Stanford Research Systems RGA100, Operating Manual And Programming Reference

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Overview of the RGA 10-3
SRS Residual Gas Analyzer
Overview of the 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.
The quadrupole probe is a mass spectrometer sensor consisting of an ion source, a
quadrupole mass filter, a Faraday cup and an optional electron multiplier (Option 01).
Ions are created from the residual gas of a vacuum system by electron impact ionization.
Ions of a particular mass-to-charge ratio have stable trajectories through the mass filter,
depending on the DC and RF voltages applied to the quadrupole rods. The selected ions
are collected in a Faraday cup or multiplied in an electron multiplier.
The ECU box (3”” x 4”” x9””) contains all the electronics necessary to operate the RGA. It
connects directly to the probe’’s feedthru flange, and also to a host computer. Its regulated
power supplies set the ionizer voltages, the filament’’s electron emission current, the high
voltage across the electron multiplier and the RF/DC levels on the quadrupole filter. A
logarithmic transconductance amplifier converts ion currents into voltages that are read
by an A/D converter. A microprocessor and control firmware direct the operations of the
spectrometer, the data acquisition, and the communications through the RS232 serial link.
The electronics operate from a single 24 +/-2 V DC power supply. The peak current
requirement is about 2A. A universal input (90-264VAC, 47-63Hz) switching power
supply is provided as an option (Option 02) so that the system may be operated directly
from a line cord.