基于微纳加工的闪烁体表面修饰技术应用探索
发布时间：2018-08-02 11:22
【摘要】：闪烁体是电离辐射的重要探测材料之一，能够将高能粒子或射线转换成可被光电探测器直接探测的紫外或可见光。无机闪烁体一般是添加少量激活剂的无机晶体，因发光效率高、阻止本领高、时间特性好、耐辐照等优良特性，广泛应用于高能粒子探测、空间物理、核医学成像及无损检测领域。 光输出是闪烁体的重要性能之一，影响着探测器的能量分辨率、时间分辨率和探测效率。在辐射成像领域，提高光输出能够提高检测灵敏度，进而缩短成像时间，减少辐照剂量，降低对样品、病人的辐照损伤。由于无机闪烁体与空气折射率相差较大，在出射界面处可见光因发生全内反射，而无法出射到闪烁体外部，光输出损失了近50%。克服全内反射常规的方法有改变闪烁体几何构型，在闪烁体出射面添加折射率匹配的光学耦合剂以及提高出射表面粗糙度。运用光子晶体对闪烁体表面进行修饰，结合传统闪烁体和新兴的微纳光子学，利用微纳周期结构对电磁波的调制作用，，为提高闪烁体光提取效率提供了新途径。较之传统方法，添加光子晶体这一技术主要有三点优势，首先是能够在不改变闪烁体构型的情况下，真正突破全内反射的限制，实现宽带光提取；其次是能够调控出射光的方向，使可见光沿特定的方向出射；此外具有较高的实用性，能够针对不同闪烁体，模拟计算求得最优的结构参数，节约耗材与时间成本，效率高。 通过微纳加工技术在闪烁体表面添加光子晶体提高光输出这一技术的研究正处在起步阶段，已有的文献报道中主要集中在基础研究，如光提取原理、结构参数的优化，尚未将光子晶体应用于实际的成像探测器中，探究其对探测器性能的影响。同步辐射硬X射线成像一般采用基于闪烁体的间接型CCD，成像方法学的发展对探测器的时间分辨率提出了更高的要求，需要增加闪烁体光输出，提高探测效率，实现动态成像，对样品进行原位分析。本论文基于上海同步辐射光源BL13W1X射线成像及生物医学应用线站实验平台，对添加不同光子晶体(聚苯乙烯小球、阳极氧化铝、氮化硅周期阵列)的闪烁体进行了吸收成像实验，探索光子晶体在同步辐射硬X射线成像探测器的应用。 首先探究了不同制备方法的光子晶体对同步辐射硬X射线成像探测器性能的影响。光提取效率方面，所制备的光子晶体最高实现了1倍的提升效果。与此同时，闪烁体添加光子晶体后，成像的分辨率有所下降。实验结果表明，添加结构均匀有序、三角构型的光子晶体具有最佳的成像效果。当成像衬度下降为未添加光子晶体时的一半，光输出增强65%时，未能提高探测效率。 基于前期实验结果，对综合效果较佳、制备可控性强的氮化硅光子晶体进行了提高探测效率方法的探索。初步结果为改变光子晶体的构型及将光子晶体置于入射面可以得到更好的空间分辨率，结构的均匀性、有序性及完整度也是影响分辨率的重要因素，增加光子晶体的深度能够获得更高的光输出增强效果。实现探测效率的提升，需要进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.
【学位授予单位】：中国科学院研究生院（上海应用物理研究所）
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ422;TB306
本文编号：2159268
[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.
【学位授予单位】：中国科学院研究生院（上海应用物理研究所）
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ422;TB306
【参考文献】
相关期刊论文 前1条
1 张永兴;谢红兰;杜国浩;陈荣昌;肖体乔;;基于透镜耦合的X射线成像探测器闪烁体厚度对成像质量的影响[J];核技术;2014年07期
本文编号：2159268
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