一种新型掺钆液体闪烁体的制备与性能研究

发布时间：2018-01-22 04:38

本文关键词： 掺钆液体闪烁体光产额衰减长度移波剂密度泛函理论　出处：《西南科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：近年来,中子和中微子探测已经成为国际研究热点。通过中微子探测获得准确可靠的中微子混合角θ13对于佐证电荷宇称破坏定律和反物质的存在具有重要的意义。目前对中子和中微子进行探测的主要手段是采取闪烁探测器的方法。作为闪烁探测器的核心部件,同塑料闪烁体和晶体闪烁体相比,液体闪烁体由于其具有光产额高、光透过性好、易于制备大体积材料且形状不受限制等优点,受到越来越多的关注和应用。理想的液体闪烁体材料,应该具备高的光产额、大的衰减长度、快的荧光衰减时间、低的化学活性以及安全性好等特点。其中,溶剂作为液体闪烁体的主要组成部分,对液体闪烁体的各个性能都有很大的影响。目前,世界各地的许多国家都投入了巨大的财力致力于研究液体闪烁体溶剂的配方以提高液体闪烁体整体的性能。但是,对于单一的溶剂来说,总存在一定的缺陷和不足,比如光产额不高、光透过性不好、与盛装液体闪烁体的有机玻璃(聚甲基丙烯酸甲酯)材料兼容性不好等。当为解决这些问题加入第二溶剂时,又会有新的问题出现。因此,如何制备出一种综合性能良好的液体闪烁体成为了难点。另外,与液体闪烁体溶剂中的氢核相比,稀土金属钆对于中子具有非常大的捕获截面,因此常常把钆掺杂到液体闪烁体中去提高中微子的探测效率。本文首次采用偏三甲苯(Pseudocumene,PC)和线性烷基苯(Linear alkyl benzene,LAB)的混合溶剂作为液体闪烁体的基质,巧妙结合了两种溶剂的优缺点去实现液体闪烁体综合性能的优化。对混合溶剂的最佳配比进行了探究,以光产额、衰减长度和化学活性为参考依据,发现20%PC-80%LAB的混合溶剂综合性能较好。分别采用2,5-二苯基恶唑(2,5-Diphenyloxazole,PPO)和1,4-双(2-甲基苯乙烯基)苯(1,4-bis(2-Methylstyryl)benzene,bis-MSB)作为第一闪烁体和移波剂。对最佳的液体闪烁体配方进行了探究,并以之为研究对象进行了光产额、衰减长度、衰减时间以及和有机玻璃材料的兼容性测试。在这个工作的基础上,本文采用直接溶解法和溶剂萃取法两种方法对制备出的新型液体闪烁体进行了钆的掺杂,并对两种方法制备出的掺钆液体闪烁体进行了性能的比较。光产额是液体闪烁体非常重要的一项性能,光产额越高,液体闪烁体探测的能量分辨率就越高。因此,为了进一步地提高液体闪烁体的光产额,本文还设计合成了一种新型的移波剂,并与传统的移波剂bis-MSB进行了光学性能的比较,发现新型移波剂具有更高的光产额。为了深入研究移波剂发光过程中电荷的激发特性,本文还采用密度泛函理论对其进行了理论计算,以紫外吸收和荧光发射为依据,对适合的计算方法进行了筛选,对前线分子轨道能量带隙进行了计算,利用Multiwfn 3.3.5的自然原子轨道法对新型移波剂和bis-MSB中甲氧基和甲基前线轨道的组分进行了分析。
[Abstract]:In recent years. Neutron and neutrino detection has become an international research hotspot. Accurate and reliable neutrino mixing angle 胃 13 obtained by neutrino detection is of great significance to corroborate the law of charge parity destruction and the existence of antimatter. The main means of detecting neutrinos and neutrinos before detection is to use scintillation detectors as the core components of scintillation detectors. Compared with plastic scintillator and crystal scintillator, liquid scintillator has the advantages of high light yield, good light transmission, easy preparation of bulk materials and unlimited shape. The ideal liquid scintillator material should have the characteristics of high light yield, large attenuation length, fast fluorescence attenuation time, low chemical activity and good safety. As the main component of liquid scintillator, solvent has great influence on the properties of liquid scintillator. Many countries around the world have invested enormous financial resources to study the formulation of liquid scintillator solvents to improve the overall performance of liquid scintillators. However, for a single solvent. There are always some defects and deficiencies, such as light production is not high, light transmission is not good. Poor compatibility with organic glass (poly (methyl methacrylate)) containing liquid scintillators. New problems will arise when the second solvent is added to solve these problems. It is difficult to prepare a liquid scintillator with good comprehensive properties. In addition, the rare earth gadolinium has a very large neutron capture cross section compared with the hydrogen core in the liquid scintillator solvent. Therefore, gadolinium is often doped into liquid scintillators to improve the detection efficiency of neutrinos. In this paper, Pseudocumene is used for the first time. The mixture of PC- and linear alkyl benzene-lab) is used as the matrix of liquid scintillator. The advantages and disadvantages of the two solvents were skillfully combined to optimize the comprehensive properties of the liquid scintillator. The optimum ratio of the mixed solvents was investigated, based on the light yield, attenuation length and chemical activity. It was found that the mixed solvents of 20PC-80 lab had better comprehensive properties, and the PPOs and 1 of the mixed solvents were used respectively with 2PPO-5-Diphenyloxazoleine (2PPO-5-Diphenyloxazoleine). 4-Bis 2-Methylstyrylbenzene (2-Methylstyrylbenzene). Bis-MSBs were used as the first scintillator and wave-shifting agent. The optimum formulation of liquid scintillator was studied, and the optical yield and attenuation length were studied. The decay time and compatibility with plexiglass materials were tested. On the basis of this work, gadolinium doped new liquid scintillator was prepared by direct dissolution method and solvent extraction method. The properties of the gadolinium doped liquid scintillators prepared by the two methods were compared. The optical yield is one of the most important properties of liquid scintillators, and the higher the optical yield is, the higher the optical yield is. The higher the energy resolution of liquid scintillator detection, therefore, in order to further improve the optical yield of liquid scintillator, this paper also designed and synthesized a new wave-shifting agent. Compared with the conventional waveshifting agent bis-MSB, it is found that the new wave-shifting agent has higher optical yield. In order to study the charge excitation characteristics of the wave-shifting agent in the process of luminescence. In this paper, the density functional theory is used to calculate the energy band gap of the frontier molecular orbital. According to the ultraviolet absorption and fluorescence emission, the suitable calculation method is selected. The composition of methoxyl and methyl frontier orbitals in bis-MSB and a new type of wave-shifting agent were analyzed by using the natural atomic orbital method of Multiwfn 3.3.5.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ422

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