A fast triple-GEM detector for high-rate charged-particle triggering

Abstract Triple-GEM detectors with pad readout has been tested at the CERN PS T11 Hadron Beam Facility. A time distribution RMS of 6 ns has been obtained with an Ar/CO 2 /CF 4 (60/20/20) gas mixture, achieving a substantial improvement with respect to Ar/CO 2 (70/30), where an RMS of 10 ns was obtained. This resulted in an efficiency of about 96% in a 25 ns time-window (and a total efficiency of 99.7%), suggesting that these detectors could be interesting devices for triggering at the typical LHC interaction rate.