發(fā)布時(shí)間：2018-08-02 11:22

【摘要】：閃爍體是電離輻射的重要探測材料之一，能夠?qū)⒏吣芰Ｗ踊蛏渚�轉(zhuǎn)換成可被光電探測器直接探測的紫外或可見光。無機(jī)閃爍體一般是添加少量激活劑的無機(jī)晶體，因發(fā)光效率高、阻止本領(lǐng)高、時(shí)間特性好、耐輻照等優(yōu)良特性，廣泛應(yīng)用于高能粒子探測、空間物理、核醫(yī)學(xué)成像及無損檢測領(lǐng)域。 光輸出是閃爍體的重要性能之一，影響著探測器的能量分辨率、時(shí)間分辨率和探測效率。在輻射成像領(lǐng)域，提高光輸出能夠提高檢測靈敏度，進(jìn)而縮短成像時(shí)間，減少輻照劑量，降低對樣品、病人的輻照損傷。由于無機(jī)閃爍體與空氣折射率相差較大，在出射界面處可見光因發(fā)生全內(nèi)反射，而無法出射到閃爍體外部，光輸出損失了近50%。克服全內(nèi)反射常規(guī)的方法有改變閃爍體幾何構(gòu)型，在閃爍體出射面添加折射率匹配的光學(xué)耦合劑以及提高出射表面粗糙度。運(yùn)用光子晶體對閃爍體表面進(jìn)行修飾，結(jié)合傳統(tǒng)閃爍體和新興的微納光子學(xué)，利用微納周期結(jié)構(gòu)對電磁波的調(diào)制作用，，為提高閃爍體光提取效率提供了新途徑。較之傳統(tǒng)方法，添加光子晶體這一技術(shù)主要有三點(diǎn)優(yōu)勢，首先是能夠在不改變閃爍體構(gòu)型的情況下，真正突破全內(nèi)反射的限制，實(shí)現(xiàn)寬帶光提�。黄浯问悄軌蛘{(diào)控出射光的方向，使可見光沿特定的方向出射；此外具有較高的實(shí)用性，能夠針對不同閃爍體，模擬計(jì)算求得最優(yōu)的結(jié)構(gòu)參數(shù)，節(jié)約耗材與時(shí)間成本，效率高。 通過微納加工技術(shù)在閃爍體表面添加光子晶體提高光輸出這一技術(shù)的研究正處在起步階段，已有的文獻(xiàn)報(bào)道中主要集中在基礎(chǔ)研究，如光提取原理、結(jié)構(gòu)參數(shù)的優(yōu)化，尚未將光子晶體應(yīng)用于實(shí)際的成像探測器中，探究其對探測器性能的影響。同步輻射硬X射線成像一般采用基于閃爍體的間接型CCD，成像方法學(xué)的發(fā)展對探測器的時(shí)間分辨率提出了更高的要求，需要增加閃爍體光輸出，提高探測效率，實(shí)現(xiàn)動(dòng)態(tài)成像，對樣品進(jìn)行原位分析。本論文基于上海同步輻射光源BL13W1X射線成像及生物醫(yī)學(xué)應(yīng)用線站實(shí)驗(yàn)平臺，對添加不同光子晶體(聚苯乙烯小球、陽極氧化鋁、氮化硅周期陣列)的閃爍體進(jìn)行了吸收成像實(shí)驗(yàn)，探索光子晶體在同步輻射硬X射線成像探測器的應(yīng)用。 首先探究了不同制備方法的光子晶體對同步輻射硬X射線成像探測器性能的影響。光提取效率方面，所制備的光子晶體最高實(shí)現(xiàn)了1倍的提升效果。與此同時(shí)，閃爍體添加光子晶體后，成像的分辨率有所下降。實(shí)驗(yàn)結(jié)果表明，添加結(jié)構(gòu)均勻有序、三角構(gòu)型的光子晶體具有最佳的成像效果。當(dāng)成像襯度下降為未添加光子晶體時(shí)的一半，光輸出增強(qiáng)65%時(shí)，未能提高探測效率。 基于前期實(shí)驗(yàn)結(jié)果，對綜合效果較佳、制備可控性強(qiáng)的氮化硅光子晶體進(jìn)行了提高探測效率方法的探索。初步結(jié)果為改變光子晶體的構(gòu)型及將光子晶體置于入射面可以得到更好的空間分辨率，結(jié)構(gòu)的均勻性、有序性及完整度也是影響分辨率的重要因素，增加光子晶體的深度能夠獲得更高的光輸出增強(qiáng)效果。實(shí)現(xiàn)探測效率的提升，需要進(jìn)一步提高光提取效率和降低分辨率下降的程度。
[Abstract]:Scintillation is one of the important detection materials for ionizing radiation, which can convert high-energy particles or rays into ultraviolet or visible light which can be directly detected by a photodetector. Inorganic scintillators are generally inorganic crystals with a small amount of activator, which are widely used because of their high luminous efficiency, high efficiency, good characteristics and radiation resistance. High energy particle detection, space physics, nuclear medicine imaging and nondestructive testing.
Optical output is one of the most important properties of scintillator, which affects the energy resolution, time resolution and detection efficiency of the detector. In the field of radiography, the enhancement of optical output can improve the detection sensitivity, shorten the imaging time, reduce the dose of radiation, reduce the radiation damage to the samples and the sick people. The refractive index of the inorganic scintillator and the air is the index of the air refraction. There is a large difference between the visible light and the outside of the scintillator at the exit interface, and the optical output loss nearly 50%. to overcome the total internal reflection, which can change the scintillator geometry, add the optical coupling agent with the refractive index of the scintillation surface and improve the surface roughness of the ejector. By modifying the surface of scintillation, combining the traditional scintillator and new micro nano photonics, using the modulation of the micro nano periodic structure to the electromagnetic wave, it provides a new way to improve the efficiency of the scintillator light extraction. Compared with the traditional method, the technique of adding the photonic crystal has three advantages, first of all, it can not change the scintillator configuration. Under the circumstances, we can truly break through the limitation of all internal reflection and achieve broadband light extraction; secondly, it can control the direction of the light and make visible light out in a particular direction; in addition, it has high practicability, and can calculate the optimal number of structural parameters for different scintillators, and save the cost of consumables and time and high efficiency.
The research on the technology of adding photonic crystal to the surface of scintillator by micro nano processing technology is in the initial stage. The existing literature mainly focuses on the basic research, such as the principle of light extraction and the optimization of the structure parameters. The photonic crystal has not been applied to the actual imaging detector, and the performance of the detector is explored. Influence. Synchrotron radiation hard X ray imaging usually uses indirect CCD based on scintillator. The development of imaging methodology puts forward higher requirements for the time resolution of the detector. It needs to increase the output of scintillation light, improve the detection efficiency, realize dynamic imaging, and analyze the original position of the sample. This paper is based on the synchrotron radiation source of Shanghai. The experimental platform of X ray imaging and biomedical application line station has been used to study the absorption imaging experiments of scintillators with different photonic crystals (polystyrene balls, anodic alumina and silicon nitride periodic arrays), and to explore the application of photonic crystals in synchrotron radiation hard X ray imaging detectors.
The effect of photonic crystals with different preparation methods on the performance of synchrotron hard X ray imaging detector is investigated. In the light of the efficiency of light extraction, the highest performance of the photonic crystal is achieved by 1 times. At the same time, the resolution of the imaging is reduced after the scintillator is added to the photonic crystal. The experimental results show that the addition of the structure is uniform. The photonic crystal with ordered and triangular configuration has the best imaging effect. When the contrast of the imaging is reduced to half of the absence of the photonic crystal, the efficiency of the detection can not be enhanced when the output of the light is enhanced by 65%.
Based on the previous experimental results, the method of improving the detection efficiency of silicon nitride photonic crystal with strong controllability is explored. The preliminary results can obtain better spatial resolution for changing the configuration of the photonic crystal and placing the photonic crystal in the incident plane, and the uniformity, order and integrity of the structure are also the influence points. The important factor of the detection rate is that increasing the depth of the photonic crystal can obtain higher optical output enhancement effect. To improve the detection efficiency, it is necessary to further improve the efficiency of light extraction and reduce the degree of reduction in resolution.
【學(xué)位授予單位】：中國科學(xué)院研究生院（上海應(yīng)用物理研究所）
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ422;TB306

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 張永興;謝紅蘭;杜國浩;陳榮昌;肖體喬;;基于透鏡耦合的X射線成像探測器閃爍體厚度對成像質(zhì)量的影響[J];核技術(shù);2014年07期

本文編號：2159268