Alignment Procedure written by John Crum
Last Revised on 04/10
Routine Alignment Procedure for 4000EX (#1)
Start with the beam condensed to crossover at 5,000X magnification with a specimen in place.
Remember, beam current should be about 5µA above dark current (use Bias:Fine to adjust)
Make sure Spot Size = 1, and beam is centered (use condenser shifts). Most of the following beam
alignments are done using knobs and buttons located on the lower right-side pull out console.
A. Gun Tilt Alignment
Desaturate the filament until the filament image is visible. Make the surrounding halo symmetrical using
the gun tilts (Deflector:Gun button depressed and using the DEF X and Y knobs in the lower right pullout drawer).
Or, using the same set of knobs, make the current density as great as possible i.e. attain the brightest beam.
B. Condenser Stigmation
Stigmate the filament image while the Stigmator:Condenser button is depressed and using the DEF X and Y knobs.
The center bright spot should be bright and circular. Resaturate the filament.
C. Gun and Condenser Shift Alignment
Center the beam on Spot Size 1 with the Deflector:Gun button depressed using the SHIFT X and Y knobs in the
lower right pullout drawer. Change to Spot Size 4 and condense the beam to crossover, then center the beam using
the condenser SHIFT X and Y knobs on the upper panel (either side of column). Go back to Spot Size 1 and repeat
centering the condensed beam using gun deflector shift knobs until the beam stays centered.
This may have to be repeated 3-5 times.
D. High Voltage Centering
Change the magnification to 50,000X and depress the Wobbler:HT button (lower left side of upper right console).
Depress the Deflector:BRIT TILT button (upper right side of upper left console). Use the X and Y DEF knobs
(either side of column below the Condenser Shift knobs) to make the center unmoving portion of the image coincide
with the screen center. Now, recheck accuracy using the binoculars, using the Video camera or increasing magnification to 100,000X.
E. Objective Aperture Alignment
Insert the desired Objective Aperture and condense the beam. Depress the Function:DIFF button (upper side of upper
right console). Center the aperture to the beam. Press the Function:MAG 1 button and spread the beam. Repeat every
time objective aperture is changed or taken out.
F. Objective Stigmation
Find an appropriate are of the sample to stigmate on- a small dark object such as gold particle. Increase Magnification
to 100,000X. Spread the beam to the size of the screen and insert video camera. Depress the Deflector:OBJ STIG button
(upper right side of upper left console) and focus the image using the X and Y DEF knobs (lower pair, either side of column)
to obtain an astigmatism-free image. Increase magnification to 200,000X and repeat the focusing and stigmation.
G. Condenser Aperture Alignment
As the condenser aperture warms up, it will need to be centered. At 5,000X magnification and beam centered, spread
the beam just until the large viewing screen is filled. Center the aperture image so that it fills the screen evenly.
Repeat as necessary
Advanced Alignment and Other Procedures
A. Image Wobblers
1. Tilt: Obtain a beam at 5000mag. All controls are in the right hand pullout drawer. Condense the
beam to crossover. Push the "COND ALIGN Tilt" button. Turn "DEF WOB:Tilt" switch to "X" and use the Shift and
Def knobs on the X side to converge the moving beam. Flip the "DEF WOB:Tilt" switch to "Y" and use the Shift
and Def knobs to converge the moving beam. It should appear as a tight, unmoving beam. Turn off "COND ALIGN:Tilt."
2. Shift: Use Diffraction mode to align. Obtain a condensed beam at 5000mag, as above. Push the
"COND ALIGN:Shift" button. Select DIF mode (upper right hand console). Flip the "DEF WOB:Shift" to "X."
Converge the beam as above. Repeat for Y using the Y DEF and SHIFT knobs.
3. Adjust Wobbler Frequency and Amplitude as needed.
B. Engineer Mode
Used to save alignment by an experienced user or qualified engineer.
PRTEST M1 or PRTEST M2 Gives list of lens, deflectors, and stigmators
DADJ (0 to turn off, 1 to turn on)
C. Rod Insertion and Removal
1. Mount grid on holder carefully.
2. Check O-ring for lint, hairs, etc. This is extremely important! Use the dissection scope and the red-ended forceps.
3. Insert the rod into the goniometer, with the tab on the rod fitting into the slot on the goniometer. Push the rod while
turning, just until the rod moves in, then stop turning. If the rod is turned at this point, before the specimen chamber is
evacuated, the column will be vented.
4. Change the position of the silver switch on the goniometer and push the red button the console (right hand side). On
the vacuum display panel on the left side of the scope, change the position of the black knob to "Off."
5. Allow the specimen chamber to pump for 15 to 20 minutes (or longer).
6. Insert rod by turning clockwise. "Allow the column to pull the rod in, slowly. Monitor the Column Ion Pump pressure gauge
(on the power supply in the back of the room). If the pressure rises off scale, stop inserting the rod and let the vacuum recover.
7. Turn black knob on left side to "Manual."
D. Bake Out Procedure
Occasionally, the column ion pump (SIP) may need to be baked out. For instance, after the column has been vented
(intentional or accidental) and the Column SIP does not recover within a reasonable time (1-2H), then the column SIP
should be baked at least overnight, if not over the weekend. First, remove the specimen rod. Push the "Bake Out" button
(located in the left hand pullout drawer. On the left hand side of the scope, on the vacuum display panel, turn the "SIP"
switch on. Open the door on left hand side just behind the column. This will help keep the scope cool.
When the bake out is done, turn the "SIP" switch on the vacuum display panel off. Set up a fan to blow on the SIP
(use the door on the left side of the column). Wait about three hours, or until both sides of the SIP magnet are cool.
Turn off the "Bake" switch in the left side pullout drawer. The column SIP should come on in a few seconds, and the
pressure should decrease steadily. On the power supply in the back, turn the Pirani gauge selector to 'Column.'
It should read in the green shaded area with the green light on (see picture).
E. Changing High Voltage
The microscope should be left at 300kV when not in use (to protect the HT tank). If 400kV is desired, it must be
raised slowly (to protect the filament). On the FasTEM computer (the left monitor and upper keyboard in the rolling
cart on the right of the console), select the FasTEM client program. Click on the "HT" menu tab. Change the
"Target Voltage" to 400 and press the "UP" button. The high tension will increase over approximately 16 minutes.
When a session is complete, return the HT to 300kV by following the same procedure above, except insert the
value 300 in the Target box, and push the DOWN button.
For FasTEM to work, both programs need to be running- FasTEM Server, FasTEM client.
If commands are not being acted upon, close then restart the programs. Seek help from Staff if needed.