Energy Resolution of a Single GEM Detector

We investigated the characteristics of a developed gas electron multiplier (GEM) detector by measuring the 5.9 keV X-ray of the Fe-55 isotope. The energy resolution linearly decreased with increasing GEM voltage. As the drift voltage increased up to 150 V, the energy resolution continuously decreased. The saturation value of the energy resolution was achieved at a drift voltage of over 150 V. In the case of the induction voltage (V[ind.]), when V[ind.] is smaller than 500 V and larger than 800 V, the eective gain increases. In our GEM detector, the energy resolution is stable at a drift field of above 1.35 kV/cm (400 V), a GEM voltage of above 480 V, and an induction voltage of around 600 V.