Aging measurements with the Gas Electron Multiplier (GEM)

Continuing previous aging measurements with detectors based on the Gas Electron Multiplier (GEM), we investigated a 31×31 cm2 triple-GEM detector, as used in the small area tracking of the COMPASS experiment at CERN. With a detector identical to those installed in the experiment, long-term high-rate exposures to 8.9 keV X-ray radiation were performed to study its aging properties. In standard operation conditions, with Ar/CO2 (70:30) gas filling and operated at an effective gain of 8.5×103, no change in gain and energy resolution is observed after collecting a total charge of 7 mC/mm2, corresponding to seven years of normal operation. bservation confirms previous results demonstrating the relative insensitivity of GEM detectors to aging, even when manufactured with common materials.