Teledyne T101, Operation Manual, Page: 269 / 375

Teledyne ML - T101 Operation Manual Principles Of Operation
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10.4.4. PHOTO MULTIPLIER TUBE (PMT)
The T101 uses a photo multiplier tube (PMT) to detect the amount of fluorescence
created by the SO
2
and UV light reaction in the sample chamber.
Figure 10-13. PMT Assembly
A typical PMT is a vacuum tube containing a variety of specially designed electrodes.
Photons from the reaction are filtered by an optical high-pass filter, enter the PMT and
strike a negatively charged photo cathode causing it to emit electrons. A high voltage
potential across these focusing electrodes directs the electrons toward an array of high
voltage dynodes. The dynodes in this electron multiplier array are designed so that each
stage multiplies the number of emitted electrons by emitting multiple, new electrons.
The greatly increased number of electrons emitted from one end of the electron
multiplier is collected by a positively charged anode at the other end, which creates a
useable current signal. This current signal is amplified by the preamplifier board and
then reported to the motherboard.