Conversion of a X-ray position sensitive detector for use in a thermal neutron tomographic system

A gaseous position sensitive detector originally designed to operate with X-rays has been modified for using in thermal neutron tomographic systems. This modification included the replacing of the standard argon–methane mixture by ³He-enriched helium. Due to its low-density, helium should be submitted to a relatively high pressure in order to increase its stopping-power for the products emerging from the ³He(n,p)³H nuclear reaction. High pressure however, creates tightness problems. To mitigate this difficulty some heavy gases have been mixed to helium, reducing thus the range of the particles. In this work, three gases have been studied: pure ³He-enriched helium, and its mixture with argon–methane and with propane. For each case the parameters governing the performance of a detector coupled to a tomographic system, such as spatial resolution, linearity and response homogeneity have been determined. Besides that, the modulation transfer function and the distance resolution curve for a tomographic system incorporating a detector filled with those three different gases have been measured. The best spatial resolution – around 800 μm – has been obtained with a helium–propane mixture. This kind of detector is intended to equip thermal neutron tomographic systems, to perform non-destructive assay, exploiting thus the capability of this particle to pass through heavy materials where a X-ray tomography would not work properly. For an equivalent resolution, a tomographic system using a detector of this kind would require a much shorter acquiring time with regard to the first generation systems, since a sample translation is no longer necessary.     

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.     

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。     

影响接触显微成像分辨率的若干因素分析

分析了影响软X射线接触显微成像分辨率的若干因素,如：记录过程中的辐射损伤,后续放大设备读出引进的误差,以及菲涅尔衍射效应等,并且提出改善分辨纺的一些实用方法。     

真随机脉冲X射线CCD信号发生器

真随机脉冲X射线CCD信号发生器采用FPGA控制,产生幅度可调、时间间隔服从指数分布的真随机信号.针对传统的真随机数生成器(TRNG)中存在资源开销大、可移植性差的问题,采用了一种基于振荡器抖动和相位噪声的随机数发生器实现方法.该真随机数发生器以FPGA内部门电路构成的环形振荡器电路作为随机源,并采用两种不同的伪随机处...     

X射线CCD式电缆偏心在线检测装置的研制

介绍了X射线CCD应用于电缆偏心在线检测系统的检测原理和一个检测装置的结构，该装置硬件由扫描驱动系统、X射线发生器组件、数据采集部分和高性能计算机系统组成。给出了该装置在实际运行中的效果，以及与其他电缆偏心检测技术的特点比较。     

秦山一期棒位探测器的改进

简单介绍了棒位探测器的功能,重点介绍了棒位探测器运行多年来存在的主要问题及提高其可靠性的改进措施,并对改进效果作了简要评价.     

X射线CCD式电缆偏心在线检测装置的研制

基于X射线CCD的电缆偏心在线检测改进技术大大提高了检测装置的测量精度和响应速度.文中介绍了X射线CCD应用于电缆偏心在线检测系统的检测原理和-个检测装置的结构,该装置硬件由扫描驱动系统、X射线发生器组件、数据采集部分和高性能计算机系统组成.给出了该装置在实际运行中的效果,以及与其他电缆偏心检测技术的特点比较.     

高位置分辨平行板雪崩室的研制

描述了灵敏面积为 10 0 mm× 10 0 mm和 150 mm× 150 mm两维位置灵敏雪崩室。采用分块结构 ,电极从两端分前后点引出 ,增加了延迟线的长度 ,延迟线跨边连接和在大气中直接封真空技术。在流动的 4 2 0 Pa的正庚烷气体中 ,用2 52 Cf裂变源对探测器的性能进行了测试 ,得到Δx=Δy=1mm的位置分辨。     

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.     

50nm及50nm以下同步辐射X射线光刻光束线设计

X射线光刻相对于其他下一代光刻技术而言有许多优点,比如其工艺宽容度大、成品率高、景深大、曝光视场大、成本低等,更为重要的是,其技术已经比较成熟。对于100nm同步辐射X线光刻系统而言,它采用的波长通常为0．7-1．0nm,而当光刻分辨率达到50nm以下时,采用的同步辐射X射线波长范围应该为0．2—0．4nm。探讨了在北京同步辐射3B1A光刻束线上进行50nmX射线光刻的可能性。     

一个二维位置灵敏X射线探测器的研制

本文报道-个二维位置灵敏X射线探测器的研制.探测器采用多丝正比室(MWPC)结构,有效面积200×200mm2,采用阴极感应读出,由电荷重心法确定入射X射线位置.经测试,探测器的位置分辨(fwhm)好于0.4mm.     

Improved plasma position detection method in EAST Tokamak using fast CCD camera

To control the steady-state operation of Tokamak plasma, it is crucial to accurately obtain its shape and position. This paper presents a method for use in rapidly detecting plasma configuration during discharge of the Experimental Advanced Superconducting Tokamak device. First, a visible/infrared integrated endoscopy diagnostic system with a large field of view is introduced,and the PCO.edge5.5 camera in this system is used to acquire a plasma discharge image. Based on the analysis of various traditional edge detection algorithms, an improved wavelet edge detection algorithm is then introduced to identify the edge of the plasma. In this method, the local maximum of the modulus of wavelet transform is searched along four gradient directions, and the adaptive threshold is adopted. Finally, the detected boundary is fitted using the least square iterative method to accurately obtain the position of the plasma. Experimental results obtained using the EAST device show that the method presented in this paper can realize expected goals and produce ideal effects;this method thus has significant potential for application in further feedback control of plasma.     

数字辐射扫描成像系统水平分辨率的提高

对辐射成像无损检测系统中的水平采样模型和模糊影响进行了分析，提出重叠采样提高水平扫描分辨率的方法，并通过实验测量水平冲击响应函数，利用逆滤波算法对采样模糊后的图像进行了恢复。     

BaF2正电子寿命谱仪时间分辨率的改进

介绍了不同材料,不同形状的封装对BaF2晶体光收集的影响。使用聚四氟乙烯薄膜对BaF2晶体作伞状封装,光收集效果较好,在此条件下,常规正电子湮灭寿命谱仪的时间分辨率在^22Na能窗下达到180ps。     

On the design of a monolithic 4-bounce high resolution X-ray monochromator

A monolithic monochromator (+n, −n, −m, +m) made of a single block of Ge crystal designed for CoK_α1 radiation was developed and tested numerically and experimentally by means of X-ray diffraction. The advantage of monolithic devices is their mechanical stability and the alignment of such optics is much easier than with polylithic optics, but the development of these devices is rather demanding. The presented monochromator belongs to a group of coplanar in-line devices, which means that the input beam is parallel with the output beam. For the estimation of the spectral and angular properties of a diffracted beam of this monochromator (such as bandpass width, output divergence and input acceptance) we used a numerical approach which we call spectral-angular function. It takes into account both the vertical and the horizontal divergence of the input radiation and uses two-beam X-ray dynamical theory of diffraction. Experimentally, the monochromator was tested by means of X-ray diffraction (synchrotron radiation testing) and the results from this characterization are presented. The influence of the vertical divergence on the spectral distribution of the diffracted beam is discussed and compared with previously published analytical results.     

High resolution X-ray photon-counting detector with scintillator-deposited charge-coupled device

We report on a new photon-counting detector possessing unprecedented spatial resolution and moderate spectral resolution for 0.1-100 keV X-rays. It consists of an X-ray charge-coupled device (CCD) and a scintillator. The scintillator is directly coupled to the back surface of the X-ray CCD. Low-energy X-rays below 10 keV can be directly detected by the CCD. The majority of hard X-rays above 10 keV pass through the CCD but can be absorbed by the scintillator, generating visible photons. We coupled needlelike CsI(Tl) on the front surface of the back-illuminated (BI) CCD. The high detection efficiency of BI CCDs in the visible band enables us to collect visible photons emitted from the CsI(Tl) efficiently, leading to the moderate spectral resolution of 28.4% at 22.1 keV and 25% at 59.5 keV. We also investigated the imaging capability of our device and demonstrated high resolution imaging with an accuracy of 10 /spl plusmn/3 /spl mu/m at 17.4 keV.     

A high resolution multipurpose ESCA instrument with X-ray monochromator

The design and performance of a new high resolution multipurpose instrument are described and illustrated. The instrument comprises a high-power, fine-focusing e^?-gun, a high speed rotating anode, a double focusing multi-crystal X-ray monochromator, a monochromatic UV-source with a toroidal grating, a fine-focus variable energy e^?-source, a four-element electrostatic e^?-lens system, a large 36 cm hemispherical electrostatic analyzer, a 12 cm wide electron multi-detector system and a dedicated computer system. Various sample probes for gases, liquids and solids are discussed. The instrument is shown to reach an energy resolution of at least 0.23 eV with X-ray excitation at a sufficient intensity to enable the study of gases.A number of illustrative examples of the proved instrumental performance is presented. A new “line-sharpening” effect, due to post-collision interaction in Auger electron spectra, is revealed due to the high spectrometer resolution. The strongest vibrational components of the C 1s ESCA line from methane are for the first time resolved. High resolution spectra are also presented for solids, e.g. the spin-orbit split Si 2p line is well resolved into two components and new resolved structures appear in the Ag and Au valence bands. Calculated density of states are found to be in good agreement with these structure rich d-bands. Phonon excitation accompanying the photoionization process is discussed in relation to its causing additional broadening of the Si 2p lines.     

Development of a low-energy high resolution X-ray camera for high-energy gamma photon background environments

Although a high-energy gamma camera can obtain images of ¹³⁷Cs distribution by detecting the 662-keV gamma photons, its spatial resolution is reduced because high-energy gamma photons penetrate the edge of the pinhole collimator. To solve this problem, we developed a low-energy X-ray camera that detects the characteristic X-ray photons (32–37 keV) that are emitted from ¹³⁷Cs to obtain high resolution images. We used a 45 × 45 × 1-mm-thick NaI(Tl) scintillator that was encapsulated in 0.1-mm-thick aluminum and optically coupled to a 2-inch square, position sensitive photomultiplier tube (Hamamatsu Photonics, PSPMT:H12700 MOD) as an imaging detector. The imaging detector was encased in a 2-cm-thick tungsten alloy container and a pinhole collimator was attached to its camera head. The spatial resolution and sensitivity were ～5 mm full-width at half-maximum and ～0.6 cps/MBq for the 1.5-mm pinhole collimator 10 cm from the collimator surface, respectively. We administered 5 MBq of ¹³⁷Cs to a soybean seedling, imaged the distribution of radionuclides for six hours, and successfully obtained a high resolution image of it with our developed X-ray camera. We believe our camera will be a powerful tool for such ¹³⁷Cs imaging in plants.     

基于PSD的X射线光束位置探测器设计

位置灵敏探测器(Position sensitive device,PSD)是一种利用光电二极管表面电阻的光电子位置传感器,具有高速度、高分辨率、可靠性好等优点。本文描述了将PSD用于X射线条件性能测试的结果,给出了基于PSD的X射线光束位置探测器(X-ray beam position monitor,XBPM)的一个具体设计方案,并进行了相应估算,初步表明了其可行性。