MDS Alignment
All 3 modes have their own alignment
Photo Mode**Press MDS PHOTO button**
Set up all imaging conditions:
• Spot Size (1 or 2)
• Alpha Angle (2 or 3)
• Magnification (40-60k)
• Dose (15-20 e-/Å2/sec)
After you set up dose, record your C3 lens value so that you can find the correct dose without having to recalculate it
How to calculate specimen and image dose and dose rate
Example:
Io = 15 e/Å2/sec
Mi = 40,000x
If M s = 1.25 for screen
1 piAmp/cm2 = 625 x 10-12 e/Å2/sec
Is = 23.4 PiAmp/cm2
Relationship of dose or dose rate between object and detector
Object intensity = I0 = Ii Mi2
Ii = I0/ Mi2 Ii = Is/ Ms
2
Screen intensity = Is = I0 Ms2/ Mi
2
Dose Calculation (e-/Å2/sec)
Go to a completely open area (no ice or carbon, just vacuum)
Go to 50,000x Magnification
*Your dose at 50k in pA/cm2 is equal to
the dose in e-/Å2/sec
Adjust the following settings to obtain the
desired dose for your sample:
• Size of your beam (using Brightness knob)
• Spot Size
• Exposure time
MDS Focus
**Press MDS FOCUS button**
Should be set up the same way as MDS PHOTO
• Be in MAG 1
• Select desired spot size, alpha angle and magnification
*generally these settings should all the be same as the settings in PHOTO mode
MDS Search
**Press MDS SEARCH button**• Go to MAG 1
• Repeat Voltage Axis Alignment
• Go to Spot Size of 5 (you may also have to do the spot size alignment at this point if they are misaligned)
• Spread beam clockwise (using Brightness)
until you hear a beep
• Press SA DIFF
• Adjust DIFF FOCUS knob until the beam
is the desired size
Aligning MDS Photo and MDS Search
• After setting up MDS SEARCH mode, go back to MDS PHOTO
• Find an area of interest such as ice contamination
• Center that area in Photo mode using the trackball
• Press MDS FOCUS
• Press MDS SEARCH
• If the area of interest is not in the center than press PLA and use your DEF/STIG X and Y knobs to bring the area to the center
• Turn off PLA
Alignment of Search Mode
Photo Mode Misaligned Search Mode:Use PLA & def/stig x y to center area of interest
Aligned Search Mode