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