Changes in Luminescence of Ce:yag Crystals Under Ionizing Radiation Treatment

Radiation induced changes in the luminescence spectrum under influence of UV light, γ-rays, electrons and protons for several concentrations of Ce$\text{}^{3+}$ ions as well as Mg$\text{}^{2+}$ ions in yttrium-aluminum garnet crystals were investigated. To irradiate with γ and electron as grown crystals were used while for proton irradiations the crystals were thermally annealed. For small concentrations of cerium ions (≈0.01 at.%) an increase in the luminescence (about 100%) was observed after gamma irradiation with a dose of 10$\text{}^{5}$ Gy. This increase was due to the growth in Ce$\text{}^{3+}$ ions concentration after γ-irradiation (≈50%), due to the Ce$\text{}^{4+}$ → Ce$\text{}^{3+}$ recharging reaction. For highly doped Ce:YAG crystals (0.1 at%, 0.2 at.%) also an increase, but much smaller (4%), for the Mg codoped crystals (0.1 at.%) was observed. After 1 MeV electron irradiation in the over-threshold type interaction a decrease in luminescence is observed due to the domination of the Ce$\text{}^{3+}$ → Ce$\text{}^{4+}$ ionization process. In the case of the proton irradiation, for small fluencies (≈10$\text{}^{13}$ particles/cm$\text{}^{2}$) an increase in luminescence is observed due to the domination of the recharging processes of Ce$\text{}^{4+}$ ions. For larger fluencies (>10$\text{}^{14}$ particles/cm$\text{}^{2}$) a decrease takes place due to a high level of radiation defects.