低能X射线工业CT探测器光电转换效率的研究

光电转换效率是低能工业CT探测器的重要性能参数。分析了几种常用闪烁晶体的发光效率、几何尺寸、发光波长等参数对光电转换效率的影响,并通过实验测试比较了不同厚度(闪烁体沿X射线方向的尺寸)的CsI(TI)和CdWO4闪烁体探测器的光电转换效率。证明在低能工业CT中,CsI(TI)比CdWO4更适合用作X射线探测器闪烁体材料,且闪烁体的厚度对光电转换效率的影响很大。这对优化工业CT系统探测器闪烁体的选型与尺寸设计具有一定的参考价值。     

低强度脉冲射线测量中的统计起伏分析

分析了闪烁探测器在低强度脉冲γ射线测量中的统计起伏现象,指出探测器输出信号的涨落不仅与达到测点的γ射线注量率、时间分布、空间分布、能量分布的统计性有关,而且还与射线和探测器的作用、能量沉积、荧光光子发射和传输、荧光光子与光阴极作用、光电子和打拿级的作用等随机事件的统计特性有关。详细推导了统计起伏的计算公式,并给出了3种型号的闪烁体与9815B型光电倍增管组成的闪烁探测器在给定测量下限时的统计起伏计算值。     

国产锗酸铋(BGO)闪烁体荧光的硅光二极管读出方法的研究

研究了硅光二极管的一般特性,用宇宙线μ子作为检验粒子,用硅光二极管测量了国产BGO闪烁体的光电子产额,对探测器的能量分辨、噪声和硅光二极管的带电粒子效应也进行了测量。     

闪烁光纤阵列用于高能射线成像的可行性研究

本文通过对塑料闪烁光纤阵列在高能X或γ射线下的特性研究,分析了利用闪烁光纤阵列作为高能成像探测器的可能性。采用了基于蒙特卡罗的模拟方法,分析了闪烁光纤在高能射线下所成图像的质量,并且模拟计算了表征图像质量的信噪比(SNR),探测量子效率(DQE)以及调制传递函数(MTF)。通过这些计算得到闪烁光纤阵列有着传统闪烁屏所不具有的一些特性,把闪烁光纤的这些特点应用于高能成像中是完全可行的。     

X光电离室标准探测器研制及应用

在电离室的内部设置探测器并采用大的电离室腔体,可直接测量气体吸收、降低气体密度分布梯度、避免由于气压不稳、窗膜吸收和窗口尺寸等引起的不确定性.本文分析了引起X光强度测量不确定度的各个因素,给出X光电离室标准探测器的测量不确定度好于5%.     

几种常用闪烁体受^30Coγ源辐照前后探测器灵敏度比对

在闪烁体耐辐照特性研究中,通过比较闪烁体受辐照前后闪烁探测器系统灵敏度的变化,说明在大辐照剂量后闪烁探测器是否处于正常工作状态。利用三通道脉冲X射线源（平均能量800keV）、DPF脉冲中子源（D-T中子能量14．4MeV）,通过实验标定几种常用闪烁探测器对脉冲中子、脉冲X射线的相对灵敏度值。所用闪烁体包括Ф40mm,不同厚度的CeF3,NaI（T1）和BaF2等无机晶体及ST-401,ST-142Z,NE111等塑料闪烁体。     

YAP伴随α粒子探测器的研制

研制了一种可安装于D-T中子发生器内的伴随α粒子探测器.该探测器选用直径30 mm、厚0.5 mm的掺铈铝酸钇(YAP:Ce)闪烁体,可密封于D-T中子发生器内.采用蓝宝石玻璃作耐高温光学法兰,粒子在YAP闪烁体中产生的光信号经过蓝宝石玻璃传到光电倍增管光阴极上.光电倍增管阳极输出α粒子的电脉冲信号.探测器输出负信号的前沿下降时间约为6 ns;对241Am 5.486 MeV α粒子的能量分辨率约为5.4％.在高压倍加器用作D-T中子源时,在15 kcps计数率下,该探测器对3.5MeV伴随α粒子的能量分辨率约为27％,峰谷比达到10:1.YAP闪烁体及蓝宝石玻璃经8 h400℃烘烤后,该探测器的时间性能和能量分辨性能未发生改变.实验表明研制的探测器满足了密封D-T中子发生器的制造工艺要求,可安装于小型D-T中子发生器内用作伴随α粒子探测器.     

高能工业CT探测器能谱响应影响校正研究

高能X射线工业CT探测器系统的能谱响应是一重要的特性参数。用实验方法测定探测器的能谱响应曲线存在很多困难。本工作利用Monte-Carlo模拟程序计算了CdWO₄探测器模块的能谱响应曲线,分析了9MeV驻波电子直线加速器X射线束的能量、剂量角分布以及X射线束能谱硬化对探测器模块探测效率的影响,为线阵探测器系统的一致性校正、非线性校正等提供了理论计算参数,并应用于工业CT图像校正,取得了满意的效果。     

几种常用闪烁体受60Coγ源辐照前后探测器灵敏度比对

在闪烁体耐辐照特性研究中,通过比较闪烁体受辐照前后闪烁探测器系统灵敏度的变化,说明在大辐照剂量后闪烁探测器是否处于正常工作状态.利用三通道脉冲X射线源(平均能量800keV)、DPF脉冲中子源(D-T中子能量14.4MeV),通过实验标定几种常用闪烁探测器对脉冲中子、脉冲X射线的相对灵敏度值.所用闪烁体包括φ40mm,不同厚度的CeF3,NaI(T1)和BaF2等无机晶体及ST-401,ST-1422,NE111等塑料闪烁体.     

高能X射线实时成像技术及固体线性阵列探测器研究

该项目主要研究高阻和低阻硅光二极管阵列探测器的设计及制备工艺,闪烁晶体阵列及隔离层、光反射层的加工装配,两种阵列之间的耦合,线性阵列探测器封装技术,线性阵列探测器性能测试,阵列探测器信号处理及线性扫描二维像的数据获取和图像处理技术,空间分辨和密度分辨率的影响因素等,从而掌握固体线性阵列探测器这一中、高能X射线实时成像和CT成像的核心技术,研制成功固体线性阵列探测器成像单元,掌握线性扫描二维成像技术。     

薄窗型多阳极气体探测器研究进展

薄窗型气体探测器是最近发展并用于低能量加速器质谱探测技术。该探测器的入射窗采用氮化硅膜,薄而均匀,分辨率高,目前已在低能量粒子探测技术中得到初步应用,显示出广泛的应用前景。本文主要从薄窗型气体探测器基本原理、薄氮化硅膜与Mylar膜的对比、不同质子数Z的低能量粒子脉冲高度对比、薄窗型气体探测器与硅探测器的对比,以及应用等方面进行阐述。     

内充气正比计数管测量37Ar活度中壁效应的理论研究

通过分析³⁷Ar衰变产生的X射线和俄歇电子在内充气正比计数管灵敏体积中的逃逸及计数管在³⁷Ar活度测量中的壁效应,得出X射线在正比计数管中的逃逸是产生壁效应的主要原因,提出了压力指数外推方法。使用MCNP模拟X射线和俄歇电子在内充气正比计数管中的输运,模拟结果与理论分析结论一致。比较模拟得出的壁效应值与实验测量的壁效应值可知,实验给出的壁效应值是可信的。本工作的研究结果为37Ar测量方法提供了理论支持。     

Application of CMOS charge-sensitive preamplifier in triple-GEM detector

1 Introduction With novel materials and advanced technique of printed circuit board (PCB) and micro-electronics be- ing used in MPGD, over the past two decades, great progress has been made in MPGD[1], and as a new type of MPGD, the GEM[2] detector was developed during the late 1990s. Standard GEM from CERN is a thin, two-side copper-coated Kapton foil, perforated with a high density of holes etched using a photolitho- graphic process. The diameter of these holes is about 70 μm (ext…     

Performance of Argon-Xenon Mixtures in a Gas Proportional Scintillation Counter for the 0.1–10 keV X-Ray Region

The performance of a gas proportional scintillation counter filled with either pure Xe or Ar-Xe mixtures is described for the 0.1-10 keV X-ray energy range. It is shown that the spectra tail distortion exhibited by Xe filled gaseous detectors for soft X-rays below 2 keV is reduced if Ar-Xe mixtures are used. The peak-to-valley ratio increases by a factor of about 2 or 3 as the Xe concentration is reduced from 100% to 5%. Moreover, the energy resolutions for such mixtures are similar to the ones for pure Xe.     

High energy X-ray computed tomography for industrial applications

A high energy X-ray computed tomography (CT) system with an electron linear accelerator was developed to image cross-sections of large-scale and high-density materials. An electron linear accelerator is used as the X-ray source. The maximum X-ray energy is 12 MeV, and the average energy is around 4 MeV. The intensity of the X-ray fan beam passing through the test object is measured by a 15-channel detector array. CWO (CdWO₄) scintillators and photodiodes are used as the X-ray detectors. The crosstalk noise due to scattering of X-ray photons by adjacent detectors is reduced to less than 1.6% by installing tungsten shields between the scintillators. Extra channels are used to compensate for base line shift of the circuits. These techniques allowed attainment of a dynamic range of more than 85 dB and a noise level comparable to the signal amplitude of X-rays transmitted in a 420-mm thick iron block. A spatial resolution of 0.8 mm was confirmed with an iron test piece 200 mm in diameter     

The Successful Operation of Hole-Type Gaseous Detectors at Cryogenic Temperatures

We have demonstrated that hole-type gaseous detectors, gas electron multipliers and capillary plates (CPs) can operate at temperatures down to 77 K. For example, a single CP can operate at gains above$10^3$in the entire temperature interval between 77 and 300 K. The same CP combined with CsI photocathodes operates perfectly well at gains of 100–1000, depending on the gas mixture. The obtained results open new fields of applications for CPs as detectors of ultraviolet light and charged particles at cryogenic temperatures: liquid noble gas time-projection chambers, detectors for weakly interacting massive particles or liquid Xe scintillating calorimeters, and cryogenic positron-emission tomography.     

A new glass GEM with a single-sided guard-ring structure

The gas electron multiplier (GEM) is a gaseous detector that is widely used in many applications. Our glass GEM (G-GEM) comprises a photo-etchable glass (PEG3, HOYA Corporation, Japan). Our research indicated that it shows superior performance compared with other gas detectors. In this article, a new type of G-GEM is introduced. It has a guard-ring structure around the holes in order to improve the spark tolerance by reducing the total capacitance of each hole structure. A measured gas gain of approximately 7500 is attained for this new G-GEM with a single-sided guard-ring structure using a gas mixture of Ar (90%) and CH₄ (10%) in the gas flow mode. An energy resolution of 17.3% (FWHM) is also achieved with a collimated 6 keV X-ray beam. The results of a 10 to 12 hour gas gain stability measurements are also shown.     

在电子驻波直线加速器上获得小束斑电子束

近年来高效率探测器阵列数字辐射照相技术已经用于无损探伤实时在线图象处理检测。厚在则重的关键部位的微小缺陷，需要用加速器产生的高能电子束作为焦点打靶产生Ｘ射线进行无损探伤检测。     

用激光束测试和标定气体径迹探测器

近年来利用激光束产生的电离径迹对径迹探测器进行测试、标定和监测已成为一种强有力的通用方法。本文介绍这种方法的基本原理、实验装置以及它的若干应用。     

带增益的气体探测器读出ASIC的研制

设计了用于带增益的气体探测器比如GEM、RPC等读出的ASIC,实现对探测器信号的放大、成形和对后续实时采样ADC的驱动电路.电荷增益和成形时间可调,有利于探测器不同增益下性能的研究,也扩展了芯片的应用范围.由于成形电路引入的噪声变得显著,在低电荷增益下,ENC会随增益下降而增加.芯片采用Chartered 0.35μm2P4M CMOS工艺,论文介绍了芯片的详细设计和仿真结果.