摘要
针对等离子体X射线成像诊断高空间分辨率的需求,本文提出了一种基于超环面石英晶体衍射聚焦元件的钛靶X射线高分辨率聚焦成像结构,研究分析了超环面晶体成像的原理及特性。为证明超环面晶体具有高空间分辨率特性,基于X射线衍射追迹原理对球面及超环面晶体的X射线衍射进行性能仿真,在保持射线源及成像物体不变的条件下,对比分析了不同晶体面形结构的衍射成像结果,计算得到球面晶体和超环面晶体在弧矢方向上的成像空间分辨率分别约为40μm和5μm。仿真结果表明超环面晶体作为X射线衍射分光元件较传统的球面晶体具有强聚焦、高空间分辨率的特点,是较为理想的X射线衍射分光元件。此外,本文利用特征峰能量为4.75 keV的钛靶激光装置、IP板以及超环面石英晶体完成了X射线背光成像实验研究,其中超环面石英晶体的子午面和弧矢面半径分别为295.6 mm和268.5 mm,晶格常数2d=0.2749 nm,实验获得了清晰的栅格成像图。实验结果表明该超环面石英晶体能够对钛靶X射线进行衍射成像,并能获得较高的成像空间分辨率。实验中获得的超环面石英晶体衍射的最终成像空间分辨率为10μm。
Objective Fusion energy based on inertial confinement fusion(ICF)is both efficient and environment friendly.It is necessary for ICF research to diagnose weak X-ray signals by focusing on imaging.Because the crystal has a periodic and regular arrangement of internal atoms and the lattice spacing is close to the order of X-ray wavelength,the X-ray diffraction spectrometer can obtain relevant information about the X-ray source using the crystal as the spectroscopic element;thus,the crystal spectrometer is an important part of the spectrum diagnostic instrument.Several types of crystals that are currently being developed have some issues.Planar crystals,for example,do not have the ability to focus rays.Likewise,the cylindrically bend crystal spectrometers are not suitable for diagnostic experiments using coupled fringe cameras.The application of spherically bend crystals for self-luminous imaging requires Bragg angle close to 90°,limiting the imaging energy spectrum selection range.As a result,the development of a crystal spectrometer for diagnosing X-rays with both strong-focus performance and high-resolution is an urgent need for plasma X-ray diagnosing technology for the current ICF devices with ever-increasing performance.This paper proposes a toroidal quartz crystal that can perform focused imaging on Ti-target X-ray at 4.75 keV.The results of simulations and experiments show that after the Ti-target X-rays are diffracted by the toroidal quartz crystal,they have good imaging focusing performance on the sagittal and meridional planes and can achieve high spatial resolution imaging results.Methods A quartz crystal with a toroidal structure was proposed in this paper.First,the imaging principles and properties of spherical and toroidal crystals were investigated and analysed.Then,to demonstrate that the toroidal crystal had high-resolution properties,the X-ray diffraction of spherical and toroidal crystals was simulated in this paper using the X-ray diffraction tracing principle.The diffraction results of various crystal structures were compared and analysed while the radiation source and imaging object remained constant.Then,the imaging spatial resolution of spherical and toroidal crystals in the sagittal plane was calculated.In addition,a Ti-target laser device,an IP plate,and a toroidal quartz crystal were used to complete the X-ray backlight imaging experiment.The imaging results of the toroidal crystal were obtained through actual experiments and the actual resolution was calculated.Finally,the differences between the actual and simulated results were analysed.The related influencing factors were discussed in this paper.Results and Discussions The toroidal crystal’s X-rays have good imaging spatial resolution in the meridional and sagittal planes.The imaging grid’s length in both directions is 500μm,which meets the imaging magnification relationship,and the shape of the imaging grid has almost no deformation[Fig.4(b)].The toroidal crystal has a spatial resolution of aproximately 5μm in the meridional and sagittal planes[Fig.5(b)and Fig.5(d)].The simulation of focusing imaging on spherical and toroidal crystals indicates that the circular spot can be better focused and imaged after being diffracted from the toroidal crystal.The size of the imaging spot is roughly equal to the size of the original source.In addition,the sizes of the imaging spots on the meridional and sagittal planes are nearly equal(Fig.6).From the simulation of the focused imaging of the source,it can be concluded that the toroidal quartz crystal proposed in this paper has strong-focus characteristics and can effectively focus the source,thereby improving the intensity of rays,which is useful for subsequent data processing and analysis.The actual experiment of diffraction focusing imaging on a Ti-target laser device with a pulse width of 920 ps and energy of 1137.34 J can achieve the resolution of 10μm.Conclusions We propose a toroidal quartz crystal and conduct a simulation study based on X-ray diffraction tracing using a toroidal crystal and a spherical crystal of the same material under the same conditions.The focused imaging image of X-rays diffracted by toroidal crystals has a high spatial resolution in the meridional and sagittal planes,as determined by comparing and analysing the imaging results of X-rays diffracted by two crystals of different structures.Metal grids in both planes can be clearly distinguished,and the imaged metal grids show almost no deformation.The imaging result data is used to calculate the simulated imaging spatial resolution,which is approximately 5μm.The Ti-target laser device is used as the source in the experiment to test the effect of diffraction imaging of the quartz crystal’s toroidal structure.The backlight imaging experiment yields a focused imaging image with a magnification of five on both the meridional and sagittal planes.The spatial resolution of X-ray diffraction imaging of toroidal quartz crystal is estimated to be 10μm.The imaging spatial resolution obtained by the simulation and imaging spatial resolution measured by the experiment differs slightly.The difference depends on the actual source’s size,geometric aberrations,and crystal defects.In future,we intend to discuss the aforementioned factors that influence resolution.In conclusion,the quartz crystal with the toroidal structure proposed in this paper has the ability of strong-focus and high-resolution,which can meet the requirements for the spectral diagnosis of high energy density plasma.
作者
姚童
黎淼
施军
尚万里
杨祖华
王峰
杨国洪
韦敏习
孙奥
Yao Tong;Li Miao;Shi Jun;Shang Wanli;Yang Zuhua;Wang Feng;Yang Guohong;Wei Minxi;Sun Ao(College of Optoelectronic Engineering,Chongqing University of Posts and Telecommunications,Chongqing 400065,China;Key Laboratory of Optoelectronic Technology and Systems,Ministry of Education,Chongqing University,Chongqing 400041,China;Research Center of Laser Fusion,China Academy of Engineering Physics,Minayang,Sichuan,621900,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2021年第21期63-71,共9页
Chinese Journal of Lasers
基金
国家自然科学基金(61604028)、重庆市留学创新基金项目(cx2018023)、等离子体物理重点实验室基金项目(6142A04180207)。
关键词
材料
超环面石英晶体
X射线衍射
聚焦
成像空间分辨率
materials
toroidal quartz crystal
X-ray diffraction
focusing
imaging spatial resolution
作者简介
通信作者:黎淼,limiao@cqupt.edu.cn。
