Operation principles and properties of the multi-GEM gaseous photomultiplier with reflective photocathode

Gas Electron Multipliers with a reflective photocathode deposited on the surface of the first multiplying element are very attractive devices for photon detection and imaging over large area at moderate cost. They combine production and operation simplicity, high sensitivity to single photons, fast time response and accurate localization. In this work we present in detail the mechanisms governing the operation of these photon detectors. The results of electron extraction, transfer, multiplication and detection processes in this multi-element structure are presented and analyzed. We discuss the role of important elements and parameters influencing the detectorʹs operation and performance: the GEM geometry, the choice of the different electric fields and the gas mixture.