The micro-imaging station of the TopoTomo beamline at the ANKA synchrotron light source

The TopoTomo bending magnet beamline at the ANKA synchrotron facility in Karlsruhe (Germany) operates in the hard X-ray regime (above 6 keV). Recently, an X-ray micro-imaging station has been installed at TopoTomo. For typical imaging applications, a filtered white beam or from 2009 on a double-multilayer monochromator is used. In order to optimize the field of view and the resolution of the available indirect pixel detectors, different optical systems have been installed, adapted, respectively, to a large field of view (macroscope) and to high spatial resolution (microscope). They can be combined with different camera systems, ranging from 14-bit dynamic range CCDs to fast CMOS cameras. The spatial resolution can be brought substantially beyond the micrometer limit by using a Bragg magnifier. Due to the moderate flux of the beamline compared to insertion-device beamlines on third generation light sources, special emphasis has been put on the efficiency of the detectors via a dedicated scintillator concept. The layout of the beamline optics makes optimal use of the coherence properties. Thus, absorption contrast, phase-contrast and analyzer-based imaging can be applied. Additionally, white beam synchrotron topography is performed, using digital indirect X-ray pixel detectors as well as X-ray film.     

Structured LiI scintillator for thermal neutron imaging

We are currently developing high-resolution high-efficiency microcolumnar LiI films for thermal neutron imaging. The films are produced by the vapor deposition of LiI on a fiber-optic substrate and hermetically sealed in a specially designed aluminum package. Our work has produced up to 1.2-mm-thick films with column diameters of approximately 30 μm. We have also performed imaging studies by optically coupling some of these films to a fiber-optic taper-based charge-coupled device. The imaging performance of the system was experimentally evaluated at Radiation Monitoring Devices, Inc., as well as at the thermal neutron port of the University of Massachusetts Lowell Research Reactor. The LiI films exhibited excellent scintillation characteristics with a spatial resolution as high as 4.5 lp/min (line pairs per millimeter). This paper outlines the film characterization and performance evaluation conducted during the course of the study. The new sensor described here is expected to usher in the development of large-area high-resolution digital thermal neutron detectors with improved detection efficiency and dynamic range and faster readout times than the current sensors     

On neutron phase contrast imaging

Improving the spatial resolution conditions in a neutron imaging experiment enables the detection of phase-based contrast in addition to attenuation contrast. Addressing not only the amplitude but also the phase of radiation in an imaging experiment allows for obtaining additional information about the sample. The so-called neutron phase contrast method improves imaging results mainly by edge enhancement which increases the visibility of sub-resolution structures and of low attenuation contrast materials. These effects have been found at high intensity synchrotron X-ray sources before and have been applied to neutron imaging recently. However, the excellent coherence conditions and spatial resolution of imaging instruments at state-of-the-art synchrotron sources can hardly be compared to neutron imaging. Nevertheless, edge enhancement has been found for increased resolution (coherence) conditions in neutron experiments as well. As for X-ray instruments the effects have been explained by diffraction, although typical interference fringes have never been recorded. In contrast this article will explain the effects measured with neutron radiation by refraction and total reflection. Both of these do not require high spatial coherence. Therefore improved resolution and not increased coherence will be considered as precondition to obtain the reported signals and to understand the results. Considerations concerning relaxed collimation requirements for improved detector resolutions will be presented as a consequence.     

X-ray energy separation method using a CdTe semiconductor X-rayimaging sensor and photon counting method

A multichannel X-ray imaging sensor using a CdTe compound semiconductor radiation detector in photon counting mode was developed and tested for digital X-ray imaging and an X-ray energy separation capability. The X-ray imaging sensor was constructed of CdTe detector elements at a pitch of 0.25 mm. High band amplifiers, discriminators, and counters attached to each element formed the pulse counting circuit. Charge pulses generated by absorbed X-ray photons were directly counted and separated into two energy regions. Digitized X-ray images containing energy information were thus obtained. Using this sensor two separate X-ray images of different energy can be obtained simultaneously. A 256-channel X-ray imaging sensor was prepared and used to provide spatial resolution measurement for an X-ray charge. Low and high energy images of a hand phantom were thus obtained and both a soft tissue image and a bone image were produced using an energy subtraction method     

Structural distortion effect in the cobalt ions implanted TiO2 films

TiO₂ thin films were prepared by direct current magnetron sputtering on glass substrates, then were implanted by cobalt ions, and finally annealed at 400 and 500 °C for 50 min, respectively. They were identified as an anatase structure by X-ray diffraction (XRD). Scanning electron microscope (SEM) images showed that the grain sizes of the films grow with increasing annealing temperature. The energy dispersive X-ray (EDX) measurements indicated that the ratio of the cobalt atoms number and total atoms number of cobalt and titanium in the Co-TiO₂ films was about 2.51%, and X-ray photoelectron spectroscopy (XPS) results revealed that the cobalt existed in the films as Co²⁺. The element distribution of cobalt along cross-section of the films was studied by EDX, as the results showed that the cobalt diffused deeply into the films after annealing. The high resolution transmission electron microscopy (HRTEM) images were used to affirm the anatase structure of the Co-TiO₂ films, and edge dislocations were further found in the HRTEM images, which could be attributed to the effect of the implantation.     

A high position resolution X-ray detector: an "Edge on" illuminated capillary plate combined with a gas amplification structure

We have developed and successfully tested a prototype of a new high position resolution hybrid X-ray detector. It contains a thin-wall lead glass capillary plate converter of X-rays combined with a microgap parallel-plate avalanche chamber operating in various gas mixtures at 1 atm. The operation of these converters was studied in a wide range of X-ray energies (from 6 to 60 keV) at incident angles varying from 0-90/spl deg/. The detection efficiency, depending on the geometry, photon's energy, incident angle and the mode of operation was between 5-30% in single step mode and up to 50% in a multi-layered combination. Depending on the capillary's geometry, the position resolution achieved was between 50-250 /spl mu/m in digital form and was practically independent of the photon's energy or gas mixture. The usual lead glass capillary plates operated without noticeable charging up effects at counting rates of 50 Hz/mm/sup 2/ and hydrogen treated capillaries-up to 10/sup 5/ Hz/mm/sup 2/. The developed detector has several important potential advantages over the exciting X-ray detectors and may open new possibilities for medical imaging, for example in mammography, portal imaging, radiography (including security devices), as well as many other applications.     

Real-time flat-panel pixel imaging system and control for X-ray andneutron detection

We present in this paper industrial nondestructive X-ray and neutron testing applications with a real-time digital imaging device and control system X-View based on active matrix flat-panel imager technology. X-View consists of X-ray or neutron converters, arrays of amorphous silicon (a-Si:H) thin-film transistors and photodiodes, a fast real-time electronic system for readout and digitization of images and appropriate computer tools for control, real-time image treatment data representation, and off-line analysis. Some basic image-quality parameters and different objects were assessed for quantitative and qualitative analysis. Results show a wide dynamic range (16 bits ADC resolution) and lack of blooming, a high frame rate (up to 25 fps), and rapid image capture. Images are directly displayed, on-line, on a PC monitor and archived in a digital form for radiography and radioscopy procedures and limitless industrial applications in X-ray and neutron inspections     

Tuning magnetic properties of Co/Pt thin films using energetic ions

In this paper, we present the changes occurring in Co/Pt bi- and multi-layer thin films modified under wide range of ion energy and species and fluence. We have shown the possibility of achieving controlled tuning of magnetic properties of the Co/Pt thin film system. Monte Carlo simulation results for ion-induced atomic displacements were used to explain the observed effects of ion-irradiation interface mixing across the Co/Pt interfaces. Phase formation has been explained in the light of heat of formation rule. On the other hand, we propose that ion induced point defect clustering governs the changes occurring in the structural and the magnetic properties.     

光电子放大的X射线全息实时成像系统

本介绍一种将同步辐射X射线成像与电子光学显微技术结合起来的实时记录方法。通过加速阳极对电子束的加速，控制其波长，再经过一个中心对称的电磁透镜系统的放大，最后到达CCD记录并输出，通过计算机实时重构出高分辨率的显微图像。该放大系统还可以应用到同步辐射的X射线相衬、显微和层析方面。对同步辐射应用技术的发展将产生不可估量的影响。     

Biomedical research at LIPSION - Present state and future developments

Since its commissioning in 1998 the high energy ion nanoprobe LIPSION has been developed into a versatile tool for a variety of applications in biomedical research. It includes quantitative trace element analysis with sub-micron spatial resolution and 3D-element imaging, as well as 2D- and 3D-microscopy of density distributions. The analytical methods base on particle induced X-ray emission spectrometry (PIXE) and PIXE-tomography, Rutherford backscattering spectrometry (RBS), as well as scanning transmission ion microscopy (STIM) and STIM-tomography.The continuous developments led to improved capabilities for trace element analysis. For sub-micron analysis the spatial resolution could be improved to 0.3 μm for high resolution work and to 0.5 μm for routine analysis. On the other hand, LIPSION was optimized for high sample throughput in quantitative element imaging maintaining a lateral resolution of 1-2 μm. Recently the methods of PIXE- and STIM-tomography of biological specimens have been extended to limited angle tomography to avoid the complicated preparation of free-standing samples.Besides its analytical applications, the nanoprobe is also used for targeted irradiation of living cells with counted single ions for radiobiological research. It is capable of irradiating up to 20,000 cells per hour. Furthermore, we have developed a technique to achieve confined cell growth based on the proton beam writing technique (PBW) and agar. The paper presents an overview of the current biomedical research fields at LIPSION and gives an outlook on prospective developments.     

数字化线阵CCD扫描X射线成像系统

介绍了一种数字化线阵CCD扫描X射线成像系统的原理性样机,其主要特点是用窄束X射线成像,从系统结构上抑制了散射对成像的影响,在满足图像质量的情况下降低了成像所需的X射线剂量.介绍了系统设计的理论基础,讨论了系统的软、硬件组成,并测量了系统的成像性能.     

基于催化聚合的同步辐射X射线成像标签

同步辐射X射线显微成像具有极高的空间分辨率、很好的穿透深度和优秀的能量分辨,因而在纳米分辨细胞成像领域具有巨大的应用潜力。然而,目前X射线显微技术多用于细胞结构成像,而和该技术相适合的特异性识别细胞内重要生物靶标的分子探针仍较缺乏。本工作利用同步辐射X射线良好的能量分辨特点,经体外化学催化反应成功制备了同步X射线可见的成像标签,成像分辨率达到30 nm。研究结果为进一步制备X射线敏感的分子探针,实现对细胞内生物分子的特异性识别和成像打下了良好的基础。     

Post-irradiation examination of a fuel pin using a microscopic X-ray system: Measurement of carbon deposition and pin metrology

The paper presents some interesting aspects associated with X-ray imaging and its potential application in the nuclear industry. The feasibility of using X-ray technology for the post-irradiation examination of a fuel pin has been explored, more specifically pin metrology and carbon deposition measurement. The non-active sample was specially designed to mimic the structure of an AGR fuel pin whilst a carbon based material was applied to the mock up fuel rod in order to mimic carbon deposition. Short duration low energy (50 kV) 2D digital radiography was employed and provided encouraging results (with respect to carbon deposition thickness and structure measurements) for the mock up fuel pin with a spatial resolution of around 10 μm. Obtaining quantitative data from the resultant images is the principal added value associated with X-ray imaging. A higher intensity X-ray beam (90 kV) was also used in conjunction with the low energy set-up to produce a clear picture of the cladding as well as the interface between the lead (Pb mimics the uranium oxide) and stainless steel cladding. Spent fuel metrology and routine radiography are two additional tasks that X-ray imaging could perform for the post-irradiation examination programme. Therefore, when compared to other techniques developed to deliver information on one particular parameter, X-ray imaging offers the possibility to extract useful information on a range of parameters.     

高保真中子输运计算的多级加速理论及应用

为解决高保真中子输运计算耗时严重的问题,本文提出了多级加速理论。其中,针对迭代求解过程,采用迭代加速的思路,即通过等价的低分辨率系统加速以减少迭代次数;针对瞬态求解,采用时间步加速方法,通过建立多级预估校正系统,实现在大时间步长下开展准确的高保真中子输运计算。最终引入不同分辨率系统的概念,将时间步加速方法与迭代加速方法整合形成一套完整的多级加速理论,并将其应用到精细化中子物理计算程序HNET中。采用典型瞬态基准题验证HNET程序加速效果。数值结果表明：多级加速理论能够在保证高保真中子输运计算精度的同时,极大地提升计算效率。     

Nanoscratch study of ZnO thin films deposited using radio frequency magnetron sputtering

In this study, a radio frequency magnetron sputtering system was used to deposit zinc oxide (ZnO) thin films onto langasite substrates. The thickness of the ZnO film increased from 0.3 to 1.2 μm upon increasing the deposition power from 100 to 200 W. The predominant growth orientation was along the c-axis (0 0 2); the intensities of the signals in the X-ray diffraction spectrum increased significantly upon increasing the film thickness. Scanning electron microscopy images revealed columnar structures in the ZnO films and the morphology of ZnO grains is found to be continuous and dense. It is attributed that oxygen chemisorbs on the target and cases a surface layer of adsorbed oxygen. We suggest that the more neutral ion bombardment on the growing film which induces the higher sputtering rate of the growing film. From in situ imaging of scratched tracks, measurement of the coefficient of friction was an effective means of detecting the occurrence of structural defects in the microstructures. We also found that the chemical compositions of ZnO films prepared under various deposition powers could be investigated using X-ray photoelectron spectroscopy.     

X-ray CCD相机在杆箍缩二极管X射线焦斑诊断中的应用

针孔成像法是诊断杆箍缩二极管X射线焦斑的常用方法。本文建立基于增感屏、光锥耦合、CCD相机的X-ray CCD相机系统,取代针孔成像法中基于闪烁体、物镜、CCD相机的图像获取系统,提高了诊断系统的紧凑性。对所建立的X-ray CCD相机系统的空间分辨能力进行了测试,系统的空间分辨能力受增感屏限制,使用铅制分辨卡测得系统的空间分辨率为5lp/mm,使用刀口法测得调制传递函数为0.5时的频率为1.5lp/mm。测试结果表明,在针孔成像倍率为0.5时,可满足1.5 mm左右的X射线焦斑诊断的需要。并开展了杆箍缩二极管侧面焦斑诊断实验,获得了侧面焦斑图像,且进行了图像复原处理。     

Quality assessment system for curved crystal X-ray optics

Doubly curved crystal X-ray optics provide intense focused monochromatic beams from laboratory X-ray tube sources. These optics are employed in crystallography and X-ray fluorescence systems and may find application to imaging. It is increasingly important to understand how optic defects impact performance for these systems. A simulation model was developed to assess the effects of misalignment and optic defects on system parameters such as intensity, beam size and resolution. Simulation results were compared to optics measurements. Rapid reproducible measurements of optics quality are important both for performing systematic studies of optics defects and for assessing individual optics. A simple operator-independent alignment technique was developed that was also beneficial in ensuring optimal beam intensity in analysis systems. The measurements and simulations were in good agreement and provided insight into essential optics parameters.     

Fuel retention study in fusion reactor walls by micro-NRA deuterium mapping

Nuclear Reaction Analysis (NRA) with a ³He ion beam is a powerful analytical technique for analysis of light elements in thin films. The main motivation for ³He focused beam applications is lateral mapping of deuterium using the nuclear reaction D(³He,p)⁴He in surfaces exposed to a tokamak plasma, where a lateral resolution in the μm-range provides unique information for fuel retention studies.At the microprobe at the Jo?ef Stefan Institute typical helium ion currents of 300 pA and beam dimensions of 4 × 4 μm² can be obtained. This work is focused on micro-NRA studies of plasma-facing materials using a set-up consisting of a silicon partially depleted charge particle detector for NRA spectroscopy applied in parallel with a permanently installed X-ray detector, an RBS detector and a beam chopper for ion dose monitoring. A method for absolute deuterium quantification is described. In addition, plasma-deposited amorphous deuterated carbon thin films (a-C:D) with known D content were used as a reference.The method was used to study deuterium fuel retention in carbon fibre composite materials exposed to a deuterium plasma in the Tore Supra and TEXTOR tokamaks. The high lateral resolution of micro-NRA allowed us to make a detailed study of the influence of topography on the fuel retention process. We demonstrated that the surface topography plays a dominant role in the retention of deuterium. The deep surfaces inside the castellation gaps showed approximately two orders of magnitude lower deuterium concentrations than in areas close to the exposed surface.     

Effect of swift heavy ion irradiation on spray deposited CdX (X = S, Te) thin films

Cadmium sulfide and cadmium telluride thin films are irradiated with high energy heavy ion beam to study the irradiation induced effects in these films. The polycrystalline thin film samples deposited by spray pyrolysis are irradiated with 60 MeV Oxygen ions using tandem Pelletron accelerator. The X-ray diffraction patterns exhibit a reduction in peak intensities in both CdS and CdTe films. The grain size decrease with fluence is observed for both CdS and CdTe films, with more decrease for CdTe films. The AFM results support this observation. The films show opposite trend in the variation of electrical resistivity with irradiation fluence. A decrease in resistivity is observed for CdS films due to an increase of carrier concentration arising by the creation of sulfur vacancies during the irradiation. The creation of sulfur vacancies is confirmed by XPS studies. The stoichiometric changes seen from XPS studies support this observation. An enhancement of grain boundary scattering due to the reduction of grain size leads to the increase of electrical resistivity for CdTe films.     

IBA of ZrO2:Yb/Si thin films produced by the spray pyrolysis method

A spray pyrolysis method was used to produce thin films of ZrO₂ doped with different Yb concentrations on Si(1 0 0). The films of these ionic semiconductors have potential applications as solid electrolytes in modern ceramic fuel cells of second generation. The determination of the atomic composition of the films is very important because it strongly affects the chemical and thermal stability, as well as electrical properties of the films. A combination of two Ion Beam Analysis (IBA) methods was applied to obtain the atomic composition of the films. A nuclear reaction analysis (NRA) method using a low energy deuterium beam was applied to measure the oxygen content of the films. Heavy ion Rutherford backscattering (HI-RBS) method using a ¹²C³⁺ beam was applied to measure the Yb and Zr atomic profiles of the samples. X-ray diffraction (XRD) and ellipsometry were also employed to determine structural properties and refractive index of the films, respectively. The IBA, XRD and the ellipsometry supply a wide range of information about the film layers, which can be used for qualification as well as for feedback to the films production.