粒状磷光增感屏点扩展函数的蒙特卡罗研究

磷光增感屏的内禀性质对磷光增感屏的成像性能影响很大.基于米氏(Mie)散射理论,计算得到磷光增感屏在不同颗粒尺寸和不同颗粒堆积密度情况下的散射系数和吸收系数.然后利用Monte Carlo(MC)方法模拟了可见光光子在磷光增感屏Gd₂O₂S:Tb(GOS)内的散射和吸收事件,得到磷光增感屏内不同位置处的可见光收集效率.利用MCNP程序模拟X射线束在磷光增感屏内的能量沉积分布,得到了金属-磷光增感屏总的点扩展函数(PSF).结果表明,在兆伏X射线成像系统中,使用小颗粒尺寸和高堆积密度的GOS磷光屏,可以改善增感屏系统的空间分辨率.     

X射线增感屏的图象信息传输特性分析

本文采用Monte Carlo方法详细模拟了不同能量光子与增感屏的作用过程,对于一种稀土(Gd₂O₂S:Tb)增感屏,计算了出射可见光子数的概率分布、平均出射光子数、统计因子、X射线检测效率以及DQE等.增感屏出射可见光子数的概率分布曲线均有三个峰,随着入射X射线能量的增加,各峰之间距离增大,相对强弱对比增大;其余各曲线在Gd原子K壳层结合能(50.24keV)附近,均有突变.这些结果提供了增感屏图象信息传输性能的基本参数,为深入研究增感屏及成象系统的量子噪音传输特性提供指导.     

环形电子束积分图像诊断技术

 采用图像诊断方法对高能环形电子束形状及空间尺寸进行了研究,以高能脉冲环形电子束轰击高Z靶材料产生脉冲X射线,X射线经过X射线增感屏转换为可见光,用单次图像采集系统获取可见光的积分图像。为满足诊断所需的空间分辨和系统灵敏度,通过理论计算确立了靶的材料、厚度及X射线增感屏的型号和厚度等参数。根据测试环境,设计了系统的现场安装结构,系统基本满足测试要求。分析从实验中获取的图像,可知环形电子束的内径为36.5 mm,环厚为1 mm,环形不均匀,水平方向电子束强。     

X射线检测中高分辨率CCD相机及图像采集装置设计

通过选择ISD0 17AP型化妆品级CCD芯片和分析其主要性能 ,设计微光高分辨率制冷CCD相机的制冷电路 ,驱动时钟电路 ,输出信号A/D转换电路及微机EPP(增强并行口 )方式快速数据采集电路 ,研制X射线数字成像检测中慢扫描、高分辨率制冷CCD相机和图像采集装置 ,并和射线转换屏、光学系统等组成X射线数字成像系统。实验表明相机及其数据采集装置达到设计要求     

X射线增感屏点扩散函数的Monte Carlo模拟

研制了一通用的Monte Carlo程序来研究X射线增感屏以及成象系统的性能,该程序主要包括三部分,分别描述了所发生的相应的物理过程：X射线的散射和吸收,次级电子的作用及可见光子的扩散,对程序进行了验证,对于一种Gd2O2S:Tb增感屏,计算了其在不同入射X射线能量下的点扩散函数。     

稀土硫氧化物固溶体在X射线激发下的发光与应用

本文用稀土氧化物高温硫化法合成了(Y1-xLax)2O2S:Tb(0.002)、(Y1-xGdx)2O2S:Tb(0.002)和(Gd1-xLax)2O2S:Tb(0.002)三个二元稀土硫氧化物固溶体体系.研究了在X射线下激发它们的发光亮度、发射光谱.研究了激活剂Tb3+离子浓度对体系发光的影响.在上述实验的基础上,选择了其中的几种发光材料,研制出X射线增感屏,测定了屏的技术参数。     

闪光X射线高速摄影荧光转换屏的设计和性质研究

本文描述了用于中间弹道高速摄影荧光转换屏的设计特点、性能测试和实验结果。文中讨论了Gd2O2S:Tb和(Zn,Cd)S对X射线的吸收系数、发光效率以及荧光光谱与变象管S-20阴极光谱灵敏度曲线相匹配的相关曲线;测试了转换屏的相对发光强度、分辨率及其余辉。实验证明本屏发光亮度比钨酸钙屏高60倍左右,屏分辩率达51p/mm,余辉时间为8μs,多幅摄影结果证明第一幅的图象对第二幅照片无“拖尾”现象,本屏已达到了中间弹道高速摄影转换屏的实用水平。     

CCD固体成像器件性能测试方法的研究

CCD图像传感器是目前科学成像领域主流的固体成像器件。一般而言, 当成像系统中使用CCD器件时, 首先需要测量它的一些性能指标, 这是判断该CCD器件是否满足整个系统性能要求的重要依据。对CCD成像器件性能的测试方法进行了探讨, 涉及的参数包括增益、噪声、电荷转移效率、线性和满阱电荷等。研究重点是如何应用扩展像素边界反应方法及同位素X射线方法检测CCD的电荷转移效率, 以及利用X射线方法测量器件的增益。最后以理论研究为基础, 发展并提出了一套切实可行的CCD器件检测方法, 同时基于E2V公司4K×4K芯片CCD203_82进行了性能测试实验, 实验结果也验证了本文提出的测试方法的可行性和可靠性。     

X射线增感屏用纳米CaWO4的Pechini溶胶-凝胶法制备及其光学性能

采用Pechini溶胶-凝胶法制得纳米级CaWO4荧光粉,通过X射线衍射图、扫描电镜和发射光谱对其形貌和发光性能进行了研究,结果表明750℃条件下所得样品为纯相CaWO4晶体,在X射线激发下发射峰位于420nm,与感蓝胶片的光谱灵敏度匹配良好。其粒径在纳米量级且粒度分布集中是该方法所得CaWO4荧光粉的突出优点。将此荧光粉制成X射线增感屏并与市售同类产品相比,该增感屏可使感光片的成像质量显著提高。     

PC-EL型X射线固体图象增强屏

一、概 述 目前,一些国家的科技人员正在积极研制来用光电导材料(以下简记为PC)和电致发光材料(以下简记为EL)制备PC-EL型X射线固体图象增强屏.在表1中,列举了固体图象增强屏与其它的X射线显象装置如普通萤光屏、增强管电视系统以及胶片的特点.固体增强屏除了响应速度慢不能用于快速移动的对象之外,其余的性能都是可取的.它的分辨率可以比普通萤光屏及增强管电视显示器高出2—3倍,对比度γ值高出2-4倍,亮度比普通萤光屏大10—50倍.此外,它重量轻,容易操作,价钱便宜. 北京师范学院半导体器件厂在冶金工业部有色金属研究院和北京环境保护…     

新型高功率微波探测器

 通过对半导体材料中载流子迁移率的特性分析，在原HPM探测器的基础上，提出了探测器中半导体传感器的新设计，使探测器的检测灵敏度提高一个量级；同时研制成功S波段HPM探测器。在传感器的加工方面采用了新的工艺，并对电源进行了改进，使之功能完善、使用简单、具有实用性。其电源偏压在40V时，X波段的探测器在60kW时输出检测脉冲信号幅度高达9V，S波段的探测器在600kW时输出检测脉冲信号幅度高达10V，可适用于10～500ns脉宽的HPM功率测量。     

Development and testing of novel stripixel detectors for the silicon vertex tracker at PHENIX

As a part of the upgrades for the PHENIX detector at RHIC,a silicon vertex tracking detector is planned. This detector will consist of two pixel layers followed by two strip-pixel layers in the barrel region,an d four mini-strip layers in the endcap region. As a part of the development phase of the vertex detector, we have set up three sensor testing facilities at Brookhaven National Laboratory, at State University of New York, Stonybrook, and at University of New Mexico to characterize the preproduction sensors, and develop our testing and quality assurance plans. Preliminary results from these test are presented here. Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”, Budapest, Hungary, 4–9 August 2005.     

Metrological characteristics of thermal video fire detection systems

We consider the possibilities for designing a new hardware and software system for fire detection, based on combination of video analytics technology and analysis of IR signals from sensors in the mid-IR and thermal IR ranges. We consider the parameters (in particular, the maximum distance for detection of the seat of a fire) for IR sensors based on various photodetectors. As a detector in the visible range, designed for early smoke or open flame detection based on analysis of sequential images of a scene, we suggest using a standard IP network camera.     

数字式X射线辐射扫描成像系统及其应用

数字化图像具有非常突出的优点和广泛的应用,而Ｘ射线成像在医学诊断和工业无损检测等领域占据非常重要的地位,因此Ｘ射线成像的数字化必将成为一种趋势。文章介绍了数字式Ｘ射线辐射扫描成像的特点、原理及其应用前景。采用气体电离室探测器阵列完成了３２路数字式Ｘ射线辐射扫描成像装置系统,其空间分辨率达到０．５ｍｍ,并且获得了比较满意的Ｘ射线图像效果。     

红外碳硫传感器信噪比改善方法研究

应用于钢铁、矿物等检测的红外碳硫仪的研制在国内的研究还存在诸多问题,由于其在红外检测中位于一个非常敏感的区域,国内高精度红外碳硫传感器的研究迫切需要迈上新台阶。其检出限和检测精度要达到国际先进水平还存在传感器的气室工艺不够、探测器与光源的资源限制、信号的调制方式落后等问题。当然也存在信号的前期滤波、信号后期处理方面的原因。本文针对当前红外碳硫传感器的研究现状,对改善信噪比的方法进行探究和分析,并提出了相应的解决措施和具体思路。     

Readout electronics testing of the CMS Tracker modules with LT setup

The tracking part of the CMS detector will be built with ∼16000 silicon detector modules, and kept at −10°C for the ten years of the operation of the LHC. All the model materials need to be verified of having a good performance at this low temperature, before their installation into the CMS Tracker. In order to track performance quality, assurance tests are done with two different systems. Of the two setups used, the LT system module is the one that is used to identify whether the performance of readout electronics and leakage current flowing on the silicon sensors is affected by low temperature. In this paper a detailed layout of the CMS TOB modules and their front-end hybrids are presented. In addition, the LT testing results of the 190 TOB modules that were produced and tested in 2004 by the FNAL-CMS group are given. The text was submitted by the author in English.     

Linear optical coherence tomography system with extended measurement range

Optical coherence tomography (OCT) sensors traditionally use scanning optical delay lines with moving parts and a single detector. OCT systems with a linear detector array (linear OCT or L-OCT) are simple and robust, but a detector with approximately 10,000 pixels is needed for an imaging depth of 2mm, which is necessary for most biomedical applications. We present a new optical setup for L-OCT with an increased measurement range. An additional grating performs a reduction of the spatial frequencies of the fringe pattern on the detector without loss in the signal-to-noise ratio, so the signal can be sampled with a minimal number of pixels. The theory for this approach is addressed and the first measurements are presented.     

锥束CT平板探测器成像的余晖建模与校正方法

锥束CT具有高效率和高精度的显著特点, 在医学成像与工业无损检测等领域已得到广泛应用, 但余晖的存在降低了CT图像的质量. 本文借鉴余晖多指数衰减模型的思想, 结合平板探测器输出信号的实际衰减规律, 提出了一种新的基于多指数拟合的余晖衰减建模及校正方法. 首先进行了基于平板探测器的锥束CT成像实验, 结果表明平板探测器各像素的余晖衰减规律具有良好的一致性, 且余晖衰减规律与初始灰度的大小无关; 其后根据建立的余晖衰减模型实现了余晖的快速校正, 并分析比较了余晖校正前后投影图像和切片图像质量, 表明余晖校正后的零件轮廓清晰度得到了显著提升. 该方法无需获取探测器闪烁体成分及其衰减时间常数, 便于实际锥束CT成像系统的余晖检测与校正. 关键词： 余晖 平板探测器 锥束CT 多指数衰减     

Optimal Data Acquisition Methods for Single-Pixel Imaging

Single-pixel imaging is an image reconstruction technique, which uses spatially modulated illumination of an object and a single-pixel detector collecting the light scattered by the object. This technique is complementary to the conventional imaging based on multipixel matrices and becomes especially interesting when one needs to go beyond the capabilities of the standard silicon-based sensors, e.g., to perform imaging in the infrared range. One of the factors that limit the resolution of the reconstructed images is the signal-to-noise ratio during the data acquisition. We propose several methods for processing the photodetector signal and develop a universal method to determine the optimal pixel number in light patterns with respect to illuminance of the object. We use these methods to capture the standard test images and discuss their advantages.     

Application of magnetomechanical sensors for modal testing

A new modal testing technique using magnetomechanical sensors is proposed in this paper. To list some advantages of this technique, sensors are cost-effective and require no direct physical contact with a structure. The specific application made in this paper is the modal testing for the bending vibration of a solid circular beam. The theoretical analysis explaining the principle of the magnetostrictive sensor-based modal testing is presented for beam bending. The present results are compared with those obtained by the use of standard accelerometers. Although the application of this technique is made to relatively simple problems, the potential of magnetomechanical sensors for modal testing has been revealed.