R. Bouclier et al., "The Gas Electron Multiplier (GEM)" [ Full
Article | Questions & Answers | IIB Home Page ] 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 amplificat