. Remove OBJECTIVE and SELECTED AREA apertures
4. Goniometer at 0^O tilt.
5. Sample removed and single-tilt sample stage rod inserted.
6. All vacuum states acceptable (GUN,COL,CAMERA-green, SPEC-yellow; film desiccator sealed).
7. Logout.

IF, AT ANY TIME, YOU HAVE ANY QUESTIONS - ASK FOR HELP