An aging study of double GEMs in Ar-CO/sub 2/

An aging study was performed using double GEMs and a printed circuit readout board (PCB) with an intense X-ray source in an ultra clean Argon-CO/sub 2/ gas environment. The detector was irradiated continuously for about 1000 hours without interruption until a large amount of charge was accumulated. A single-wire chamber served as a monitoring device to check the beam and ambient conditions and gas chromatography was used to ensure no hydrocarbon materials were present in the gas mixture. The detector could withstand more than 25 mC/mm/sup 2/ with only a slight sign of aging and the charge accumulated is presumably sufficient to conduct large-scale and long-term experiments in intense radiation fields.