BRIEF OPERATING INSTRUCTIONS FOR THE ZEISS EM 900

Please note: These instructions are intended only for individuals who have had prior training on this instrument. If at any point you have a question about the instrument's operation or performance, please ask for assistance.

1. Turn on the water valve. Turn on the power with the Mains Key Switch to 80 kV. Turn on the nitrogen gas.

2. The pumping system will now establish the proper vacuum in the column. When the vacuum is established the "OPEN V3" light will illuminate on the console and on the column next to the V3 valve. Open valve V3.

3. Check the following: Image mode on the microscope should be at "HR" and the magnification should be 3000. There should not be a specimen in the beam path. If the scope was not left in this condition, make the necessary adjustments.

4. The green beam button should be illuminated. Push it to turn on the high voltage. The red beam button should now be lit to indicate that the high voltage is on. Now check to be sure the vacuum is still OK. Push the FIL button to turn on the filament. The FIL button should now also be illuminated.

5. Centering the Illumination: Turn the small brightness knob counter clockwise to crossover. Center the beam with the beam alignment knobs. Set the large brightness knob to position 5 (fifth dot). Now reduce the filament heating slowly by turning the knob counter clockwise to undersaturate the filament. Align the filament image if necessary with the filament precentering knobs.

6. Using the small brightness knob focus the filament. Carefully (slowly) resaturate the filament by turning the filament heating knob clockwise. The shadow should just disappear. Reset the large brightness knob to position 3.

7. With the beam still at crossover center the beam with the beam alignment knobs. Now use the small brightness knob to go back and forth through crossover. If the beam spot does not expand concentrically, adjust the condenser aperture alignment as demonstrated in class. When the alignment is complete, you should be able to turn the small brightness knob clockwise and the beam should spread to evenly fill the screen. You will always work with the beam between crossover and to the clockwise direction or

"low side" of crossover.

8. Aligning and Stigmating the Imaging System: Turn the large brightness knob completely counterclockwise to position 1. Turn the small brightness knob clockwise to overfocus. Set the imaging mode to "D". With the small brightness knob and the small focusing knob adjust for the caustic figure. The P1 stigmator will help you get the caustic figure as close to a 3 pointed star as is possible. Return the large brightness knob to position 3 and the image mode to "HR".

9. Centering the Objective Aperture: Insert a specimen into the beam with the imaging mode still at "HR". Be sure a piece of tissue or plastic (not a grid bar or an empty space) is in the path of the beam. Switch to imaging mode "D". Focus the diffraction spot to its minimum size with the small fine focus knob and the small brightness knob. Insert and center the objective aperture (the cluster of small apertures is the third position in). Switch the imaging mode back to "HR". Reduce the brightness and adjust the magnification as needed.

10. ONLY IF NEEDED: Correcting Objective Astigmatism: Image mode should be on "HR" and you will need to use the holey grid. Adjust the microscope to about 25-50% higher magnification than you plan to use. With a specimen in the beam, center a small hole on the focusing screen. Focus the hole. Now overfocus the hole. You will see the black Fresnel fringe. Check to see if the fringe is even all around the hole by going back and forth through focus a few times. If the fringe is uneven, use the objective stigmator controls (carefully) to adjust it.

Special Notes:

IF YOU NEED TO LEAVE THE ROOM FOR ANY REASON OR FOR ANY PERIOD OF TIME BE SURE THAT YOU DEFOCUS THE BEAM AND TURN OFF THE HIGH VOLTAGE.

TO CHANGE A SPECIMEN - Turn off the beam and close V3. Remove the specimen holder from the microscope by turning the airlock counter clockwise. Remove the holder using the appropriate tool from the kit. DO NOT TOUCH THE CARTRIDGE OR THE SLIDE. Close the airlock slightly while you insert the grid into the specimen holder. REMEMBER THAT TURNING THE CAP TO THE LEFT WILL LOOSEN IT - TO THE RIGHT WILL TIGHTEN IT. MAKE SURE THE CAP IS NOT CROSS-THREADED, TOO TIGHT OR TOO LOOSE. Reopen the airlock and insert the specimen holder with reference to the locking pin. Close the airlock by turning it completely clockwise. PUSH IN THE PUMP button on the console to evacuate the airlock. Disengage the airlock rod and slide it into the three o'clock position. Wait until the LOCK IN light goes on and then about 30 seconds more. Then continue to insert the specimen. You may leave the specimen in the airlock, but out of the beam as you do your initial alignment. It will be ready to insert when you need it.

TO TAKE A PHOTO load the film as demonstrated in class. Adjust the numbering as necessary for your records. Focus your specimen using binoculars on the focusing screen. The small screen is also the photometer, so leave it in place as you adjust the brightness so that the exposure time will be 2 seconds. Bring both screens up at the same time. Push the lit exposure button. The light will go out. When it comes back on the screens should be lowered.

TO TURN OFF THE MICROSCOPE:

When you have finished microscopy for the day:

1. Spread the beam by turning the small brightness knob clockwise (so the beam is not at crossover). Reduce the magnification to 3000.

2. Turn off the filament by pushing the FIL button. Now turn off the high voltage by pushing the RED beam button.

3. Remove your specimen as demonstrated in class and replace the specimen cartridge in the airlock as described previously. The cartridge may be left in the outermost position as demonstrated in class.

4. Close valve V3.

5. Turn the microscope key to OFF. Wait for about 3 minutes until you hear the dry nitrogen gas fill the column, then turn off the nitrogen gas cylinder. Turn off the water valve.

6. Remember to log your filament time and the amount of film you used in the log book.

7. The room should be NEAT and LOCKED when you are done.

LMB 3/02