Configuring "V5 Extraction" Ion Source Parameter; 10Configuring "V6/V7 Inner Deflection" Ion Source Parameter; 11Configuring "V8 Reserve" Ion Source Parameter; 12Configuring "V9 Wehnelt" Ion Source Parameter - Pfeiffer Vacuum QMA 4X0 Operating Instructions Manual

Operation
proved by reducing the "Field Axis" value, there may be contamination or mechanical problems (e.g.
ion source not correctly centered, or assembled in a tilted position). The "Surface ions" chapter shows
how normal and so-called EID ions can be differentiated with the aid of the "Field Axis" parameter.
7.9.9 Configuring "V5 Extraction" ion source parameter
The extraction voltage (V5 Extraction) accelerates the ions from the ionization area toward the rod sys-
tem.
Procedure
1. Adjust "V5 Extraction" to maximum peak height.
2. Also optimize the "Focus" value if the value of "V5 Extraction is changed.
7.9.10 Configuring "V6/V7 Inner Deflection" ion source parameter
The deflection voltages ("Deflection", "DEFI" and "DEFO") direct the ions through the 90° deflection ca-
pacitor. In the QMG, in Faraday operation, they are automatically switched to ground potential. The two
deflection plates are on positive potential for negative ions and on negative potential for positive ions
respectively. The mass filter accelerates the ions to the deflection unit and directs them to the SEM.
One deflection voltage
The inner deflection plate is on potential "V6 Inner Deflection", the outer deflection plate is directly con-
nected to the Faraday cup and electrometer pre-amplifier EP1 and is thus on ground potential. The opti-
mum value is determined by the ion formation potential "Ion Reference" and to a certain extent by the
SEM voltage.
Reference values
● Ion Reference: 120 V | 40 V
● Inner Deflection: 300 V | 200 V
Procedure
► Adjust the "Inner Deflection" until the maximum peak height is achieved.
► Optimize the "Inner Deflection" again whenever you change the "SEM Voltage" value.
7.9.11 Configuring "V8 Reserve" ion source parameter
Potential V8 is used in special cases.
7.9.12 Configuring "V9 Wehnelt" ion source parameter
The Wehnelt voltage is only used with the axial ion source.
7.9.13 Adjusting resolution
Procedure
► Do not set "Resolution" to a higher value than the measuring task requires.
► Pay attention to the interdependency between the "Field Axis" and "Resolution" parameters.
► If the peak width across the mass range is irregular, correct it by means of adjustments on the
7.9.14 Adapting HF cable polarity
Procedure
► Try to improve the sensitivity or peak form by interchanging the HF cables on the analyzer.
► Perform the optimization with both polarities and then select the best variant.
If reversing the polarity changes the sensitivity by more than 50%, this indicates contamination or me-
chanical errors.
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– The sensitivity and stability get better the wider the peaks are.
QMH high-frequency generator.
– For interchanging, set "First" to 0 and "Autorange Mode" to "SAMPLE".