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Transpector CPM Operating Manual
4.2 Theory of Operation
Many gas analysis applications involving pressures too high for direct exposure to
the quadrupole sensor (pressures greater than 1.0E-4 Torr/mbar) require a
pressure converter to reduce the pressure and keep the sensor at high vacuum.
With a pressure converter, a quadrupole sensor may be used for high pressure
applications such as sputtering, Chemical Vapor Deposition (CVD), etch, vacuum
furnace analysis, and laser gas analysis.
Transpector CPM pressure is the pressure inside the closed ion source (CIS). The
nominal operating pressure inside the closed ion source is approximately
2E-4 Torr. Since the conductance between the closed source and the sensor
manifold is 0.7 L/s and given the effective pumping achieved using the turbo
molecular pump attached to this manifold, the pressure in the mass analyzer region
is approximately 23 times lower than in the closed source. Thus, with the source at
~2E-4 Torr, the pressure in the manifold is approximately 1.0E-5 Torr.
Pressure converters use orifices and/or capillaries to reduce the partial pressure of
the gas-mixture, typically by a fixed proportion, with minimum mass discrimination.
An orifice, a small disk with a defined hole, acts as a conductance limitation. When
both the volume and the high vacuum pump speed are constant, the orifice hole
size determines the pressure at the sensor. Orifices are available in various sizes
to cover various pressure ranges.
CAUTION
FabGuard Explorer and FabGuard display total pressure
inside the closed ion source.
Optimum performance is obtained when the total
pressure display reads ~2x10
-4
Torr measured in low
energy mode (40 eV, 200
A).
Operation in high energy mode (70eV, 2000
A) will give
an inaccurate total pressure reading.
4.3 Instrument Overview
4.3.1 Input/Output (Aux I/O)
This section describes the available input and output (I/O) for Transpector CPM.
See
for a pinout diagram.
Transpector CPM has two digital inputs for manual emission control, one digital
relay output for emission status, and one analog input.
