X-ray fluorescence imaging with polycapillary X-ray optics

X-ray fluorescence spectrometry imaging is a powerful tool to provide information about the chemical composition and elemental distribution of a specimen. X-ray fluorescence spectrometry images were conventionally obtained by using a μ-X-ray fluorescence spectrometry spectrometer, which requires scanning a sample. Faster X-ray fluorescence spectrometry imaging would be achieved by eliminating the process of sample scanning. Thus, we developed an X-ray fluorescence spectrometry imaging instrument without sample scanning by using polycapillary X-ray optics, which had energy filter characteristics caused by the energy dependence of the total reflection phenomenon. In the present paper, we show that two independent straight polycapillary X-ray optics could be used as an energy filter of X-rays for X-ray fluorescence. Only low energy X-rays were detected when the angle between the two optical axes was increased slightly. Energy-selective X-ray fluorescence spectrometry images with projection mode were taken by using an X-ray CCD camera equipped with two polycapillary optics. It was shown that Fe Kα (6.40 keV) and Cu Kα (8.04 keV) could be discriminated for Fe and Cu foils.     

Utilization of phoswich detectors for simultaneous,multiple radiation detection

Summary A phoswich radiation detector is comprised of a phosphor sandwich in which several different phosphors are viewed by a common photomultiplier. By selecting the appropriate phosphors, this system can be used to simultaneously measure multiple radiation types (alpha, beta, gamma and/or neutron) with a single detector. Differentiation between the signals from the different phosphors is accomplished using digital pulse shape discrimination techniques. This method has been shown to result in accurate discrimination with highly reliable and versatile digital systems. This system also requires minimal component count (i.e., only the detector and a computer for signal processing). A variety of detectors of this type have been built and tested including: (1) a triple phoswich system for alpha/beta/gamma swipe counting, (2) two well-type detectors for measuring low levels of low energy photons in the presence of a high energy background, (3) a large area detector for measuring beta contamination in the presence of a photon background, and (4) another large area detector for measuring low energy photons from radioactive elements such as uranium in the presence of a photon background. An annular geometry, triple phoswich system optimized for measuring alpha/beta/gamma radiation in liquid waste processing streams is currently being designed.     

Development of single-beam wide-field infrared imaging to study sub-cellular neuron biochemistry

Multi-beam wide-field imaging using synchrotron mid-infrared light sources coupled with focal plane array detectors has provided a major breakthrough to the field of bio-spectroscopic imaging. The ability to collect sub-cellular molecular images in minutes has opened the door to a new era of biochemical studies. Although a multi-beam approach is the superior method to this form of imaging, it requires a specialized set of beamline optics, which may not be compatible with existing mid-infrared microscopy beamlines, or research programs/applications currently in place (some of which do not require an imaging component). In this investigation we demonstrate that a single-beam approach can be utilized in a similar manner to multi-beam imaging, to collect sub-cellular biochemical images of brain neurons in a rapid time frame, without extensive modification of an existing beamline configuration. This study uses an applied example, imaging the same neuron in situ within a brain tissue section, with both synchrotron and thermal sources. The results highlight the advantage of improved spatial resolution/image quality and spectral quality (signal to noise ratio) that is obtained when a high magnification and high numerical aperture objective (52×, 0.65) is coupled to a synchrotron mid-infrared lightsource with a focal plane array detector. The approach we report may prove to be particularly appealing to numerous existing mid-infrared beamlines, allowing straightforward integration of sub-cellular biochemical imaging with existing non-imaging research applications.     

Energy resolved X-ray fluorescence imaging based on a micropattern gas detector

A simple system for energy resolved X-ray fluorescence imaging using a room temperature, 2-D sensitive Micro-Hole and Strip Plate (MHSP) operating in pure xenon is proposed. The Micro-Hole and Strip Plate is an electron multiplier with two stages of avalanche production, one of them in the holes and another one in the anode strips. The X-ray interaction via photoelectron absorption in the xenon produces a number of electrons proportional to the incoming X-ray energy. The electron cloud is, then, amplified in the two amplification stages, resulting in a charge pulse that is also proportional to the detected X-ray energy. The 2-D capability is achieved in the Micro-Hole and Strip Plate by using two orthogonal resistive lines, one connecting the anode strips on the bottom face of the Micro-Hole and Strip Plate and the other one connecting the strips structured on the Micro-Hole and Strip Plate top surface. This low cost detector has an active area of 28 × 28 mm², an intrinsic position resolution of σ∼ 125 µm, an energy resolution of about 825 eV (Full Width at Half Maximum) at 5.9 keV and a count rate capability as high as 0.5 MHz. Fluorescence images were obtained by irradiating the sample with X-rays and using a pinhole placed between the sample and the detector window. Elemental map discrimination for different samples, image amplification and detector parameters, are presented.     

基于光强传输方程的多模式成像

在显微成像中,对于相位的恢复和定量相位的成像,基于光强传输方程的定量相位成像是一种有效的方法。在沿光轴分布的光强中采集一系列强度图像,利用数值差分估计光强在聚焦面处的一阶轴向微分并通过求解光强传输方程直接得到相位信息。该方法不需要复杂的干涉装置和参考光束,且能够在传统的明场显微镜下实现定量相位成像。近年来,光强传输方程在国内外得到广泛研究和关注,在自适应光学、X射线衍射光学、电子显微学、光学显微成像等领域中显现出巨大的应用前景。本文提出了一种基于光强传输方程的多模式成像系统,将传统的显微镜和计算成像结合起来,赋予了传统显微镜获得定量相位的能力。采用该系统对未染色的花粉粒以及海拉细胞的有丝分裂过程进行了显微观察,验证了系统的多样性与可靠性。     

Spectral source profiling with a photodiode array

A computer controlled Reticon photodiode array was used for source profiling by juxtapositioning the detector with the exit slit of a stigmatic monochromator, with the long axis of the array parallel to the slit. The sources to be studied were imaged on the monochromator entrance slit and the individual elements of the array detected light of a specific wavelength emitted from a different portion of the source as it appeared at the exit slit. The 512 array elements covered 12.5 mm of slit length. Larger or smaller portions of the source may be studied depending on the optics used to form the image on the entrance slit. Vertical profiles required only simple lenses for imaging. Profiles in horizontal direction were made quite simply by placing a Dove prism in the optical path to rotate the image 90°. Use of the system for elemental emission profiles for the nitrous oxide-acetylene flame and inductively coupled plasma is reported.     

The development of a sensitive near-IR Raman system

This paper describes the development of a highly sensitive near-IR laser Raman system which has been designed and built in our laboratory. The system comprises both a micro and macro sample handling facility. The approach that we have adopted uses a conventional spectrograph with a charge coupled device detector and optics optimized for the 700–1000 nm spectral region. The laser source is a tunable titanium sapphire laser which provides intense radiation in the 700–900 nm spectral region. We show that the spatial resolution and spectral sensitivity that can be obtained with the microscope attachment are excellent. A comparison between data obtained from our system and that from an FT-Raman system is given.     

以六氟异丙醇为溶剂的聚甲醛凝胶渗透色谱研究

研究了均聚和共聚甲醛在六氟异内醇中的凝胶渗透色谱（ＧＰＣ）。对共聚甲醛出现的缔合现象从主链结构作了解释，并找到了避免缔合的方法；对共聚甲醛ＧＰＣ淋洗曲线上的异常小峰从聚合机理角度进行了探讨，推测得到小峰所对应的物质。确定了以六氟异丙醇为溶剂的聚甲醛的凝胶色谱表征方法，并探索采用凝胶色谱－粘度计联用法得到分子量和分子量分布结果。     

Characterization of an energy dispersive X-ray fluorescence imaging system based on a Micropattern Gaseous Detector

An energy dispersive X-ray fluorescence (EDXRF) imaging system based on a Micropattern Gas Detector has already shown good results for different applications. An X-ray tube, a pinhole camera and a Micro-Hole and Strip Plate (MHSP) based detector are the main components of the experimental system. The detector uses an MHSP in a Xe atmosphere at 1 bar, and acting as a photon counting device, i.e., it is capable to record each single event retaining the energy and the interaction position (2D-sensitive detector) information of the incident photon, demonstrating to be a promising device for EDXRF imaging applications. This work presents studies of energy resolution, energy linearity and spatial resolution/elemental mapping as a function of image magnification of the system.     

应用于助航系统的赋形曲面光学系统研究

非对称式光度系统技术可以实现光能量的收集与再分配，已经广泛应用于照明领域。基于非成像光学理论的自由曲面照明光学设计具有体积小、设计自由度高、出光光形准确可控等优点。通过采用自由曲面对LED进行合理的二次配光，可以实现绿色环保的照明，给未来照明行业的发展指明了新的方向。本文通过对关于LED自由曲面的光学设计进行研究，提出了一种满足侧边发光照明方式的自由曲面透镜设计方法。将得到的自由曲面透镜实体模型作为立式滑行道边灯透镜设计的基本结构。仿真与实验结果表明，仅用一颗LED光源即可实现联邦航空局（FAA）对立式滑行道边灯的光强分布要求。     

Crystal optics for hard-X-ray spectroscopy of highly charged ions

A twin crystal-spectrometer assembly, operated in the focusing compensated asymmetric Laue geometry has been developed for accurate spectroscopy of fast highly charged heavy ions in the hard-X-ray region. Coupled to the focusing crystal optics is a specially developed two-dimensional position-sensitive X-ray detector which is necessary for retaining spectral resolution also for fast moving sources. We summarize the crystal optics and demonstrate the usefulness of the instrument for spectroscopy of both stationary and fast moving X-ray sources. Results are reported from several tests employing a ¹⁶⁹Yb gamma-ray source and the Lyman radiation of one-electron Pb⁸¹⁺ ions traveling at a velocity corresponding to β ≡ v/c ≈ 0.59. The features of the instrument presented may be useful in many applications where it appears difficult to make the leap from conventional X-ray energy measurements to wavelength-dispersive spectroscopy based on crystal optics.     

Dual wavelength excitation fluorescence detector for capillary electrophoresis using a pulsed bi-colour light emitting diode

A simple and novel two-colour fluorescence detector for capillary electrophoresis was created using a single bi-colour light emitting diode (LED), multi-band pass excitation and emission filters and a single detector. Excitation light from a blue/red (470/635 nm) bi-colour LED was filtered through a 390/482/563/640 nm multi-band bandpass filter, with emitted light filtered through a 446/523/600/677 nm multi-band bandpass filter before being detected using a photon counting detector. Sequential pulsing of the blue/red LED and deconvolution of the collected fluorescence data allowed extracted electropherograms to be obtained corresponding to excitation with the blue and red LEDs. Optimisation of the pulsed LED conditions revealed an optimum LED on-time of 50 ms, off-time of 30 ms with a pulsed current of 40 mA, giving an effective data acquisition rate of 6.25 Hz. The characteristics of this system were validated by the simultaneous separation and determination of six fluorescent dyes: fluorescein, FITC, coumarin 334, dibromo(R)fluorescein (Ex/Em 470/525 nm), and Cy 5 and the Agilent Bioanalyser DNA dye (Ex/Em 635/670 nm). Under optimum conditions, the detection limits for FITC, fluorescein and Cy 5 were 69 nM, 42 nM and 289 nM (S/N = 3), respectively. These were lower than those obtained with continuous operation of the individual wavelengths at a constant current of 20 mA, but were slightly higher than those obtained using dedicated single wavelength filter combinations designed specifically for use with these fluorophores. The intraday repeatability (n = 6) of migration times was less than 1.0% and less than 3.4% for peak areas, while interday (n = 3) migration time and peak area reproducibility were less than 0.9% and 3.6%, respectively. This simple detector is capable of performing quantitative two-wavelength excitation without the need for complex optics and light source configurations.     

A wavelength-dispersive arrangement for wafer analysis with total reflection X-ray fluorescence spectrometry using synchrotron radiation

Currently, the only apparent means to enhance the detection power of the TXRF technique would be to increase the intensity of the primary beam. Using synchrotron radiation, the most powerful X-ray source available, unfortunately, not only the fluorescence signal of the contaminant elements is increased, but also in equal measure, the intensities of the Si–K radiation from the wafer together with the scattered radiation. This results in an overloading of the energy-dispersive Si (Li) detector systems used hitherto, with the effect that the available primary intensity cannot be fully exploited. Wavelength-dispersive systems are free of such problems; they generate less detector background and can withstand higher count rates. Due to their small angle of acceptance, however, their detection efficiency is quite low. In this contribution we propose a wavelength-dispersive TXRF solution, which is optimized with regard to higher efficiency on the basis of large area multilayer mirrors in combination with a position-sensitive detector. The count rates in relation to energy-dispersive instruments and the energy resolution of the new system have been calculated using ray-tracing techniques.     

Performance of a gaseous detector based energy dispersive X-ray fluorescence imaging system: Analysis of human teeth treated with dental amalgam

Energy dispersive X-ray fluorescence (EDXRF) imaging systems are of great interest in many applications of different areas, once they allow us to get images of the spatial elemental distribution in the samples. The detector system used in this study is based on a micro patterned gas detector, named Micro-Hole and Strip Plate. The full field of view system, with an active area of 28 × 28 mm² presents some important features for EDXRF imaging applications, such as a position resolution below 125 μm, an intrinsic energy resolution of about 14% full width at half maximum for 5.9 keV X-rays, and a counting rate capability of 0.5 MHz. In this work, analysis of human teeth treated by dental amalgam was performed by using the EDXRF imaging system mentioned above. The goal of the analysis is to evaluate the system capabilities in the biomedical field by measuring the drift of the major constituents of a dental amalgam, Zn and Hg, throughout the tooth structures. The elemental distribution pattern of these elements obtained during the analysis suggests diffusion of these elements from the amalgam to teeth tissues.     

Synthesis of densely branched poly(methyl methacrylate)s via ATR copolymerization of methyl methacrylate and ethylene glycol dimethacrylate

Densely branched poly(methyl methacrylate)s have been synthesized by copolymerization of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) using atom transfer free radical polymerization (ATRP). By employing the phenyl and benzyl esters of 2-bromo-2-methylpropionic acid as the initiators with 2,2-bipyridyl and Cu(I)Cl it has been possible to use high field ¹H nuclear magnetic resonance spectroscopy to evaluate in some detail the composition and structure of the branched PMMAs obtained. Parallel molar mass size exclusion chromatographic analysis using a multi-angle light scattering detector with a refractive index detector (MALS/SEC) has allowed the branched architecture of the products to be confirmed. Rather remarkably, high yields of branched PMMAs can be obtained without crosslinking using MMA/EGDMA molar feed ratios of up to 5/1 by appropriate adjustment of the molar feed of initiator. In particular by maintaining the EGDMA/initiator molar feed ratio ∼1/1 fully soluble products can be obtained that are densely branched since this feed ratio ensures that on average each living primary chain initiated contains on average only one branching EGDMA segment. As might be expected this controlled free radical process offers better control in the synthesis of branched polymer than the corresponding system we have reported using conventional free radical polymerization, and unlike the latter which requires the use of a chain transfer agent, the ATRP system requires no additional chain regulating component. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2375–2386, 2007     

Determination of the elemental distribution in a sample using neutron induced gamma-ray emission tomography

The factors that affect accurate, quantitative results to be obtained by neutron induced gamma-ray emission tomography are stated. The technique, which is a combination of neutron activation analysis with computerised gamma-ray emission tomography, would be enhanced by the use of multiple detector assemblies, in geometrical configurations, which simultaneously record the gamma-rays emitted and improve detection efficiency. Developments in the past few years in positron emission tomography (PET) where scanners made of single scintillation block detectors, cut into smaller segments, to form individual crystal detector elements and packed in ring around the radioactive object, are discussed. The coincident detection efficiency for annihilation photons and cascade gamma-rays for such systems are considered and the possibilities of carrying out NIGET with coincident gamma-ray tomography are explored whilst indicating some of the limitations. This is an area which requires further, intense investigation and has an impact on a wide range of applications, particularly in the biomedical field.     

Total reflection X-ray fluorescence spectrometers for multielement analysis: status of equipment

Multielement analysis by total reflection X-ray fluorescence spectrometry has evolved during two decades. At present commercial equipment is available for chemical analysis of all types of biological and mineral samples. The electronic industry has also benefited from scientific and technological developments in this field due to new instrumentation to determine contamination on the surface of silicon wafers (the equipment will not be covered in this paper). The basic components of the spectrometers can be summarized as follows: (a) excitation source; (b) geometric arrangement (optics) for collimation and monochromatization of the primary radiation; (c) X-ray detector; and (d) software for operation of the instrument, data acquisition and spectral deconvolution to determine the concentrations of the elements (quantitative analysis). As an optional feature one manufacturer offers a conventional 45° geometry for direct excitation. Personal communications of the author and commercial brochures available have allowed us to list the components used in TXRF for multielement analysis. Excitation source: high-power sealed X-ray tubes, output from 1300 to 3000 W, different mixed alloy anodes Mo/W are used but molybdenum, tungsten and copper are common; single anode metal ceramic low power X-ray tubes, output up to 40 W. Excitation systems can be customized according to the requirements of the laboratory. Detector: silicon–lithium drifted semiconductor detector liquid nitrogen cooled; or silicon solid state thermoelectrically cooled detector (silicon drift detector SDD and silicon-PIN diode detector). Optics: multilayer monochromator of silicon–tungsten, nickel–carbon or double multilayer monochromator. Electronics: spectroscopy amplifier, analog to digital converter adapted to a PC compatible computer with software in a Windows environment for the whole operation of the spectrometer and for qualitative/quantitative analysis of samples are standard features in the production of this instrument. The detection limits reported in the literature are presented; pricing, analytical capability, ease of operation, calibration and optical alignment as well as technical support are also discussed.     

Experimental optimization of p-polarized MAIR spectrometry performed on a fourier transform infrared spectrometer.

Optimized experimental conditions of infrared p-polarized multiple-angle incidence resolution spectrometry (p-MAIRS) for the analysis of ultrathin films on glass have been explored. When the original MAIRS technique is employed for thin-film analysis on a substrate of germanium or silicon, which exhibits a high refractive index, an established experimental condition without optimization can be adapted for the measurements. On the other hand, the p-MAIRS technique that has been developed for analysis on a low-refractive-index material requires, however, optimization of the experimental parameters for a 'quantitative' molecular orientation analysis. The optimization cannot be performed by considering only for optics in the spectrometer, but for optics concerning the substrate should also be considered. In the present study, an optimized condition for infrared p-MAIRS analysis on glass has been revealed, which can be used for quantitative molecular orientation analysis in ultrathin films on glass.     

Confocal microscopic X-ray fluorescence at the HASYLAB microfocus beamline: characteristics and possibilities

The possibilities of performing non-destructive elemental analysis in three dimensions on a variety of heterogeneous materials by means of an innovative variation of the microscopic X-ray fluorescence analysis (μ-XRF) method are described. Next to employing focusing optics for concentration of the primary beam of X-rays, a second optical element between the sample and the energy-dispersive detector is used in confocal μ-XRF. Thus, only X-ray fluorescence signals from a cube-like volume (within certain limits imposed by the absorption of the radiation in the sample) can be arbitrarily positioned within the sample. The distribution of major, minor and trace elements (down to the sub-ppm concentration level in some matrices) along lines and planes within the sample can be visualized with a spatial resolution of the order of 15–40 μm. The lowest detectable amounts in confocal mode using pink-beam excitation are situated at the sub-femtogram level.     

四维扫描透射电子显微镜技术：从材料微观结构到物性分析

扫描透射电子显微镜(Scanning transmission electron microscopy,STEM)目前已经达到了原子级分辨率,并且由于其具有灵活的多通道成像能力以及强大的与谱学分析相结合的特点,因此在材料科学、生命科学等领域展现出强大的微尺度表征能力。但传统STEM的探测器受单像素积分式探测机制的限制,使其只能收集特定角度的散射电子,这导致不仅丢失了散射电子的角分辨信息,还降低了入射电子的剂量效率,因此迫切需要发展全新成像技术来实现高通量、高电子剂量效率成像。近年来,电子探测技术和分区或像素化探测器的研发联合计算机运算、存储能力的大幅提高,推动了四维扫描透射电子显微镜技术(Four-dimensional scanning transmission electron microscopy,4D-STEM)的蓬勃发展,并为最大化、最高效挖掘散射电子信息带来希望。在采集4D-STEM数据时,会聚电子束在样品平面上进行二维扫描,与此同时使用一块具有高帧速、高动态范围以及高信噪比的像素化阵列式探测器在远场收集二维的衍射数据。因为这些衍射数据是角度解析的,所以既可以用来进行常规的...