Development and applications of the gas electron multiplier

The Gas Electron Multiplier (GEM) has been recently developed to cope with the severe requirements of high luminosity particle physics experimentation. With excellent position accuracy and very high rate capability, GEM devices are robust and easy to manufacture. The possibility of cascading two or more multipliers permits to achieve larger gains and more stable operation. We discuss major performances of the new detectors, particularly in view of possible use for high rate portal imaging and medical diagnostics.