Secondary electron multiplier

A secondary electron multiplier (SEV) is a device for amplifying electron signals and can be used as a stand-alone component or as part of a larger system such as a photomultiplier tube (PMT).
The impact of a free primary electron on a certain surface within the vacuum structure produces several free electrons of lower energy, whereby the acceleration voltage between the electrodes essentially determines the multiplication factor.
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With the help of a secondary electron multiplier, even the smallest electron currents or even individual electrons can be amplified with high time resolution by several orders of magnitude to such an extent that they are available as a measurable quantity.

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