152
4 Maintaining the MSD
To clean the ion source
Major contamination
In the event of a diffusion pump backstream or other major contamination, the
other source components must be cleaned (ultrasonically but not abrasively) or
replaced.
3 Abrasively clean the surfaces that contact the sample or ion beam.
Use an abrasive slurry of alumina powder and reagent-grade methanol on a cotton
swab. Use only enough force to remove the discolorations; polishing the parts is
not necessary. Also abrasively clean the discolorations where electrons from the
filaments enter the source body.
4 Rinse away all abrasive residue with reagent-grade methanol.
Make sure all abrasive residue is rinsed way before ultrasonic cleaning. If the
methanol becomes cloudy or contains visible particles, rinse again.
5 Separate the parts that were abrasively cleaned from the parts that were
not abrasively cleaned.
6 Ultrasonically clean the parts for 15 minutes in each of the following
solvents:
Ultrasonically clean each group of parts separately.
• Methylene chloride (reagent-grade)
• Acetone (reagent-grade)
• Methanol (reagent-grade)
7 Place the parts in a clean beaker. Loosely cover the beaker with clean
aluminum foil.
&$87,21
The filaments, source heater assembly, and insulators cannot be cleaned ultrasonically.
Replace these components if major contamination occurs.
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