Lead tungstate crystals for the ALICE/CERN experiment

Luminescence of the PbWO 4 :5% Cd crystal

“…5b). Under irradiation in the regular exciton absorption region of PbWO 4 (with E irr =4.2 eV), E a =0.05-0.06 eV. This value is much smaller than E a~0 .1 eV recently obtained by us for many PbWO 4 crystals studied.…”

“…In [3], no influence of Cd on the luminescence characteristics was found at the study of the PbWO 4 :135 ppm Cd crystal, probably, because of a too small (~0.01 %) Cd concentration. In the PbWO 4 :5 % Cd crystal, the concentration of Cd 2+ is much larger than the expected Pb 2+ losses via evaporation (0.1 % [4]). One may expect that in this case Cd 2+ ions can not only fill all the empty Pb 2+ sites but also form the local CdWO 4 -like phase in the PbWO 4 crystal lattice.…”

“…Our studies [5] carried out at a large number of the undoped PbWO 4 crystals allow to assume that the low-temperature green emission can be ascribed to the exciton of the WO 4 2--type localized near a defect. Most probably, this defect arises from the lead deficiency in the regular PbWO 4 -ion vacancies.…”

“…In [7], the disintegration of the exciton and defect-related states was observed in PbWO 4 , revealing itself in the appearance of the thermally stimulated luminescence (TSL). To obtain more information on the Decay time (µs)…”

“…In the search of a PbWO 4 scintillator efficiency increase, it was found that doping of PbWO 4 with Cd 2+ results in a considerable improvement of light yield as compared with undoped crystals. In the PbWO 4 :5 % Cd crystal grown by Czochralski method in air in Furukawa Co., the largest light yield of the blue emission (50-70 pe/MeV) was obtained among undoped and doped PbWO 4 crystals [1].…”