CsI photocathode: new results on photon ageing

In the recent years considerable progress has been made in the development of gaseous electron multiplier (GEM) based photon detector consisting a solid photocathode. Cesium iodide (CsI) is known to be the best photocathode as photon converter. This is because of their higher Quantum Efficiency (QE) in Ultra Violet (UV), X-ray UV and X-ray energy ranges and their relatively high stability against ambient air and gas environment. Photon detectors, which is capable of single photon counting, can reach dimension of few square meter or more and can be operated at high magnetic field. Such detectors are employed in particle and astroparticle physics experiments for particle identification using Ring Imaging CHerencov (RICH) technique. It has been observed that the QE of CsI photocathode decreases once exposed to photon irradiation and/or by exposed to humid air and hence it affects the detector performance. The aim of present work is to study the degradation of CsI photocathode by UV photons irradiation