Stanford Research Systems RGA100, Operating Manual And Programming Reference

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The SRS RGA 2-3
SRS Residual Gas Analyzer
The SRS RGA
The SRS RGA is a mass spectrometer consisting of a quadrupole probe , and an
Electronics Control Unit ( ECU ) which mounts directly on the probe’’s flange, and
contains all the electronics necessary to operate the instrument.
Electronics Control
Unit (ECU)
Ionizer
Quadrupole Probe
Figure 1Quadrupole Head Components
The probe is a specially engineered form of quadrupole mass spectrometer sensor that
mounts directly onto any standard 2 3/4" CF port of a vacuum chamber. It is described in
detail in the RGA Probe chapter of this manual. The total probe equipment consists of
three parts: the
ionizer (electron impact), the quadrupole mass filter and the ion
detector . All of these parts reside in the vacuum space where the gas analysis
measurements are made. The detector measures the ion currents directly (Faraday Cup)
or, using an optional electron multiplier detector (Option 01), measures an ion signal
proportional to the ion current. A stainless steel tube (CF Full nipple) covers the probe
assembly with the exception of the ionizer.
The ECU is a densely packed box of electronics (3”” x 4”” x 9””) that connects directly to
the probe’’s feedthru-flange and also to a host computer. It is described in detail in the
““RGA Electronics Control Unit”” chapter of this manual. It includes several regulated
power supplies, a microprocessor, control firmware, and a standard RS232
communications port. It is powered by either an external 24 VDC (@2.5 Amps) power
supply or an optional built-in power module (Option 02) which plugs directly into an AC
outlet. A unique, temperature-compensated, logarithmic picoammeter built into its box
measures the ion currents collected by the Faraday cup (FC), or electron multiplier
(CDEM). The electrometer is completely autoranging and measures both positive and
negative currents with the same accuracy and resolution. Its operating range covers
current magnitudes between 10
-7
and 10
-15
A, providing six orders of magnitude dynamic
range during single mass measurements and scans, and detectable partial pressures better
than 10
-13
Torr during electron multiplier detection.
The instrument is completed with the RGA Windows software package that runs on IBM
compatible PC’’s. The intuitive graphical user interface allows measurements to be made
and displayed in a variety of modes. The program is fully interactive and measurements
are set up quickly and easily with the click of a mouse. The software also supports
multiple head operation when more than one RGA head is needed. Please refer to the
RGA Windows chapter of this manual, and the RGA On-Line Help files, provided with