同步辐射EDXAFS和EDXRD联用方案

许多材料研究中,都需要采用X射线吸收精细结构谱学(X-ray Absorption Fine Structure,XAFS)和X射线衍射(X-ray Diffraction,XRD)技术测量材料的短程和长程有序结构信息,而如何同时快速地测量是开展原位动态研究的一个关键。本文提出了一种结合能量色散X射线吸收精细结构谱(Energy-dispersive X-ray Absorption Fine Structure,EDXAFS)和能量色散X射线衍射(Energy-dispersive X-ray Diffraction,EDXRD)的测试方案,该方案利用同步辐射白光,理论上可以提供微秒量级的表征速度和时间分辨能力,为真实环境下材料结构的原位实时表征提供了一种可能方法。     

自背光法辐射不透明度实验研究

针对星光Ⅱ装置的实际条件,提出了以金箔背侧 X 光辐射作为样品加热源兼作背光源的特色自背光法,研究了辐射不透明度(自由程)实验方法。以波长为 0.35 μm,能量约 80 J,脉宽约 700 ps的强激光注入特色自背光靶,用空间分辨透射光栅配 X 光 CCD 由同一发打靶测得了半样品靶的源区、透射区和自发射区三区能谱分布图象,又由不同发次打靶分别测得了源谱、透射谱。样品材料为厚度 0.5 μm 和 1 μm,密度为 2.7 g/cm3的铝膜,以及密度为 0.042g/cm3,厚度为 42 μm 的碳氢发泡材料。实验由不同打靶发次测得的源谱和透射谱,初步获得了样品的谱分辨质量吸收系数,进而用空间分辨透射光栅谱仪、由同一发打靶获得了样品考虑自发射的谱分辨质量吸收系数。对样品温度、密度条件进行了相应的实验与理论研究。初步讨论了热碳元素辐射不透明度(Opacity)。     

自背光法辐射不透明度实验研究

针对星光Ⅱ装置的实际条件,提出了以金箔背侧X光辐射作为样品加热源兼作背光源的特色自背光法,研究了辐射不透明度(自由程)实验方法。以波长为0.35μm,能量约80J,脉宽约700ps的强激光注入特色自背光靶,用空间分辨透射光栅配X光CCD由同一发打靶测得了半样品靶的源区、透射区和自发射区三区能谱分布图象,又由不同发次打靶分别测得了源谱、透射谱。样品材料为厚度0.5 μm和1 μm,密度为2.7g/cm~3的铝膜,以及密度为0.042g/cm~3,厚度为42μm的碳氢发泡材料。实验由不同打靶发次测得的源谱和透射谱,初步获得了样品的谱分辨质量吸收系数,进而用空间分辨透射光栅谱仪、由同一发打靶获得了样品考虑自发射的谱分辨质量吸收系数。对样品温度、密度条件进行了相应的实验与理论研究。初步讨论了热碳元素辐射不透明度(Opacity)。     

X射线荧光分析原级能谱分布的MCNP模拟

X射线荧光分析中,入射激发能谱是影响元素特征荧光强度大小的直接因素。本文使用MCNP程序模拟不同条件下电子打靶后的X射线能谱分布,计算结果能够反映不同条件下特征谱线和连续谱线的特点。模拟能谱数据可用于X射线荧光分析的数据处理。     

应用于在线测厚的多靶式特征X射线发生装置初步设计

由于设计的需要,利用铜靶、铁靶进行了特征X射线的产额与靶源的距离、靶源夹角关系的实验研究,当靶源距离越近、靶源夹角为70°时产生的特征X最多;在实验基础上设计了射线产额高,体积小、质量轻,靶片转换方便的特征X射线发生装置。     

基于晶体衍射的X射线偏振源

基于X射线的晶体衍射,实验设计并搭建了X射线偏振源.该X射线偏振源主要包括X射线光管和用于起偏的布拉格晶体.当X射线以45°角入射到晶体表面上时,经过布拉格衍射,可以得到线偏振的X射线;当X射线的入射角度偏离45°时,将产生部分偏振X射线.实验中利用微通道铅玻璃板做准直器,很好地保证了入射角的大小和X射线的透过率.实验中使用的晶体是LiF晶体和CaF2晶体,并分别用连续能量的X射线和单一能量的特征X射线入射到晶体上,产生能量分别为6.10和4.54 keV的线偏振源,并利用二次衍射的方法对产生的偏振源进行了测量.     

基于X射线相干衍射成像的元素分布成像

基于上海光源软X射线谱学显微线站的特点和相干X射线衍射成像(CDI)技术,对软X射线相干衍射成像方法的一个重要应用:元素分布成像及含量分析进行了模拟研究。推导了CDI相比双能分析算法并进行了理论模拟,估算了能够分辨的最小物质含量,并分析了CDI实验噪声等因素对元素分布成像的影响。所得结果可对软X射线CDI的实际应用提供理论指导。     

X射线荧光分析中原级谱分布的计算

X射线荧光分析中,X射线管产生的原级谱的分布对荧光分析的影响很大。尤其是在元素间吸收增强效应的校正过程中,基本参数法要求准确获得X射线原级谱的强度分布。使用MCNP程序模拟不同加速电压、不同靶材料、不同铍窗厚度等条件下电子打靶后的X射线能谱分布,为X射线荧光分析仪研制过程优化X光管靶材、管压等提供依据,实现高精度的X射线荧光分析。     

一种测量高强度直流X光机辐射能谱的方法

介绍了一种康普顿散射法测量高强度直流X射线能谱的方法,分析了X光机辐射谱与散射谱强度的关系表达式。在测量系统中使用能量分辨能力较好的高纯锗探测器,通过测量X光机照射低原子序数材料的散射能谱,再根据不同能量X射线在该散射立体角上的散射截面回推,从而获得X光机的辐射能谱。最后,给出了X光机的工作电压分别为15、80和100 kV时,散射法测量得到的钨靶X射线辐射谱。     

具有窄谱特性的X光管原型设计与GEANT4仿真

为获得近似单能的窄谱X射线源,本文设计了一种双靶结构的X光管。仿真实验结果表明通过设置不同材料的靶可以得到不同能量段的窄谱X射线。由于第二个靶设置在X光管的外部,可以方便的实现能量切换。此外,本文还利用仿真方法验证了窄谱X射线源在减轻硬化伪影方面的作用。本文的研究结果可为研制窄谱X射线源提供参考。     

Excited Electron Temperature and Molecular Vibration Temperature During Transition from Filamentary Discharge to Glow Discharge in Surface Discharge in Air

A dielectric barrier surface discharge device was used to investigate the transition from a filamentary discharge to a glow discharge in air at different gas pressures. Discharge images and waveforms of the applied voltage and discharge current were recorded simultaneously, and it was found that the discharge could transit from filamentary to glow with the decrease in pressure. Optical emission spectra during the transition from a filamentary discharge to a glow one were recorded. Excited electron temperature can be determined from the ratios of the relative intensities of spectral lines while molecular vibration temperature can be measured by analysing spectral lines of the N2 second positive band system. The results show that both the excited temperature and molecular vibration temperature increase with the decrease in the gas pressure. Qualitative explanations are given.     

X射线管足跟效应的蒙特卡罗模拟与分析

X射线管的足跟效应是影响其性能的重要因素。为研究足跟效应对X射线能谱分布的影响,利用MCNP5软件构建了X射线管仿真模型,并设置了不同空间位置分布的探测器组,通过改变靶角、管电压和靶材料等参数研究X射线管的性能。仿真得到了靶角对X射线能谱的影响,以及在不同空间方位上X射线强度的分布,最后综合仿真结果得到了靶角、管电压以及靶材料对足跟效应的影响规律。仿真的方法和结果对X射线管的设计和使用提供了一定的理论指导。     

可控中子及X射线源测井技术发展现状及趋势

随着核仪器技术的进步以及安全健康的工业发展需求,具有人工可控性的中子源及X射线源逐步在测井领域得到推广应用,为油气等矿产资源的勘探开发提供了关键技术手段。可控中子及X射线源测井技术是以中子发生器或X射线管产生的中子或X射线与地层物质作用,通过探测中子、伽马或X射线从而进行地层孔隙度、密度、油气饱和度和元素含量的测井技术。本文概述了可控中子及X射线源测井技术,回顾了其发展历程;介绍了可控中子及X射线测井技术在数值模拟、仪器研制及数据处理方法方面的研究现状及应用,并展望了可控中子及X射线源测井技术的发展前景,认为未来可控中子及X射线源测井技术可从以下三个方面开展研究：分析不同射线在能量、时间及空间的分布规律,开展探测理论基础研究;联合不同学科优势,开展多类型多模式的新型仪器研制;增强谱数据校正及解析方法研究,开展谱信息综合分析及应用。     

Preliminary results of optical emission spectroscopy by line ratio method in the RF negative ion source at ASIPP

Optical emission spectroscopy (OES) using the trace rare gases of Ar and Xe have been carried out in a radio frequency (RF) driven negative ion source at Institute of Plasma Physics, Chinese Academy of Science (ASIPP), in order to determine the electron temperature and density of the hydrogen plasma. The line-ratio methods based on population models are applied to describe the radiation process of the excited state particles and establish their relations with the plasma parameters. The spectral lines from the argon and xenon excited state atoms with the wavelength of 750.4 and 828.0 nm are used to calculate the electron temperature based on the corona model. The argon ions emission lines with the wavelength of 480 and 488 nm are selected to calculate the electron density based on the collisional radiative model. OES has given the preliminary results of the electron temperature and density by varying the discharge gas pressure and RF power. According to the experimental results, the typical plasma parameters is T_e ≈ 2–4 eV and n_e ≈ 1×10 ¹⁷– 8×10¹⁷ m⁻³ in front of plasma grid.     

在线低能气体离子源

材料中氦和氢积累可引起材料性能的恶化甚至失效。为研究材料内氦和氢的存在形式、氦与氢及缺陷的相互作用、气泡的形成和演变过程以及各种因素的影响,建立一套离子束能量最高20keV的潘宁型气体离子源引出和聚焦系统,与200kV透射电镜联机,在离子注入现场原位观察氦和氢不同注入浓度下材料内部的微观结构及变化过程。对离子源进行氦离子的起弧、引出和聚焦测试。离子源在15–60mA放电电流范围内稳定地工作。在5×10–3Pa和1.5×10–2Pa工作气压下,放电电压约380V和320V。低气压下引出离子束流比高气压下大,且引出束流随放电电流和吸极电压的增加而增加。等径三圆筒透镜有显著聚焦作用,在距透镜出口150cm处,离子束流密度提高一个量级以上。能量10keV左右的氦离子获得束流密度约200nA·cm–2的离子束,可满足多种材料进行在线离子注入和原位电镜观测的需要。     

Spectroscopic studies of intense pulse discharge in hydrogen

Spectroscopic methods were used to study the properties of intense pulse discharge in a gas. It is shown that in the initial stage of the process, while the discharge is contracting onto the axis of the chamber, the velocity of the luminous front is as high as 6–8 · 10⁶ cm/sec. A calculation of the number of ionized atoms is carried out. Experiments in which the luminosity of the pulse discharge plasma was investigated are described. The results of intensity measurements on the spectral lines of a hydrogen plasma are presented.The authors take this opportunity to express their sincere indebtedness to L. A. Artsimovich and M. A, Leontovich for valuable discussions and for their constant interest in the work.     

利用多毛细管准直器测量X射线光源焦斑尺寸

设计了一种测量X射线光源焦斑尺寸的方法：多毛细管准直器法。整体玻璃毛细管X射线准直器是由数10⁵根内径为几微米的单玻璃毛细管组成的X射线光学器件,X射线光源发出的发散X射线光束被多毛细管准直器约束后变为准平行束。准平行束的截面直径是X射线光源焦斑直径的函数,通过测量准平行束不同位置处的截面直径,利用线性拟合可得到X射线光源的焦斑直径。分别利用多毛细管准直器法和常用的小孔成像法测量了同一微焦斑X射线光源的焦斑直径,测量结果分别为60.8和59.4μm。多毛细管准直器法对焦斑直径在亚微米量级或更小X射线源的焦斑尺寸测量中将显示出更多的优势。     

Measurement of the first Townsend's ionization coefficient for atmospheric pressure neon by a dielectric barrier discharge

Fast photography and optical emission spectroscopy are implemented in a 5 mm neon gap dielectric barrier discharge (DBD) at atmospheric pressure with quartz glass used as the dielectric layer. Results show that it starts with a Townsend discharge and ends at a sub-normal glow discharge in neon DBD. Based on the Townsend discharge, the first ionization coefficient of neon is measured. The measurements are consistent with those at low pressure. Optical emission spectroscopy indicates that the spectra are mainly composed of atomic lines of neon, molecular bands and molecular ion bands originating from inevitable gas impurities (mainly nitrogen). Moreover, spectral lines emitted from atomic neon corresponding to the transitions (2p⁵ 3p → 2p⁵ 3s) are predominant. Although the second positive system of N₂(C³Π_u → B³Π_g) is observed, their intensities are too weak compared with neon's spectrum. The molecular nitrogen ion line of 391.4 nm is observed. It reveals that Penning ionization between high energy neon excited states and the inevitable gas impurities plays an important role in the value of the α coefficient.     

Investigation of laser plasma dynamics using the X-ray spectra of multicharged ions

Results are reported on the study of the structure of optically thick laser plasmas from the intensity of X-ray spectral lines. The analysis of plasma images provides information about the average velocity of the plasma expansion, the hydrodynamic efficiency and the rate of the target evaporation.     

Low Energy Plasma Focus as an Intense X-ray Source for Radiography

Study on X-ray emission from a low energy (1.8 kJ) plasma focus device powered by a 9 μF capacitor bank, charged at 20 kV and giving peak discharge current of about 175 kA by using a lead-inserted copper-tapered anode is reported. The X-ray yield in different energy windows is measured as a function of hydrogen filling pressure. The maximum yield in 4π-geometry is found to be (27.3±1.1) J and corresponding wall plug efficiency for X-ray generation is 1.52±.06%. X-ray emission, presumably due to bombarding activity of electrons in current sheath at the anode tip was dominant, which is confirmed by the pinhole images. The feasibility of the device as an intense X-ray source for radiography is demonstrated.