Radioluminescent nanostructures provide a pathway to the fabrication of next-generation scintillators with tunability in composition, size, and morphology, and spectral and temporal properties, as well as scalable processing. Here we create a 3D millimeter-scale solid-state scintillators from SrLuF Ce3+, Pr3+ (SrLuF) core-shell nanostructures, integrating nanoscale building blocks into self-assembled macroscopic crystals. These scintillators exhibit single-digit nanosecond decay times, linear response, resistance to radiation-induced degradation, and optical emission yields within an order of magnitude of YAG Ce3+. We select a SrLuF host lattice owing to its high effective atomic number, wide band gap, and low phonon energy, which together support efficient 4f-5d radiative transitions from Ce3+ and Pr3+ activators while suppressing afterglow. We create a library of core-shell nanoscintillators with undoped SrLuF shells and cores spanning compositions from undoped SrLuF to fully doped SrCeF or SrPrF. Time-resolved and steady-state X-ray excited optical luminescence (XEOL) reveal broadband emission at 310 nm (Ce3+) and 335 nm (Pr3+) with biexponential decays in the sub-nanosecond (100-500 ps) and sub-15 ns (4-13 ns) regimes, demonstrating tunable radiative efficiency and ultrafast dynamics. Ensemble performance of the mm-scale superlattices is characterized under both continuous-wave and femtosecond high-intensity excitation, revealing high light yield, linear response, and radiation hardness under extreme irradiation of ultrafast 50fs X-ray pulses up to 5mJ per mm2 corresponding to a peak intensity of 1013 W per cm2. Together, these results establish a design framework for stable, bright, and tunable scintillation platforms with applications in precision health, space exploration and hard X-ray imaging at next-generation free-electron laser facilities.

Neutrinos offer a unique window into the world around us, allowing us to probe otherwise unreachable regions like the interior of stars and the depths of the earth, as well as potentially offering a mechanism for monitoring nuclear activity. Both pure-water and organic liquid scintillators have been used as the detection medium of large-scale neutrino detectors. Organic liquid scintillators offer higher sensitivity at lower energies, which is desirable for many applications, but detection of the Cherenkov radiation required for directional sensitivity is very difficult. A possible solution is to use water-based liquid scintillators (WbLSs), where some fraction of the water is replaced with a micellar solution of the liquid scintillator. This can enhance the detection sensitivity beyond that of pure water, without significantly affecting the ability to leverage the topological Cherenkov signature. Very specific scintillation properties are required to achieve this goal: the scintillation decay time should be significantly slower than that of the Cherenkov emission, so timing-based discrimination of Cherenkov light from scintillation can be applied. At the same time, the light yield should be high enough to enhance the overall sensitivity of the detector, but without losing too much of the Cherenkov light. In this study, we report a new water-based liquid scintillation cocktail based on a 9-methylcarbazole fluorescent dye and a linear alkylbenzene solvent. The proposed composition offers 13.8 ns scintillation decay time and 368 nm emission that matches the desired properties.

Scintillators based on Tl salts that provide high densities and high effective atomic numbers are currently being investigated for their possible use in radioisotope identification applications. Ce-doped Tl2LaCl5, in particular, has been the leading compound of those studied, showing good light output and energy resolution. The analogous Tl2CeCl5 has received much less attention, and the information known about it is rather incomplete. This paper focuses on the scintillation and optical properties of Tl2CeCl5 single crystals and compares them to those of Tl2LaCl5:Ce to better evaluate the effect of full substitution of La with Ce.

Eu-doped CsBr films (CsBr:Eu) exhibit excellent sensitivity for X-rays and are superior storage phosphors for high energy (MeV) photon radiography applications when coupled with thick copper or tungsten substrates. We report on the growth of micro-columnar CsBr:Eu films on copper substrates for megavolt (MV) X-ray imaging applications. Our films exhibit dense uniformly distributed micro-columns with an average diameter of similar to 10 mu m and a sharp, needle-like top. The advantage of this micro-columnar structured film is that the light can be channeled through the narrow columns to improve both light transmission and spatial resolution. We also determined the optimal Eu concentration in CsBr for the best storage phosphor performance. Growth of uniformly thick, micro-columnar structured films up to 2 mm was achieved on 2 '' x 2 '' metallic substrates, which were then characterized by optically-stimulated luminescence (OSL) coupled with X-ray excitation. Furthermore, 5 mm thick film growth demonstrates the potential to scale up to even thicker films.

Zinc tungstate is a semiconductor known for its favorable photocatalytic, photoluminescence, and scintillation properties, coupled with its relatively low cost, reduced toxicity, and high stability in biological and catalytic environments. In particular, zinc tungstate evinces scintillation properties, namely the ability to emit visible light upon absorption of energetic radiation such as x rays, which has led to applications not only as radiation detectors but also for biomedical applications involving the delivery of optical light to deep tissue, such as photodynamic therapy and optogenetics. Here, we report on the synthesis of zinc tungstate nanorods generated via an optimized but facile method, which allows for synthetic control over the aspect ratio of the as-synthesized anisotropic motifs via rational variation of the solution pH. We investigate the effect of aspect ratio on their resulting photoluminescent and radioluminescent properties. We further demonstrate the potential of these zinc tungstate nanorods for biomedical applications, such as photodynamic therapy for cancer treatment, by analyzing their toxicological profile within cell lines and neurons.

The 16th International Conference on Inorganic Scintillators and their Applications (SCINT 2022) was organized by the Los Alamos National Laboratory, and held in Santa Fe, NM, USA, from September 19 to October 23, 2022. More than 200 colleagues from nearly 20 different countries finally participated in the conference. The program consisted of five invited and ten keynote lectures, and 74 oral and 46 poster contributions. A special memorial session was devoted to Prof. Richard T. Williams. Extended exhibition with altogether about ten exhibitor stands provided another link to the market applications behind the research. An intense and structured research and development in the field of scintillators was represented by 15 sessions oriented toward various material technologies including nanomaterials, metamaterials, and classical bulk single crystals and optical ceramics. Their characterization, modeling, and underlying physical mechanisms description constituted the subject of a major part of conference contributions. Finally, various applications of inorganic scintillators were presented and discussed.

The absolute light yield of a scintillator, defined as the number of scintillation photons produced per unit energy deposited, is a useful quantity for scintillator development, research, and applications. Yet, literature data on the absolute light yield of organic scintillators are limited. The goal of this work is to assess the suitability of the EJ-204 plastic scintillator from Eljen Technology to serve as a reference standard for measurements of the absolute light yield of organic scintillators. Four EJ-204 samples were examined: two manufactured approximately four months prior and stored in high-purity nitrogen, and two aged approximately eleven years and stored in ambient air. The scintillator response was measured using a large-area avalanche photodiode calibrated using low energy γ-ray and X-ray sources. The product of the quantum efficiency of the photodetector and light collection efficiency of the housing was characterized using an experimentally-benchmarked optical photon simulation. The average absolute light yield of the fresh samples, 9100 ± 400 photons per MeV, is lower than the manufacturer-reported value of 10400 photons per MeV. Moreover, the aged samples demonstrated significantly lower light yields, deviating from the manufacturer specification by as much as 26%. These results are consistent with recent work showcasing environmental aging in plastic scintillators and suggest that experimenters should use caution when deploying plastic scintillators in photon counting applications.

We have synthesized several morphologies and crystal structures of MgWO4 using a one-pot hydrothermal method, producing not only monoclinic stars and large nanoparticles but also triclinic wool balls and sub-10 nm nanoparticles. Herein we describe the importance of reaction parameters in demonstrating morphology control of as-prepared MgWO4. Moreover, we correlate structure and composition with the resulting photoluminescence and radioluminescence properties. Specifically, triclinic-phase samples yielded a photoluminescence emission of 421 nm, whereas monoclinic-phase materials gave rise to an emission maximum of 515 nm. The corresponding radioluminescence data were characterized by a broad emission peak, located at 500 nm for all samples. Annealing the wool balls and sub-10 nm particles to transform the crystal structure from a triclinic to a monoclinic phase yielded a radioluminescence (RL) emission signal that was two orders of magnitude greater than that of their unannealed counterparts. Finally, to confirm the practical utility of these materials for biomedical applications, a series of sub-10 nm particles, including as-prepared and annealed samples, were functionalized with biocompatible PEG molecules, and subsequently were found to be readily taken up by various cell lines as well as primary cultured hippocampal neurons with low levels of toxicity, thereby highlighting for the first time the potential of this particular class of metal oxides as viable and readily generated platforms for a range of biomedical applications.

Li-containing elpasolite scintillators are currently investigated for their ability to detect both thermal neutrons and gamma photons with a single inorganic crystal. The scintillation is typically triggered by using an activator such as Ce. However, when Tl, also a luminescent ion, is present in the matrix, competition between the two centers Tl and Ce can occur. In this study, we are using Ce doped Tl2LiYCl6 to investigate this competition. To this end, the Ce (which substitutes Y) concentration is varied from 0 to 1 in the Tl2LiY1-xCexCl6 composition. In the low concentration range in which Ce remains a dopant, the photo- and radioluminescence spectra show that the scintillation of Tl2LiYCl6:Ce is mostly dominated by recombination on intrinsic luminescent centers. For cerium concentrations higher than x = 0.02, very different emissions can be easily distinguished from the photo- and radioluminescence of undoped and low Ce doped Tl2LiYCl6 crystals. These emissions are attributed to the formation of a second phase Tl2CeCl5, identified by X-ray diffraction. We conclude that the intrinsic luminescence related to Tl dominates the scintillation in the range of concentration for which Ce does substitute on the Y-site.

Theia would be a novel, "hybrid" optical neutrino detector, with a rich physics program. This paper is intended to provide a brief overview of the concepts and physics reach of Theia. Full details can be found in the Theia white paper [1].

The High Energy Physics community can benefit from a natural synergy in research activities into next-generation large-scale water and scintillator neutrino detectors, now being studied for remote reactor monitoring, discovery and exclusion applications in cooperative nonproliferation contexts. Since approximately 2010, US nonproliferation researchers, supported by the National Nuclear Security Administration (NNSA), have been studying a range of possible applications of relatively large (100 ton) to very large (hundreds of kiloton) water and scintillator neutrino detectors. In parallel, the fundamental physics community has been developing detectors at similar scales and with similar design features for a range of high-priority physics topics, primarily in fundamental neutrino physics. These topics include neutrino oscillation studies at beams and reactors, solar, and geological neutrino measurements, supernova studies, and others. Examples of ongoing synergistic work at U.S. national laboratories and universities include prototype gadolinium-doped water and water-based and opaque scintillator test-beds and demonstrators, extensive testing and industry partnerships related to large area fast position-sensitive photomultiplier tubes, and the development of concepts for a possible underground kiloton-scale water-based detector for reactor monitoring and technology demonstrations. Some opportunities for engagement between the two communities include bi-annual Applied Antineutrino Physics conferences, collaboration with U.S. National Laboratories engaging in this research, and occasional NNSA funding opportunities supporting a blend of nonproliferation and basic science R&D, directed at the U.S. academic community.

Six Mg2+ co-doped Lu3Al5O12:Ce scintillating garnet films prepared by liquid phase epitaxy, with Mg concen-tration from 0 to 3000 ppm, were irradiated by X-rays and underwent a series of thermoluminescence mea-surements from 10 to 720 K. The thermoluminescence signal of epitaxial films originated purely from electron recombination at Ce ions. It was found that the area of all the peaks present in thermoluminescence glow curves decreased rapidly with the increase of Mg concentration; for 3000 ppm, the decrease was by 4-5 orders of magnitude. Moreover, the bright burn effect was significantly suppressed by Mg co-doping. Possible explana-tions, i.e., trap concentration reduction or increased competition in free electron capture between thermolu-minescence traps and Ce4+ centers, were discussed.

Thermally stimulated luminescence (TSL) is a very well established experimental technique that finds use on a daily basis in several fields, ranging from radiation dosimetry, to archeological and geological dating, and to investigation of defects in insulators and semiconductors. The solution of the Schrödinger equation for electrons in a periodically varying potential shows that there are bands in energy in which the electrons are allowed to stay. The one-trap/one-recombination model so far presented and discussed is very successful in explaining the TSL features observed in real materials, namely, the shape of the detected glow peaks and their dependence upon trapped charge concentration, heating rate, and trap depth. A typical TSL recording instrument is composed by a sample chamber with a temperature controlled heating system, a light detector, and the associated electronics for signal processing. The heating system should provide reproducible and controllable heating profiles.

The carrier trapping and recombination mechanisms occurring in Ce-doped silica fibers, produced by a sol-gel technique, are investigated by combining temperature-dependent steady-state X-ray-excited luminescence, wavelength- and time-resolved scintillation measurements, and wavelength-resolved thermally stimulated luminescence, focusing especially on the temperature range from 10 to 320 K. The scintillation decay features a decay time of the order of tens of nanoseconds, characteristic of the parity- and spin-allowed 5d-4f radiative transition of Ce3+ ions. In addition, a slow and complex decay contribution in the microsecond timescale is detected. We interpret these features as due to the radiative recombination at Ce centers of carriers freed from a continuous distribution of trapping sites in the forbidden gap as well as to the occurrence of an athermal tunneling recombination process between traps and Ce3+ ions. This interpretation is reinforced by good agreement between independent evaluations of trap depths and lifetimes obtained by both the numerical analysis of scintillation time decays and thermally stimulated luminescence experiments.

Abstract New developments in liquid scintillators, high-efficiency, fast photon detectors, and chromatic photon sorting have opened up the possibility for building a large-scale detector that can discriminate between Cherenkov and scintillation signals. Such a detector could reconstruct particle direction and species using Cherenkov light while also having the excellent energy resolution and low threshold of a scintillator detector. Situated deep underground, and utilizing new techniques in computing and reconstruction, this detector could achieve unprecedented levels of background rejection, enabling a rich physics program spanning topics in nuclear, high-energy, and astrophysics, and across a dynamic range from hundreds of keV to many GeV. The scientific program would include observations of low- and high-energy solar neutrinos, determination of neutrino mass ordering and measurement of the neutrino CP-violating phase $$\delta $$ δ , observations of diffuse supernova neutrinos and neutrinos from a supernova burst, sensitive searches for nucleon decay and, ultimately, a search for neutrinoless double beta decay, with sensitivity reaching the normal ordering regime of neutrino mass phase space. This paper describes Theia, a detector design that incorporates these new technologies in a practical and affordable way to accomplish the science goals described above.

The title compound, thallium magnesium trichloride, has been identified as a scintillator with both moderate gamma-stopping power and moderate light yield. Knowledge of its crystal structure is needed for further development. This work determines the crystal structure of TlMgCl3 to be hexagonal P63/mmc (No. 194) and isostructural with RbMgCl3, contrary to previously reported data. This structure was obtained by single-crystal X-ray diffraction and was further confirmed by neutron diffraction measurements. Extending neutron diffraction measurements to high temperature, the data show that TlMgCl3 maintains this crystal structure from 290 K up through 725 K, approaching the melting point of 770 K. Anisotropic thermal expansion coefficients increase over this temperature range, from 31 to 38 × 10−6 K−1 along the a axis and from 19 to 34 × 10−6 K−1 along the c axis.

The impact of PPO concentration in LAB micelles on the luminescence decay time is determined.

Following the observation of large increases in light output of BaBrCl:Eu single crystals using AuBr3 as an additive in the melt, the impact of this process on the scintillation properties of other Br-based scintillating materials is investigated in an attempt to assess its broader use. Results for Cs2LiLaBr6:Ce and BaBr2:Eu single crystals with various Ce and Eu concentrations are presented. The results indicate that such an additive has very different effects in the two investigated materials. Although AuBr3 is not incorporated in the two crystalline matrices, it increases remarkably, by up to a factor 2, the light yield of BaBr2:Eu in a similar manner to that observed for BaBrCl:Eu, but is at best ineffective in the case of Cs2LiLaBr6:Ce. The improvements detected in the case of BaBr2:Eu are related to a substantial reduction in the long lived scintillation decay tails as well as in the thermally stimulated luminescence amplitude with respect to the crystal grown without AuBr3 in the melt. These improvements are, however, associated with a reduction in the energy resolution of these crystals related to a worse energy response non-proportionality. In the case of Cs2LiLaBr6:Ce, no clear improvements in either the light yield or the scintillation decay time are visible in the case of low Ce content, while a reduction of light yield upon AuBr3 addition caused by luminescence quenching phenomena is observed for high Ce concentration.