2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)
DOI: 10.1109/nssmic.2003.1351802
Institute of Electrical and Electronics Engineers, IEEE Transactions on Nuclear Science, 3(51), p. 1103-1110, 2004
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In recent years the scintillation properties of several cerium-doped rare earth oxyorthosilicate scintillators, Ln2SiO5:Ce where Ln = Y, La - Lu, have been reported and, in some cases, extensively studied. In addition, binary and ternary compounds such as (Lu,Y)2SiO5:Ce, (Lu,Gd)2SiO5 and (Lu,Y,Gd)2SiO5:Ce have been reported. All of these crystals have either monoclinic P or C structures with characteristic SiO4 tetrahedra and trivalent cations occupying two unique crystallographic positions. The trivalent cerium activator ions are assumed to occupy the cation lattice sites and possibly interstitial positions as well. The excited 5d state of Ce3+ is split into 3 observable levels with luminescence emission occurring only from the lowest 5d level to the 4f ground state (∼3 eV) with a Stokes shift of ∼ 0.5 eV. The band gap is about 6 eV, and the index of refraction is close to 1.8, with some variation according to crystallographic axes. Despite these similarities, important differences remain among the crystals including scintillation efficiency, decay time, rise time, and afterglow. In this paper, we report thermoluminescence measurements between 10K and 350K that allow the determination of trapping levels that may influence scintillation properties. The thermoluminescence data shows that the various scintillators compositions have surprisingly dissimilar sets of traps that may at least partially explain some of the differences in their scintillation properties.