Compositionally Disordered Doped with Cerium Crystalline Garnet Type Materials for Brighter and Faster Scintillations

Ce-doped tetracationic garnets (Gd, M)3Al2Ga3O12(M = Y, Lu) form a family of new multipurpose promising scintillation materials. The aim of this work was to evaluate the scintillation yield in the materials of quaternary garnets activated by cerium ions with partial isovalent substitution of the matrix-forming gadolinium ions by yttrium or lutetium ions.Materials were obtained in the form of polycrystalline ceramic samples, and the best results were shown by samples obtained from the raw materials produced by the coprecipitation method. It was found that ceramics obtained from coprecipitated raw materials ensure a uniform distribution of activator ions in the multi-cationic matrices, which enables the high light yield and fast scintillation kinetics of the scintillation. It was demonstrated that the superstoichiometric content of lutetium/gadolinium in the material is an effective method to suppress phosphorescence accompanied scintillation. For ceramics with the composition (Gd, Lu)3Al2Ga3O12 , a scintillation yield of more than 50.000 ph/MeV was achieved. The scintillation kinetics was measured to be close to the kinetics with a decay constant of 50 ns.In terms of the set of the parameters, the developed scintillation materials are close to the recently developed alkali halide materials LaBr3:Ce, GdBr3:Ce. Moreover, they have high mechanical hardness, are characterized by the absence of hygroscopicity, and are better adapted to the manufacture of pixel detectors used in modern devices for medical diagnostics.

Surface Structure and Electronic Properties of Lu3Al5O12

Lu3Al5O12 (LuAG) is a famous scintillator that has the advantages of high efficiency, high light yield, and fast decay after being doped with active ions. F centers (oxygen vacancies with two electrons) and antisite defects are the most important defects and can greatly affect the scintillation performance in the bulk materials. However, the surface defects that strongly affect the spectrum of a single crystal (SC) and single crystal film (SCF) and the effect on the electronic properties have not been investigated. In this context, we investigate the surface structural and electronic properties of Lu3Al5O12 using first-principles calculations. The Lu atoms are six-fold and seven-fold coordinated with the O atoms on the S1 and S2 surfaces. The surface oxygen vacancies and antisites have considerably lower formation energies than for the bulk. The oxygen vacancies in the bulk introduce the occupied states in the band gap. The surface electronic states are mainly located on the oxygen atoms and can be eliminated via oxygen vacancies.

Gd-admixed (Lu,Gd)AlO3 single crystals: breakthrough in heavy perovskite scintillators

We report a breakthrough concept for a bulk single crystal as a heavy aluminum perovskite scintillator, where due to bandgap engineering by a balanced Gd admixture in a Lu cation sublattice, the scintillation performance dramatically increases. In an optimized composition of (Lu, Gd)AlO3:Ce (LuGdAP:Ce), the light yield approaches 21,000 phot/MeV, which is close to that of classical but much less dense YAP:Ce and 50% higher than the best LuYAP:Ce reported in the literature. Moreover, contrary to LuYAP:Ce, the LuGdAP host maintains a high effective atomic number close to that of LuAP:Ce (Zeff = 64.9), which is comparable to commercial LSO:Ce. An enormous decrease in afterglow on the millisecond time scale and acceleration in the rise time of the scintillation response further increase the application potential of the LuGdAP host. The related acceleration of the transfer stage in the scintillation mechanism due to diminishing electron trap depths is proven by thermally stimulated luminescence (TSL). Furthermore, we quantitatively characterize and model the energy transfer processes that are responsible for the change in the photoluminescence and scintillation decay kinetics of Ce3+ in the LuGdAP matrix. Such an innovative (Lu, Gd)AP:Ce scintillator will become competitive for use in applications that require heavy, fast, and high light yield bulk scintillators.

Determination of Position Resolution for LYSO Scintillation Crystals Using Geant4 Monte Carlo Code

LYSO scintillation crystals, due to their significant characteristics such as high light yield, fast decay time, small Moliére radius, and good radiation hardness, are proposed to be used for the electromagnetic calorimeter section of the Turkish Accelerator Center Particle Factory (TAC-PF) detector. In this work, the center of gravity technique was used to determine the impact coordinates of an electron initiating an electromagnetic shower in a LYSO array, in a calorimeter module containing nine crystals, each 25 mm × 25 mm in cross-section and 200 mm in length. The response of the calorimeter module has been studied with electrons having energies in the range 0.1 GeV-2 GeV. By using the Monte Carlo simulation based on Geant4, the two-dimensional position resolution of the module is obtained as σ R mm = 3.95 ± 0.08 / E ⊕ 1.91 ± 0.11 at the center of the crystal.

Mn2+ induced significant improvement and robust stability of radioluminescence in Cs3Cu2I5 for high-performance nuclear battery

Fluorescent type nuclear battery consisting of scintillator and photovoltaic device enables semipermanent power source for devices working under harsh circumstances without instant energy supply. In spite of the progress of device structure design, the development of scintillators is far behind. Here, a Cs3Cu2I5: Mn scintillator showing a high light yield of ~67000 ph MeV−1 at 564 nm is presented. Doping and intrinsic features endow Cs3Cu2I5: Mn with robust thermal stability and irradiation hardness that 71% or >95% of the initial radioluminescence intensity can be maintained in an ultra-broad temperature range of 77 K-433 K or after a total irradiation dose of 2590 Gy, respectively. These superiorities allow the fabrication of efficient and stable nuclear batteries, which show an output improvement of 237% respect to the photovoltaic device without scintillator. Luminescence mechanisms including self-trapped exciton, energy transfer, and impact excitation are proposed for the anomalous dramatic radioluminescence improvement. This work will open a window for the fields of nuclear battery and radiography.

Feasibility Study of an Alcohol-Based Liquid Scintillation Detector and Its Application

This paper proposes a new base material, a mixture of alcohol and water, for liquid scintillators. A possibility of using alcohol as a new detection solution in a particle detector is described. A liquid scintillator is widely used in various fields because of its high light yield. In addition, it is very important to develop a stable liquid scintillator for particle detectors or other medical applications. To date, there have been no previous R&D studies elsewhere for the use of alcohol in particle detectors, and no market products are available of this type. Thus, there is a room for improvement. This paper describes the brief synthesizing process of the alcohol-based liquid scintillator by varying the mixing ratio of each component that makes up the liquid scintillator. The several feasible physical and optical properties of an alcohol-based liquid scintillator were investigated and presented. Finally, as one of its applications, a range (beam-path length) measurement using an electron beam in medical physics is introduced after irradiating an alcohol-based liquid scintillator with electron beam energies of 6~12 MeV. The measurement results were compared with a Monte Carlo simulation, Novalis Tx, a phantom, and a CT image. In the near future, the new alcohol-based liquid scintillator could be used for particle detector or medical imaging applications.

Highly Efficient Copper Halide Scintillators for High-Performance and Dynamic X-ray Imaging

Progress towards high performance X-ray detection and dynamic imaging applications, including nondestructive inspection, homeland security, and medical diagnostics, requires scintillators with high light yield, reasonable decay time, low cost, and...

Light Yield Response of Neutron Scintillation Screens to Sudden Flux Changes

We performed a study of the initial and long term light yield of different scintillation screen mixtures for neutron imaging during constant neutron irradiation. We evaluated the light yield during different neutron flux levels as well as at different temperatures. As high frame rate imaging is a topic of interest in the neutron imaging community, the decay characteristics of scintillation screens are of interest as well. Hence, we also present and discuss the decay behavior of the different scintillation screen mixtures on a time scale of seconds. We have found that the decay time of ZnS:Cu/6LiF excited with a high neutron flux is potentially much longer than typically stated. While most of the tested scintillation screens do not provide a significant improvement over currently used scintillation screen materials, Zn(Cd)S:Ag/6LiF seems to be a good candidate for high frame rate imaging due to its high light yield, long-term stability as well as fast decay compared to the other evaluated scintillation screens.