Advanced Aging study on Triple-GEM Detectors

We present here a new study of the aging of Triple-GEM detectors in contaminated environment. The goal of this experiment is to evaluate the influence of the ionization power of particles on the longevity of the gaseous detectors and therefore determine the best configurations required to reliably reproduce the classical aging phenomena in laboratory. A 100 cm² triple-GEM detector operating in Ar/CO₂ (70/30%) was irradiated simultaneously with low energy X-rays and 5.5 MeV alpha particles. Hydrocarbons and Si-based molecules were added to the gas mixture in order to accelerate the aging and simulating many years of slow gas pollution. We measured the evolution of the detector performance in two irradiated zones and we performed a systematic chemical analysis of the GEM foils to measure the polymer concentration and thus the potential aging effects. The detector collected a total charge of 165 mC/cm² in the two irradiated sectors with no performance loss. Chemical analysis revealed a greater Si-based polymers concentration in the region irradiated with alpha particles. This is due to their higher ionization power, with respect to low energy X-rays, which generate denser electron avalanches and, thus, a higher polymerization rate. Further studies have to be performed in order to validate this result, at different experimental conditions and with different detector technologies.