5
Ion Source and Inlet Valve
Ion Source
Thermo Scientific
DSQ II Hardware Manual
169
Filament
A filament contains an electron lens, filament, filament spacer, and reflector. It is positioned
on top of the ion source and plugs into the 3-pin filament connector on the ion source board.
An electron lens (the metal cylinder enclosing the filament and reflector) prevents positive
ions from traveling up the electron beam, extending the life of the filament. It is located
between the filament and the ion volume. The voltage applied to the electron lens affects the
flux of electrons that enter the ion volume. Notice that the filament is a rhenium wire inside
the electron lens that is electrically heated to produce electrons by thermionic emission.
A reflector is located inside the electron lens, and repels electrons emitted by the filament
toward the ion volume. Filaments and reflectors are maintained at negative potential relative
to the ion volume, usually -70 V. The electrons emitted by the filament are accelerated into
the ion volume. The filament spacer is a ceramic ring that aligns the filament with the
electron entrance hole in the ion source block and ion volume. Likewise, the filament retainer
clip is a metal clip that ensures good alignment and fit of the filament to the source block.
Figure 87.
Filament
1
Filament Retainer Clip
3
Filament Spacer
2
Filament and Reflector (inside Electron Lens)
4
Electron Lens
4
3
1
2
Summary of Contents for DSQ II
Page 1: ...DSQ II Hardware Manual 120299 0002 Revision C December 1 2009 ...
Page 4: ......
Page 8: ......
Page 36: ...1 Basic Operations Shutting Down the GC MS System 20 DSQ II Hardware Manual Thermo Scientific ...
Page 198: ...5 Ion Source and Inlet Valve Inlet Valve Upgrade 182 DSQ II Hardware Manual Thermo Scientific ...
Page 202: ...6 Prefilter and Quadrupole 186 DSQ II Hardware Manual Thermo Scientific ...
Page 206: ...7 Ion Detector Electron Multiplier 190 DSQ II Hardware Manual Thermo Scientific ...
Page 242: ...226 DSQ II Hardware Manual Thermo Scientific Index ...