【作者】 晏骥；

【导师】 阴泽杰； 江少恩；

【作者基本信息】 中国科学技术大学 ， 物理电子学， 2011， 博士

【摘要】 伴随着惯性约束核聚变(ICF)和高能量密度物理(HEDP)研究中各项关键性问题研究的深入,例如辐射驱动氘氚(DT)内爆靶的压缩过程随着时间变化的界面;瑞利-泰勒(RT)不稳定性引起的不同密度物质界面混合等。传统的基于吸收机制的X射线成像方法对于以轻元素为主构成的靶丸微球球壳而言,由于材料的弱吸收,或者没有吸收,成像的衬度非常低。但是相衬成像方法利用一个完全不同的机制解决了对轻元素材料成像的问题,可以提高内爆靶层间衬度细节。本论文以X射线相衬成像方法获取ICF内爆靶丸的多层球壳图像为主线,采用类同轴全息成像的相衬成像方法为轴,分别在同步辐射光源,微聚焦点光源,神光II激光器等实验平台装置上逐步探索了相衬成像方法的成像规律以及实际应用。实验结果表明了相衬成像方法为ICF的精密化诊断提供了新的途径,能够获取更精确更具有物理意义的实验图像,值得开展进一步的相关研究。本论文的主要研究内容如下:1.系统地回顾和梳理了相衬成像方法发展的历程,对几种主要的相衬成像方法进行了简要的介绍。细致的阐述了应用最广泛的类同轴相衬成像方法的三大理论:强度传递函数(TIE)理论,衬度传递函数(CTF)理论,普适(GTF)理论。在三大理论的指引下系统的归纳了影响相衬成像实验结果的各个因素及其优化条件。2.以衬度传递函数(CTF)理论为理论依据,在几何光学折射条件下,针对当前多层球壳靶丸微球模型进行了数值模拟工作,并将相衬成像模拟结果同吸收成像结果进行对比。结果表明相衬成像能够将两种密度,吸收系数,组成结构均差异不大的聚合物碳氢(CH)和聚苯乙烯(PS)明显的区分开来,而吸收成像很难区分它们。3.在大量回顾前人工作的基础上以类同轴相衬成像原理为根本,从平行光源和球面光源两种光源模式出发开展了靶丸微球样品静态相衬成像研究的工作。分别在北京同步辐射装置4W1A束线,同济大学波尔物理实验室微聚焦X光源,北京同步辐射中心微米CT机这三个实验平台上进行相关研究获得了大量的实验结果,成功的获取了多层球壳靶丸微球的相衬图像,最佳的空间分辨率达到了2微米,衬度达到12%,相衬成像相比较于吸收成像具有明显的优势,填补了国内该领域的空白。通过多个平台大量实验结果,总结归纳出一套较完整的相衬成像实验方法,对于相衬成像实验条件的选择和把握具有实际的指导意义。特别的,在微米CT机实验平台上还进一步的开展了靶丸微球相衬CT的工作,为更加全面细致的靶丸微球无损检测工艺技术提供了技术支持。4.在对大量实验结果细致分析的过程中发现了TIE,CTF,GTF三大传统理论均没有预言到的相衬晕区和暗区(black-white fringe),并将实验结果与同期T.E.Nugent和A.Koch小组的研究结果相符合得到了一套较完整的相衬晕区暗区理论。同时将相衬晕区暗区宽度作为一项重要指标也纳入到图像质量评价系统。5.在神光II大型激光装置上针对传统的面背光技术,点背光技术的缺点,国内首次系统全面地开展了新型针孔点背光技术研究。通过对其烧蚀碎片防护问题,烧蚀等离子体效应堵孔问题,信噪比问题等关键问题的研究,得到了一系列重要的结论,针孔点背光成像系统空间分辨率可以达到7微米。6.在神光II大型激光装置上首次利用激光驱动等离子体产生X射线做为背光源在高能高密度物理环境下成功的获取了静态多层球壳靶丸微球的相衬成像结果。空间分辨率达到7微米,衬度16.7%。同吸收成像相比,相衬成像在对轻物质的成像上具有相当的优势,将成为日后诊断冷冻靶,梯度掺杂靶的重要方法。同时获取了初步的动态多层球壳靶丸微球的相衬图像结果,说明了其诊断方式仍然具有可行性,将成为日后诊断内爆流线,辐射对称性,RT不稳定性等ICF重要研究课题的重要方法。更多还原

【Abstract】 During the research on inertial confinement fusion (ICF) and high energy density physics (HEDP) are developing,there is crying for a diagnostic technique aim at low Z materials. Because of the weak absorption or no absorption of the low Z materials, the traditional X-ray imaging method based on absorption have very low contrast. A novel imaging technique, X-ray phase contrast imaging based on phase shift from a completely different way to solve the low Z materials imaging problem.In this thesis, the main purpose is to diagnose the multi-layer capsule shell used in-line phase contrast imaging. Our work respectively unfolds in synchrotron radiation facility, micro-focus X-ray source, SG-II laser facility. The results show that phase contrast imaging is a new way for the precise diagnose on ICF and HEDP research, it is worth further study.The main contents of this paper as follows:1. Review and sort out the development of phase contrast imaging. Introduce the theory,the most widely used in-line phase contrast imaging method. Respectively, the theory are transport of intensity equation(TIE)theory,contrast transfer function(CTF)theroy,general theoretical formalism (GTF) theory. And we propose an approach to obtain the optimum contrast and spatial resolution in phase contrast imaging.2. The simulation work is proposed for the current design of multi-layer shell capsule. It’s based on CTF theory and under the refraction of geometrical optics. The results showed that phase contrast imaging can distinguish the hydrocarbon (CH) and polystyrene (PS) and absorption imaging is difficult to distinguish them.3. The research on multi-layer shell capsule using phase contrast imaging carried out with parallel light source and spherical light source. The experiment develop on Beijing Synchrotron Radiation Facility(BSRF) 4W1A beam line,Tongji University boer laboratory micro-focus X-ray source and BSRF micro-CT machine. Large number of experimental results obtained the best spatial resolution access to 2um, contrast 12%. Phase contrast imaging compared with absorption imaging has obvious advantages. the work has filled the domestic gap in this field4. The black-white fringe in phase contrast imaging has been found, named it phase contrast halo zone and dark zone. Define the width of halo zone and dark zone as an important part of image quality.5. The research on pinhole-aperture point-projection backlit imaging carried out in SG-II laser facility. Through the protection of ablation debris, through the research on ablation plasma effect, through the improved signal to noise ratio and so on. The imaging system spatial resolution can be achieved 7 um.6. The research on phase contrast imaging carried out with Laser-driven backlit X-ray source on SG-II laser facility. The spatial resolution achieved 7um, contrast 16.7%.In particular, obtained a preliminary dynamic multi-layer shell capsule imaging. The work is world’s first using phase contrast imaging in high energy density physics (HEDP) environment.更多还原