Status & Tuning Parameters
Collector Tab
Thermo Fisher Scientific
Prima PRO & Sentinel PRO Mass Spectrometers User Guide
8-9
The RMS Sample Tube Temperature is the RMS sample tube heater
temperature set point and control.
The Faraday Deflector parameter is the voltage applied to the
deflector electrode that directs the ion beam into the Faraday
collector. The Faraday detector is mounted off-axis on both Faraday
only and
Faraday / SEM dual detector systems.
The Multiple Deflector parameter is the voltage applied to the
deflector that directs the ion beam into the SEM.
This is an optional micro channel plate (MCP) used to increase the
dynamic range of the instrument to permit measurement of species at
low (ppm and lower) concentrations.
The Multiplier Voltage controls the gain of the SEM (Prima PRO
analyser uses an MCP). Varying the voltage output can vary the gain
of this detector from x10 to approximately x10000. Typically, the
gain is set to 2000 for a standard single MCP SEM and 10000 for a
dual MCP SEM.
In conventional sector mass spectrometers, compensation for errors
in analyser geometry, magnet fringing field effects, and beam
aberrations, resulting from localized, contamination induced charge
effects, is achieved with difficulty by adjusting the magnet position.
The Prima PRO analyser overcomes this by fixing the position of the
magnet and providing a quadrupole lens (quad lens) to compensate
for and adjust the position of the refocused beam image. A
complicated impractical series of magnet adjustments is therefore
replaced with a single voltage adjustment of the quad lens.
The quad lens DAC voltage can be varied from -25 V to +25 V but,
in practice, a variation of a few volts positive or negative is usually
sufficient to achieve a symmetrical, flat-topped peak that provides
good, long-term precision from the analyser.
The Resolution Deflector electrode provides Z plane deflection of
the ion beam through one of two available resolving slits. The
Sample Tube
Temperature
Collector Tab
Faraday
Deflector
Multiplier
Deflector
Multiplier Voltage
Negative and
Positive Quad
Lens Voltages
Resolution
