Charge Amplification of GEM-Based Gas Deiedors

The operation of a gas electron multiplier (GEM) detector equipped with a multiwire proportional chamber (MWPC) or a micro strip gas chamber (MSGC) was examined. The additional gain provided by the GEM permitted the operation of the combined detector at substantially reduced voltages, thus increasing its reliability. The GEM + MWPC detector showed a very good gain uniformity of 2% variation throughout the active detector area. The single GEM detector achieved effective gains of above 3 000 with pure Ar by the effect of avalanche confinement.