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Status & Tuning Parameters
Source Tab
If the limit is set too low, then the filament may take some time to
regulate when it is first switched on, or may fail to emit at all.
If the value is too high, then there is a danger that the filament might
blow, burn out, due to excess current.
When switched on, filaments will run in limit for a short period until
the surface attains temperature and the required level of electron
emission is reached. Ideally, current limits are set about 0.4 A higher
than the normal running current.
Filament Integrity
Filament integrity will indicate OK when the filament circuit is
continuous and Failed when open circuit, normally indicating a
filament failure. If maintenance has just been performed on the
instrument check that all cable harnesses have been reconnected
before assuming a filament failure.
Filament selection between filaments 1 and 2 is made in Control
Centre from the
Emission
tab.
If the first running filament fails, consideration should be given to
scheduling a routine source change. This is particularly important
where analytical data is critical and an unscheduled shutdown caused
by failure of a second filament could have additional consequences.
Half Plate 1 and 2
Two 1/2 plates positioned after the source block are used to focus
Output Voltages
and steer the ion beam. The potential difference between the two
plates represents the deflection voltage and can be varied in the range
-100 V to +100 V by adjusting the Deflection Voltage setting on the
Peak Shape tab
in Control Centre.
The mean voltage for the 1/2 plates represents the focus potential and
can be varied in the range 0 V to 960 V by adjusting the Focus
Voltage on the
Peak Shape tab
in Control Centre.
In Current Limit
In Current Limit indicates that the filament current is in limit and that
emission control is not yet established. This is normal for a few
seconds while the filament heats up after switching on.
OK indicates that emission control has been attained and the
filament is NOT in current limit.
Ion Energy
This supply provides the energy to accelerate the ionized sample
molecules out of the source and into the magnetic field where they
will separate according to their respective mass / charge ratio. The
Ion Energy value is nominally 1000 V for 150 amu mass range
Thermo Fisher Scientific
Prima PRO & Sentinel PRO Mass Spectrometers User Guide
8-3
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