This work deals with the optimization of bismuth silicate, Bi4Si3O12 (BSO) scintillation crystals as candidates for future high energy physics experiments at colliders involving the registration of both scintillation and Cherenkov light. Crystals with a high transparency in UV-band and a high timing resolution are required for this application. Czochralski process was employed for BSO crystal growth in Pt crucibles in a dynamic growth atmosphere. After the growth of a series of crystals in air, as well as mixed Ar-air static and dynamic atmospheres, it was shown that the mixed atmosphere minimizes Bi2O3 evaporation and reduces the amount of Pt dissolved in the melt by several times. This caused the reduction in the number of foreign inclusions in the grown crystals, providing a transparency of over 70 % in the > 300 nm range, a light output of up to 2140 ph/MeV, an energy resolution of 21.5 % at 662 keV gamma-rays, while a coincidence time resolution was improved from 148 to 125 ps.

The work deals with timing characteristics of garnet scintillation materials, especially for applications like time-of-flight PET or future collider experiments. While cerium-activated oxide scintillation single crystals are known for their fast performance due to rapid d-f relaxation in Ce 3+ . Meanwhile, the extended scintillation decay time of Gd 3 (Al,Ga) 5 O 12 :Ce (GAGG:Ce), the brightest oxide scintillator, still does not meet the requirements for the upgrade 2 of the central part of the LHCb electromagnetic calorimeter in CERN. Additionally, GAGG:Ce and other Ga-containing scintillators are typically grown in large sizes exclusively in Ir crucibles. Attempts to substitute Ga with Sc in the gadolinium garnet Gd 3 (Al,Sc) 5 O 12 :Ce (GSAG:Sc,Ce) grown from Mo crucibles resulted in a significant decrease in light yield compared to GAGG:Ce, although without a notable improvement in timing.The results obtained in this work certify that tuning the doping concentrations of Ca2+ and Mg2+ ions provides the enhancement of timing performance of Ce-doped YAG and GAGG scintillators due to elimination of carrier traps and acceleration of carrier transport to luminescence centers, independently on the host composition. Apart of that, YAG is more promising as host, because it can be obtained in cheap W/Mo crucibles in contrast to GAGG and other Ga-containing crystals. Due to the synergy between Ca2+ and Mg2+ dopants in garnets hosts, we demonstrated that improved combination of light yield and decay time can be achieved in Ce-doped garnets, i.e. larger number of prompt photons can be generated for fast-timing applications. At the same time, Sc,Ca codoped YAG:Ce is another promising approach to get fast scintillation crystals with a high light yield that may be grown by a cheap technology from W crucibles.

Particle physics experiments running at future accelerator facilities will rely on fast timing detectors to cope with high event pileup and to enhance particle identification capabilities. Direct band gap engineered semiconductor nanostructures show a high potential for emission of prompt photons due to quantum confinement, standing out in fast timing and high light yield with potential low cost production, thus triggering interest in the high energy physics community. In this contribution, characterization results of the scintillation properties of some promising nanomaterial scintillators will be presented and an overview of possible light-based detector designs based on these nanomaterials will be given, focusing on the NanoCal Blue Sky project of the European project AIDAinnova, a new generation of shashlik calorimeters. First results, obtained during test beam activities, will be presented as well.

The material requirements for gamma-ray detectors for medical imaging applications are multi-fold and sensitivity is often overlooked. High effective atomic number (Z eff ) Cherenkov radiators have raised the attention in the community due to their potential for harvesting prompt photons.A material with one of the highest Z eff and thus low gamma-ray attenuation length is thallium chloride (TlCl). By doping TlCl with beryllium (Be) or iodine (I), scintillation photons are produced upon gamma-ray interaction on top of the prompt Cherenkov photon signal. We report on the performance of TlCl: Be, I for fast timing applications, in particular time-of-flight positron emission tomography and prompt gamma imaging.Scintillation with a measured effective decay time of about 60 ns can be used for energy discrimination. On top, about 3% of the photons are produced promptly, forming a precise time-tagger. The timing capability of different geometries and readout strategies was investigated utilizing both populations of photons. For instance with silicon photomultiplier readout and absence of energy discrimination, a CTR of about 360 ps FWHM was measured for small (~3x3x3 mm³) TlCl crystals. With energy discrimination and time walk correction this figure improves to 230 ps, while with micro-channel plate photomultiplier tube readout even sub-100ps timing performance is possible.

Among the two-dimensional hybrid organic-inorganic perovskites, PEA2PbBr4 is one of the best scin-tillators combining high light yield and fast nanosecond decay time. However, it has limited sensitivity to X-ray and positron emission tomography because of insufficient mass density and effective atomic number. In this article, we show that exchanging the halide from bromide to iodide allows to shorten the absorption length as much as two times for X-ray energies. We present a detailed study on scintillation properties of self-grown samples of PEA2PbI4 crystal, which we compare with the previously reported results for PEA2PbBr4 crystal. The synthesis method of PEA2PbI4 crystal is based on dissolving the perovskite precursors in hydroiodic acid, which is then stirred and left for evaporation. Our measure-ments include the characterizations with optical, X-ray, and g-ray sources. We observe two emission bands of PEA2PbI4 crystal centered at 532 (green) and 660 (red) nm, and we link them to the scintillation mechanisms involving exciton and surface defect states. We also report the scintillation light yields of 1,000 and 10,000 photons/MeV at room temperature and 10 K, respectively, and the coincidence timing resolution full width at half maximum of 138 ps, and the fast component in scintillation decay curve of 0.5 ns. This fast component is much faster than that of 13.4 ns of PEA2PbBr4 crystal, and with two times shorter absorption length, it secures better opportunities in timing applications in particular time-of -flight positron emission tomography and high energy physics.(c) 2023 Elsevier Ltd. All rights reserved.

A series of Cs0.2Rb0.8Ca1-xEuxBr3 (0 ≤ x ≤ 0.08) crystals doped with different concentrations of Eu2+ were grown using the Bridgman-Stockbarger method.The work describes the influence of Eu2+ concentration on the luminescent and kinetic properties of Cs0.2Rb0.8Ca1-xEuxBr3 crystals,as well as on their scintil-lation performance.The maximum in the radioluminescence spectra of these crystals shifts from 439 to 446 nm with increasing europium concentration.The scintillation decay times of Cs0.2Rb0.8Ca1-xEuxBr3 lengthen with the Eu2+ content.The best light output of 33600 photons/MeV is obtained for Cs0.2Rb0.8Ca0.93Eu0.07Br3,and the best energy resolution of 6.9％ is found for Cs0.2Rb0.8Ca0.94Eu0.06Br3.

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.

After the discovery of a cross-luminescence (CL) in BaF2 in 1982, a large number of CL scintillators were investigated. However, no CL scintillator superior to BaF2 has been discovered, and the research of CL scintillators has subsided. Recent technological development in medical imaging and high-energy physics created a new demand for ultra-fast scintillators further supported by the development of UV-sensitive semiconductor photodetectors. As a consequence, renewed interest in CL scintillators appeared. To satisfy the requirements of fast timing applications high photo-detection efficiency, e. i. a good spectral match between the scintillator and photodetector must be achieved. Cesium-based ternary chlorides could provide a red-shift (∼1.5 eV) of CL towards the sensitive region of the photodetector (PMT or SiPM) while keeping light output and timing characteristics comparable to BaF2.

A novel crystal scintillator of RbBa2I5:Eu2+ was grown by the Bridgman-Stockbarger method. Its luminescence and scintillation properties were investigated. Under X-ray excitation, the crystal demonstrates blue lumines-cence peaking at 436 nm associated with 4f(6)5d(1)-> 4f(7) radiative transitions of Eu2+ ions. The main X-ray luminescence decay constant is 800 ns. The light output of RbBa2I5:3%Eu2+ sample under 662 keV excitation is 58,200 ph/MeV.