An aging study of triple GEMs in Ar–CO2

An aging study was performed using triple GEMs and a print circuit board (PCB) with an intense X-ray radiation source. The GEM chamber consists of three identical GEMs and a large gas gain (6000) was shared by them. The chamber and its gas circulation line was carefully cleaned and constructed with stainless steel materials. The detector was irradiated continuously about 750 h without interruption until a large amount of charge was accumulated. A single-wire counter served as a monitoring device to check the beam and ambient conditions. The quality of the Ar–CO2 gas was checked by gas chromatography and no measurable amount of hydrocarbons were found. 27 mC/mm2 was accumulated with no noticeable degradation and no deposit or discoloration was found in an optical check.