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Transpector MPH Operating Manual
Partial Pressure
The partial pressure is the pressure of a specific chemical component of a
gas mixture. The sum of all the partial pressures is the total pressure.
Pole Zero
See
Center Voltage
.
Quadrupole
A quadrupole is a mass filter consisting of four parallel electrodes or poles
(hence quadrupole) arranged in a square array. Opposite poles are
connected together electrically such that an electric field of hyperbolic
geometry is produced. The potentials applied to these poles are a
superposition of variable DC and RF voltages, generally of fixed RF
frequency.
Repeller (Electron)
The electron repeller is an electrode located on the opposite side of the
filament than the anode. The repeller is usually biased at the same
potential as the negative side of the filament, or a more negative potential.
Residual Gas Analyzer
A residual gas analyzer is an instrument which is used to determine the
quantities and chemical nature of gases present in a vacuum system. The
instrument is typically a mass spectrometer equipped with an open ion
source.
Resolution
Resolution is the ability of a mass filter to select between nearby masses.
It is typically measured as the mass of the peak divided by the width of a
given mass peak at 10% or 50% of the peak maximum intensity.
Secondary Electron
A secondary electron is an electron emitted from a surface when that
surface is struck by a sufficiently energetic ion, electron, neutral molecule
or photon.
Sensitivity
The sensitivity of a mass spectrometer is the ratio of ion current at a
specified mass from a specified gas to the partial pressure of that gas,
suitably corrected for background. The specified gas is typically nitrogen,
measured at 28 AMU, although argon at 40 AMU is sometimes used
instead, depending on the instrument.
Total Pressure
The total pressure is the force per unit area exerted by a gas on the walls
of its container. It is equal to the sum of all the partial pressures of the
different chemical species which comprise that gas.
