Nature of radiation resistance of LFS oxyorthosilicate crystals doped with Ce,Sc, Ca,and Y ions

Optical and luminescence characteristics of Lu_2+2ySi_1-yO_5+y (LFS) scintillation crystals are studied before and after irradiation with doses to 45 Mrad from a ⁶⁰Co source. LFS crystals were doped with Ce³⁺, Sc³⁺, Ca²⁺, and Y³⁺ ions with various concentrations. The dependence of the radiation resistance of LFS crystals on Ce ion concentration is detected. For the crystal of composition Ce:Sc:Ca:Y:LFS, it was found that its optical transmission (OT) and pulsed cathodoluminescence (PCL) spectra before irradiation do not differ from the spectra measured after irradiation with a dose of 45 Mrad within experimental error. The nature of the radiation resistance of rare-earth lutetium oxyorthosilicates (LFS) is discussed.     

New radiation resistant scintillator LFS-3 for electromagnetic calorimeters

The results of the study of optical and luminescence characteristics of new LFS-3 heavy scintillation crystals are presented. Advantages of these crystals in comparison with conventional scintillators are discussed. The radiation resistance of LFS-3 scintillation crystals is studied using an intense ⁶⁰Co radioactive source and a proton beam with an energy of 155 MeV. No changes in the optical transmission of LFS-3 crystals after their irradiation with a dose of 23 Mrad are detected.     

Growth and Study of Scintillation Properties of Orthovanadate Crystals Ca:GdVO<Subscript>4</Subscript> and Ca:YVO<Subscript>4</Subscript>

New scintillation orthovanadate crystals Ca:GdVO₄ and Ca:YVO₄ featuring intrinsic luminescence are grown. The spectra of pulsed cathodoluminescence of new scintillators and their luminescence decay time are studied. Using γ-rays with an energy of 662 keV from the ¹³⁷Cs source, total absorption spectra (so-called photopeaks) for new orthovanadate crystals are measured. It is shown that the light yield of Ca:YVO₄ and Ca:GdVO₄ crystals is 28100 photon/MeV and 14000 photon/MeV, respectively.     

Wavelength-Resolved Photoluminescence and Cathodoluminescence Decay Times of LSO:Ce Scintillator CO-Doped with Lithium and Scandium

Journal of Russian Laser Research - We study the luminescence decay times of Ce3+: Lu2SiO5 scintillator, co-doped with Sc3+ and Li+ ions, under the direct photoexcitation of Ce3+ ions at 337 nm and...     

Radiation Resistance of Yb:LaSc<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript> and Yb:LuYSiO<Subscript>5</Subscript> Laser Crystals

The optical transmission (OT) spectra of Yb:LaSc₃(BO₃)₄ and Yb:LuYSiO₅ laser crystals have been analyzed before and after irradiation from a ⁶⁰Co source with doses up to 45 Mrad. The OT spectra of the Yb:LuYSiO₅ crystal are found to be the same (within the measurement error) before and after irradiation. The irradiation of the 10 at.%Yb:LaSc₃(BO₃)₄ crystal significantly changes its OT spectra in a wide spectral range (330 to 700 nm). A 975-nm laser based on a previously irradiated 4 at.%Yb:LuYSiO₅ crystal has exhibited a differential efficiency of 23% under diode pumping. The up-conversion luminescence spectra in the visible range of the crystals under study have been explained.     

Structure of the Room-Temperature 2.5 eV <Emphasis Type="Italic">α</Emphasis>-Quartz Single-Crystal Pulsed Cathodoluminescence Band

We study the room-temperature (RT) pulsed cathodoluminescence (PCL) spectrum of a high-purity synthetic α-quartz single crystal. The spectrum consists of two wide bands with intensity maxima at 415 and 490 nm (2.99 and 2.53 eV). The band at 490 nm (2.5 eV) is polarized in the XY crystal plane (perpendicular to the third-order symmetry axis) and possesses a structure with three peaks at 480±2, 487±2, and 493±2 nm (2.58±0.01, 2.55±0.01, and 2.52±0.01 eV). The intensities of the peaks at 480±2 and 493±2 nm increased with increase in the irradiation dose up to 45 kGy. Peaks are equidistant at the energetic scale. The energy separation between the peaks Δ = 0.03 ± 0.01 eV is equal in order of magnitude to energies of Li _x O _y molecular vibrations and to the energy of the optical phonon in α-quartz. We propose an explanation of the experimental data obtained. According to this explanation, the structure observed may be attributed to the amplitude modulation of the quartz 2.5 eV emission band by the crystalline electric fields on frequencies of optical phonons. The nonequilibrium phonons may arise during the electron-beam irradiation.     

Influence of defects on scintillation properties of oxyorthosilicate crystals Ce:Sc:LFS

New scintillation crystals Ce:Sc:Li:LFS and Ce:Sc:Ca:LFS based on lutetium oxyorthosilicate are grown. Optical characteristics and the decay time of new scintillators are studied. For Ce:Sc:Ca:LFS crystals, it is shown that oxygen vacancies dominate in the energy transfer in the matrix transmission range of 3.46–6.26 eV. It is found that the high density of oxygen vacancies at the lower part of the Ce:Sc:Ca:LFS crystal leads to a decrease in the scintillation time to 22–26 ns.     

Emission of Molecular Nitrogen upon Electron Bombardment of Pyrolytic Aerogel SiO2 and Aluminum

JETP Letters - It is found that the emission intensity of the 2+ band system of the N2 molecule (C3Πu → B3Πg transition) under electron bombardment of pyrolytic aerogel SiO2 in air...     

P5+ Ion Doped Gd2SiO5:Ce3+ Scintillation Crystal

Bulletin of the Lebedev Physics Institute - Ce3+, P5+, Ca2+, and Zn2+ ion doped Gd2SiO5 crystals are grown by the Czochralski method. The pulsed cathodoluminescence spectra, light yield, and...     

Room-Temperature 2.5 eV Pulsed Cathodoluminescence Band of High-Purity Silicon Dioxide

We study the room-temperature (RT) pulsed cathodoluminescence (PCL) spectra of a set of pure synthetic (both crystalline and amorphous) silicon dioxide samples. We show that the PCL spectra of all samples (both amorphous and crystalline) possess bands with intensity maxima in the region of 487 – 500 nm (2.54 – 2.48 eV). These bands are the most intense in the PCL spectra of disordered materials. We investigate the annealing behavior of RT PCL spectra of the crystalline and amorphous samples. Annealing has no significant effect on this emission. We demonstrate that the surface area of the material plays no role in the emission of PCL bands at 415 and 490 nm in the spectra of α-quartz single crystal and crystalline powder with grain sizes of 10 – 100 μm. Our results show that the bands in the region of 2.5 eV are the universal property of all synthetic pure SiO₂ samples. The nature of the SiO₂ emission band in the region of 2.5 eV is not clear; we discuss two possible explanations. The first one is based on considering the intrinsic emission due to self-trapped exciton (STE) decay with the transient O-O (oxygen–oxygen) bond formation. The second one is based on the role of Li ions in the emission process.