R. Bouclier et al.,
"The Gas Electron Multiplier (GEM)"
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We describe operating principles and results obtained with a
new detector element: the Gas Electrons Multiplier (GEM).
Consisting of a thin composite sheet with two metal layers
separated by a thin insulator, and pierced by a regular matrix of open
channels, the GEM electrode, inserted on the path of electrons in a
gas detector, allows to transfer the charge with an amplification
factor approaching ten.
Uniform response and high rate capability are
Coupled to another device, multiwire or micro-strip
chamber, the GEM electrode permits to obtain higher gains or less
critical operation; separation of the sensitive (conversion) volume
and the detection volume has other advantages: a built-in delay
(useful for triggering purposes), and the possibility of applying high
fields on the photo-cathode of ring imaging detectors to improve
Multiple GEM grids in the same gas volume allow to obtain
large amplification factors in a succession of steps, leading to the
realization of an effective gas-filled photomultiplier.
Last modified: 5 Dec 1996,