X-ray scattering in X-ray fluorescence spectra with X-ray tube excitation - Modelling, experiment, and Monte-Carlo simulation

X-ray scattering may contribute significantly to the spectral background of X-ray fluorescence (XRF) spectra. Based on metrological measurements carried out with a scanning electron microscope (SEM) having attached a well characterised X-ray source (polychromatic X-ray tube) and a calibrated energy dispersive X-ray spectrometer (EDS) the accuracy of a physical model for X-ray scattering is systematically evaluated for representative samples. The knowledge of the X-ray spectrometer efficiency, but also of the spectrometer response functions makes it possible to define a physical spectral background of XRF spectra. Background subtraction relying on purely mathematical procedures is state-of-the-art. The results produced by the analytical model are at least as reliable as those obtained by Monte-Carlo simulations, even without considering the very challenging contribution of multiple scattering. Special attention has been paid to Compton broadening. Relevant applications of the implementation of the analytical model presented in this paper are the prediction of the limits of detection for particular cases or the determination of the transmission of X-ray polycapillary lenses.     

Two-colored Laser Circulation System for Monochromatic Tunable Hard X-ray Source

A two-colored laser pulse circulation system for a monochromatic tunable hard X-ray source via laser electron Compton scattering is investigated. The demonstration system of the X-ray source is under construction at the University of Tokyo. It consists of the X-band (11.424 GHz) electron linear accelerator and two Nd: YAG laser systems. The main advantage of this system is a monochromatic tunable hard X-ray. It is calculated that the X-ray intensity will be about 10⁸ photons/s. In order to enhance the X-ray intensity for medical applications such as dual energy X-ray CT, a two-colored laser pulse circulation system has been designed. The laser pulse circulation experiment without an electron beam has been carried out by using a Nd: YAG laser fundamental wave (50 mJ) and a second harmonics wave (25 mJ). The result shows that the X-ray intensity can be enhanced by a factor of 10 times higher (i.e., up to 10⁹ photons/s). This work is a part of the JST (Japan Science and Technology Agency) project. The entire X-ray source system is a part of a larger national project on the development of an advanced compact medical accelerator sponsored by the NIRS (National Institute for Radiological Science). The University of Tokyo and KEK are responsible for the X-ray source.     

激光同步辐射源特性的线性康普顿散射分析

激光同步辐射源（Laser Synchrotron Source,简称LSS）是利用强激光与相对论电子束散射,产生准单色、能量可调的X射线脉冲的新型X射线源。本文介绍了LSS的线性康普顿散射理论;分析了LSS的主要特性,包括X射线通量、脉冲时间结构、能谱等。     

A novel Z-axis diffractometer for X-ray diffraction and fluorescence studies

Recently several X-ray techniques have been demonstrated to have high potential for providing needed structural information to understand the many physical and chemical phenomena that occur at surfaces and interfaces. In this article we will describe an instrument that facilitates the performing of these types of measurements and allows for the investigation of the gas-liquid interface using a variety of synchrotron X-ray scattering techniques. This instrument employs the z-axis diffraction geometry in which the detector has two degrees of freedom while the sample (the gas-liquid interface) has only one degree of freedom — rotation around the vertical axis. A distinctive feature of this diffractometer is that it leaves a fixed illuminated footprint on the liquid interface and allows for an accurate determination of the relative scattering or fluorescence intensity at very shallow angles. The unique capabilities of this novel instrument have been demonstrated at synchrotron facilities in a variety of X-ray techniques: grazing incidence diffraction (GID), shallow angle reflection (SAR), near total external fluorescence (NTEF) and EXAFS experiments from the surface of liquids     

一种生物X射线小角散射光束线站自动换样溶液蠕动装置

利用同步辐射X射线小角散射技术可以研究溶液中蛋白质的结构信息。但是在实验过程中,高通量的X射线易造成蛋白质的辐射损伤,发生结构变化。本文介绍了一种自动换样溶液样品蠕动装置,在实验过程中利用Hamilton的PSD/4注射泵控制样品上下运动,减小单位体积照射时间以降低X射线对蛋白质的辐射损伤。此外,通过对注射泵、准直调节台和样品/缓冲液支撑台的协调控制实现了自动换样、回样和清洗功能,提高了实验效率。在上海光源生物X射线小角散射实验站进行了实验,通过对静止模式和蠕动模式下溶菌酶的散射曲线及回旋半径的测量,表明该装置可达到很好的防辐射损伤效果,实现了预期的样品蠕动装置功能。     

Rayleigh to Compton ratio with monochromatic radiation from an X-ray tube (preliminary results)

Results on the Rayleigh to Compton ratio (R/C) for elements and compounds with low atomic number (5 ? Z ? 12) are presented. These materials are difficult to identify and characterize with other radiological techniques because of their very close linear attenuation coefficients. A transportable setup for R/C measurements was assembled and tested. This comprises an X-ray tube, in which the output radiation is partially “converted” to monochromatic radiation emitted by a secondary target. The experimental results are compared with theory, determined through coherent and incoherent scattering cross sections.     

生物样品的同步辐射定量分析

叙述了用同步辐射微探针对生物薄样中向量元素进行定量分析的方法，利用自制的微束标樯测定每个测量点的向量元素面密度并同时根据其在１７－２０ｋｅＶ能区中的Ｃｏｍｐｔｏｎ散射强度确定该测量点的样品质量厚度，成功地实现了元素浓度测量。     

Monochromatic X-ray sources based on a mechanism of real and virtual photon diffraction in crystals

A source of monochromatic X-ray radiation is wanted in industry, science, medicine and so on. Many ways of making such a source are known. The present work describes two mechanisms for the creation of a monochromatic X-ray beam, which are parametric X-ray radiation (PXR) and bremsstrahlung diffraction (DBS). Both the experiments were carried out using an electron beam at a microtron. During the first experiment, the DBS process was investigated as a scattering of the Bremsstrahlung (BS) beam on the crystallographic surfaces of tungsten and pyrolytic graphite crystals. The second experiment consisted in the registration of the PXR and DBS yield during the passage of the electrons through the same crystals as in the first experiment. The spectral and orientation radiation characteristics and simulation results obtained for the DBS and PXR processes are presented. It is shown that the usage of mosaic crystalline targets is rather useful in order to obtain a monochromatic X-ray source based on bremsstrahlung diffraction from moderately relativistic electrons.     

同步辐射反射法测定液体结构方法研究

用北京同步辐射装置4W1C光束线Huber五圆测角仪反射法测定液体结构的实验方法.以Na2SO4溶液的散射实验为例,简单介绍了样品池构造、散射几何布局、样品准直、扫描条件和扫描方式;详尽叙述了实验散射强度数据的校正方法,如样品池窗口净吸收、空气散射、偏振校正、吸收校正和几何校正等;演示了溶液结构函数和径向分布函数的计算方法,包括Compton散射强度和乱真峰的扣除技巧.研究表明,用同步辐射反射法获得了高质量的X射线散射数据.     

Unbiased Monte Carlo simulation of the Compton profile

Recent comparisons between analytical (deterministic) computations using the code SHAPE, and Monte Carlo (MC) simulations of Compton scattering using different codes show discrepancies in the shape of the Compton peak (the so-called Compton profile), specially for medium-low energy X-ray excitation. Considering the analytical computations as a reference model, the standard approach adopted for generating the Compton profile in different MC codes (EGSnrc, MCNP, MCSHAPE) has been studied comparatively in order to discover a reason for the difference. Apparently there is a bias in the profile generation which is common to all the codes and is related to the assumption of completely populated atomic orbitals contributing to the scattering. Such an assumption does not agree with the equivalence condition between the integrated Compton profile in the Impulse Approximation (IA) and the Waller-Hartree (WH) scattering function.In this article, we report the comparisons mentioned above for a paradigmatic case and propose an unbiased MC algorithm for the simulation of the Compton scattering.     

Similarity in Pressure Dependence among Separation Factors of Thermal Diffusion Column in Total-Reflux Operation

Research on laser Compton scattering gamma-ray-based nuclear transmutation has been carried out to identify a method of reducing the hazards of long-lifetime radioactivity of nuclear waste. To study the photonuclear reaction experimentally, a laser Compton scattering gamma-ray facility was built on a storage ring at NewSUBARU and ~17MeV gamma-ray photons were produced. An investigation on the reaction rate of radioactive iodine waste was carried out. Based on the characteristics of laser Compton scattering gamma rays, a cylindrical target was adopted for the irradiation experiment. The radioactivity of the irradiated target was measured and the transmutation reaction rate was deduced. Experimental results were close to simulation findings.     

基于RMC程序的用康普顿轮廓进行束缚态电子多普勒展宽修正研究

堆用蒙特卡罗程序RMC具备中子、光子、电子耦合输运能力，能完成精确的屏蔽计算，其中光子输运过程采用光子数据库进行了康普顿散射模拟。本文对康普顿散射物理原理及多普勒展宽方法进行分析，使用康普顿轮廓数据对束缚态电子进行多普勒展宽修正，实现了RMC程序对自由电子和束缚态电子的选择性处理。通过核素算例测试，观察到了多普勒能谱展宽的效应，证明了该方法的正确性。通过对典型压水堆组件的计算和对比，验证了用康普顿轮廓进行束缚态电子多普勒展宽修正的必要性和正确性。     

Imaging of implantation defects by X-ray topography combined with surface acoustic wave excitation

X-ray topographs of the He-implanted LiNbO₃ crystals under 10 μm-surface acoustic wave excitation were taken using monochromatized synchrotron radiation provided by the European Synchrotron Radiation Facility (ESRF, Grenoble). Measurements were made in the stroboscopic mode, i.e. by synchronizing the electron bunch frequency with the resonant frequency of the acoustic wave excitation in the 300 MHz range. These X-ray diffraction images showed plane acoustic wave propagation through the LiNbO₃ crystals as well as wave front distortions due to scattering by extended defects. Secondary spherical waves were observed for the first time as a result of the strong interaction between the acoustic waves and the sub-micron size density perturbations.     

Nondestructive analysis by combined X-ray tomography on a synchrotron radiation facility

A nondestructive X-ray analysis technique combining transmission tomography, fluorescence tomography and Compton tomography based on synchrotron radiation is described. This novel technique will be an optional experimental technique at SSRF's hard X-ray micro-focusing beamline under construction at present. An experimental result of combined X-ray tomography is obtained in NE-5A station of PF. The reconstructed images of test objects are given.     

Effects of internal scattering on X-ray microtomography imagereconstruction

A computer simulation is used to study the problem of internal scattering for targets that are imaged using X-ray microtomography. A strategy is outlined for selecting X-ray energy and image resolution based on properties of the material being imaged. The X-ray scanning process is simulated by applying a Monte Carlo technique to a modeled target that emulates the material properties of a microelectronic device. The X-ray photons are subject to photoelectric absorption, Rayleigh scattering, and Compton scattering. The simulation applies a method of high-resolution image reconstruction based on discrete Fourier transforms. Examples of reconstructed images that have 0.5-μm spatial resolution are shown for images of simulated lead and aluminum targets     

Incoherent-scatter computed tomography with monochromaticsynchrotron x ray: feasibility of multi-CT imaging system forsimultaneous measurement-of fluorescent and incoherent scatter x rays

We describe a new system of incoherent scatter computed tomography (ISCT) using monochromatic synchrotron X rays, and we discuss its potential to be used in in vivo imaging for medical use. The system operates on the basis of computed tomography (CT) of the first generation. The reconstruction method for ISCT uses the least squares method with singular value decomposition. The research was carried out at the BLNE-5A bending magnet beam line of the Tristan Accumulation Ring in KEK, Japan. An acrylic cylindrical phantom of 20-mm diameter containing a cross-shaped channel was imaged. The channel was filled with a diluted iodine solution with a concentration of 200 μgI/ml. Spectra obtained with the system's high purity germanium (HPGe) detector separated the incoherent X-ray line from the other notable peaks, i.e., the iK_α and K_β1 X-ray fluorescent lines and the coherent scattering peak. CT images were reconstructed from projections generated by integrating the counts In the energy window centering around the incoherent scattering peak and whose width was approximately 2 keV. The reconstruction routine employed an X-ray attenuation correction algorithm. The resulting image showed more homogeneity than one without the attenuation correction     

X-ray absorption spectroscopy and X-ray photoelectron spectroscopy studies of CaSO4:Dy thermoluminescent phosphors

Extended X-ray absorption fine structure (EXAFS) measurements have been carried out on CaSO₄:Dy phosphor samples at the Dy L₃ edge with synchrotron radiation. Measurements were carried out on a set of samples which were subjected to post-preparation annealing at different temperatures and for different cycles. The EXAFS data have been analysed to find the Dy-S and Dy-O bond lengths in the neighbourhood of the Dy atoms in a CaSO₄ matrix. The observations from EXAFS measurements were verified with XANES and XPS techniques. On the basis of these measurements, efforts were made to explain the loss of thermoluminescence sensitivity of CaSO₄:Dy phosphors after repeated cycles of annealing at 400 °C in air for 1 h.     

In-situ observation technique of electrodeposition reaction by X-ray from synchrotron source

A specified technique using X-ray from synchrotron sources was developed to contribute the optimization of the condition of electrodeposition directly. For this purpose, the design of the confinement equipped with electrodes has been optimized. Some case studies such as an alloy formation of Ce with Ni have been examined in-situ under the X-ray irradiation. Still a lot of tasks remains to apply the real system of electrolyzer, by the combination of XAFS and imaging technique, redox reactions occurring inside the un-visible confinements would be well identified.     

Determination of global and local residual stresses in SOFC by X-ray diffraction

Solid Oxide Fuel Cell (SOFC) is a high-performance electrochemical device for energy conversion. A single cell is composed of five layers made of different ceramic materials: anode support, anode functional layer, electrolyte, cathode functional layer and cathode. The mechanical integrity of the cell is a major issue during its lifetime, especially for the electrolyte layer. Damage of the cells is mainly due to the high operating temperature, the “redox” behaviour of the anode and the brittleness of the involved materials. Since residual stresses are known to play a significant role in the damage evolution, it is important to determine them.For this purpose, residual stresses in an anode-supported planar SOFC were measured by X-ray diffraction. Firstly, macroscopic stresses in each phase of each layer were studied using the sin²ψ method on a laboratory X-ray goniometer at room temperature. This technique enables the calculation of residual stress of the material from the measurement of the crystal lattice deformation. The electrolyte has been found under bi-axial compressive stress of ?920 MPa. Secondly, X-ray measurements controlling depth penetration were made in the electrolyte using grazing incidence method. The results show that the stress is not homogenous in the layer. The first five micrometers of the electrolyte have been found less constrained (?750 MPa) than the complete layer, suggesting a gradient of deformation in the electrolyte from the interface with the Anode Functional Layer to the free surface. Finally, local stress measurements were made on the electrolyte layer by X-ray synchrotron radiation that allows high accuracy measurement on the (sub-) micrometer scale. Polychromatic and monochromatic beams are used to determine the complete strain tensor from grain to grain in the electrolyte. First results confirm the macroscopic stress trend of the electrolyte. These X-ray techniques at different scales will contribute to a better understanding of the residual stress in the electrolyte layer and thus to the involved damage mechanisms.     

基于高能X射线散射的高原子序数物质探测方法

针对核材料的探测问题,利用其高原子序数（Z）的特性,提出了基于散射能谱解析识别物质原子序数的方法。该方法通过对X射线与物质相互作用所产生的散射光子的测量和分析来进行物质识别,这些光子包括正电子湮没光子、轫致辐射光子和康普顿散射光子,携带了物质原子序数的信息。蒙特卡罗模拟计算结果表明,该方法能够分析核素的原子序数,尤其对核材料等高Z物质的分析更为有效。采用LaBr₃(Ce)探测器测量了基于7MeV电子直线加速器的多个样品的散射能谱,结果表明,该方法能有效区分高原子序数物质。