A CEM has a high surface resistance. When a potential is applied between the input and output end of the CEM, the resistive surface forms a continuous dynode. A dynode has the property of emitting secondary electrons when primary particles impinge upon it (Fig. 5). This process is called secondary electron emission.
The secondary electrons are accelerated down the channel by a positive bias until they strike the surface again and generate further secondary electrons. This avalanching process continues until an electron cloud containing about 10e8 electrons is generated. If the electron cloud is collected with an anode, a single pulse is produced that appears on the oscilloscope as shown in Fig. 7. For an input of one primary particle a CEM thus produces an electron cloud of about 100 million electrons. The output pulses can be detected easily by using a discriminator, a preamplifier and a counter.

The output pulse is amplified by a pulse preamplifier when it remains above the discriminator level in the pulse-counting system. For every output pulse of the CEM the preamplifier transforms the negative signal into a standard rectangular pulse that is fed into a counter (Fig. 8).

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