Effects of fast neutrons and gamma components on color centers and activator glow in Lu2SiO5:Ce scintillator crystals.

Optical absorption, photo-excitation, gamma-ray and thermally stimulated luminescence of a cerium-doped scintillation crystal Lu 2 SiO 5 :Ce were studied prior and after irradiating with fast neutrons fluencies of 1015-5∙1017 cm−2 in reactor, and after gamma-irradiation from 60Co for comparison. It is shown that at neutron fluencies >1015 cm−2 F centers (absorption band 5.2 eV), Ce3+/Ce4+ (4.75 eV) and Ce3+/F + (4.25 eV), as well as Ce4++V O (2.85 eV) and V Lu or V Si (2.3 eV) centers are generated in the LSO:Ce crystal structure. These induced defects are generated more intensively under neutron irradiation than when irradiated with gamma-quanta to dose of 5·107 Gy. Basing on the analysis of the gamma-excited luminescence of Ce3+ centers after various neutron fluencies and the results of thermal and photo impacting, several energy transfer mechanisms were suggested: reabsorption of activator luminescence by color centers, as well as charge capture with the formation of hole and electronic centers. LSO:Ce crystals can be recommended as a scintillation detector of fast neutron up to a fluency of 1016 cm−2 with a gamma-ray up to a dose of 106 Gy. Additional doping of LSO:Ce with Ca2+ ions results in the stabilization of visible optical transparency to gamma-irradiation up to a dose of 107 Gy. • Neutron irradiation of LSO:Ce leads to a decrease of the Ce activator luminescence. • When Ca is introduced the γ-dose up to 107Gy do not change the optical transparency. • Neutron fluency 1015cm−2 generates color centers more effective than γ-dose 5·107Gy. • Annealing of neutron-induced defects recovers the Ce3+ activator gamma-luminescence. [ABSTRACT FROM AUTHOR]