微型X射线数字成像系统研究

X射线数字成像检测与诊断技术是X射线检测的发展趋势,微型X射线数字成像系统采用X射线敏感CCD面阵探测器作为射线探测元件,具有体积小、分辨率高、实时性好的特点。本文研制了基于X射线敏感CCD的微型X射线数字成像系统,介绍了整个系统的组成,阐述了X射线敏感CCD的工作原理,选定了系统采用的X射线敏感CCD,设计了CCD探测器的驱动电路、模数转化电路、数据采集与通讯电路、图像获取及处理软件等。该系统采用USB2.0接口与计算机进行通讯,直接采用USB接口电源供电,无需外部电源,结构简单。分辨率测试表明,该系统的分辨率>10lp/mm。     

一种新型曲面晶体成像系统的研制

为了对诊断目标进行瞬态辐射成像,提出了研制X射线聚焦成像系统,主要器件为一各向同性的X射线点光源及超环面弯曲晶体成像器.X射线照射至被成像物体后再投射到超环面晶体,经该凹面晶体聚焦后在X射线探测器表面成像.讨论了超环面晶体在布拉格几何结构中的聚焦成像特性,提出利用X射线源进行二维优化成像的适用条件.利用模拟软件对网格物体进行仿真成像,研究像距及光源尺寸对成像空间分辨力的影响,并据此确定了实验参量.设计的超环面弯晶采用云母材料,子午面曲率半径为290 mm,弧矢面曲率半径为190 mm.利用该系统进行了X射线背光成像实验,实验结果表明:系统的成像空间分辨力最高可达到34μm,能够满足聚爆辐射成像的要求;在光源尺寸较大时像距变化对成像效果有明显影响.     

惯性约束聚变靶丸高精度X射线数字成像

为了实现惯性约束聚变(ICF)靶丸几何尺寸的高精度、高效率检测,开展了靶丸X射线数字化成像系统的设计与研制。首先,分析了X射线直接投影成像和X射线透镜耦合显微成像的适用范围,根据ICF靶丸尺寸小、吸收衬度弱的特点,确定了基于X射线透镜耦合显微成像的技术路线。然后,分析了影响系统成像分辨率、图像衬度和测量效率的关键因素,确定了低几何放大成像,低电压、小焦点、高功率X射线源及高分辨CCD探测的总体技术方案,该方案能够有效抑制相衬效应和半影误差,解决了现有X射线数字成像设备测量靶丸时边缘扩展严重、尺寸测量误差大的问题。最后,对系统的性能进行了分析测试,实验结果表明,系统成像衬度良好,成像效率较高,分辨率优于0.5μm。靶丸几何尺寸的测量不确定度可达0.9μm(k=2),满足ICF靶丸几何尺寸高精度、高效率的检测需求。     

X线阵探测器实时成像系统的设计

为了解决工业无损检测x线的数字化成像问题。本文介绍了一种基于TCP／IP通信协议的X射线无损检测扫描成像系统,阐述了探测器数据接收与成像的基本原理及技术实现,进行了系统硬件和软件的设计。试验结果表明,X-SCANX射线线阵列探测器可以实现16bit高速图像数据获取。空间分辨率可达0．4mm。并取得了比较满意的x射线图像效果。     

用于弹道研究的脉冲X射线诊断系统

文章介绍了SCANDIFLASH脉冲X射线诊断系统的组成特点和应用实例,阐述了X胶片、CCD图像传感器和CR技术等几种成像方式的优缺点,分析了影响图像清晰度的原因,并针对弹道实验特点提出了防护方案.     

静态锥束CT成像系统的几何标定方法研究

采用X射线源阵列的静态CT成像系统为消除机械运动伪影,提高重建图像质量以及扫描成像效率提供了有效途径。高效、准确的几何标定方法是对X射线源阵列标定的关键。提出通过对一个已知三维标定模板的一次投影成像,采用最小二乘的直接线性变换法实现X射线成像系统的内、外参数准确估计的方法,以此方法用于静态CT扫描成像系统的几何标定。实验和仿真结果表明,该标定方法无需辅助装置,避免了满足要求条件的多次投影成像的过程;不受标定模板空间姿态的限制,一个X射线源与探测器的几何标定只需一次投影成像过程,方法简单、准确、易于操作,适于平面探测器的静态锥束X射线源阵列的成像系统几何参数的准确标定。     

用于弹道研究的脉冲X射线诊断系统

文章介绍了SCANDIFLASH脉冲X射线诊断系统的组成特点和应用实例，阐述了X胶片、CCD图像传感器和CR技术等几种成像方式的优缺点，分析了影响图像清晰度的原因，并针对弹道实验特点提出了防护方案。     

高、低能X射线数字成像内视仪的研制

提出了利用闪烁屏和科学级CCD相机研制适用于高、低能工业X射线成像检测内视仪的方法。结合科研工作中对内视仪性能的要求，研究了闪烁屏和科学级CCD的性能，设计了CCD的驱动电路、制冷电路和微机EPP方式远距离数据快速采集电路和相应软件。研制了完整的仪器并进行了实验，和常用的X射线数字成像系统相比，具有对比灵敏度和空间分辨率高，图像质量好的特点。     

铝合金铸件检测中的X射线DR技术应用

本文简要介绍了(DR)X射线直接数字成像检测技术和数字成像的基本原则,从过程应用的角度分析了数字成像的空间分辨率、像素、密度分辨率、空间分辨率与密度分辨率的关系,信噪比(信噪比)量子探测效率(DQE)等技术的解释;同时,在本文中一个典型的面板检测器DR成像测试系统的工艺实践,总结了铝合金铸件的X射线铝合金铸件的DR特征及常见缺陷图像的特征,铝合金铸件典型缺陷R图像,对类似工程具有重要的参考价值。     

高质量X射线检测数字化成像及图像采集

X射线数字成像检测是工业无损检测的新技术.非胶片实时数字成像检测以其高效率、低成本,特别是数字图像的可交换性和存储方便等特点成为射线检测的发展趋势.通常使用的由射线像增强器、视频摄像机、图像采集卡和计算机组成的系统成像质量差且只能在低能X射线下使用,作者经过反复研究和实验,研制了基于单晶闪烁屏和科学级CCD相机的可用于高、低能X射线高分辨率、高对比灵敏度数字成像检测系统.介绍了整个检测系统的组成,设计了科学级制冷CCD相机、预处理电路、A/D转换电路、微机EPP方式快速数据采集电路和软件等.给出了某铝铸件(厚150mm)在加速器高能X射线下的成像结果.实验证明该系统比普通像增强器和视频相机组成的系统具有适应射线能量范围宽和成像质量好的优点(成像时间长一些).系统的空间分辨率大于3lp/mm, 检测物体50mm(等效钢厚)以上时,对比度灵敏度小于1%.     

Compact water-window transmission X-ray microscopy

We demonstrate sub-100 nm resolution water-window soft X-ray full-field transmission microscopy with a compact system. The microscope operates at λ = 3.37 nm and is based on a 100 Hz table-top regenerative debris-free droplet-target laser-plasma X-ray source in combination with normal-incidence multilayer condenser optics for sample illumination. High-spatial-resolution imaging is performed with a 7.3% efficiency nickel zone plate and a 1024 × 1024 pixel CCD detector. Images of dry test samples are recorded with exposure times of a few minutes and show features smaller than 60 nm.     

Confocal imaging with bilateral scanning and array detectors

A novel arrangement for confocal microscopy is presented, in which the key elements are the use of an array detector such as a CCD for confocal image collection and the use of one double-sided scanning mirror element for bilaterally scanning the object and collecting the data on the CCD. The resulting arrangement is shown to be capable of confocal imaging with high photon efficiency under adjustable conditions of confocality and varying image acquisition rates, i.e. from slow speed up to real-time imaging. Either laser or conventional light sources may be utilized. In addition to CCD registration, direct observation by eye of the confocal image in fluorescence is also possible.     

Quantitative measurement of hard x-ray spectra for high intensity laser produced plasma

X-ray line spectra ranging from 17 to 77 keV were quantitatively measured with a Laue spectrometer, composed of a cylindrically curved crystal and a detector. Either a visible CCD detector coupled with a CsI phosphor screen or an imaging plate can be chosen, depending on the signal intensities and exposure times. The absolute sensitivity of the spectrometer system was calibrated using pre-characterized laser-produced x-ray sources and radioisotopes. The integrated reflectivity for the crystal is in good agreement with predictions by an open code for x-ray diffraction. The energy transfer efficiency from incident laser beams to hot electrons, as the energy transfer agency for specific x-ray line emissions, is derived as a consequence of this work.     

A Digital Scintillation Detector for the MEDIANA Medical Diagnostic Station

A digital position-sensitive X-ray imaging scintillation detector has been designed for the MEDIANA medical diagnostic station of the Kurchatov Synchrotron Radiation Center (the Kurchatov Institute). A single-crystal CsI(Tl) scintillator 8 mm thick is used as a screen with approximately 100% detection efficiency for X rays with energies as high as 100 keV. A CCD matrix of dimensions 1024 × 1024 pixels is the photodetector. The spatial resolution is five line pairs per mm in a field of vision of 35 × 35 mm for 100-keV X rays.     

A multielectrode X-ray detector

A multielectrode vacuum photoemission detector for X-ray tomography of plasmas at the ITER facility is described. The detector characteristics have been investigated with an X-ray source. The spectral response of the detector to X-ray photons with energies of 3–30 keV has been determined. The spatial and angular dependences of the X-ray detection efficiency are presented. The useful signal of the ITER facility has been estimated.     

DEVELOPMENT OF AN X-RAY FLUORESCENCE SPECTROMETER FOR ENVIRONMENTAL SCIENCE APPLICATIONS

The performance of a new X-ray spectrometer is presented. The device was designed originally to be employed in environmental sciences, and allows the use of different types of primary radiation sources, such as a radioactive source (²⁴¹Am) or tubes with anodes of different metals (Rh or W). Among the advantages of this spectrometer are the possibility of exchanging detectors to improve efficiency at different X-ray energy ranges [such as Si (Li), Si-PIN, hyperpure Ge, or CdTe detectors], to attach it to a wavelength dispersive system, and its use in vacuum or atmospheric pressure. Furthermore, it is feasible to modify the geometry so a secondary target may be installed for using polarized X-rays as exciting radiation.     

A transition radiation detector based on thin inorganic scintillators

The possibility of designing a prototype of the scintillation transition radiation detector (Sci-TRD) based on a thin (～200 μm) inorganic scintillator has been investigated. Vacuum and silicon photomultipliers have been used in the measurements with inorganic scintillator samples based on LuBO₃:Ce and wavelength shifting fibers. The light collection coefficient has been measured for scintillator prototypes under exposure to X rays, and the quantity of photoelectrons has been experimentally determined by irradiating the Sci-TRD working substance with a ²⁴¹Am X ray source. The electron-hadron rejection ratio of the proposed Sci-TRD is expected to be ～30.     

High-resolution water window X-ray imaging of in vivo cells and their products using LiF crystal detectors

High contrast imaging of in vivo Chlorella sorokiniana cells with submicron spatial resolution was obtained with a contact water window X-ray microscopy technique using a point-like, laser-plasma produced, water-window X-ray radiation source, and LiF crystals as detectors. This novel type of X-ray imaging detectors is based on photoluminescence of stable electronic point defects, characterized by high intrinsic resolution. The fluorescence images obtained on LiF crystals exposed in single-shot experiments demonstrate the high sensitivity and dynamic range of this new detector. The powerful performances of LiF crystals allowed us to detect the exudates of Chlorella cells in their living medium and their spatial distribution in situ, without any special sample preparation.     

X-ray microscopy of plant cells by using LiF crystal as a detector

A lithium fluoride (LiF) crystal has been utilized as a new soft X-ray detector to image different biological samples at a high spatial resolution. This new type of image detector for X-ray microscopy has many interesting properties: high resolution (nanometer scale), permanent storage of images, the ability to clear the image and reuse the LiF crystal, and high contrast with greater dynamic range. Cells of the unicellular green algae Chlamydomonas dysosmos and Chlorella sorokiniana, and pollen grains of Olea europea have been used as biological materials for imaging. The biological samples were imaged on LiF crystals by using the soft X-ray contact microscopy and contact micro-radiography techniques. The laser plasma soft X-ray source was generated using a Nd:YAG/Glass laser focused on a solid target. The X-ray energy range for image acquisition was in the water-window spectral range for single shot contact microscopy of very thin biological samples (single cells) and around 1 keV for multishots microradiography. The main aim of this article is to highlight the possibility of using a LiF crystal as a detector for the biological imaging using soft X-ray radiation and to demonstrate its ability to visualize the microstructure within living cells.     

Imaging modes for bilateral confocal scanning microscopy

The bilateral scanning approach to confocal microscopy is characterized by the direct generation of the image on a two-dimensional (2-D) detector. This detector can be a photographic plate, a CCD detector or the human eye, the human eye permitting direct visualization of the confocal image. Unlike Nipkow-type systems, laser light sources can be used for excitation. A design called a carousel has been developed, in which the bilateral confocal scan capability can be added to an existing microscope so that rapid exchange and comparison between confocal and non-confocal imaging conditions is possible. The design permits independent adjustment of confocal sectioning properties with lateral resolutions better than, or, in the worst case equivalent to, those available in conventional microscopy. The carousel can be considered as a stationary optical path in which certain imaging conditions, such as confocality, are defined and operate on part of the imaging field. The action of the bilateral scan mirror then extends this image condition over the whole field. A number of optical arrangements for the carousel are presented which realize various forms of confocal fluorescence and reflection imaging, with point, multiple point or slit confocal detection arrangements. Through the addition of active elements to the carousel direct stereoscopic, ratio, time-resolved and other types of imaging can be achieved, with direct image formation on a CCD, eye or other 2-D detectors without the need to modify the host microscope. Depending on the photon flux available, these imaging modes can run in real-time or can use a cooled CCD at (very) low light level for image integration over an extended period.