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。     

A review on the progress of ZnSe as inorganic scintillator

Modern scintillator detectors act as an efficient tool for detection and measurement of ionizing radiations. ZnSe based materials have been found to be a promising candidate for scintillation applications. These scintillators show much-needed scintillation efficiency along with advantages such as high thermal and radiation stability, less-toxicity, non-hygroscopicity, emissions in the visible range and small decay time etc. Further, in quantum confinement regime, they show improvement in luminescent properties and size dependent emissions. In this review article, the attempt has been made to trace the progress of ZnSe based materials towards highly efficient quantum dot scintillators. Here, the fundamental process of scintillation has been explained. Factors such as doping, annealing, heavy ion irradiation which affects the scintillation response of ZnSe based scintillators have also been discussed. Method of synthesis plays a key role in optimization of quantum dot properties. Hence, it has been tried to trace the development in methods of synthesis of quantum dots. With optimized synthesis, we can extend applications of these highly efficient quantum dot scintillators for various scientific and industrial applications.     

用北京同步辐射光源研究氟化物闪烁体的荧光时间衰减特性

介绍了利用北京同步辐射光源测量闪烁体荧光时间结构特性的新方法.并用此方法测量了纯BaF_{2、CeF3晶体和粉晶样品及掺La³⁺、Ce³⁺的BaF2晶体时间衰减谱.对BaF2掺稀土元素的测量结果表明,La³⁺和De³⁺的掺入对BaF2时间衰减慢成分均有一定的抑制作用,但从理论上分析两种掺杂对慢成分的抑制机制并不相同.}     

A neodymium-loaded liquid scintillator

One promising approach to the search for neutrinoless double beta (0ν2β) decay is the use of liquid scintillators with double β-decay sources dissolved in them. The ¹⁵⁰Nd isotope is the one best suited to observing this process. Samples of liquid scintillators based on linear alkylbenzene with a neodymium mass fraction of 0.32% are described in this work; neodymium 4-methyloctanoate was used as a Nd-loaded additive. The spectral-luminescent and scintillation properties of the new materials were studied. The possibility of using the obtained compounds in experiments to search for 0ν2β decay is demonstrated.     

Evidence for a three-phonon giant resonance state in 40Ca nuclei

Inelastic scattering of 40Ca on 40Ca at 50 MeV/A has been measured in coincidence with protons at the GANIL facility. The SPEG spectrometer was associated with 240 CsI(Tl) scintillators of the INDRA 4pi array, allowing for the measurement of complete decay events. The missing energy method was applied to these events. For events with excitation energy between 42 and 55 MeV, a direct decay branch by three protons towards the low energy states of 37Cl gives the first evidence for a 3-phonon state built with giant resonances.     

Luminescence properties of Ce3+ doped gadolinium-calcium-silicaborate glass scintillator

In this work, the Ce³⁺ doped gadolinium-calcium-silicaborate glass scintillators of the composition ratio 25Gd₂O₃:10CaO:10SiO₂:(55−x)B₂O₃:xCeF₃, have been fabricated by using the melt-quenching technique. The doping concentration of the Ce³⁺ was varied from 0.05 mol% to 2.5 mol%. The 4f-5d transition of the Ce³⁺ allowed scintillation with a fast decay time. The absorption spectrum, X-ray induced emission spectrum, photo luminescence spectrum, laser luminescence spectrum and decay time of the scintillators were measured for studying the luminescence properties. From the X-ray induced emission spectrum result, we checked the trend between doping concentration and light yield. The laser induced luminescence spectrum was measured while changing the temperature from 300 K to 10 K. We also measured the decay time by using the laser excitation of the 0.15 mol% Ce³⁺ doped glass scintillator.     

Influence of defects on scintillation properties of oxyorthosilicate crystals Ce:Sc:LFS

New scintillation crystals Ce:Sc:Li:LFS and Ce:Sc:Ca:LFS based on lutetium oxyorthosilicate are grown. Optical characteristics and the decay time of new scintillators are studied. For Ce:Sc:Ca:LFS crystals, it is shown that oxygen vacancies dominate in the energy transfer in the matrix transmission range of 3.46–6.26 eV. It is found that the high density of oxygen vacancies at the lower part of the Ce:Sc:Ca:LFS crystal leads to a decrease in the scintillation time to 22–26 ns.     

DMANS——一种新型荧光闪烁体染料的寿命与能量转移的研究

本工作对一种新型荧光闪烁体染料——4-二甲胺基—4''硝基芪(DMANS)在不同介质中的光谱行为和能量转移进行了研究,发现介质的极性大小以及介质和染料间的能量转移对该闪烁体染料的荧光量子产率和闪烁发光延迟具有重大影响。研究对选择基体材料和合理组成闪烁材料配方有一定的参考价值。     

Scintillation properties of the Yb-doped YAlO3 crystals

Yb³⁺-doped YAlO₃ single crystals were grown by the Czochralski method with a radio frequency heating system. The starting melt compositions of Y_1−xYb_xAlO₃ were varied as x=0.02, 0.1, 0.2, 0.3 and 0.45. Photo- and thermo-luminescence characteristics including emission decays were measured within 4–300 K. Very fast charge transfer luminescence of Yb³⁺ was found, with the typical double peak spectrum at 345 and 525 nm. At room temperature the photoluminescence and scintillation decay curves show a leading subnanosecond decay component without any additional slower processes. The high density of Yb-rich YAlO₃ makes this material a promising candidate for fast scintillators.     

塑料闪烁体基质到溶质的能量传递

本文研究了以聚苯乙烯为基质,添加具有不同光谱荧光性质溶质的二元塑料闪烁体的发光.测量了闪烁体的激发光谱,荧光光谱,γ射线,X射线和紫外线激发的相对发光强度及其与溶质浓度的关系,测量了聚苯乙烯吸收波长和溶质吸收波长激发下的发光衰减及其与溶质浓度的关系.讨论了基质到溶质的能量传递机制.     

CdWO4 crystal scintillators from enriched isotopes for double beta decay experiments

Cadmium tungstate crystal scintillators enriched in ¹⁰⁶Cd and ¹¹⁶Cd were developed. The produced scintillators exhibit good optical and scintillation properties, and a low level of radioactive contamination. Experiments to search for double beta decay of ¹⁰⁶Cd and ¹¹⁶Cd are in progress at the Gran Sasso National Laboratories of the INFN (Italy). Prospects to further improve the radiopurity of the detectors by recrystallization are discussed.     

Characteristics of a stilbene scintillation crystal in a neutron spectrometer

Various organic scintillators are commonly used as the detecting material for neutrons, but these detectors are less sensitive to gamma rays. In particular, stilbene crystals and BC501A (NE213, EJ301) have good pulse-shape discrimination (PSD) between neutron and gamma-ray events, and have been selected as the media for fast-neutron detection among the organic, inorganic and plastic materials in a mixed radiation field. Although some of the scintillation characteristics of stilbene crystals have been studied, the detailed scintillation characteristics of the crystal are not completely understood. In this study, the light yield, decay time and pulse shape discrimination capability of a stilbene crystal were measured because this crystal is an optimized detector in a large flux of neutrons such as those might be found in cyclotron and charged particle accelerator facilities. The pulse-shape discrimination of neutrons and gamma rays with a stilbene crystal was measured using a ²⁵²Cf neutron source at room temperature. A neutron tagger module was used for the neutron and gamma separation using the charge comparison method in real time. The total pulse width for the charge integration and the delay from the peak-to tail start time were optimized for a better neutron and gamma separation. The relative light yield and decay time of the stilbene crystal scintillator were also measured.     

Role of hot electron transport in scintillators: A theoretical study

Despite recent intensive study on scintillators, several fundamental questions on scintillator properties are still unknown. In this work, we use ab‐initio calculations to determine the energy dependent group velocity of the hot electrons from the electronic structures of several typical scintillators. Based on the calculated group velocities and optical phonon frequencies, a Monte‐Carlo simulation of hot electron transport in scintillators is carried out to calculate the thermalization time and diffusion range in selected scintillators. Our simulations provide physical insights on a recent trend of improved proportionality and light yield from mixed halide scintillators. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Modification of scintillation characteristics of CdWO4 by doping with different ions

We studied doping CWO with several different dopant ions in order to create new heavy and fast scintillators by quenching the efficient but slow scintillation in CWO. Transmittance, excitation–emission spectra, decay time and the light yield were measured for the dopants of Cs, La, Si, Bi, Na, Nb and Pb. None of them caused efficient quenching. Trivalent ions seem to degrade crystal transparency, while monovalent ions do not seem to cause quenching. While heavy doping of Pb causes quenching to some extent, crystal growth is not easy for heavy doping. Heavy doping of the same wolframite structure crystal should be further examined.     

Energy resolution and non-proportionality of scintillation detectors – new observations

According to the present knowledge, the non-proportionality of the light yield of scintillators appears to be the fundamental limitation of energy resolution and it is related to the intrinsic properties of the crystals. However, several observations collected in the last 10 years suggest more complex processes in the scintillators. First, the study of undoped NaI and CsI crystals showed that the non-proportionality and energy resolution are very sensitive to the accidental traces of impurities. For some crystals, like CsI(Tl), ZnSe(Te), undoped NaI at liquid nitrogen temperature and finally for NaI(Tl) at temperatures reduced below 0 °C, an influence of slow components of the light pulses on energy resolution and non-proportionality is observed. A common conclusion of these observations is the fact that the highest energy resolution, and particularly the intrinsic resolution measured with scintillators, characterized by two components of the light pulse decay, is obtainable when the spectrometry equipment integrates the whole light of both components. In the limiting case, the afterglow could be considered also as a very slow component destroying the energy resolution. The aim of this work is to summarize all above observations looking for their origin.     

Nemo double-beta-decay experiments

To investigate double beta decay processes the NEMO collaboration developed an electron tracking detector made of Geiger cells for track reconstruction and plastic scintillators for energy measurements. The prototype, NEMO-2, is described and results onββ decay of¹⁰⁰Mo,¹¹⁶Cd,⁸²Se and⁹⁶Zr are given. A brief presentation of the status and design parameters of a new detector NEMO-3, which is approximately 20 times larger, will also be given.     

Growth and Study of Scintillation Properties of Orthovanadate Crystals Ca:GdVO<Subscript>4</Subscript> and Ca:YVO<Subscript>4</Subscript>

New scintillation orthovanadate crystals Ca:GdVO₄ and Ca:YVO₄ featuring intrinsic luminescence are grown. The spectra of pulsed cathodoluminescence of new scintillators and their luminescence decay time are studied. Using γ-rays with an energy of 662 keV from the ¹³⁷Cs source, total absorption spectra (so-called photopeaks) for new orthovanadate crystals are measured. It is shown that the light yield of Ca:YVO₄ and Ca:GdVO₄ crystals is 28100 photon/MeV and 14000 photon/MeV, respectively.     

Study of the filter method for neutron pulse-height distributions measured with organic scintillators

Identification of neutron sources is of interest in several fields, such as homeland security or basic nuclear physics. Organic scintillators offer the possibility to unfold fast-neutron energy spectra. Since organic scintillators are sensitive to neutrons and gamma-rays, a method to discriminate these two types of particles is required. This paper is focused on investigation of the discrimination properties of the filter method by using a new procedure. We compare the results of an experimental filter method to a digital pulse-shape discrimination (PSD) method based on charge integration. In addition, these methods are compared to the simulation results obtained with the MCNPX-PoliMi code. The experimental and numerical investigations were performed with a ²⁵²Cf spontaneous-fission neutron source. The integration of the number of counts gave the relative differences between the experimental filter and digital PSD neutron pulse-height distributions (PHDs) and simulated PHDs less than approximately 5% in the range between 60 keVee and 1.715 MeVee of light output. Above 1.715 MeVee, the PSD method has advantages over the filter method, due to the filter method having significantly worse counting statistics. The results show that the filter method has potential for robust neutron measurements when the PSD method cannot be applied, such as for ‘old’ organic plastic scintillators without PSD capability.     

Kinetics of nonequilibrium processes excited in broad-band dielectrics by synchrotron radiation

Luminescence spectroscopy with subnanosecond time resolution is used to study features of nonequilibrium processes excited in several broad-zone dielectrics (mainly inorganic scintillators) by pulses of synchrotron radiation (SR). When excitation density exceeds a certain level, which is different for each material, there is an abrupt change in the kinetics of relaxation of the nonequilibrium states. This change is accompanied by nonuniform broadening or shortwave shifting of the luminescence spectrum and a drop in quantum light yield. The decay time for natural luminescence decreases by 1–3 orders, to nanoseconds, and is independent of temperature within the range 80–450 K. The build-up stage disappears in the kinetics of luminescence of Ce³⁺-centers and decay time is reduced by a factor of 2–4. Density effects are found to be independent of the conditions under which the material is exposed to SR. A model is proposed in which density effects are related to nonradiative energy transfer from the upper excited states of the luminescence centers to external quenching centers. The contribution of the space charge induced by SR is also examined. Ural State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 120–135, November, 1996.     

Studying the characteristics of scintillation counters in a beam of relativistic particles

In this work, the results of the measurements of characteristics of 40-cm and 2-m scintillation counters irradiated by a particle beam with a momentum of 7 GeV/c from the accelerator of the Institute for High Energy Physics are presented. The scintillators used in counters are BC-404 and BC-408 scintillators. The counters are viewed from both ends by R1828-01 photomultiplier tubes. The PMT signal spectra are well described by a convolution of the Landau and Gaussian distributions. Their width is determined mainly by fluctuations of ionization energy losses. The time distributions of the signals obey the Gaussian law. For the 40-cm counter, the time resolution is σ(T) = 88 ps; for the 2-m counter, it varies from 120–160 ps in its center to ~100 ps near the end.