电子探针中x光分光谱仪的波长分辨力

本文讨论了电子探针中ｘ光分光谱仪的波开分辨力。除Ｘ光谱线的自然宽度外，弯晶光谱仪的分辨力是由一些实际因素决定的。     

椭圆石英弯晶的积分衍射效率标定

椭圆弯晶谱仪具有测谱宽度大,能谱分辨力高等特点,并在"神光II"激光惯性约束聚变实验研究中得到了很好的应用。利用X射线衍射仪铜(Cu)靶X射线管作为X射线线光源,选取合适厚度滤片,抑制Cu-Kβ线及韧致辐射,测量了Cu-Kα能点处二氧化硅石英椭圆弯晶的积分衍射效率和摆动曲线半高全宽,并开展了针对上述两个重要参数随晶体弯曲曲率半径改变的测试验证,预估了能谱分辨力。结果表明,椭圆弯晶的积分衍射效率和摆动曲线半高全宽对晶体弯曲半径改变敏感,通过提高晶体弯曲度可增强晶体"镶嵌"效果。该结果可为下一步优化设计多用途性椭圆弯晶谱仪,以及完善X射线光谱定量化测量提供了数据支撑。     

北京安科慧生科技有限公司成功研制新型X射线荧光光谱仪

X射线荧光光谱仪,是土壤中重金属元素分析的手段之一,而其中的双曲面弯晶,又是X射线荧光光谱仪性能提升的关键技术,但该技术长期被美国一家分析仪器公司掌握和封锁。为此,北京安科慧生科技有限公司自2015年开始进行科研攻关,如今,已成功研制出X射线荧光光谱仪的核心部件--全聚焦型双曲面弯晶,成为世界上第二家拥有此项技术的公司,并依据这项核心技术,成功研制出便携式X射线荧光光谱仪,可用于土壤重金属污染限值检测。     

椭圆弯晶谱仪分析器研制

针对激光惯性约束核聚变辐射的X射线分析,可得到关于等离子体电子密度、温度、电荷分布等重要信息.研究的X射线弯晶谱仪分析器是用来诊断X射线光谱,进而实现对激光惯性约束核聚变的控制.探讨了椭圆弯晶谱仪理论原理,分析了积分反射率和质量吸收系数.弯晶谱仪采用LiF弯晶分析器,椭圆焦距2c为1 350 mm,椭圆离心率e为0.958 6,晶体布拉格角范围为30°至60°.在此对LiF弯晶分析器的制作工艺进行详细描述.实验结果表明,该晶体分析器对X射线的分辨率(λ/Δλ)可达900以上,能够用来对激光等离子体的X射线光谱进行诊断.     

椭圆弯晶谱仪波长分辨能力的改进

讨论了椭圆弯晶谱仪的波长分辨能力。在假设谱线的固有宽度可以忽略的情况下,对两种实际影响椭圆弯晶谱仪波长分辨能力的主要因素,即光源空间尺寸和非理想椭圆分光晶面进行了分析。分别对上述两种情况进行了数学建模和数值模拟仿真。定量地分析了非理想椭圆晶面和光源空间尺寸对椭圆弯晶X射线谱仪波长分辨本领的影响程度,并给出了出射狭缝宽度与椭圆弯晶谱仪波长判读加宽的关系。从理论上论证了光源空间尺寸在限制谱仪的波长分辨能力方面仍然起关键主导作用;结合椭圆分光晶体的结构参数,合理地选择出射狭缝宽度,可使谱仪达到足够好的光谱分辨率和信噪比。用搭建的实验平台进行了实验测试,结果表明,当出射狭缝宽度(2δ)为10mm时,实测的谱线半高全宽(Δλ)为3.1×10-3nm;2δ为4mm时,Δλ为2.3×10-4nm,实测结果佐证了仿真结果的正确性。     

一种新型曲面晶体成像系统的研制

为了对诊断目标进行瞬态辐射成像,提出了研制X射线聚焦成像系统,主要器件为一各向同性的X射线点光源及超环面弯曲晶体成像器.X射线照射至被成像物体后再投射到超环面晶体,经该凹面晶体聚焦后在X射线探测器表面成像.讨论了超环面晶体在布拉格几何结构中的聚焦成像特性,提出利用X射线源进行二维优化成像的适用条件.利用模拟软件对网格物体进行仿真成像,研究像距及光源尺寸对成像空间分辨力的影响,并据此确定了实验参量.设计的超环面弯晶采用云母材料,子午面曲率半径为290 mm,弧矢面曲率半径为190 mm.利用该系统进行了X射线背光成像实验,实验结果表明:系统的成像空间分辨力最高可达到34μm,能够满足聚爆辐射成像的要求;在光源尺寸较大时像距变化对成像效果有明显影响.     

X射线单色成像用透射式对数螺线晶体分析器

利用对数螺线晶体在大视场范围内的保角特性,研究了一种用于等离子体X射线单色成像的透射式对数螺线晶体分析器。与反射式弯晶成像谱仪相比,该分析器具有单能成像视场更大,实现相同放大倍数时的空间排布简单等优点。根据晶体衍射成像原理及对数螺线晶体的表面方程,分析了透射式对数螺线晶体分析器的成像原理以及成像性能,包括子午、弧矢放大倍数以及视场大小等。以铜靶X射线源为背光源,用研制石英晶体透射对数螺线分析器对网丝直径为100μm的金属网格进行了单色背光成像实验。实验结果表明,晶体分析器的空间分辨力约为30μm,子午和弧矢方向视场分别达到15.938 7mm和5.900 6mm。     

双道X射线分光光谱仪及其与扫描电子显微镜的匹配

本X光谱仪是一种线性全聚焦弯晶谱仪。装备在扫描电镜上后,可使之兼具电子探针X光微区分析仪的功能。本文重点讨论了X光光谱仪的几何精度、分光晶体的制备、光谱仪与电子光学镜筒的匹配衍射峰值强度的提高、本底噪音的减低以及同轴光学显微镜的匹配等问题。X光谱仪的总几何精度应为±1′,重复精度为6″。实际结果表明,元素分析范围为B~5(Be~4)～U~(92);波长分辨率△λ/λ为1～5×10~(-3)(Na~(11)～U~(92))及1～5×10~(-2)(B~5～F~9),可分开Cu,Fe,Ti等元素的K_(α1,α2)谱线,Ti-6A1-4V合金中VK_(α1),VK_(α2)及TiK_β谱线;波长重复性为0.00014A;探测限对Na~(11)～U~(92)为10~(-3)％量级,B~5～F~9为10~(-2)％量级。     

用热解石墨晶体作色散和聚焦光学元件的激光等离子体源的超快X射线光谱仪

由于激光等离子X射线源的光子通量显著低于同步辐射源的光子通量且射线为所有方向的各向同性辐射,所以,很需要具有大的集光立体角和高的积分反射率的光学元件,用热解石墨(PG)晶体作色散和聚焦元件可满足上述要求。由于PG晶体为嵌镶结构,所以可给出很高的积分反射率,而PG薄膜还可安装在任意形状的模具上构成任意形状的光学元件。此外,特殊形状的嵌镶聚焦使这些晶体甚至在弯曲的情况下,也可作为高分辨率X射线光学元件。基于上述元件特性,可以设计出有高集光效率的色散光学元件,用于激光等离子体源超快X射线光谱检测。文中描述了PG弯晶在一台改型的von HAMOS光谱仪中的应用,使用这台光谱仪,测量了飞秒激光器产生等离子体发射的X射线的光谱分布。讨论了产生的X射线在时间分辨扩展X射线吸收精细结构(EXAFS)分析中的应用。实验表明,通过优化晶体特性和光谱仪几何设置,可以实现对过渡金属K边的高分辨率EXAFS测量。     

氟化锂椭圆弯晶分析器的特性及应用

设计了测试能量范围为0.6~6 keV的椭圆弯晶谱仪。此谱仪利用椭圆自聚焦原理,晶体分析器采用氟化锂材料,椭圆焦距为1 350 mm,离心率为0.958 6,布拉格角范围为30~65°。在神光Ⅱ靶室进行了实验,入射激光波长为0.35 μm,激光功率约为1.6×10¹⁴ W/cm²,与厚度为100 μm的钛平面靶法线夹角约为45°。实验结果证实,弯曲的氟化锂晶体具有极佳探测效果,弯晶分析器对波长为0.2~0.35 nm的X射线的分辨率可达500~1 000,同时具有等光程而便于空间分辨测量的优点,在同样距离条件下比平晶分析器高一个数量级的收光效率,故适合于激光等离子体X射线的光谱学研究。     

Design and performance of a versatile curved-crystal spectrometer for high-resolution spectroscopy in the tender x-ray range

A complete in-vacuum curved-crystal x-ray emission spectrometer in Johansson geometry has been constructed for a 2-6 keV energy range with sub natural line-width energy resolution. The spectrometer is designed to measure x-ray emission induced by photon and charged particle impact on solid and gaseous targets. It works with a relatively large x-ray source placed inside the Rowland circle and employs position sensitive detection of diffracted x-rays. Its compact modular design enables fast and easy installation at a synchrotron or particle accelerator beamline. The paper presents main characteristics of the spectrometer and illustrates its capabilities by showing few selected experimental examples.     

Design and performance of a curved-crystal x-ray emission spectrometer

A curved-crystal x-ray emission spectrometer has been designed and built to measure 2-5 keV x-ray fluorescence resulting from a core-level excitation of gas phase species. The spectrometer can rotate 180 degrees, allowing detection of emitted x rays with variable polarization angles, and is capable of collecting spectra over a wide energy range (20 eV wide with 0.5 eV resolution at the Cl K edge) simultaneously. In addition, the entire experimental chamber can be rotated about the incident-radiation axis by nearly 360 degrees while maintaining vacuum, permitting measurements of angular distributions of emitted x rays.     

High-resolution,energy-dispersive microcalorimeter spectrometer for X-ray microanalysis

We have developed a prototype X-ray microcalorimeter spectrometer with high energy resolution for use in X-ray microanalysis. The microcalorimeter spectrometer system consists of a superconducting transition-edge sensor X-ray microcalorimeter cooled to an operating temperature near 100 mK by a compact adiabatic demagnetization refrigerator, a superconducting quantum interference device current amplifier followed by pulse-shaping amplifiers and pileup rejection circuitry, and a multichannel analyser with computer interface for the real-time acquisition of X-ray spectra. With the spectrometer mounted on a scanning electron microscope, we have achieved an instrument response energy resolution of better than 10 eV full width at half-maximum (FWHM) over a broad energy range at real-time output count rates up to 150 s^?1. Careful analysis of digitized X-ray pulses yields an instrument-response energy resolution of 7.2 ± 0.4 eV FWHM at 5.89 keV for Mn Kα_1,2 X-rays from a radioactive ⁵⁵Fe source, the best reported energy resolution for any energy-dispersive detector.     

等离子体诊断用成像型软X射线三色谱仪设计

围绕激光惯性约束聚变研究中内爆靶丸的辐射流诊断需求,设计了一种兼顾空间成像功能的三色软X射线谱仪。该谱仪的设计中心能点为210eV、680eV和800eV,能谱分辨率E/ΔE为5~10。采用X射线掠入射光学结构,实现了三个能点的一维聚焦成像,在1mm视场内空间分辨率优于10μm。采用X射线周期多层膜,获得了三个能区的能谱响应,多层膜测试结果满足设计要求。以光学设计和多层膜为基础,建立了系统的光线追迹模型,分析了可控的空间位置误差和瞄准误差对系统光谱分辨和空间分辨的影响,为装调方案及瞄准方法设计提供了精度依据。该谱仪与条纹相机结合,可用于我国强激光装置上的等离子体诊断实验。     

Calculation of the Johann error for spherically bent x-ray imaging crystal spectrometers

New x-ray imaging crystal spectrometers, currently operating on Alcator C-Mod, NSTX, EAST, and KSTAR, record spectral lines of highly charged ions, such as Ar(16+), from multiple sightlines to obtain profiles of ion temperature and of toroidal plasma rotation velocity from Doppler measurements. In the present work, we describe a new data analysis routine, which accounts for the specific geometry of the sightlines of a curved-crystal spectrometer and includes corrections for the Johann error to facilitate the tomographic inversion. Such corrections are important to distinguish velocity induced Doppler shifts from instrumental line shifts caused by the Johann error. The importance of this correction is demonstrated using data from Alcator C-Mod.     

三晶体多轴联动同步辐射X射线荧光光谱仪

针对上海光源X射线吸收精细结构光谱仪对灵敏度和分辨率的要求,研制了三晶体多轴同步辐射X射线荧光光谱仪。其采用一台双晶单色器提供实验X射线,用3块凹面晶体构成系统主体色散结构,并在竖直平面内组成相交的罗兰圆实现荧光分析,可实现10°范围内的布拉格角变化。光谱仪通过高精度控制驱动设备使位移平台实现了3块晶体的4轴联动和总台的2轴联动,其中对位移平台的各轴精度达到了单步长移动25nm,可以实现高分辨率的三维扫描工作。编写了探测器的驱动软件,提高了驱动器的测试灵敏度和分辨率。最后,利用国际通用的实验物理控制系统——EPICS(Experiment Physics and Industrial Control System)完成了整个系统软件的设计,实现了系统各部分的精确控制、自动测量、数据分析和结果显示与存储等功能,构成了一套完整的基于同步辐射光源的高精度高分辨率X射线荧光光谱分析系统。采用钴元素作为测试样品进行了分析实验,结果显示:该光谱仪单次测量时间小于1.5s,测试精度达到0.4eV,分辨率为0.1eV。光谱仪可以完成对样品荧光的采集和分析,操作时间、精度、分辨率和重复性等性能指标均优于现有国内、外设备,目前已成功应用于上海光源XAFS线站的各项科学实验中。     

Quantitative EDS and WDS X-ray microanalysis of semiconductor materials: Principles and comparisons

The basic principles and procedures for performing accurate X-ray microanalyses on semiconductor materials as well as the differences and advantages of EDS (energy-dispersive spectroscopy) and WDS (wavelength-dispersive spectroscopy) are presented. Many of the techniques discussed are the result of extensive experience with some photovoltaic materials such as CuInSe₂, GaAs, CdTe, CdS, CdSnP, InP, ZnP, and amorphous Si-based alloys. Results of an experiment designed to compare the performance of an energy-dispersive X-ray spectrometer (EDS) and a wavelength-dispersive X-ray spectrometer (WDS) on some semiconductor materials are presented. CdTe, CdSe, CuInSe₂, ZnSe, and InSb standards were used to measure the k-ratios with pure element standards employing both types of X-ray spectrometers to demonstrate the ability of each to measure elemental compositions under various operating conditions. Both types of spectrometers were utilized on a Cameca MBX electron microprobe at identical X-ray take-off angles. The EDS spectrometer was found to perform equal to the WDS spectrometer when integral peak-to-background ratios were greater than seven, when the X-ray line being measured was greater than about 1,000 eV, and when adjacent peaks were separated by more than three times the detector energy resolution.     

用于测量激光等离子体X射线的椭圆弯晶谱仪

研制了一种椭圆弯晶谱仪用于测量0.44～0.81 nm激光等离子体X射线光谱.该谱仪采用X射线CCD作探测器,用PET(2d＝0.874 nm)晶体作色散和聚焦元件,将晶体弯曲并粘贴在离心率和焦距分别为0.9586和1350 mm的椭圆形不锈钢基底上.对该谱仪在"星光Ⅱ"激光装置上进行了打靶实验,实验结果表明其光谱分辨率接近1000.