Loss of light efficiency in CsI(Tl) scintillating screens for beam imaging in the keV energy range

The demand of scintillating screens for ion beam imaging has been growing during the last years for several applications, including the real time monitoring of ion beam profiles in nuclear physics research laboratories. Research and development activities, started at INFN-LNS several years ago, have been focused on the development of ion beam diagnostic devices operating in very low energy (<100 keV) and intensity (<105 particles per second) ranges. Scintillating crystals with high efficiency are available for such purposes but a protracted beam irradiation induces radiation damage in the lattice, thus implying a decrease of its light yield. In this paper we report on the dependence of the light efficiency of a CsI(Tl) scintillating screen as a function of the fluence of low energy 16O ions, by means of image analysis techniques.