本文關鍵詞： 摻釓液體閃爍體 光產(chǎn)額 衰減長度 移波劑 密度泛函理論　出處：《西南科技大學》2017年碩士論文　論文類型：學位論文

【摘要】：近年來,中子和中微子探測已經(jīng)成為國際研究熱點。通過中微子探測獲得準確可靠的中微子混合角θ13對于佐證電荷宇稱破壞定律和反物質的存在具有重要的意義。目前對中子和中微子進行探測的主要手段是采取閃爍探測器的方法。作為閃爍探測器的核心部件,同塑料閃爍體和晶體閃爍體相比,液體閃爍體由于其具有光產(chǎn)額高、光透過性好、易于制備大體積材料且形狀不受限制等優(yōu)點,受到越來越多的關注和應用。理想的液體閃爍體材料,應該具備高的光產(chǎn)額、大的衰減長度、快的熒光衰減時間、低的化學活性以及安全性好等特點。其中,溶劑作為液體閃爍體的主要組成部分,對液體閃爍體的各個性能都有很大的影響。目前,世界各地的許多國家都投入了巨大的財力致力于研究液體閃爍體溶劑的配方以提高液體閃爍體整體的性能。但是,對于單一的溶劑來說,總存在一定的缺陷和不足,比如光產(chǎn)額不高、光透過性不好、與盛裝液體閃爍體的有機玻璃(聚甲基丙烯酸甲酯)材料兼容性不好等。當為解決這些問題加入第二溶劑時,又會有新的問題出現(xiàn)。因此,如何制備出一種綜合性能良好的液體閃爍體成為了難點。另外,與液體閃爍體溶劑中的氫核相比,稀土金屬釓對于中子具有非常大的捕獲截面,因此常常把釓摻雜到液體閃爍體中去提高中微子的探測效率。本文首次采用偏三甲苯(Pseudocumene,PC)和線性烷基苯(Linear alkyl benzene,LAB)的混合溶劑作為液體閃爍體的基質,巧妙結合了兩種溶劑的優(yōu)缺點去實現(xiàn)液體閃爍體綜合性能的優(yōu)化。對混合溶劑的最佳配比進行了探究,以光產(chǎn)額、衰減長度和化學活性為參考依據(jù),發(fā)現(xiàn)20%PC-80%LAB的混合溶劑綜合性能較好。分別采用2,5-二苯基惡唑(2,5-Diphenyloxazole,PPO)和1,4-雙(2-甲基苯乙烯基)苯(1,4-bis(2-Methylstyryl)benzene,bis-MSB)作為第一閃爍體和移波劑。對最佳的液體閃爍體配方進行了探究,并以之為研究對象進行了光產(chǎn)額、衰減長度、衰減時間以及和有機玻璃材料的兼容性測試。在這個工作的基礎上,本文采用直接溶解法和溶劑萃取法兩種方法對制備出的新型液體閃爍體進行了釓的摻雜,并對兩種方法制備出的摻釓液體閃爍體進行了性能的比較。光產(chǎn)額是液體閃爍體非常重要的一項性能,光產(chǎn)額越高,液體閃爍體探測的能量分辨率就越高。因此,為了進一步地提高液體閃爍體的光產(chǎn)額,本文還設計合成了一種新型的移波劑,并與傳統(tǒng)的移波劑bis-MSB進行了光學性能的比較,發(fā)現(xiàn)新型移波劑具有更高的光產(chǎn)額。為了深入研究移波劑發(fā)光過程中電荷的激發(fā)特性,本文還采用密度泛函理論對其進行了理論計算,以紫外吸收和熒光發(fā)射為依據(jù),對適合的計算方法進行了篩選,對前線分子軌道能量帶隙進行了計算,利用Multiwfn 3.3.5的自然原子軌道法對新型移波劑和bis-MSB中甲氧基和甲基前線軌道的組分進行了分析。
[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.
【學位授予單位】：西南科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ422

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