Stanford Research Systems RGA100, Operating Manual And Programming Reference

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8-12 Filament Replacement
SRS Residual Gas Analyzer
Probe Assembly
RGA Mounting Flange
Ionizer
Vacuum Chamber
Vacuum Port
RGA Cover Nipple
Figure 2 Probe Removal for Filament Replacement
6. Immediately carry the probe to a clean, dust-free area and secure it in an upright
position. Avoid contamination using handling procedures compatible with high
vacuum requirements.
7. Using the clean, flat-head screwdriver remove the single screw that connects the
repeller to the longer filament rod and pull out the cage exposing the filament and the
anode grid.
8. Before replacing the filament, visually inspect the entire ionizer. Check for loose,
damaged, misaligned and contaminated components. Some discoloration of the
ionizer parts is common, but heavy buildup on the grids and plates is a sign of severe
contamination. If problems are detected, a complete ““Ionizer Replacement””
procedure should be carried out at this time. Otherwise, continue with the filament
replacement procedure.
9. Inspect the filament, and become acquainted with the way in which it is mounted on
the filament rods: The SRS RGA filament is of a circular shape and made out of very
thin, thoria-coated iridium wire. Two platinum tabs, spot-welded at opposite ends of
its circumference, provide electrical connection to the rods that deliver the power
during emission. Precision machined slots define the exact placement of the filament
tabs along the two rods and a small ““screw and nut”” set secure each tab in place.
10. Without removing the nuts, loosen the two screws that hold the filament in place
enough to pull the filament out the ionizer assembly. Discard the old filament.
11. Leave enough clearance between each nut and the top of its corresponding alignment
slot to slide the platinum tabs of the new filament during installation.
12. Open the filament box and pick up the filament by one of its platinum tabs with the
clean tweezers.
13. Very carefully slide the filament into position, until the platinum tabs fall into the
slots. Do not bend or twist the filament. Do not scratch the Thoria coating!
14. Tighten the screws while pressing the nuts against the rods with the tweezers, making
sure the tabs are centered in the slots.