MKS Instruments UK Ltd
Microvision2 Hardware Manual – SP101015.102 August 2010
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9. Analyser Maintenance
9.1 Overview
The quadrupole analyser is the front end of your mass-spectrometer, it produces electrical signals which,
when presented to your electronics display the contents of your vacuum chamber in a meaningful fashion.
The analyser can be broken down into four separate areas by virtue of their function.
1. The ion source or ioniser
This is located at the top (furthest from the flange) of the analyser and its function is to take a representative
sample of molecules and atoms from the vacuum chamber, convert them into ions and present them to the
quadrupole filter.
2. The quadrupole filter
This is the centre section of the analyser. Its function is to take the ion beam generated in the source,
separate the various ions by their mass to charge ratio (m/e) and present the single selected m/e to the
collector.
3. The detector
This area of the quadrupole analyser is "hidden" inside the flanged housing. Its function is simply to convert
the filtered ion beam presented by the quadrupole filter into a small electrical current, which can be passed
to the electronics for amplification and subsequent display to the outside world.
4. The flanged housing
This is the only part of the analyser seen under normal operating conditions. Comprising of an industry
standard 2.75" Conflat® flange with an electrical feedthrough carrying the various supplies and signals to
and from the quadrupole analyser.
All quadrupole analysers require periodic maintenance, the regularity of which is determined by their use.
The cleanliness of the vacuum, hours of operation and the type of sample being analysed all have an effect
on the analyser’s performance.
Apart from these considerations there are times when the analyser will require maintenance and these are
when accidents happen i.e. the vacuum is vented with the filaments on, or someone forgets to turn on the
water cooling for the oil diffusion pump.
Routinely there is only one area of the analyser that requires any maintenance, this is the ion source. The
ion source contains two filaments, only one of which will be in use at any one time. The filament is heated to
approximately 2000 deg K at which temperature it emits electrons, which are used to produce the ions
required by the quadrupole filter. At this high temperature, there are two deleterious effects;
