This report gives a review of the radiation damages induced by gammas and energetic hadrons in inorganic scintillating materials. We discuss the creation and recovery of color centers in ...scintillating materials under gamma and high energy proton irradiation, the two main causes of irradiation in High Luminosity LHC. The induced phosphorescence and the production of radioisotopes in heavy and light inorganic scintillators and in surrounding construction materials, as well as their influence on the possible design of the detector working in a high dose rate environment, are also described.
A new inorganic scintillation material based on Ba-Gd silica glass doped with cerium (BGS) is fabricated and studied. With the highest light yield among heavy glasses at the level of 2500 ph/MeV and ...fast scintillation response, the new scintillator ensures a good coincidence time resolution of < 230 ps FWHM for 511 keV γ-quanta from a 22Na source and SiPM readout. In addition to good performance in γ-quanta detection, the material demonstrates capability for efficient detection of low-energetic neutrons. The scintillator is produced by exploiting the standard industrial glass technology, which allows for an unlimited scaling up the conversion of raw material into a high-quality scintillator at a high rate. The glass can be casted in application-specific molds, so minimizing the material losses. The presented glass scintillator has potential for further improvement of its light output and scintillation response time.
The influence of co-doping of Gd3Al2GA3O12:Ce (GAGG:Ce) scintillator with magnesium on the rise time of luminescence response was studied in two GAGG:Ce crystals grown in nominally identical ...conditions except of Mg co-doping in one of them. Time-resolved photoluminescence spectroscopy and free carrier absorption techniques were exploited. It is evidenced that the Mg co-doping decreases the rise time down to sub-picosecond domain. Meanwhile, the light yield decreases by ∼20%. Thus, the feasibility of exploitation of the fast rise edge in luminescence response for ultrafast timing in scintillation detectors is demonstrated. The role of Mg impurities in facilitating the excitation transfer to radiative recombination centers is discussed.
•Photoluminescence rise time is compared in GAGG:Ce and GAGG: Ce,Mg.•Sub-picosecond photoluminescence rise time is revealed in GAGG:Ce,Mg.•The role of Mg in facilitating the excitation transfer is discussed.
A novel technique for testing the timing properties of scintillators is presented. The technique is based on transient absorption (TA) induced in a scintillating material by a selective excitation of ...the activator ion. A figure of merit to assess the timing properties of scintillators is suggested. This parameter was estimated for a set of cerium doped lutetium–yttrium oxyorthosilicate (LYSO:Ce) bars, which have been fabricated for Barrel Timing Layer sensor of Compact Muon Solenoid detector (CMS BTL) and exhibited different timing properties, and compared with the results obtained by conventional coincidence time resolution (CTR) measurements. The figure of merit applied for the tested bars shows a strong correlation (Pearson's correlation coefficient R = 0.95) with the CTR. These results suggest that the TA technique could be used as an experimental method to expand in a complementary way the extensive qualification procedure of LYSO:Ce crystals that will be performed for the production of the CMS BTL detector.
•Coincidence time resolution correlates with activator population rise time.•Population rise time can be probed by transient absorption in femtosecond domain.•Transient absorption can be exploited for testing of scintillator timing properties.
Non-linear absorption spectroscopy in pump and probe configuration has been used to test the population of non-equilibrium carriers in Ce-doped Y3Al5O12 (YAG), Lu3Al5O12 (LuAG), and Gd3AlxGa(5-x)O12 ...(GAGG) crystals with and without codoping by Mg2+ ions. A faster rise time of the induced optical density has been observed in all crystals codoped with Mg with respect to that in Mg-free samples. A significant difference in the time evolution of the differential optical density in GAGG with respect to YAG and LuAG crystals has also been measured. In both GAGG:Ce and GAGG:Ce,Mg an absorption band with maximum in the blue-green range and a decay time of 1.4ps is present. This band is due to the absorption by free electrons before they are trapped or re-captured by Ce3+ ions. A broad absorption band in the yellow-red region with very short rise time and a decay time longer than 150ps has been observed in all the Ce-doped garnets under study and can be attributed to the absorption from the Ce3+ excited states.
Gadolinium-yttrium- aluminum-gallium garnets (GYAGG) doped and codoped with Eu, Tb, and Ce were manufactured as ceramics to develop long-wavelength phosphors for high-brightness white light sources ...based on cathodoluminescence (CL). The CL light yield (LY) of Tb-doped ceramics at high-intensity electron beam excitation is shown to be more than twice as high as that of the conventional phosphor YAG:Ce, whereas codoping with Eu to redshift the chromaticity results in reducing the LY approximately to the level of YAG:Ce. The LY might be substantially improved by using a mix of Tb- and Eu-doped GYGAG powders instead of a single codoped GYGAG to produce ceramic phosphor. The high LY is explained by favorable contribution of Gd sublattice in excitation transfer to activator ions. Chromaticity of phosphors GYGAG:Tb, Eu can be tuned in a wide range by varying the ratio of Tb to Eu concentration. They are radiation resistant and stabile in the temperature range from 300 to 450 K.
Cathodoluminescence; Light yield; Europium; Terbium; Chromaticity.
We provide evidences that multicomponent garnet-type Ce-doped crystal GAGG (Gd3Al2Ga3O12) is a promising scintillator to be applied in harsh irradiation environments, particularly, in high-energy ...physics experiments and reactor research facilities, where long-term operation is mandatory. Applicability of this scintillator for the upgrade of the detectors at future accelerators with high luminosity like High luminosity LHC is considered and GAGG:Ce with different codopings is compared with Ce-doped oxyorthosilicate crystals, which are currently also strong candidates for such applications. It is shown that the irradiation with 24 GeV protons at a fluence of 5x1014 p/cm2 has no significant effect on optical absorption in the spectral range of the scintillator emission. The contribution of radioisotopes formed in the material by irradiation with protons to the noise pedestal and the noise energy equivalent due to harmful radio-luminescence excited by the radionuclides remains negligible at short gates in collider experiments. Moreover, we show that the irradiation-generated color centers absorb outside the spectral range of Ce luminescence. These centers do not significantly affect the dynamics of nonequilibrium carriers, which is responsible for the timing properties of the scintillator. The density of free carriers decays with a characteristic time of 2 ps, while the decay constant for trapped carriers is ∼50 ns both before and after irradiation.
•Luminescence intensity due to hadron-induced isotopes is similar in GAGG and LSO.•Proton fluence of up to 5x1014 p/cm2 does not affect timing properties of GAGG:Ce.•GAGG is prospective for radiation detectors in harsh radiation environments.
Luminescence and photo-thermally stimulated defects creation processes are studied for a Pr3+-doped PbWO4 crystal at 4.2–400K under excitation in the band-to-band, exciton, and charge-transfer ...transitions regions, as well as in the Pr3+-related absorption bands. Emission spectra of Pr3+ centers depend on the excitation energy, indicating the presence of Pr3+ centers of two types. The origin of these centers is discussed. The 2.03–2.06eV emission, arising from the 1D2→3H4 transitions of Pr3+ ions, is found to be effectively excited in a broad intense absorption band peaking at 4.2K at 3.92eV. By analogy with some other Pr3+-doped compounds, this band is suggested to arise from an electron transfer from an impurity Pr3+ ion to the crystal lattice W6+ or Pb2+ ions. The dynamics of the Pr3+-related excited states is clarified. In the PbWO4:Pr crystal studied, the concentration of single oxygen and lead vacancies as traps for electrons and holes is found to be negligible.
•Luminescence and defects creation processes in PbWO4:Pr single crystal investigated.•Existence of Pr3+-related luminescence centers of two types revealed.•Charge transfer origin of the intense 3.92eV absorption/excitation band suggested.•Dynamics of the Pr3+-related excited states clarified.•Negligible concentration of single oxygen and lead vacancies in PbWO4:Pr concluded.
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