Ce3+掺杂闪烁玻璃的研究进展

闪烁玻璃由于制备工艺简单,尺寸灵活可控,成本低廉等优点,有望成为中国环形正负电子对撞机(CEPC)中强子量能器的候选材料。其中,以Ce³⁺发光中心掺杂闪烁玻璃有较好的闪烁性能。玻璃基质可以分为氧化物玻璃、卤化物玻璃和微晶玻璃。本文根据Ce³⁺掺杂不同玻璃基质分类,重点关注了Ce³⁺掺杂闪烁玻璃的光学透过率、光产额、衰减时间等闪烁性能和抗辐照特性。并且,总结了国内外以及闪烁玻璃合作组的最新研究成果。针对不同玻璃体系的研究现状,从玻璃组成与制备工艺等两个方面探讨了玻璃性能提升手段。最后,对Ce³⁺掺杂闪烁玻璃未来的研究发展方向做出了展望。     

富集10B的Ce:Li6Lu(10BO3)3晶体生长及其闪烁性能

为了提高中子探测效率, 以富集¹⁰B的H₃¹⁰BO₃为原料, 通过提拉法生长了富集¹⁰B的Ce:Li₆Lu(¹⁰BO₃)₃晶体。X射线激发发射光谱测试表明: 其发光峰位于360~480 nm, 属于Ce³⁺离子典型的5d - 4f跃迁发光, 其闪烁发光效率为BGO晶体的3.9倍。在350 nm紫外光和¹³⁷Cs所发出的662 keV的γ射线激发下测得的衰减时间分别为21.0 ns 和31.7 ns, 在¹³⁷Cs辐射源激发下所测得的相对光输出是CsI(Tl)晶体的20%, 能量分辨率为9.7%。在慢化²⁵²Cf中子源激发下可以观测到明显的中子全能峰, 其能量分辨率为33%。上述研究结果表明, Ce:Li₆Lu(¹⁰BO₃)₃晶体具有较高的闪烁效率、快的衰减时间和良好的中子探测效率, 是一种具有应用前景的中子探测用闪烁晶体。     

Zr4+共掺对Cs2LaLiBr6:Ce晶体的中子/伽马甄别性能的影响

中子探测技术广泛用于国土安全、核材料安全检测以及高能物理等领域,由于3He资源紧缺,近年来急需开发出能够同时甄别中子/伽马的新型闪烁晶体, Cs₂La Li Br₆:Ce(CLLB:Ce)晶体具有良好的中子/伽马甄别能力、优异的能量分辨率以及高的光输出,但其中子/伽马甄别性能有待进一步提高。本研究采用垂直布里奇曼法成功生长了Zr⁴⁺共掺杂的CLLB:Ce晶体。通过不同表征手段研究了Zr⁴⁺共掺杂CLLB:Ce晶体的结构和组分,结果表明Zr⁴⁺成功掺入基质材料且对基质晶体结构不产生明显的影响,Zr⁴⁺共掺杂后没有产生新的发光中心,紫外衰减时间约为27.0 ns,仍具有较快的荧光衰减。Zr⁴⁺共掺杂CLLB:Ce晶体的品质因子(Figure of Merit, FOM)从1.2提高到1.5,表明其中子/伽马甄别能力得到改善。结合热稳定性和闪烁衰减时间,探讨了衰减时间对FOM的影响机制,Zr⁴⁺共掺杂可以抑制浅电子陷阱...     

Ce3+掺杂Li2O-MgO-Al2O3-SiO2玻璃的结构与荧光猝灭现象

采用熔融淬冷法制备了不同浓度Ce³⁺离子掺杂的20Li₂O-5MgO-20Al₂O₃-55SiO₂玻璃闪烁材料。采用X射线衍射(XRD)、高分辨透射电镜(HRTEM)技术、密度检测等方法研究了玻璃的微观结构随Ce³⁺离子掺杂浓度的变化规律, 采用荧光分光技术检测了玻璃的紫外光致激发光谱(PLE)、发射光谱(PE)。研究结果表明: 在不对称的晶体场作用下, Ce³⁺离子5d能级被劈裂为5个组分; 随着玻璃基质内Ce³⁺离子掺杂浓度增大, 玻璃的非晶化程度加深; 5d能级的劈裂宽度随之增大, 由此导致激发带向低能量端展宽、发射光谱明显红移; Ce³⁺离子的荧光发射强度随Ce³⁺离子掺杂浓度先升高、后降低, 浓度猝灭过程成为其荧光发射效率降低的主要原因。     

离子交换和热处理对贵金属掺杂硅酸盐玻璃光致发光的影响

贵金属纳米颗粒-玻璃复合材料是一种重要的非线性材料。利用光致发光谱及配位场理论, 深入研究了离子交换及氢气热处理对硅酸盐玻璃中贵金属离子的引入、还原、成核及生长过程的影响, 发现延长离子交换时间有利于提高玻璃中金属离子的浓度。对于掺Ag⁺硅酸盐玻璃, 不仅存在孤立Ag⁺离子, 同时也存在Ag₂⁺团簇。H₂中热处理后, 样品中孤立Ag⁺离子浓度迅速降低, 同时出现Ag₃²⁺团簇。对于掺Cu⁺硅酸盐玻璃, 仅存在孤立Cu⁺和Cu²⁺, 没有发现Cu⁺团簇的发光峰, Cu²⁺的存在造成Cu⁺的发光强度显著降低。掺Ag⁺硅酸盐玻璃经H₂热处理后, 再经过第二次离子交换往玻璃中掺Cu⁺是十分困难的。     

高效X射线紫外发光稀土纳米闪烁体及其活体X射线激活肿瘤治疗应用（英文）

基于X射线纳米闪烁体的光响应疗法是一种新兴的有良好应用前景的活体肿瘤治疗策略,迫切需要开发具有高效X射线激发紫外发光性能的纳米闪烁体.然而,由于当前纳米闪烁体的X射线紫外发光性能仍较弱,实现高效的X射线激活肿瘤治疗仍然是一个巨大的挑战.为此,我们发展了一种新型的具有良好X射线紫外发光性能的Gd³⁺/Ce³⁺共掺杂的LiLuF₄纳米闪烁体,并将其应用于活体肿瘤治疗.通过优化基质材料、掺杂剂和能量传递设计合成的纳米闪烁体,其X射线紫外发光强度比传统的Ce³⁺单掺杂材料增强了约18倍.我们进一步将纳米闪烁体与一氧化氮(NO)前体结合以概念验证研究纳米闪烁体的应用.在X射线照射下,该纳米复合物能够可控地产生NO,并在X射线诱导的NO和放射治疗协同作用下实现了优异的抗肿瘤效果.此外,X射线激活的NO治疗可以抑制肿瘤向肝脏转移,抑制肿瘤再生,延长小鼠存活率.这项工作有望推动纳米闪烁体的发展及其在活体深层组织疾病治疗中的应用.     

Gd3+为敏化剂的掺Tb3+硅酸盐闪烁玻璃

实验制备了以Tb³⁺为激活剂、Gd³⁺为敏化剂的硅酸盐闪烁玻璃, 研究了Tb₂O₃和Gd₂O₃含量对玻璃密度和玻璃折射率, 以及对玻璃在紫外光激发和X射线激发条件下的光学光谱特性的影响. 通过研究Tb³⁺/Gd³⁺共掺闪烁玻璃的激发与发光特性、荧光寿命, 结合稀土离子能级结构, 分析了Gd³⁺→Tb³⁺离子之间的能量转移与传递机制. 结果表明：在紫外激发条件下, 大量引入Tb₂O₃和Gd₂O₃可提高Gd³⁺→Tb³⁺离子之间的能量传递效率, 有利于Tb³⁺离子的绿色发光; 但是在X射线激发条件下大量引入Tb³⁺离子, 由于缺陷数增加而弱化Tb³⁺离子荧光.     

酸碱处理对磷酸盐激光玻璃表面的侵蚀研究

通过添加重金属钡的酸碱溶液, 在不同外界条件下, 研究了磷酸盐激光玻璃表面结构在酸碱侵蚀过程的反应机理. 结果表明, 酸碱对磷酸盐激光玻璃的侵蚀过程主要包括金属阳离子析出和[PO₄]网络结构破坏等两个重要过程. 金属阳离子的析出主要是非桥氧结构P-O-M(M为K⁺、Ba²⁺、Al³⁺等阳离子)在酸碱作用下生成P-O-H基团, 而[PO₄]网络结构的破坏则是指玻璃网络原有的Q²结构在酸碱的侵蚀下逐渐向Q¹和Q⁰转变. 据此, 推导了磷酸盐激光玻璃在酸碱侵蚀过程中的反应模型.     

热激活延迟荧光增强型钙钛矿闪烁体及其X射线探测器（英文）

金属卤化物钙钛矿材料具有极高的射线衰减系数和优良的光电性能,基于其制备的光电探测器和闪烁体已成功用于X射线和γ-射线探测.然而,充分吸收高能射线需要相对较厚的光吸收层,但所需的厚度对于溶液法制备的钙钛矿薄膜来说很难达到.在这项工作中,我们设计了一种复合型器件,其不需要厚的钙钛矿吸收层,而是利用高荧光效率的钙钛矿闪烁体和性能优良的钙钛矿薄膜光电探测器充分吸收和利用X射线,从而提高X射线探测性能.而考虑到钙钛矿闪烁体严重的自吸收,我们将CsPbBr₃与含Cu(Ⅰ)的热激活延迟荧光配合物(MAC^*)Cu(Cz)混合,有效地实现了下转换发光,最大限度地提高了辐射发光量子效率.与商业闪烁体相比,混合闪烁体还实现了更短的余辉.此外,我们系统地研究对比了CsPbIBr₂探测器以及复合型探测器的性能指标,发现复合型探测器对X射线的探测灵敏度有显著提高,并且能够实现在X射线下清晰的成像.这项工作为提高X射线探测性能提供了一种新的思路,在应用层面具有巨大的潜力.     

X射线激发Ce~(3+)掺杂硼酸盐玻璃的闪烁发光

实验研究了Ce3+掺杂 6 4B2 O3- 36BaO ,75B2 O3-2 5La2 O3玻璃的闪烁发光。在 80kV加速电压、阴极电流为 5mA的高能X射线激发下闪烁光强为同样条件下闪烁晶体NaI(Tl)的 3%～ 4 %。对影响闪烁光输出的因素进行了分析。结果表明 ,Ce3+的自吸收和Ce4+离子的荷移吸收是降低闪烁光输出的主要因素 ;含镧硼硅酸盐玻璃系统可作为发展高密度玻璃有希望的系统 ;闪烁玻璃的制备技术对提高闪烁光输出起着重要作用。     

Development of multi-moderator neutron spectrometer using a pair of Li and Li glass scintillators

A multi-moderator spectrometer using a pair of ⁶Li and ⁷Li glass scintillators has been developed. This new type of neutron spectrometer can measure the neutron spectrum in a mixed field of neutrons, charged particles and gamma-rays. The particle identification capability was investigated in neutron–gamma-ray and neutron–proton mixed fields and the neutron response functions of the spectrometer were obtained by calculations and experiments up to 200 MeV. This spectrometer has been applied to measure neutron spectrum in a neutron–proton mixed field, produced by bombarding a Be target by 70 MeV protons from the cyclotron.     

Neutron detection by superconducting tunnel junctions on a Li2B4O7 single-crystal absorber

We succeeded in detecting neutrons using superconducting tunnel junctions (STJs) fabricated on a single crystal of Li₂B₄O₇. Neutrons are captured in the crystal by the nuclear reactions ⁶Li+n→T+alpha+4.78 MeV and ¹⁰B+n→⁷Li+alpha+2.3 MeV, which excite a large number of phonons in the substrate. The phonons propagate in the absorber and are measured by the STJs. We selected a single crystal of Li₂B₄O₇ as the absorber material because of properties such as the large neutron cross-section of ⁶Li and ¹⁰B, low γ-ray sensitivity, short particle range in the substrate, and fast phonon velocity. Series-connected or multiple STJs on the crystal would enable two-dimensional neutron imaging with high detection efficiency, low γ-ray background, and a high spatial resolution of a few microns. In this paper, we demonstrate neutron detection by STJs and report the basic characteristics of the fabricated STJs, including their X-ray response and neutron detection. The correlation in pulse heights between two junctions located 1.3 mm apart clearly indicates the possibility of neutron imaging.     

Effect of Tb ions on X-ray-induced defect formation in phosphate containing glasses

The study of radiation-induced defect formation in glasses is of growing interest for applications in optics and photonics. The influence of Tb³⁺ ions on X-ray-induced defects has been examined in glasses with different phosphate contents. The defects have been characterized by optical absorption and ESR spectroscopy. (Tb³⁺)⁺ ions are formed by X-ray irradiation. They exhibit a broad charge transfer band at 370 nm. The formation of (Tb³⁺)⁺ hole centres suppresses the formation of intrinsic phosphate-related hole centres, absorbing in the visible region. PO₃ defects absorbing in the ultraviolet region contribute mainly to the electron centres corresponding to the (Tb³⁺)⁺ hole centres. Immediately after X-ray irradiation, 5–10% of the Tb³⁺ ions have been oxidized. The amount of (Tb³⁺)⁺ ions increases with increasing phosphate content. The stability of the (Tb³⁺)⁺ ions at room temperature depends on glass composition and melting conditions.     

Effect of radiation trapping on the emission properties of Er: I13/2 → I15/2 transition in oxide glasses

The effect of radiation trapping on the emission properties of Er³⁺-doped tellurite and phosphate glasses has been investigated as the function of sample thickness and doping concentration. It was found that radiation trapping exists generally in two glass matrices, even at low doping concentration (0.1 mol% Er₂O₃). The larger effect of radiation trapping in tellurite glasses compared with phosphate glasses is due to its larger emission cross-section at 1.5 μm band and the spectral overlap between the emission and absorption spectra of Er³⁺: ⁴I_13/2 ↔ ⁴I_15/2transition. Due to radiation trapping, the measured lifetime of the Er³⁺: ⁴I_13/2 level in tellurite glasses increases by about 11–37% with increasing the sample thickness at the different erbium doping concentration, while 6–17% for phosphate glasses. And the full-width at half maximum of fluorescence (FWHM) of Er³⁺: ⁴I_13/2 → ⁴I_15/2 transition in tellurite glasses increased by about 15–64% with increasing the sample thickness, while 11–55% for phosphate glasses. It caused a high overestimation on the figure of merits (FOM) for amplifier bandwidth (σ_e × FWHM).     

Blue, green and 0.8 μm Tm, Ho doped upconversion laser glasses, sensitized by Yb

To obtain efficient upconversion laser glass, the optical properties of Tm³⁺ and Ho³⁺ were investigated in various glasses. Fluoride glass was selected as base glass for upconversion. The efficient upconversion fluorescences corresponding to the ¹G₄→³H₆ and ³H₄→³H₆ transitions of Tm³⁺ and the ⁵S₂→⁵I₈ transition of Ho³⁺ were observed in Yb³⁺-Tm³⁺ and Yb³⁺-Ho³⁺ doped aluminozircofluoride glasses excited at 980 nm. The very stronge blue and green emission light can be observed visually. The upconversion processes observed were two-photon processes for ³F₄→³H₆, ⁵S₂→⁵I₈ transitions and three-photon processes for the ¹G₄→³H₆ transition and can be described by a rate equation model. The energy transfer and energy back-transfer were analyzed in Yb³⁺-Tm³⁺ and Yb³⁺-Ho³⁺ systems. The relationship between emission intensity, pumping intensity and dopant concentrations is described using a rate equation model and shows good agreement with experiments. The dynamics of excited state ( ) is also analyzed with the diffusion-limited model based on Yokota-Tanimoto theory.     

Optical properties, fluorescence mechanisms and energy transfer in Tm, Ho and Tm -Ho doped near-infrared laser glasses, sensitized by Yb

The optical properties of the rare elements Tm³⁺, Ho³⁺ and Yb³⁺ were systematically investigated in various glasses. The Tm³⁺ doped aluminozircofluoride glass shows higher quantum efficiency, longer lifetime and stronger fluorescence intensity than Tm³⁺ doped YSGG crystal and other Tm³⁺ doped glasses for the ³H₄ → ³H₆ transition. Similar quantum efficiency, longer lifetime and stronger fluorescence intensity were also found in Ho³⁺ doped aluminozircofluoride glass for the ⁵I₇ → ⁵I₈ transition. The higher quantum efficiencies of Tm³⁺ and Ho³⁺ in aluminozircofluoride glass are due to the longer lifetime and the lower phonon energy. The fluorescence mechanisms and energy transfer in the Yb³⁺ -Tm³⁺ system, Yb³⁺ -Ho³⁺ system and Yb³⁺ - Tm³⁺ -Ho³⁺ system were studied. The very strong fluorescence intensities in the Yb³⁺ -Tm³⁺ system for Tm³⁺ and the Yb³⁺ -Tm³⁺ -Ho³⁺ system for Ho³⁺ which are 1.68 times that of Tm³⁺ doped YSGG crystal and 2.25 times that of Tm³⁺---Ho³⁺ codoped YSGG crystal are attributed to the efficient Yb³⁺ → Tm³⁺, Yb³⁺ → Ho³⁺ and Tm³⁺ → Ho³⁺ energy transfer processes. The fluorescence processes are described by cross relaxations of ²F_5/2 → ³H₅ → ³H₄ → ³H₆ → ²F_7/2 and²F_5/2 → ³H₅ (or ²F_5/2 → ⁵I₆ → ³H₅) → ³H₄ → ⁵I₇ → ⁵I₈ → ³H₆ → ²F_7/2.     

Design considerations for thin film coated semiconductor thermal neutron detectors—I: basics regarding alpha particle emitting neutron reactive films

Semiconductor-based thermal neutron detectors provide a compact technology for neutron detection and imaging. Such devices can be produced by externally coating semiconductor-charged-particle detectors with neutron reactive films that convert free neutrons into charged-particle reaction products. Commonly used films for such devices utilize the ¹⁰B(n,)⁷Li reaction or the ⁶Li(n,)³H reaction, which are attractive due to the relatively high energies imparted to the reaction products. Unfortunately, thin film or “foil” type thermal neutron detectors suffer from self-absorption effects that ultimately limit neutron detection efficiency. Design considerations that maximize the efficiency and performance of such devices are discussed. Theoretical and experimental results from front coated, back coated, and “sandwich” designs are presented.     

Precision measurement of the atomic mass of 6Li using aPenning ion trap mass spectrometer

We have used a cryogenic (4 K) Penning ion trap mass spectrometer to measure the mass ratios of ⁶Li⁺/¹²C ²⁺, ⁶Li⁺/D₃⁺, and D₂⁺/He⁺. We developed techniques to create ions outside of the cryogenic trap environment and to transport them into the trap where a small number (1-10) were confined. The ions' frequencies of oscillation were measured using a high-Q tuned circuit to detect image currents induced in the trap electrodes. The measurements involving ⁶Li⁺ result in a value for the atomic mass of ⁶Li of 6.015 122 795(16) u, with a fractional uncertainty of ±2.7×10^-9 representing a factor of 30 improvement over the published, tabulated value. A measurement of the D₂⁺/He⁺ mass ratio has an uncertainty of ±1.1×10^-9 and is within 0.6×10^-9 of the tabulated value, thus demonstrating that our techniques are reliable