Stanford Research Systems RGA100, Operating Manual And Programming Reference

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Hardware modifications 3-19
SRS Residual Gas Analyzer
In order to scan without filament emission, uncheck the ““warn if the filament off”” box in
the ionizer settings menu of the RGA software.
RGA Cover Nipple Replacement
A stainless steel tube covers the probe assembly with the exception of the ionizer. This
tube, referred to as the RGA Cover Nipple, contributes to the overall capacitance of the
quadrupole rod assembly, and should not be removed from the probe unless it is replaced
with a similar grounded metal shield tube inside the vacuum system (see below). Failure
to replace the Cover Nipple will push the RF driving circuit out of regulation, and will
limit the operating mass range of the quadrupole filter. The tube also acts as a barrier,
preventing ions from sources other than the RGA’’s ionizer from reaching the detector
and affecting the ion current readings.
The RGA Cover Nipple consists of two non-rotatable, 2.75”” CF Flanges, connected by a
short section of 1.5”” OD tube (0.065”” wall thickness). The entire part is made out of
stainless steel type 304, and its overall length is 6.75”” (including the two flanges.)
Some experiments require being able to insert the RGA’’s probe deep into the vacuum
chamber. When a large insertion depth is required, the standard RGA Cover Nipple can
be repalced with the O100MAX Maximum Insertion nipple illustrated in Figure 10.
Figure 10 RGA Probe with Shield Tube
The O100MAX Shield tube consists of a 1.5”” OD tube welded onto the large-flange side
of a 4.5””-to-2.75”” Zero Length CF Adapter Flange. The tube has a wall thickness of
0.065”” and is strictly perpendicular (90
q r
0.2°) to the flange’’s face. The RGA’’s
quadrupole assembly is attached to the small-flange side of the Adapter Flange so that the
tube completely covers the mass filter (replacing the standard RGA Cover Nipple). This
modified probe can be mounted on any standard 4.5”” CF port of a vacuum chamber, and
the ionizer penetrates the vacuum system by roughly 7””.