Measurement of GEM parameters with X-rays

The gas electron multiplier (GEM)-based detectors have been widely developed in past years and have been proposed for many different applications. In this paper, we report on a method able to provide information on the characteristic parameters of a GEM. A single-GEM detector is illuminated with a high-intensity flux of low energy (5.9 keV) photons and all the electrode currents are measured simultaneously. From the analysis of these measurements we extracted a phenomenological and analytical model able to describe the currents induced on the electrodes as a function of electric fields and GEM voltages when the detector is exposed to a continuous ionizing radiation. This model provides information on the characteristic GEM parameters. In conclusion we briefly describe other methods able to extract in a more direct way GEM parameters.