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Pfeiffer <strong>Vacuum</strong><br />
Formula 4-4<br />
Stability condition U<br />
Formula 4-5<br />
Stability condition V<br />
Page 90<br />
Formula 4-6<br />
High-pass condition<br />
<strong>Vacuum</strong> <strong>Technology</strong><br />
0.23699<br />
Figure 4.5: Stability diagram of a quadrupole filter<br />
From Figure 4.5, it can be seen that:<br />
All ions whose parameters a and q are located in the triangle above the load lines<br />
will reach the detector<br />
U ap The ions will only reach the detector under voltage conditions = < 0.1678 .<br />
V 2 . qp Introducing the ratio between the atomic mass unit 1 amu = 1.66055 . 10 - 27 kg and the<br />
elementary charge e = 1.602 . 10 -19 A . mamu kg<br />
s = 1.0365 and multiplying it by<br />
the dimensionless mass number M of the corresponding ion yields the following conditions<br />
for U and V for the apex of the stability triangle:<br />
. - 8 10<br />
e A . s<br />
and<br />
a<br />
0.2<br />
0.1<br />
Load Line<br />
0.2 0.4 0.6 0.8 1.0<br />
kg<br />
U = 1.2122 . 10 -8 . M . 2<br />
r . 2<br />
f 0<br />
A . s<br />
kg<br />
V = 7.2226 . 10 -8 . M . 2<br />
r . 2<br />
f 0<br />
A . s<br />
0.706<br />
With the DC voltage de-energized, U = 0, all trajectories of the ions where q < 0.905 will be<br />
stable; according to Formula 4-5, these will all be masses where<br />
1.0801 . 10 7 . V A . s<br />
M > .<br />
2 . 2<br />
f kg<br />
r 0<br />
q<br />
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