Recently, we proposed a concept for a new class of near infrared (NIR) scintillators by employing efficient Eu2+ → Sm2+ energy transfer. In this article we investigate the optical spectroscopy of Sm2+ in BaBrI, CsSrI3, and CsBa2I5 halide hosts. A criterion was derived for fast Sm2+ 5d → 4f emission and a list of new potential NIR scintillators is proposed.@en

The concept of quantum-dot-in-perovskite solids pioneered by Ning and co-workers introduces a useful class of solution-processed type I heterostructures for optoelectronics applications. Concurrent searches for solution-processable detectors of ionizing radiation have focused on lead-halide perovskites. As described in this issue of ACS Nano, Cao et al. examined CsPbBr₃ nanocrystals imbedded in Cs₄PbBr₆ as a wider gap host and determined its performance and possibilities as a scintillator for X-ray imaging. In this Perspective, we describe issues and research opportunities on ionizing radiation imaging and spectroscopy based on the CsPbBr₃@Cs₄PbBr₆ composite and other perovskite-dot-in-host combinations in which the dot may be of lower dimensionality than 3, and we explore ionizing radiation detectors using halide perovskites.

@en

In many aspects measurement of the α/β ratio has advantages over other methods. It provides higher precision and higher density of excitation than is available with Compton or photoelectric effect electrons. It has been shown that the α/β ratio follows the same trends and patterns as previously found for nonproportionality of electron/ gamma photon response. The α/β ratio also correlates with intrinsic energy resolution measured with 10 keV gamma photons. Materials with high α/β ratio have high intrinsic energy resolution at high density of excitation. The same trend is observed for 662 keV gamma photons with exception of alkali halides and ZnSe:Te. We have found that alkali halides have lowintensity of quenching and performbetter than LaBr3:Ce and LaCl3:Ce at high density excitation (with α particles or 10 keV electrons). The superiority of LaBr3:Ce and LaCl3:Ce over alkali halides probably comes not from high resistivity to high density quenching, but from lack of a low density quenching which is responsible for the "hump" in an electron/gamma nonproportionality curve. We can conclude, that halide-based scintillators are the most promising for discovering new highly proportional materials. @en

Scintillators are materials that absorb a high energy particle (α,β,γ radiation) and downconvert it into a short pulse of visible or near-visible light. As determined by photon detection statistics, the ultimate energy resolution for γ-photon detection can only be approached for materials that show a perfect proportional response with γ-energy. A large amount of research has resulted in the discovery of highly proportional materials, such as SrI₂:Eu²⁺ and CsBa₂I₅:Eu²⁺. However, the resolution is still limited because of unavoidable self-absorption of Eu²⁺ emission, especially when large-sized scintillators are to be used. By co-doping with Sm²⁺, the emission of Eu²⁺ can be efficiently shifted to the far-red by exploiting nonradiative energy transfer. Herein, this new idea is applied to CsBa₂I₅, and Sm co-doped CsBa₂I₅:Eu²⁺ can be considered as the first “black scintillator” with an emission wavelength around 755 nm, a remarkable high energy resolution of 3.2% at 662 keV gamma excitation, and a scintillation decay time of 2.1 μs. The proposed double-doping principle can be used to develop an entirely new class of near-infrared (NIR) scintillators.

@en

In this article we present a method of characterizing scintillating materials by digitization of each individual scintillation pulse followed by digital signal processing. With this technique it is possible to measure the pulse shape and the energy of an absorbed gamma photon on an event-by-event basis. In contrast to time-correlated single photon counting technique, the digital approach provides a faster measurement, an active noise suppression, and enables characterization of scintillation pulses simultaneously in two domains: time and energy. We applied this method to study the pulse shape change of a CsI(Tl) scintillator with energy of gamma excitation. We confirmed previously published results and revealed new details of the phenomenon.

@en

Internal contamination with actinium-227 and its daughters is a serious drawback in low-background applications of lanthanide-based scintillators. In this work we showed the important role of nuclear γ deexcitations on the shape of the internal alpha spectrum measured in scintillators. We calculated with Bateman equations the activities of contamination isotopes and the time evolution of actinium-227 and its progenies. Next, we measured the intrinsic background spectra of LaBr3(Ce), LaBr3(Ce,Sr) and CeBr3 with a digital spectroscopy technique, and we analyzed them with a pulse shape discrimination method (PSD) and a timeamplitude analysis. Finally, we simulated the α background spectrum with Geant4 tool-kit, consequently taking into account complex α-γ-electron events, the α/β ratio dependence on the α energy, and the electron/γ nonproportionality. We found that α-γ mixed events have higher light yield than expected for alpha particles alone, which leads to overestimation of the α/β ratio when it is measured with internal 227Th and 223Ra isotopes. The time-amplitude analysis showed that the α peaks of 219Rn and 215Po in LaBr3(Ce) and LaBr3(Ce,Sr) are not symmetric. We compared the simulation results with the measured data and provided further evidence of the important role of mixed α-γ-electron events for understanding the shape of the internal α spectrum in scintillators.@en

In this paper, we investigated the relation between gamma nonproportionality and alpha particle nonproportionality. First, we collected literature data on the α/β ratio of almost all commonly used scintillators. Second, we extended the literature review with our own measurements of LaBr3:Ce α/β ratio in function of Ce3+ concentration. A strong influence of codoping on the α/β ratio of LaBr3:Ce has been observed. Finally, we conclude that the gamma nonproportionality, gamma intrinsic energy resolution, and α particle response are closely related to each other, and they are due to quenching in the high density part of ionization tracks. Though it still needs to be tested for a larger group of scintillators, α/β can be used as a single value characterizing intensity of light quenching processes in scintillators.@en