Radiation hardness of undoped CsI crystals against high energy protons

We compared radiation damages of undoped CsI for 12 GeV protons and for 60Co γ-rays between 104 and 108 rad. Degradation in optical transmission was similar in magnitude both for protons and γ-rays; it is as small as 1-3% per 1 cm thickness at 104 rad, while it is as large as or larger than 5% above 105 rad. The above feature is different for BGO or GSO:Ce, whose radiation hardness is roughly two orders of magnitude smaller regarding protons than regarding γ-rays. Recovery of damage is qualitatively similar both for proton and γ-ray irradiations; spontaneous recovery is only partial and the annealing effect of UV exposure is negligibly small. (orig.)