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Transpector MPS Operating Manual
Detection Factor
The detection factor is the ratio of the detected signal for a given ion
current from a certain substance to the detected signal for the same ion
current of nitrogen ions as measured at mass 28. For Faraday cup
detectors, the detection factor is usually 1. For electron multiplier
detectors, this factor depends on the mass and chemical nature of the ion.
Detector
The detector is that part of the mass spectrometer sensor which converts
a beam of ions into an electrical signal.
Doubly Charged Ion
For positive ions, a doubly charged ion is a parent or fragment ion where
two electrons have been removed.
Electron Energy
The electron energy is the kinetic energy of the ionizing electrons in an
electron bombardment ion source and is typically measured in units of
electron volts (eV). The electron energy is approximately equal to the
difference between the bias voltage on the filament and the anode
potential, times the electron charge.
Electron Multiplier
An electron multiplier is a
in situ
amplifier which is used to increase the
sensitivity of a mass spectrometer. When a high voltage is applied to an
electron multiplier, positive ions are accelerated into the multiplier, causing
the release of a large number of electrons per incident ion at the output.
Emission Current
The emission current is the current of electrons leaving the surface of a
heated filament.
Exit Aperture (Quadrupole)
The exit aperture is a focus lens at the ion exit (detector) end of a
quadrupole mass spectrometer. This lens is often biased by a potential
that is negative with respect to the quadrupole center voltage such that
ions are extracted from the exit end of the quadrupole and focused into the
detector.
Extractor
See
Focus Lens
.
Faraday Cup
The Faraday Cup is a detector for ions and/or electrons consisting of a cup
shaped, conductive electrode.
Filament
The filament is a fine wire or ribbon, which, when heated by means of
electrical current, emits electrons. The filament typically made of iridium
with a thorium or yttrium oxide coating.
