一种新型微束斑X射线源的研究

采用高效长寿命的LaB6单晶阴极电子枪作为电子束发射系统、轻便的等径双圆筒静电系统作为聚焦系统等技术研究了一种新型台式微束斑X射线源.通过在综合测试仪上的初步实验研究,表明该微束斑X射线源不仅可以连续辐射,而且可以脉冲辐射X射线,输出X射线束斑小、亮度高.此外,该台式X射线源具有体积小、重量轻,使用寿命长、造价低,可灵活移动等优点.     

光学仪器 X射线、紫外线及其仪器

O434.1 2005021581 一种新型脉冲微束斑X射线源的研究=Study of protable pulse X-ray sources with micro-beam[刊,中]／王凯歌(中 科院物理研究所软物质实验室．北京(100080)),牛憨笨… //光电子·激光．-2004,15(9).-1011-1015 通过控制栅极电压技术,有效地控制LaB6阴极电子 枪发射系统电子束发射的通与断,成功实现了新型台式微 束斑X射线源的脉冲辐射。该X射线源主要由3部分组     

电子束在微束斑X射线源中运动轨迹的计算

轰击金属靶面的高能电子束束斑大小,是决定微束斑X射线源最终X射线束斑尺寸的关键因素之一.当LaB₆晶体阴极发射电流为60μA时,采用5点不等距有限差分法(FDM)计算了整个仪器内旋转对称电子光学系统电场的分布,并利用Runge Kutta法从LaB₆阴极发射端面开始追踪了电子束在整个系统内部的运动,经计算,聚焦在靶面上的电子束斑直径约为600~1000nm.     

LaB6与TaC混合涂层热阴极

研究了一种LaB6与TaC混合涂层热阴极,其发射层通过均匀混合LaB6与TaC粉末得到。比较了该阴极在LaB6与TaC混合比例为1∶1, 2∶1和3∶1下的发射特性,发现混合型LaB6阴极的功函数与多晶LaB6阴极的非常接近,在3∶1的混合比例下,电极的发射电流稳定,得到的电流密度为30 A/cm2。该电极可被应用于需要大电流密度和超大面积阴极的真空电子器件及动态真空电子束设备中。     

聚焦慢速高荷态重离子束微束斑X射线源

利用电子束离子源(EBIS)或者电子束离子陷阱(EBIT)产生的慢速高电荷态重离子束轰击金属靶面,离子束与靶面作用并复合辐射特征X射线;并将高荷态离子束采用离子光学系统会聚为微细束后再与靶面作用,能够辐射出微米甚至亚微米级、纳米级的微束斑X射线.本文介绍这一新型微束斑X射线源的结构、机理及其特性等.     

微束斑X射线源聚焦系统的数值研究

本文研究了由两个磁透镜组成的电子束打靶微束斑X射线源的聚焦系统.首先利用有限元法计算了磁透镜的磁感应强度的轴上分布,在此基础上用三次样条函数插值计算了磁场的空间分布,最后用四阶Runge-Kutta法追踪了电子的运动轨迹,并给出了入射电子束经过聚焦系统后的缩小倍率.     

X射线源的静电自会聚电子枪的计算机模拟北大核心CSCD

高功率、大电流密度、细聚焦X射线源在工业无损探伤、医学成像、安全技术等领域具有广泛的应用。本文设计了一种用于X射线管的静电自会聚电子枪,该电子枪包括三部分:La B6热阴极发射体、带有矩形孔和斜槽的聚焦极、阳极。采用EBS粒子束模拟软件对该电子枪的结构进行了模拟仿真。仿真结果表明:电子枪的聚焦能力主要取决于聚焦极倾角,当聚焦极倾角为46°时,达到理想的电子束聚焦效果;随着阴栅距的增加,阳极电流以及束斑电流分布均匀性显著降低,当阴栅距为0.3 mm,可在工艺条件允许下,得到具有较大阳极电流以及理想电流分布的电子束。     

电子束蒸发沉积六硼化镧薄膜的逸出功(英文)

六硼化镧(LaB6)具有电子逸出功低、高熔点和高化学稳定性等优点,是制作热阴极和场发射阴极的理想发射体材料。而且在常规场发射尖锥表面涂敷一层LaB6薄膜能够大幅度提高场发射尖锥的发射能力。为了测量LaB6薄膜的逸出功,采用电子束蒸发技术沉积LaB6薄膜,并对薄膜进行了X射线衍射分析和X射线光电谱分析。通过测量薄膜的热电子发射特性和敷LaB6薄膜的硅尖锥阵列的场致电子发射特性确定了LaB6薄膜的逸出功,与块状LaB6多晶材料的逸出功大体相同,说明电子束蒸发沉积技术适合于制备高纯度、低逸出功的LaB6薄膜。     

X射线源的静电自会聚电子枪的计算机模拟

高功率、大电流密度、细聚焦X射线源在工业无损探伤、医学成像、安全技术等领域具有广泛的应用。本文设计了一种用于X射线管的静电自会聚电子枪,该电子枪包括三部分:La B6热阴极发射体、带有矩形孔和斜槽的聚焦极、阳极。采用EBS粒子束模拟软件对该电子枪的结构进行了模拟仿真。仿真结果表明:电子枪的聚焦能力主要取决于聚焦极倾角,当聚焦极倾角为46°时,达到理想的电子束聚焦效果;随着阴栅距的增加,阳极电流以及束斑电流分布均匀性显著降低,当阴栅距为0.3 mm,可在工艺条件允许下,得到具有较大阳极电流以及理想电流分布的电子束。     

清华大学汤姆逊散射超短脉冲X射线源研究

 介绍了清华大学加速器实验室近年来关于汤姆逊散射超短X射线源的研究工作;研究了在任意散射角度下电子束参数和激光束参数对散射光子参数的影响,给出了散射光子的参数如光子产额、脉冲长度、时间抖动等与电子束参数、激光束参数和散射角度的关系;利用实验室已有的16 MeV反波行波加速器与中国工程物理研究院激光聚变研究中心提供的ns调Q激光搭建了汤姆逊散射初步实验平台并开展了实验研究;加工了1.6-cell光阴极微波电子枪,搭建了高功率实验平台,对产生的电子束参数进行了初步测量;对汤姆逊散射超短X射线源进行了设计并开展了相关的平台建设工作,对产生的X射线脉冲参数进行了模拟。     

微束斑X射线源发射系统的数值计算

本文采用边界元法(BEM)对高亮度微束斑X射线源的LaB₆阴极、Wehnet栅极和阳极等发射系统的电位和场强分布进行了数值计算,首先计算了系统对称轴上的电位,再利用三次样条插值法和谢赫尔公式等计算了系统在考虑三次相差情况下的傍轴电场强度分布.     

Quantitative elemental analysis of individual particles with the use of micro‐beam X‐ray fluorescence method and Monte Carlo simulation

The aim of the work was to develop a Monte Carlo (MC) method and combine it with micro‐beam X‐ray fluorescence (XRF) technique for determination of chemical composition of individual particles. A collection of glass micro‐spheres, made of NIST (National Institute of Standards and Technoly) K3089 material of known chemical composition, with diameters in the range of 25–45 µm was investigated. The micro‐spheres were measured in a scanning micro‐beam XRF spectrometer utilising X‐ray tube as a source of primary radiation. Results obtained for low Z elements showed high dependence on particle size. It was found that the root mean square of concentration uncertainty, for the all elements present in the particle, increases with growing sample size. More accurate results were obtained for high Z elements such as Fe–Pb, as compared to others. The elemental percentage uncertainty did not exceed 14% for any particular sample and 6% for the whole group of the measured micro‐spheres as an average. Results obtained by the Monte Carlo method were compared with other analytical approaches. Copyright © 2009 John Wiley & Sons, Ltd.     

X射线微光刻的常规X射线光源实现方法

叙述了利用固体靶X射线光源实现X射线微光刻的方法,给出了X射线掩膜、抗蚀剂及X射线曝光的工艺过程和实验结果.     

影响X光源特性的参数研究

针对高能电子束撞击重金属靶产生轫致辐射光子, 利用蒙特卡罗方法详细研究了电子束半径与发射度以及靶的厚度对X光源特性的影响. 结果表明：电子束半径与发射度不仅是影响照射量的主要因素, 也是造成照射量分布不均匀的主要原因; 给定电子束, 存在一个靶厚度使得靶前1 m处的照射量最大. 因此, 在X射线成像系统的设计和模拟过程中, 应综合考虑电子束半径与发射度和靶厚的影响.     

A sub‐micrometer resolution hard X‐ray microprobe system of BL8C at Pohang Light Source

A microprobe system has been installed on the nanoprobe/XAFS beamline (BL8C) at PLS‐II, South Korea. Owing to the reproducible switch of the gap of the in‐vacuum undulator (IVU), the intense and brilliant hard X‐ray beam of an IVU can be used in X‐ray fluorescence (XRF) and X‐ray absorption fine‐structure (XAFS) experiments. For high‐spatial‐resolution microprobe experiments a Kirkpatrick–Baez mirror system has been used to focus the millimeter‐sized X‐ray beam to a micrometer‐sized beam. The performance of this system was examined by a combination of micro‐XRF imaging and micro‐XAFS of a beetle wing. These results indicate that the microprobe system of the BL8C can be used to obtain the distributions of trace elements and chemical and structural information of complex materials.     

同步辐射X光束空间相干性的物理分析

从量子力学的不确定原理出发，推导出光源相干性和光束相干性的关系，并应用所得的结论南步辐射Ｘ光束的空间相干性进行物理分析，讨论了Ｘ光相干我学实验对Ｘ光束的一些要求。     

0.5 mm金刚石X射线相位延迟板及偏振度的标定

在利用步辐射光源的偏振特性进行自旋相关X射线散射及吸收谱实验来研究材料的磁学性质时，需要应用圆偏振光，这就提出了对具有高通量、高偏振度' 长连续可调的圆偏振X射线的需求；另一方面标定实验所用X射线的圆偏振度也成为这一研究领域的关键技术。由于X射线多光束衍射强度与σ场和π场的光程差δ相关，通过测量圆偏振分析晶体的多光束衍射的强度分布，可以获得入射X射线的圆偏振度。实验在美国国家同步辐射光源实验室X25光束线实验站进行，光子能量为7．1keV的圆偏振X射线由线偏振X射线经过一厚度为0．5mm、晶面为[111]的金刚石晶体产生。通过测量多光束衍射强度，确定了斯托克斯参量。实验值与X射线动力学理论计算结果能较好地吻合。     

A sagittally focusing double‐multilayer monochromator for ultrafast X‐ray imaging applications

The development of a sagittally focusing double‐multilayer monochromator is reported, which produces a spatially extended wide‐bandpass X‐ray beam from an intense synchrotron bending‐magnet source at the Advanced Photon Source, for ultrafast X‐ray radiography and tomography applications. This monochromator consists of two W/B₄C multilayers with a 25 Å period coated on Si single‐crystal substrates. The second multilayer is mounted on a sagittally focusing bender, which can dynamically change the bending radius of the multilayer in order to condense and focus the beam to various points along the beamline. With this new apparatus, it becomes possible to adjust the X‐ray beam size to best match the area detector size and the object size to facilitate more efficient data collection using ultrafast X‐ray radiography and tomography.     

X‐ray spectra by means of Monte Carlo simulations for imaging applications

X‐ray tubes have a broad range of applications worldwide, including several techniques for atomic physics, like X‐ray fluorescence, as well as for medical imaging, like computed tomography. The performances of X‐ray imaging detectors have shown to be significantly sensitive to the incident beam spectrum. Therefore, an accurate knowledge of the X‐ray beam becomes necessary for the emission source characterization and the whole imaging process comprehension. Direct measurements and suitable Monte Carlo simulations may be used to establish the X‐ray spectra. Dedicated Monte Carlo simulation routines, based on the PENELOPE code, have been developed to determine the Bremsstrahlung X‐ray spectra generated by conventional X‐ray tubes. The simulated spectra have been validated by comparison with the corresponding experimental data showing an overall good agreement. The incorporation of a suitably designed virtual grid allowed to assess the angular distribution of Bremsstrahlung yield, showing a remarkable anisotropy. In addition, a dedicated program has been developed for virtual imaging, which enables to perform suitable X‐ray absorption contrast images. Also, the developed program includes a user‐friendly graphic interface to allow the upload of required input parameters, which include setup arrangement, beam characteristics, sample properties and image simulation parameters (spatial resolution, tracks per run, etc.). The software includes dedicated subroutines which handle the physical process from X‐ray generation up to detector signal acquisition. The aim of the developed program is to perform virtual imaging by means of absorption contrast and using conventional X‐ray sources, which may be a useful tool for the study the X‐ray imaging techniques in several research fields as well as for educational purposes. The performed comparisons with experimental data have shown good agreement. The obtained results for X‐ray imaging may constitute useful information for the comprehension and improvement of X‐ray image quality, like absorption contrast optimization, detail visualization, definition and detectability. Copyright © 2010 John Wiley & Sons, Ltd.