Simulations of X-ray conversion into primary electrons in GEM-based detector

Abstract

The paper presents the results of simulations of the interaction of X-rays of different discrete energies (1–25 keV) with the structure of the GEM chamber. The simulations were performed using Geant4 software. This program allowed taking into account phenomena such as the emission of photoelectrons, Auger electrons and fluorescence X-rays. As a result, the energy distributions of primary electrons formed in the absorption region of the detector (drift gap) were obtained. The distributions of primary electrons, which are the source of electron avalanches in the detector under study, are directly responsible for the distribution of pulses on the detector reading anode. Some measurements were also performed, confirming the compatibility of simulated spectra and experimental ones. The main conclusion from the simulation is the need to eliminate copper from the detector structure, especially from GEM foils and from the reading electrode, if there is an intension to record X-rays with energies above 9 keV . An observable parasitic contribution to the spectrum recorded by the detector is also given by several other materials.