Study of spatial resolution of coordinate detectors based on Gas Electron Multipliers

Spatial resolution of GEM-based tracking detectors is determined in the simulation and measured in the experiments. The simulation includes GEANT4 implemented transport of high energy electrons with careful accounting of atomic relaxation processes including emission of fluorescent photons and Auger electrons and custom post-processing with accounting of diffusion, gas amplification fluctuations, distribution of signals on readout electrodes, electronics noise and particular algorithm of final coordinate calculation (center of gravity). The simulation demonstrates that the minimum of spatial resolution of about 10 mu m can be achieved with a gas mixture of Ar-CO2 (75-25 %) at a snips pitch from 250 mu m to 300 mu m. At a larger pitch the resolution quickly degrades reaching 80-100 mu m at a pitch of 460-500 mu m. Spatial resolution of low-material triple-GEM detectors for the DEUTERON facility at the VEPP-3 storage ring is measured at the extracted beam facility of the VEPP-4 M collider. One-coordinate resolution of the DEUTERON detector is measured with electron beam of 500 MeV, 1 GeV and 3.5 GeV energies. The determined value of spatial resolution varies in the range from approximately 35 pan to 50 lam for orthogonal tracks in the experiments. (C) 2016 Elsevier B.V. All rights reserved.