The gas electron multiplier (GEM): Operating principles and applications

Introduced by the author in 1997, The Gas Electron Multiplier (GEM) constitutes a powerful addition to the family of fast radiation detectors; originally developed for particle physics experiments, the device and has spawned a large number of developments and applications; a web search yields more than 400 articles on the subject. This note is an attempt to summarize the status of the design, developments and applications of the new detector.