A gas avalanche photomultiplier with a CsI-coated GEM

We describe the operation principle and properties of a CsI-coated GEM photodetector. This type of detector performs photon detection with reflective photocathodes, which are easy to produce and have high quantum efficiency. In the proposed configuration, the detector is practically free of avalanche-induced photon feedback effects. The influence of the GEM voltage and the electric fields close to the CsI-GEM electrode on the photon detection efficiency is studied. The conditions for obtaining full extraction of photoelectrons from the photocathode and their transfer through the GEM apertures are presented.