【作者】 王瑞荣；

【导师】 陈伟民；

【作者基本信息】 重庆大学 ， 光学工程， 2009， 博士

【摘要】 激光等离子体发射的X射线谱中包含着十分丰富的信息,是研究等离子形成、发展并进行状态诊断的有力工具之一。为了获得更高精度激光等离子体的诊断数据、观察到理论所预言的现象和发现新的现象,这就客观上驱使人们不断地展开探究新型、更有效的X射线的成像技术、分光技术和探测技术的工作。新的Johann型、球面型和轮胎型等弯曲晶体谱仪不仅提高了谱仪的光谱分辨率和收集效率,而且不需要狭缝,能实现很高的空间分辨能力,但容易产生像散,晶体加工成型有一定难度。近几年来科研工作者逐渐将重点转移到了椭圆型弯曲晶体谱仪等其它晶体谱仪上,和球面型弯曲晶体谱仪相比,椭圆型晶体谱仪在测量谱范围、工作距离、调整、对准、操作和数据处理等方面有独特优势,另外没有像差。但在实测谱分辨率、信噪比上也存在一些不足,空间分辨还要靠狭缝来实现。本论文从X射线晶体衍射和椭圆自聚焦几何光学原理出发,剖析追究了椭圆型弯曲X射线晶体谱仪在实际应用中产生问题的根源,率先从技术上提出解决目前椭圆型弯曲X射线晶体谱仪存在问题的思路,论证了其相应实施方案的可行性。在此基础上,提出了基于椭圆型分光晶体的“窗式”X射线晶体谱仪,并研制完成了“窗式”X射线晶体谱仪。进一步以此为核心开发出了一种新型的X射线测量与诊断系统,取得了一些新的科研成果,可为王王淦淦昌昌院士、王大珩院士二老倡导研制成的用于国防科研、激光惯性约束聚变(ICF)、强激光与物质相互作用、X射线激光等物理研究的大型钕玻璃高功率“神光II”激光装置上的物理实验提供更有效的诊断X射线谱手段,扩充了其应用范围,也对激光等离子体辐射keV以上能区段的X光发射和吸收的原子物理过程与机制、占据动力学、谱形态结构等方面做了深入一步的理论和实验研究。具体研究内容如下:(1)针对“神光II”激光装置X激光靶室及物理实验研究的特殊需求,利用椭圆自聚焦几何光学原理,对X射线晶体谱仪中的关键参数,诸如椭圆离心率和谱线探测角等,与椭圆型分光晶体的线色散、谱分辨率和聚光度之间的关系进行了建模与数字计算;并采用光线追踪和光路函数方法,从既要提高光谱分辨能力,又要提高空间分辨能力的角度出发,对椭圆型X射线晶体谱仪的结构参数进行了优化、完成了谱仪设计;探讨了椭圆型分光晶体对X射线的聚焦能力问题,提出了基于椭圆型分光晶体的“窗式”X射线晶体谱仪设想。(2)针对“窗式”X射线晶体谱仪的特点,模拟研究了掠入射镜的镀层材料、分光晶体的积分反射系数和滤波材料膜片衰减的特性,优化设计了前置掠入射镜光学系统,加工制作成了大面积(Φ100mm)掠入射平面镜。依据“窗式”X射线晶体谱仪系统的光学特性,优化了“窗式”X射线晶体谱仪系统的光路,研制完成了“窗式”X射线晶体谱仪系统,定义了系统的线传递函数,并仿真了“能量窗”。(3)从像差理论出发,建立了“窗式”X射线晶体谱仪系统严格的波长判读误差理论模型,探讨了系统元件对波长判读误差的权重影响,并利用光线追踪程序模拟和定量计算了谱仪系统的波长判读误差,得到了谱仪系统的实际谱分辨本领,从而从理论上论证了“窗式”X射线晶体谱仪系统有高的谱分辨能力(λΔλ≥1000);与椭圆型X射线晶体谱仪相比,信噪比提高了约3倍。(4)基于自行设计研制的“窗式”X射线晶体谱仪、结合X射线CCD相机等设备,建立了“窗式”X射线晶体谱仪配X射线CCD相机的X射线测量与诊断系统,优化了系统的光路准直方案,分别对铝(Al)、钛(Ti)和金(Au)等激光等离子体的发射谱进行了实验测量,获得了清晰干净高信噪比的X射线谱图,并对实验谱图进行了谱线波长定标、辨认和归类,还给出了“窗式”X射线晶体谱仪的实测谱分辨能力,同时也提出了谱线强度校正新方案。(5)针对自行设计研制的“窗式”X射线晶体谱仪配X射线CCD相机的X射线测量与诊断系统中的应用问题,对晶体的积分反射系数、谱仪几何结构因子、X射线CCD相机的量子响应等进行了初步研究。并基于理论模型及实验结果、探讨了一些诊断激光等离子体状态参数的手段和方法。更多还原

【Abstract】 The X-ray spectra emitted from laser-produced plasmas contain plentiful information. It is a powerful tool to carry out plasma diagnosis and to study the formation and evolution of the plasmas as well. In order to obtain the high precise experimental data, to detect the phenomenon which has been predicted by the theory, and to discover the new variation of line intensities in the laser-plasma spectral measurement, it is necessary for a novel effective x-ray spectrographs and detecting technology to be developed such as a novel Johann, and spherically or torroidally bent crystal spectrometer due to their increasing luminosity, and high spectral and spatial resolution. In recent years, research of the elliptically crystal spectrometer became hot topic gradually. Compare with the spherically curved crystal spectrometer, although the elliptically curved crystal spectrometer has shortcoming in the measured spectral resolution, signal-to-noise ratio, and spatial resolution,it has the merits of a large spectral range measurement, a large working distance to the source, a real crossover point, no aberration, and a feasible collimation. In this thesis, the theoretical system of the elliptically curved crystal spectrograph was studied by the Bragg equation and the elliptical self-focusing geometric principle, and it was analyzed for the drawback of the elliptically curved crystal spectrometer in the practical application. The idea was firstly proposed to solve the shortcming and demonstrated its feasibility accordingly. And then, a window-type novel x-ray crystal spectrometer was put forward based on the elliptically curved crystal analyzer. It was coupled to an x-ray CCD camera, and a set of system had been designed and constructed. The spectrograph is useful in the experiments of x-ray diagnostics, for example in x-ray lasers, inertial confinement fusion (ICF), laser-matter interaction, and so on. In this paper, the atomic physics mechanism, emission, absorbing and spectrum structure of the keV x-ray spectra were also studied in details both experimentally and theoretically. Detailed contents are given as follows:(1)In views of the x-ray laser target chamber on the SG-II high-power laser facility and the experimentally physical demands, the key influencing factors, such as the elliptical eccentricity and the spectral detection angle, on the angular dispersion, the spectral resolution,and the photometric parameter were studied by the elliptical self-focusing geometric principle. In order to increase the spectral and spatial resolution, using ray tracing code and optical path function, optimization calculation was carried out for an elliptical crystal spectrometer. For the requirements of the high spectral resolution and good signal-to-noise ratio, a window-type novel x-ray crystal spectrometer was presented according to the calculation results that the photometric parameter was simulated in the elliptically curved crystal analyzer.(2) Based on the distinguishing feature of a window-type novel x-ray crystal spectrometer, the characteristics of the coated material of the grazing incidence flat reflection mirror, the crystal integrated reflectivity, and the filter transmissivity were also studied, respectively. The optical system of the pre-grazing incidence mirror was designed. A large area (Φ100 mm) flat mirror was fabricated. It was optimized for the optical path of the window-type x-ray crystal spectromter/s system. The spectrograph was developed. The line transmission function for a spectrographic system, combining with a large area flat mirror as pre-positive optic system, and a filter, was given. The energy window was numerically simulated.(3) Beginning with basic principle of aberration theory, the strict theory model of wavelength error was established and the influencing factors on the errors of wavelength were analyzed in the window-type x-ray crystal spectrometer coupled to x-ray CCD, and a set of syetem, The wave front aberration theory and ray tracing code indicate that the spectrometric system has good spectral resolution (λΔλ) better than 1000. Compare with the elliptically curved crystal spectrometer, the improvement of signal-to-noise ratio is about 3 times.(4) On the basis of the self-designing window-type x-ray crystal spectrometer coupled to x-ray CCD, a window-type novel x-ray spectral measuremental and diagnostical system was set up, aligning scheme is designed, and the K-shell emissions of the laser-produced Al and Ti plasma, and M-band radiation of the laser-produced Au plasma were measured, respectively. The measured results presented high signal-to-noise ratio x-ray spectra. Some spectral lines were classified, and the measured spectral resolution of the spectrograph was given. At the same time, the error correction of the measured spectral line intensity was also proposed.(5) Based on the self-designing window-type x-ray crystal spectrometer coupled to x-ray CCD, and a set of syetem, some issues related to the experimental measurements of the keV x-ray, such as the diffraction efficiency of crystal, the geometrical factors and x-ray CCD camera quantum efficiency, were discussed. According to the theoretical models, and measured spectral results, the diagnostic method of laser-produced plasma’s kinetic parameters was also pointed out.更多还原