channel electron multiplier

channel electron multiplier [¦chan·əl i¦lek‚trän ′məl·tə‚plī·ər]

(electronics)

A single-particle detector which consists of a hollow glass or ceramic tube with a semiconducting inner surface; it responds to one or more primary particle impact events at its entrance by producing, in a cascade multiplication process, a charge pulse of typically 104-108 electrons.

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Channel electron multiplier

A single-particle detector which in its basic form (see illustration) consists of a hollow tube (channel) of either glass or ceramic material with a semiconducting inner surface. The detector responds to one or more primary electron impact events at its entrance (input) by producing, in a cascade multiplication process, a charge pulse of typically 10⁴-10⁸ electrons at its exit (output). Because particles other than electrons can impact at the entrance of the channel electron multiplier to produce a secondary electron, which is then subsequently multiplied in a cascade, the channel electron multiplier can be used to detect charged particles other than electrons (such as ions or positrons), neutral particles with internal energy (such as metastable excited atoms), and photons as well. As a result, this relatively simple, reliable, and easily applied device is employed in a wide variety of charged-particle and photon spectrometers and related analytical instruments, such as residual gas analyzers, mass spectrometers, and spectrometers used in secondary ion mass spectrometry (SIMS), electron spectroscopy for chemical analysis (ESCA), and Auger electron spectroscopy. See Auger effect, Photoemission, Spectroscopy

Cutaway view of a straight, single-channel electron multiplier, showing the cascade of secondary electrons resulting from the initial, primary radiation event, which produces an output charge pulse

A related device is the channel electron multiplier array, often called a microchannel plate. The channel electron multiplier array is usually a disk-shaped device with a diameter between 1 and 4 in. (2.5 and 10 cm) and a thickness of a fraction of a millimeter, and consists of millions of miniature channel electron multiplier devices arranged with channel axes perpendicular to the face of the disk. Channel electron multiplier arrays find application as image intensifiers in night vision devices, and are employed to add either large detection area or imaging capabilities, or both, to charged-particle detectors and spectrometers. See Particle detector