Stanford Research Systems RGA100, Operating Manual And Programming Reference

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Quadrupole filter cleaning 8-21
SRS Residual Gas Analyzer
Quadrupole filter cleaning
The quadrupole mass filter is the heart of the RGA. The sensitivity and resolution of the
instrument are ultimately limited by the quality of the quadrupole field between its rods.
Deposits on the rods accumulate electrostatic charge and distort the field, resulting in
degraded performance. The deposits typically form at the entrance to the mass filter,
when the RGA is operated at high pressures or over long periods of time. They are often
seen as a discoloration of the metal but in some cases (i.e. depending on the vacuum
composition) they are invisible.
If contamination of the rods is suspected, the first step to take is a one- or two-day long
““
Probe Bakeout ””. If bakeout is not successful, the quadrupole filter will need to be
cleaned. Note that in order to clean the rods, the entire quadrupole head assembly must be
taken apart, and unless the exact nature of the deposits is known, the only sure way to
remove them will be with a very fine abrasive.
Warnings
x
The exact alignment of the rods in the quadrupole is essential to the optimum
performance of the RGA.
x
Do not scratch the surface of the rods.
x
Do not remove excessive amounts of surface material with the abrasives.
x
Use clean tools and procedures.
Equipment
x
Clean, dust-free work area.
x
Latex gloves/powder free.
x
One standard OFHC copper gasket for 2 3/4”” CF Flange. New and Clean!
x
Replacement bowed e-clips (SRS Part# 0-00579-000, 12 count)
x
Phillips head screw driver: P1 head (clean.)
x
Precision flat-head screw driver: 2.5 mm head (clean.)
x
Needle nose pliers.
x
Micro-Mesh abrasive sheets: 3200 to 12000 grit.
x
Ultrasonic cleaner.
x
Ultrasonic cleaning solution (high quality, no-rinsing residue).
x
1000 mL beaker.
x
Oil-free, dry nitrogen.
x
Distilled or de-ionized water.
x
Petri dish.
x
Clean oven ( higher than 100
q
C setting).