Growth technologies of oxide crystals in W/Mo crucibles have been developed as a low-cost alternative to conventional processes involving Ir crucibles. Carbon-containing atmosphere needed to protect crucibles from oxidation leads to the introduction of carbon into the crystal lattice and creation of carbon-related defects, which affect the scintillation performance. Meanwhile, a search for fast scintillators for the new generation of positron-emission tomographs and high-energy physics experiments at colliders is under way. Codoping with divalent cations has become an efficient way to suppress long components of scintillation decay in Ce-doped scintillators. This work addresses Y 3 Al 5 O 12 (YAG) crystals codoped with carbon, cerium activator, and divalent cations. Optical and scintillation properties of YAG:Ce,C, $\text{A}^{2+}$ crystals (A = Ca $^{2+}$ , Mg $^{2+}$ , Ba $^{2+}$ , Sr $^{2+}$ ) are systematically studied. Among all the studied garnet compounds, YAG:Ce,C,Ca $^{2+}$ crystals demonstrated the fastest scintillation decay times, which are promising for the mentioned applications. Mechanisms of scintillation process in the studied materials are discussed. The Ce $^{3+}$ /Ca $^{2+}$ ratio in YAG:Ce,C,Ca $^{2+}$ was optimized to minimize slow components in scintillation decay.

Sesquioxides of lanthanides, yttrium, and scandium are promising hosts for laser and scintillation materials; however, the crystallization of such compounds is complicated by very high melting temperatures, as well as polymorph transitions. This work reports for the first time the growth of Y2O3 and Y2−xScxO3 crystals by the Vertical Gradient Freezing method from tungsten crucibles, proposing an alternative to extremely expensive rhenium and iridium crucibles. Translucent Y2O3 samples are obtained, and their luminescent and scintillation parameters are evaluated. The main issues of Y2O3 crystallization under the proposed conditions are discussed, as well as ways of enhancing the crystal quality. Finally, polymorph transitions are avoided by decreasing the average radius of the rare earth cation by Y3+/Sc3+ substitution, providing transparent Y2−xScxO3 crystals with a cubic structure.

Ce-doped lanthanum gadolinium pyrosilicates are among the most efficient oxide scintillation crystals with a light yield of ca. 40 000 ph MeV −1 and a high energy resolution.

Bismuth germanate (BGO) is a well known high density scintillating material widely used in many applications such as high energy physics and medical imaging. Bismuth silicate (BSO) features properties similar to BGO in terms of stopping power and Cherenkov photon yield with a lower scintillation light output but faster decay time, thus being more attractive for applications in high-rate environments. Mixed crystals such as Bi-4(GexSi1-x)(3)O-12 (BGSO, with x varying from 0 to 1) make it possible to optimize decay time and light yield based on the detector needs. A characterization campaign of the optical and scintillation properties of two sets of BGSO mixed crystals with Ge fraction varying from 0 to 100% was performed. A coincidence time resolution (CTR) at 511 keV of 208 +/- 2 ps FWHM was measured for a 2 x 2 x 3 mm(3) pixel with 40% Ge, while the optimum value obtained for the effective decay time is 49.9 +/- 1.8 ns for a 6 x 6 x 0.7 mm(3) plate-shaped sample with 30% Ge. Furthermore the smallest slow decay time component achieved is 101 +/- 2 ns and is obtained for the plate-shaped sample with 30% Ge, while the largest is 236 +/- 5 ns for a pure BGO sample with the same geometry. In addition we demonstrated the possibility to efficiently separate the Cherenkov and scintillation light produced in a pure BSO sample. Such a technique could be exploited in a crystal-based dual-readout calorimeter to improve the energy resolution for hadronic showers and jets.

The feasibility to grow bulk La-GPS:Ce scintillation crystals by the Czochralski method using Mo crucibles has been reported.

Thermally stimulated luminescence (TSL) measurements with spectral resolution on undoped NaI and NaI doped with Tl, In, and Eu are presented and analyzed. Based on the trap parameters extracted, carrier release rates are calculated as a function of temperature. The parameters calculated at 300 K by whole peak fitting yield release rates which are about 1-2 orders of magnitude higher than those obtained using the initial rise method. These data can be used to test release-rate predictions of the first ab initio calculations of carrier release and capture rates on dopants in NaI by Prange et al. A kinetic model of rate equations describing energy relaxation in NaI with different activators is used to simulate the TSL experiment and suggest an interpretation of the peaks' origin(s). We found that thallium can trap either charge carrier, electron or hole, while indium is only a hole trap, and europium induces very shallow electron traps in NaI.

The factors determining the characteristics of the SrI2:Eu scintillator during processing and packing stages are considered. Using experimental and computer modeling, we selected options for processing the surfaces of scintillators, providing an improvement in their scintillation characteristics. It is shown that the method of processing the surface of crystal Sr-2:Eu size of empty set21x5 mm and empty set21x10 mm grown by method of synthesis of raw materials components, combined with the diffuse reflector Tetratex provides improved energy resolution of 3.65 % and 3.87 % respectively at 662 keV.

SrI2:Eu crystals with the activator content of 0.1-5.5% were grown by the Bridgman-Stockbarger technique. The dependences of light yield, energy resolution, optical and luminescent properties on the Eu concentration have been studied. It has been shown that with a decrease in the amount of activator to 0.3% Eu, the energy resolution at 662 keV remains below 4%. The light yield gradually diminishes with decreasing Eu concentration. This makes it possible to revise the required amount of the expensive activator for growing high performance SrI2:Eu crystals. Scintillation parameters of crystals grown by the Czochralski and Bridgman-Stockbarger technique have been compared.

This paper presents the Czochralski growth of SrI2:Eu scintillation crystals. SrI2:Eu is one among the brightest recently discovered scintillators with an excellent energy resolution for spectroscopic identification of radioactive isotopes. The Czochralski crystal growth method is optimal from the point of scaling up of crystal production with minimal investment into upgrade of crystal growth equipment. In this paper, SrI2:Eu crystals with the diameter of up to 50 mm were produced by the developed process based on the Czochralski method. The crystals are prone to cracking, and thermal fields in the crystallizer still should be optimized. Nevertheless, the scintillation parameters of detectors cut from the grown crystals are similar to that in detectors fabricated by the conventional Bridgman–Stockbarger technology. The Eu2+ activator concentration across the crystals is uniform within 5%, as well as the energy resolution, which ranges within 3.6% ± 0.1% at 662 keV. Also, the decay times under X-rays and nonproportionality of scintillation light yield on excitation energy in the range of 31–1274 keV have been determined.

A method of concentration of gas impurities contained in a melt into sealed cavities in a crystal has been proposed for the first time. This makes it possible to determine the amount of gases dissolved in the melt during crystallization by the Edge-defined Film-fed Growth (EGF) technique and the gas pressure in cavities inside the crystals. We also measure the composition of gas inclusions in crystallized melts of Al2O3, Y3Al5O12 and Bi4Ge3O12 and discuss it in connection with crystal growth procedure and quality of crystals.

The technological features of Sr-2 crystals production are discussed in this paper. The main reasons of deterioration of the purity and quality of the crystals were identified. It is shown that anionic (OH-group) is the basic impurity significantly affecting the scintillation characteristics. Some methods for quality control of Sr-2 raw materials and crystals were proposed. Raw materials with pH < 3-4 are preferable for growing high-quality crystals with excellent scintillation parameters.

Bismuth germanate shaped crystals have been grown by the EFG (Stepanov) method. The correlation between growth rate, shape of crystals, their optical and scintillation parameters has been analysed. Optical and scintillation characteristics of the EFG crystals are similar to those obtained with Czochralski grown crystals, however, growth rate in EFG is by 2.5 times larger. Also we compare the photochromic effect under UV-irradiation in EFG and Czochralski grown crystals. Material losses at fabrication of plates, pixels, and rods from EFG shaped plates may be reduced by approximate to 50% compared to large diameter boules.

A full range of BGSO crystals from BGO to BSO was grown by the Czochralksi method. A set of procedures such as changing of stoichiometry, recrystallization and thermal treatment was applied to improve optical and scintillation parameters of the crystals. The relationships between scintillation yield, energy resolution, decay constants and Si4+/Ge4+ ratio in the crystals are discussed with regard to ongoing experiments on high energy physics. Crystal composition with better energy resolution 16.2 % at 662 keV irradiation was obtained.

Mixed BGO-BSO (BGSO) scintillation crystals with structure of eulitine are promising for application in high energy physics (HEP) experiments due to low cost, high density, and reasonable light output. This work is focused on optimization of growth parameters and composition of BGSO mixed crystals. BGSO with improved energy resolution up to 16.2% at 662 keV gamma-irradiation was obtained. The effects of recrystallization and post-growth thermal treatment are discussed.

We have studied the effect of geometrical and physical parameters of additional lower heater on thermal conditions during BGO growth by the Czochralski technique, in particular, on keeping flat melt/crystal interface during the whole growth process. Numerical simulation by CGSim software was used as an efficient tool for the analysis. After revealing optimal growth conditions and hot zone design by modeling, we have modified experimental growth setup and successfully improved crystal growth process in close agreement to modeling predictions.

A strontium iodide crystal doped by europium (SrI2(Eu)) was produced by using the Stockbarger growth technique. The crystal was subjected to a characterization that includes relative photoelectron output and energy resolution for γ quanta. The intrinsic radioactivity of the SrI2(Eu) crystal scintillator was tested both by using it as scintillator at sea level and by ultra-low background HPGe γ spectrometry deep underground. The response of the SrI2(Eu) detector to α particles (α/β ratio and pulse shape) was estimated by analysing the 226Ra internal trace contamination of the crystal. We have measured: α/β=0.55 at Eα=7.7MeV, and no difference in the time decay of the scintillation pulses induced by α particles and γ quanta. The application of the obtained results in the search for the double electron capture and electron capture with positron emission in 84Sr has been investigated at a level of sensitivity: T1/2∼1015–1016yr. The results of these studies demonstrate the potentiality of this material for a variety of scintillation applications, including low-level counting experiments.

Ce, Pr, and La-doped gadolinium pyrosilicate Gd2Si2O7 (GPS) single crystals were grown by the Czochralski and Top Seeded Solution Growth (TSSG) techniques for the first time. Formation conditions of different pyrosilicate phases were determined. X-ray luminescence integral intensity of Ce-doped GPS is about one order of magnitude higher in comparison with gadolinium oxyorthosilicate Gd2SiO5:Ce (GSO:Ce). All samples demonstrate temperature stability of luminescence yield up to 400K.

In the present work, numerical modeling has been performed to analyze heat transfer and melt convection during bismuth germanate Bi4Ge3O12 (BGO) crystal growth by the Czochralski growth method. In addition to global heat-transfer modeling, the suggested model accounts for the radiative heat exchange in the crystal and melt convection together with the crystallization front formation. The model helped to analyze the modification of the growth setup made by including additional heater. The numerical predictions obtained with CGSim software agree well with available experimental data.