Development of a gaseous photon detector for Cherenkov imaging applications

This thesis is dedicated to the R&D activity aiming at a novel micro pattern gaseous photon detector based on the THick Gas Electron Multiplier (THGEM). The goal application of the novel photon detector is the detection of single photon in Ring Imaging CHerenkov (RICH) counters. The THGEM principle is derived from the Gas Electron Multiplier (GEM) one, even if the material, the production technology and the size scale are different: a THGEM is a Circuit Printed Board (PCB) coated with thin copper layers on both faces, with holes obtained by drilling. Part of the THGEM features are similar to those of the GEMs, but a number of characteristics aspects result substantially different: in fact, if the geometrical parameters can be scaled from the GEM ones, the parameters related to the electrons multiplication, which is a microscopic physical phenomenon, do not. This is why, before starting the photon detector development, we have performed a systematic study of the THGEM multiplier. A photon detector is formed coupling a multi layer THGEM-based detector with a solid state caesium iodide (CsI) photo cathode. We have studied the properties of THGEM-based photon detector prototypes. The next step of the R&D programme, not included in this thesis, is the engineering phase, needed to realise sets of large size photon detectors.