User Guide

Teledyne API M100E Analyzer Operation Manual Theory Of Operation
239
Figure 11-15: Basic PMT Design
A significant performance characteristic of the PMT is the voltage potential across the electron multiplier. The
higher the voltage, the greater is the number of electrons emitted from each dynode of the electron multiplier,
making the PMT more sensitive and responsive to small variations in light intensity but also more noisy (dark
noise). The gain voltage of the PMT used in the M100E is usually set between 450 V and 800 V. This parameter
is viewable through the front panel as test function HVPS (refer to Section 6.2.1). For information on when and
how to set this voltage, refe
r to Section 12.7.2.8.
The PMT is housed in
side the PMT module assembly (refer to Figure 11-12 and Figure 11-14). This assembly
also inclu
des the high voltage power supply required to drive the PMT, an LED used by the instrument’s optical
test function, a thermistor that measures the temperature of the PMT and various components of the PMT
cooling system including the Thermo-Electric Cooler (TEC).
04515F DCN6048