塑料闪烁体的辐照特性

利用⁶⁰Co放射源分别对3种塑料闪烁体(BC-408, EJ-200, BC-404)进行辐照损伤研究, 比较辐照前后的透射谱、发射谱及光产额的变化, 发现3种闪烁体在低剂量具有较好的抗辐照性能; 当照射剂量超过1.44×10⁴Gy时,透射谱明显变坏, 光输出减少很严重, 但发射谱却保持不变.     

Timing performance of ZnO:Ga nanopowder composite scintillators

The implementation of nanocrystal‐based composite scintillators as a new generation of ultrafast particle detectors is explored using ZnO:Ga nanopowder. Samples are characterized with a spectral‐time resolved photon counting system and pulsed X‐rays, followed by coincidence time resolution (CTR) measurements under 511 keV gamma excitation. Results are comparable to CTR values obtained using bulk inorganic scintillators. Bringing the ZnO:Ga nanocrystal's timing performance to radiation detectors could pave the research path towards sub‐20 ps time resolution as shown in this contribution. However, an efficiency boost when placing nanopowders in a transparent host constitutes the main challenge in order to benefit from sub‐nanosecond recombination times. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

High‐perfomance Ce‐doped multicomponent garnet single crystalline film scintillators

We report for the first time the optimized content and excellent scintillation properties of single crystalline film (SCF) scintillators of multicomponent Gd_3–xLu_x Al_5–yGa_y O₁₂:Ce garnet compounds grown by liquid phase epitaxy (LPE) method. The Gd_1.5Lu_1.5Al_2.75Ga_2.25O₁₂:Ce and Gd₃Al_2.75–2Ga_2.25–3O₁₂:Ce SCF show the light yield (LY) comparable with that of high‐quality bulk crystal analogues of these garnets but faster scintillation decay and very low thermoluminescence in the above room temperature range. To our knowledge, these SCF possess the highest LY values ever obtained in LPE grown garnet SCF scintillators exceeding by at least 1.5–1.6 times the values previously reported for SCF scintillators.

     

Hole traps in Lu2O3:Eu ceramic scintillators. I. Persistent afterglow

The temporal dependence of X-ray excited scintillation from Eu³⁺-activated lutetium oxide transparent optical ceramic has been studied both experimentally and theoretically. The waveform of the decay was measured on time scales ranging from to . Kinetic equations were applied and a computational model was developed to describe the observed temporal behavior. This model involves two overlapping Gaussian distributions of trap depths; those ranging from 0.58 to may contribute to afterglow.     

用于位置灵敏型中子探测器的6LiF/ZnS（Ag）闪烁体性能研究

研究了掺杂6LiF的ZnS(Ag)闪烁体对中子、γ射线的发光特性和EJ426闪烁体样品的热中子探测效率、出射光产额和γ灵敏度。EJ426的热中子探测效率为32.4%,出射光产额为8.01×103光子/中子,70 mV阈值时的γ灵敏度小于10-7,表明EJ426是较理想的闪烁体型位置灵敏中子探测器材料。     

Plastic scintillator for pulse shape neutrons and gamma quanta discrimination

This study describes a new plastic scintillator for pulse shape n-γ discrimination. The scintillator contains two activation centers with different life spans. The first activator collects the singlet excitation energy of a polymer base, and the second activator utilizes triplet excitation states. We utilized 1,4-dimethyl-9,10-diphenylanthracene (DMDPA) and tris(dibenzoylmethide) (1,10-phenanthroline)Europium(III) (Eu[DBM]₃Phen) as activators. The figure of merit for this scintillator is 1.37, which is sufficient for reliable n-γ discrimination.     

有机锡化合物掺杂聚乙烯基甲苯基塑料闪烁体的制备、光学和闪烁性能EI北大核心CSCD

传统的塑料闪烁体由于其低有效原子序数和密度,不适用于能谱探测领域。有机重金属化合物掺杂塑料闪烁体的制备为塑料闪烁体实现能谱探测提供了一种有效途径。而有机锡化合物掺杂塑料闪烁体具有高光峰灵敏度,并保留了塑料闪烁体的快衰减特性。本文通过自由基聚合的方法成功制备了不同浓度2-(三丁基锡烷基)呋喃掺杂的聚乙烯基甲苯(PVT)基塑料闪烁体,并对其光学和闪烁性能进行了测试和比较。其中掺杂20%2-(三丁基锡烷基)呋喃的PVT基塑料闪烁体的透光率可达90%,X射线激发发射光谱主峰位于425 nm处,光产额为6700 ph/MeV,能量分辨率为15.8%@662 keV,衰减时间约为4.3 ns。我们也制备了1英寸直径、掺杂20%2-(三丁基锡烷基)呋喃的塑料闪烁体,具有6300 ph/MeV的光产额和15.8%@662 keV的能量分辨率。     

X‐ray‐excited optical luminescence and X‐ray absorption fine‐structures studies of CdWO4 scintillator

X‐ray‐excited optical luminescence (XEOL) emission and excitation spectra as well as the EXAFS signal of CdWO₄ were measured in the energy region of the Cd and W absorption edges. From EXAFS refinement, structural parameters such as number of atoms, distance from the absorbing atom and width of coordination shells in the W neighborhood were determined. The role of W–O interactions on the intrinsic luminescence of CdWO₄ is discussed. The efficiencies of conversion, transfer and emission processes involved in the scintillation mechanism showed to be high when self‐trapped excitons are formed locally by direct excitation of W ions. Annihilation of these excitons provides the characteristic scintillation of CdWO₄, a broad band emission with maximum at 500 nm. The presence of two energetically different O positions in the lattice gives rise to the composite structure of the luminescence band, and no influence of extrinsic defects was noticed. A mismatch between the X‐ray absorption coefficient and the zero‐order luminescence curves corroborates that the direct excitation of Cd ions induces secondary electronic excitations not very effective in transferring energy to the luminescent group, WO₆.     

Host structure dependence of light yield and proportionality in scintillators in terms of hot and thermalized carrier transport

Several outstanding questions, including why complex halide scintillator host structures allow higher light yield and flatter electron energy response than simple monovalent metal halides, have remained unanswered by current models of luminescence in dense ionization tracks. Our measurements of nonlinear quenching kinetic order, recent literature on hot‐electron transport in scintillators, and calculations presented here of hot‐electron velocity from band structure of SrI₂ and NaI, lead us to expand our previously described diffusion and nonlinear quenching model to include hot‐electron transport. Trends in multivalent versus monovalent metal halides, heavier versus lighter halides, and halides versus oxides versus semiconductors can be predicted based on optical phonon frequency, thermalized band edge mobilities, velocity in the upper conduction bands, and hole self‐trapping. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Gleaming Uranium: An Emerging Emitter for Building X-ray Scintillators

Scintillators are a unique class of luminescent materials with specific applications towards radiation detection. The emitters within state-of-the-art scintillators are mostly limited to bismuth, cerium, europium, thallium, lead, tungsten, etc. A shared feature of these elements is the relatively high atomic number, which is responsible for high radiation stopping power and radiation-induced luminescence. Searching for new scintillating materials is an essential target aiming at specific applications. In this Concept article, we will discuss our recent works on the topic of “uranyl-bearing scintillators”. As a virgin territory in this field, uranyl-bearing scintillators show intrinsic merits for designing new materials with X-ray detection capability, that is, the large photoelectric cross-section, high X-ray attenuation efficiency, and high crystal density. In addition, we also present challenges in the further development of the uranyl-bearing scintillators.