Radiation study of Lead Fluoride crystals

Lead fluoride (PbF$_2$) crystals represent an excellent and relatively innovative choice for high resolution electromagnetic calorimeters with granularity fast timing intensity environments. For this reason two PbF$_2$ crystals, sized $5\times 5 \times 40 $ mm$^3$, were irradiated $^{60}$Co photons up to $\sim 4$ Mrad 14 MeV neutrons a $10^{13}$ n/cm$^2$ total fluence. Their loss in transmittance was evaluated at different steps of the photon neutron irradiation campaign, resulting 30% above 350 nm. With always kept dark conditions, natural thermal annealing, as well optical bleaching 400 nm light, performed on specimens, partial recovery their original characteristics.