PlasmaQuant MS Series
Mass
Spectrometer
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The 5.5 kV required to drive the detector is generated on the Detector High Voltage
Power Supply circuit board (DET HVPS PCB), located on the ion optics board, which is
on the back of the PQMS .
The High Voltage Power Supply circuit board (HVPS PCB) generates the power for the
ion optics system. It is located on the back of the PQMS, directly in front of the system
control PCB.
Figure 8-1 - Entire vacuum/mass analyzer system
8.3
Theory of Operation
This theoretical description follows the ion beam from its inception in the ion source,
through the ion optics and mass spectrometer and finally to the detector.
8.3.1
Ion Source
The high operating temperatures of inductively coupled plasma (ICP) make it ideal for
use as an ionization source for mass spectrometers. RF power applied to a plasma coil
induces strong magnetic fields inside a quartz torch to form a plasma of argon gas.
Three tubes are connected to the torch, two tubes deliver argon and a third carries the
atomized sample, also mixed with argon gas.
A glass concentric nebulizer converts the sample into an aerosol inside a temperature
controlled spray chamber. The glass transfer tube carries the aerosol from the spray
chamber to the torch. To improve sample transfer efficiency, an additional controlled
flow of argon gas enters the transfer tube accessory via a port located on the side of
the tube. This gas is known as sheath gas. The injection of sheath gas can be used for
aerosol dilution. If an injector of smaller internal diameter is used the sheath gas may
not be required.
The vacuum pressure inside the interface draws in a portion of the plasma via a small
hole at the tip of the sampler cone. Nickel cones are standard and platinum tipped
cones are available for use with corrosive samples.