Bruker Daltonik GmbH
Instrument Layout
3.1.5.5 Detector
The detector converts an ion current into an electrical current, which is then digitized
and delivered to the PC.
Modern detectors used in TOF mass spectrometers are designed as micro channel
plate detectors (Figure 3-11). A micro channel plate is a porous solid core assembly
with millions of tiny channels (
Ǿ
= 5-10µm, length = 0.5-0.8 mm), which are coated
inside with a semi-conductive layer. Every one of the microchannels works like an
electron multiplier, independent of the adjacent ones. To obtain a maximum electron
yield all these channels are electrically connected in parallel.
The multiplication process that takes place in a channel is illustrated beneath.
Im
pa
cti
ng
p
ar
tic
le
HV
Secondary electrons
Semiconducting layer
Output electrons
Glass channel wall
Figure 3-11 Principle of a micro channel
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