Time development of scintillating response in Ce‐ or Pr‐doped crystals

Abstract

Time development of a N phels /MeV photoelectron yield of various Ce and Pr-doped inorganic crystals (mainly garnets, perovskites and silicates) was studied in detail. Slow scintillation decay components influence time dependence, especially at those scintillators containing Lu as lattice ions where an increase of N phels per 1 MeV in the time span 0.25-5 µs is more than 50 %. 1 Introduction Scintillating properties and performance of various high or less efficient inorganic crystals, especially those of garnet, perovskite or silicate structures are intensively studied [1][2][3][4][5]. X-γ-or α-ray spectroscopies (pulse height spectra) are used to investigate their scintillation response and related characteristics as the N phels (E) photoelectron yield, L.Y.(E) light yield, En.Res.(E) (FWHM) energy resolution, proportionality of the yields and also time dependences of these parameters, especially N phels (E) yield (together with scintillation decay times) [1,3,4,6]. Modern scintillation detectors and applications as e.g. those for medical imaging need mechanically, chemically and thermally stable scintillation crystals characterized by (i) high light yield (at least above 10000 ph/MeV), (ii) appropriate density (above 6 g/cm 3 ), (iii) fast decays (in the time span 10-100 ns) and (iv) low afterglow or low portion of slow decay components [4,7]. Low afterglow is conditioned by suppressed presence of defects or centres responsible for slow scintillation decay processes.Afterglow can be a large problem in different applications. Occurrence of thermo-luminescence (TSL) peaks around room temperature (RT) and very slow decay components in the Ce 3+ scintillation decay were observed on LuAG:Ce crystals [8]. Trapping levels related to unspecified point defects were found on pure, Ce and (Ce,Si)-doped YAG crystal [9]. Generally, a presence of shallow traps results in slow scintillation decay processes and this should be also reflected in time development of scintillating response parameters, especially of N phels (E) photoelectron yield.The main goal of this paper is to present and summarize time dependence of scintillating response of various scintillators, especially of the N phels (E) photoelectron yield of Ce-and Pr-doped inorganic ones, based on (Y,Lu) aluminum garnets and perovskites [1,[8][9][10][11]. Time dependence of N phels (E) yield, presence of slow decay components and possible traps/defects reflected in the TSL spectra will be mentioned.

Growth and optical properties of Lu3(Ga,Al)5O12 single crystals for scintillator application

“…Except for the crystal grown under N 2 atmosphere, systematic increase of light yield was observed by increasing the Ga content. Light yield of the 20% Ga sample of 1859 phels/MeV exceeds that of the Ga-free sample grown under N 2 atmosphere, and even the typical light yield of commercially available Czochralski-grown LuAG:Ce crystals measured with the same setup, which were around 1200-1600 phel/MeV [23]. It is interesting to note that the trends in intensities of RL and the light yields do not coincide.…”

Single crystalline film scintillators based on Ce- and Pr-doped aluminium garnets

“…For example, for LuAG:Ce and LuAG:Pr SC scintillators it was determined (Mares et al, 2007) that more than 74 and 58%, respectively, of the light yield (LY) comes from the mentioned delayed recombination processes.…”

Growth and emission properties of Sc, Pr, and Ce co-doped Lu3Al5O12 epitaxial layers for scintillators

“…An increase of slow component in photoelectron yield with increase in Sc content can be tentatively explained by new stable electron traps, which were induced by the presence of Sc ions and which would delay radiative recombination at Pr 3+ ions. They may have similar origin as relatively deep traps which were found in ScCe co-doped bulk crystals [23,24]. While at low Sc concentrations the radiative recombination of an exciton trapped on Sc impurity and fast energy transfer to nearby Pr 3+ ions is a dominant process, at higher Sc concentrations likely electron trapping around Sc defect may become dominant and slow components are relatively more intense.…”