现代实验室型X射线荧光元素分布成像和形态分析技术的研究进展

近年来,随着X射线光源、单色、聚焦及探测系统的发展,在实验室可借助低功率X射线光源开展X射线荧光(XRF)和X射线吸收谱(XAS)分析.液体金属射流源等新型X射线光源系统、闭合反馈系统、电荷耦合元件和方孔微通道板等技术和计算方法的进步促进了聚焦扫描型、全场型和XRF计算机断层扫描等实验室型XRF元素空间成像技术的发展....     

腔靶X光空间特性研究

本文介绍了腔靶X光空间成像原理和方法。在国内,首次将MCP(微通道板)光电成像器件应用于激光聚变实验,将X射线测量能区扩展到亚千电子伏范围。实验中利用各种黑体腔靶,通过测量腔靶X光空间发射图象,得到了腔靶激光注入孔和腔内都存在着等离子体会聚机制,以及腔内X光发射以腔壁为主等重要信息,观察到腔靶X光输运通道存在着“堵口”现象,对测量结果进行了物理解释。     

用于脉冲星导航的X射线光子计数探测器研究

研制了用于脉冲星导航的X射线光子计数探测器原理样机, 该探测器主要由对X射线灵敏度较高的CsI光电阴极、微通道板电子倍增器和收集阳极组成. 对X射线光子计数探测器灵敏度、时间分辨率和整个系统的死时间进行了测试, 实验结果表明该探测器的灵敏度在5 keV时可达5.2× 10³ A/W, 时间分辨率可达到1.1 ns, 系统整体的死时间为100 ns. 关键词： 脉冲星导航 光子计数探测器 灵敏度 时间分辨率     

微通道板选通X射线皮秒分幅相机

本文报道的超高速摄影机可在1.2ns内连续拍摄12幅图象,每幅图象的曝光时间为100ps,空间分辨率201p/mm,它具有几何畸变小、动态范围大等特点。对MCP皮秒选通的数值模拟考虑了电子渡越时间及弥散影响。变象管研制着重解决了微通道板上微带线的欧姆损耗问题。     

微通道板型X射线探测器的脉冲信号探测能力实验分析

为了掌握微通道板探测器的X射线脉冲信号观测能力,利用X射线脉冲星地面实验装置,开展了长时间的不同流强和不同背景噪声强度下的微通道板探测器脉冲信号探测实验,并建立了一套X射线探测器脉冲观测能力评估方法,推导出基于光子计时模式下X射线探测器的脉冲信号信噪比、脉冲轮廓相似度、脉冲到达时间精度和最小可探测功率的关系表达式.实验中,利用面积20cm~2的微通道板探测器开展了8组10 000s的实验,采集到有效观测数据,然后搜索最佳脉冲周期,重构观测脉冲轮廓,估计脉冲轮廓特征参数.实验表明,微通道板探测器具备良好的X射线脉冲信号观测与恢复能力,在较弱脉冲信号强度(光子流量密度为0.05ph/cm~2/s)和较强背景噪声(背景噪声强度是脉冲信号的16倍)下获取观测脉冲轮廓的信噪比、相似度、脉冲到达时间观测精度分别为35.73、88.38%、51.53μs和64.89、89.72%、29.24μs,验证了微通道板探测器具备一定的暗弱X射线脉冲星观测能力,且微通道板探测器的脉冲探测能力随着脉冲信号强度增加、背景噪声强度减弱、累积观测时间增加而提升.     

基于X射线脉冲星导航的地面模拟系统研究

为进行X射线脉冲星导航的关键技术研究,搭建了基于X射线脉冲星导航的地面模拟系统.地面模拟系统由模拟X射线脉冲源、基于微通道板的高灵敏X射线光子探测器、电荷灵敏前放和主放电路、时间测量单元、X射线脉冲轮廓构造及X射线脉冲到达时间测量系统组成.该模拟系统可在地面模拟X射线脉冲星导航的星源的强度、周期及脉冲轮廓,实现对X射线脉冲星单光子到达时间的记录,构造X射线脉冲星脉冲轮廓,计算X射线脉冲到达时间.描述了基于X射线脉冲星导航的地面模拟系统的组成和工作原理,报道了基于X射线脉冲星导航的地面模拟系统的初步结果. 关键词： X射线脉冲星导航 微通道板光子探测器 脉冲轮廓     

X射线二极管时间特性研究

研究X射线二极管(XRD)时间特性.XRD 是构成软X射线能谱仪的主要部件，它用于激光等离子体发射软X射线谱测量.实验利用激光聚变研究中心的200TW激光器(激光能量～6J，脉冲宽度～30fs)打金箔靶产生的X射线发射谱,用滤片(Al)-XRD探测系统测量，探测信号由高频电缆(SUJ-50-10)传输和宽带示波器(TDS694C和TDS6604B)记录.实验数据进行了线性拟合和比对分析. 关键词： X射线二极管 时间特性 软X射线能谱仪 数据处理     

脉冲软X射线发生器的实验研究

本文研究了喷气式Z箍缩等离子体中软X射线(2keV相似文献   

时间积分透射光栅谱仪

本文简要介绍了使用中国科大首次研制成功的有聚酰亚胺衬底的透射光栅与北京电子学研究所研制的MCP(微通道板)构成的透射光栅谱仪,在功率密度～10~(14)W/cm~2的激光辐照条件下,成功地测到了平面Au、C、Al靶发射的软X射线能谱分布(相对值)和黑洞靶产生的软X射线能谱分布(相对值)。实验结果表明:用国内研制的透射光栅构成的时间积分透射光栅谱仪完全能用于激光等离子体实验。本文最后还提出了该设备的进一步改进方案。     

基于超快激光调制的纳秒脉冲X射线发射源

面向基础科学与空间应用研究领域对小型化超快脉冲X射线发射源的需求,设计并研制了基于激光调制光源与光电阴极X射线管的超快脉冲X射线发生器,解决了传统X射线调制发射装置重复频率低、时间稳定性差、脉冲特性差等应用难题.本文主要开展了脉冲X射线发生器的超快调制控制模块研究,并利用基于预调制的激光控制光源实现了高时间精度、高时间稳定度的超快时变光子信号以及纳秒脉冲X射线产生.理论方面,建立了脉冲X射线发生器时间响应模型,分析了出射脉冲X射线的时域时间特性.实验方面,搭建了基于超快闪烁体探测器的脉冲X射线时间特性实验测试系统,测试了激光控制光源及脉冲X射线发射源的时间特性参数.实验结果表明脉冲X射线发生器可同时实现高重频(12.5 MHz)、超快脉冲(4 ns)、高时间稳定度(400 ps)特性,且与所建立的理论模型高度符合.相比于传统X射线调制方案,脉冲时间参数指标得到了大幅提升、应用场景获得了极大拓展,本项研究有望为实现超高时间稳定性、超快脉冲X射线发射源提供新思路.     

X-ray focusing using an x-ray lens composed of multi-square polycapillary slices

A new type of x-ray lens composed of multi-square polycapillary slices(ASPXRL)used in focusing parallel x-ray beam was presented in this paper.Compared with conventional x-ray polycapillary lens,ASPXRL can provide smaller and brighter focus.The effects of the manufacturing imperfections on focusing quality of ASPXRL were evaluated with the values of transmission efficiency and discussed.It is suggested that ASPXRL has application prospects as a condenser lens for x-ray microscopy and flux collectors for x-ray analytical instruments.     

Extended depth of focus for transmission x-ray microscope

A fast discrete curvelet transform based focus-stacking algorithm for extending the depth of focus of a transmission x-ray microscope (TXM) is presented. By analyzing an image stack of a sample taken in a Z-scan, a fully in-focus image can be generated by the proposed scheme. With the extended depth of focus, it is possible to obtain 3D structural information over a large volume at nanometer resolution. The focus-stacking method has been demonstrated using a dataset taken with a laboratory x-ray source based TXM system. The possibility and limitations of generalizing this method to a synchrotron based TXM are also discussed. We expect the proposed method to be of important impact in 3D x-ray microscopy.     

Large-aperture focusing of x rays with micropore optics using dry etching of silicon wafers

Large-aperture focusing of Al K(α) 1.49 keV x-ray photons using micropore optics made from a dry-etched 4 in. (100 mm) silicon wafer is demonstrated. Sidewalls of the micropores are smoothed with high-temperature annealing to work as x-ray mirrors. The wafer is bent to a spherical shape to collect parallel x rays into a focus. Our result supports that this new type of optics allows for the manufacturing of ultralight-weight and high-performance x-ray imaging optics with large apertures at low cost.     

可变焦列阵柱面透镜均匀线聚焦系统

用两个列阵柱面透镜与非球面透镜组成变焦线聚焦系统，能将入射激光束会聚成辐照均匀、长度连续可调的焦线，它可用于Ｘ光激光实验研究．文中详细分析了焦线上光场分布的情况，给出了物理光学分析的结果，并与巳有技术作了比较．     

Non-uniform Influence of Prepulse Duration on a Nickel-Like Mo X-Ray Laser in XLIII

An experiment on a transient nickel-like Mo x-ray laser in the extreme light III (XL III) laser facility is analyzed, based on the two-dimensional hydrodynamic evolutions of a plasma under a non-uniform incident laser. Influences of the pulse duration and intensity on plasma scale length, electron density, temperature, as well as their distributions are investigated, based on which the pre-pulse character and delay time are determined according to the parameters of laser line focus on XLIII. It is found that the optimal intensity of the pre-pulse is 1.0TW/cm² with a duration of 500ps; a well modified pre-plasma can be obtained after 1.6ns under low quality line focus in the lab.     

Volume effect of laser produced plasma on X-ray emissions

An investigation of x-ray emission from Cu plasma produced by 1.054 μm Nd:glass laser pulses of 5 ns duration, at 2 × 10¹² − 2 × 10¹³ W cm⁻² is reported. The x-ray emission has been studied as a function of target position with respect to the laser beam focus position. It has been observed that x-ray emissions from ns duration plasma show a volume effect similar to subnanosecond plasmas. Due to this effect the x-ray yield increases when target is moved away relative to the best focal plane of the laser beam. This result supports the theoretical model of Tallents and has also been testified independently using suitably modified theoretical model for our experimental conditions. While above result is in good agreement with similar experimental results obtained for sub-nanosecond laser produced plasmas, it differs from result claiming filamentation rather than pure geometrical effect leading to x-ray enhancement for ns plasmas.     

Time resolved spectroscopy with femtosecond soft-x-ray pulses

The most challenging application of time resolved spectroscopy is to directly observe the structural and electronic dynamics. Here we present the combination of x-ray absorption spectroscopy with laser driven x-ray sources, offering atomic spatial and temporal resolution. Our new approaches for optimization of laser driven x-ray sources resulted in the demonstration of spatially coherent sub-20 fs x-ray pulses in a range up to several keV. We excited polycrystalline silicon with an ultrashort laser pulse and characterized the collective motion of atoms with time resolved x-ray absorption spectroscopy at a temporal resolution of less than 20 fs. Finally, we have shown the feasibility of probing the dynamics of the electronic structure of silicon and carbon with near edge x-ray absorption spectroscopy.     

Real-time icosahedral to fcc structure transition during CoPt nanoparticles formation

Nucleation and growth of supported CoPt nanoparticles were studied in situ and in real time by combined grazing incidence small-angle x-ray scattering (GISAXS) and grazing incidence x-ray diffraction (GIXD). GISAXS provides morphological features of nanoparticles as a function of size, shape and correlation distance between particles, while GIXD allows the determination of the atomic structure. We focus on the formation of ultrasmall CoPt nanoparticles, in the 1–4 nm size range at 500^○C. The structural analysis method based on the Debye equation is coupled with cluster model calculations performed by Monte Carlo simulations using a semi-empirical tight-binding potential to interpret diffraction spectra and structural transitions. Our results show that the cluster structure evolution during the growth is size-dependent and composition-dependent, yielding an icosahedral to fcc structure transition.     

Generation of picosecond hard-x-ray pulses in a femtosecond-laser-driven x-ray diode

The temporal characteristics of ultrashort hard-x-ray pulses generated in a femtosecond-laser-driven x-ray diode are investigated for what is believed to be the first time. Copper Kalpha x-ray pulses with a duration of a few picoseconds are measured with a jitter-free x-ray streak camera.     

强光1号装置上钨丝阵列的Z箍缩实验研究

本文报道了2003年在强光一号装置上进行的钨丝阵列的Z箍缩实验研究的主要结果。为了研究钨丝阵列的内爆过程和x光辐射特性，使用了x光功率谱仪和一维时空分辨x光成像系统等诊断设备。实验中由32根5微米钨丝组成的直径8mm长20mm的优化负载获得了最高能量为36.6kJ的x光产额，一维时空分辨x光成像系统的数据显示x光辐射区域以6.4×10⁶cm/s的速度减小，同时x光峰值时刻出现在等离子体被压缩到近轴区域之前。