基于读出条读出的二维位置灵敏气体电子倍增器的研制

为研发能够满足北京同步辐射(BSRF)实验要求的二维探测器,研制了基于读出条读出的二维位置灵敏X射线气体电子倍增器(GEM).实验过程中通过改进读出条的周期,并基于中科院高能所实验物理中心电子学组研制的多路电荷放大器系统与VME存储-ADC系统,对软X射线源的位置分辨率进行了精密测量且得到了优异的二维位置分辨:X方向约为84μm,Y方向约为75μm.研究了三级GEM压差之和对位置分辨的影响,并测试了探测器的位置准确度与线性.对基于阳极读出的GEM用于模拟读出测试系统得到了一定的理论认识,侧重研究了GEM探测器基于模拟读出的系统特性,给出了相关的分析与讨论.     

二维多丝室探测器读出方法的优化

中国散裂中子源将建设一台基于~3He气体的二维多丝室,作为多功能反射谱仪束线的中子探测器.基于已有的研究,为优化选择二维多丝室探测器的丝结构,本文研究了三种不同的丝结构,并采用重心读出方法和数字读出方法进行了探测器的性能测量,得到了满足多功能反射谱仪探测器需求的读出方法.实验结果表明:对同种丝结构的二维多丝室探测器,重心读出方法的位置分辨和成像性能都好于数字读出方法;基于重心法读出的多丝室探测器位置分辨率可以达到约160μm,基于数字读出方法的多丝室探测器位置分辨率可以达到约400μm.优化设计的丝结构为:基于重心读出法的阳极丝间距1.5 mm、读出通道间距4 mm,基于数字读出法的阳极丝间距1.5 mm、读出通道间距2 mm.优化设计的丝结构均能满足谱仪的位置分辨要求.     

三级GEM探测器的增益一致性实验研究

随着二维GEM气体探测器在X射线成像探测领域的应用, 三级GEM的探测结构和电场均匀性带来的增益一致性修正问题, 成为需要深入研究的课题内容。 介绍了有效探测面积为100 mm×100 mm的三级倍增GEM探测器, 共采用100路阵列读出, 每路读出Pad面积为9.5 mm×9.5 mm。 测量了55Fe放射源准直入射的全能峰谱。 实验表明, 随着时间的变化, 探测器的增益基本上保持稳定; 随气流的增大, 增益由变化明显到变化不大。 GEM探测器各个阵列单元的增益一致性良好（>80%）; 能量分辨率在0.18～0.22之间, 运用最小二乘法拟合给出增益一致性的修正结果, 修正后相差约0.1, 为GEM气体探测器的增益一致性修正方法提供了参考方案。 With the application of the two dimensional GEM gaseous detector in X ray imaging, the correction method of gain uniformity caused by triple GEM avalanche structures and electric field uniformity should be studied. The paper reported the study of the triple GEM detector with effective area 100 mm×100 mm used the Pad’s size of 9.5 mm×9.5 mm. In the test, 100 readout channels were designed. Results showed that gain remained stable over time; as air flow increases, gain from increases obviously to changes very little. Particularly, triple GEM’s gain uniformity was very good (more than 80%) and the range of energy resolution was from 0.18 to 0.22. To improve gain consistency of results, the difference value revised was obtained to be about 0.1 by the least square method. It provided a better method to improve gain uniformity of GEM detector.     

GEM探测器与X射线成像实验

使用2个GEM探测器系统,分别用作增益测量和位置分辨测量.用GEM探测器测量铜靶X射线能谱,能量分辨率为21.5%.8keV的X射线入射双层GEM探测器,实验测量x方向位置分辨为64μm,y方向位置分辨为68μm.将科研成果经过精炼、核心提取,为核与粒子物理学科的本科生开设GEM探测器和X射线成像实验,使学生对高能粒子探测技术、数据获取和处理等有整体的理解.     

三级GEM气体探测器性能的实验研究

GEM探测器是一种新型微型气体探测器(Micro-Pattern Gas Detector), 在粒子物理实验及低能X射线成像系统中有着较大的应用前景. 文章研制了一种适用于低能X射线成像和带电粒子径迹测量的三级GEM气体探测器. 使用放射源⁵⁵Fe对其气体放大特性、电荷传输效率及能量分辨本领等性能进行了实验研究, 重点研究了传输区电场对气体有效增益和能量分辨本领的影响. 实验结果表明, 三级GEM探测器的暗电流和噪声较小, 有效增益能够达到10⁵以上并稳定地工作, 对5.9keV的X射线能量分辨率可达24%, 传输区电场强度大于3000V/(cm.atm)时, 能量分辨率基本稳定在30%左右.     

植物研究用γ射线成像系统设计（英文）

为了利用正电子发射断层成像技术在植物生理功能研究中的优势,正在开发由两个探测器相向放置构成的γ射线成像系统.系统中采用的探测器是由10×10的氧正硅酸镥(LSO)晶体阵列与滨松R5900-C12耦合组成.单个LSO尺寸为1.8mm×1.8mm×10mm.根据PET应的特点,测试了该探测器的性能.所有闪烁晶体的图像在位置图谱中清楚可见;511keV全能峰处的能量分辨率位于14.5%-22%之间;符合时间分辨率随着位置灵敏光电倍增管的供给电压的增加而得到改善.这些实验结果表明,该LSO探测器适于构造高分辨率的双探测器成像系统.     

基于蛇形光路的PET探测器作用深度提取方法

为实现正电子发射断层成像(Positron Emission Tomography,PET)探测器的作用深度(Depth Of Interaction,DOI)信息获取,本文提出一种基于分光技术的探测器设计方案.探测器采用晶体单元与硅光电倍增管(Silicon Photomultiplier,SiPM)一对一耦合、蛇形光路的设计和单端Anger加权读出方法进行DOI解码.基于GATE软件进行蒙特卡罗模拟,建立8×1的LSO晶体阵列(单根晶体尺寸3.1×3.1×20mm3);模拟泛场照射获取位置查找表;并进行不同深度的模拟,获得各晶体在各深度的空间分辨率.结果显示所模拟的探测器模块DOI分辨率在1.0~6.7mm之间,平均值为3.2mm.本文提出的基于蛇形光路的PET探测器方案能在维持系统成本和复杂度的前提下实现DOI解码,提升PET系统的成像性能.     

涂硼GEM中子束流监测器物理过程的蒙特卡罗模拟

基于硼转换的GEM(Gas Electron Multiplier)探测器性能突出,计数率高达10 MHz以上,耐辐射,信号读出方式简单、灵活,位置与时间分辨率高,是下一代中子束流监测器极具优势的候选者。这种新型中子束流监测器主要由硼中子转换层、气体电离粒子放大的GEM以及二维读出电极组成。通过Geant4程序包对探测器物理过程进行蒙特卡罗(Monte Carlo)模拟,主要研究了硼中子转换层转换效率与厚度及中子波长的关系、出射粒子的能谱、不同气体比分不同气体厚度中的能量沉积、以及γ的能量沉积,计算比较了不同厚度GEM膜对快中子产生的影响。模拟结果表明,出射粒子在漂移区的能量沉积几乎与气体比分无关,硼层厚度取0.1μm以下,漂移区厚度6 mm时,可以确保出射粒子在漂移区能量完全沉积,同时具有最佳n/γ区分能力。     

软X射线能谱仪

本文描述了一个用于托卡马克杂质谱线精细测量的高分辨软X射线谱仪。谱仪采用Johann型弯晶衍射结构,以多丝正比室作探测器件。其测量范围为2—8keV(1—6),能量分辨为4.1eV(在6.4keV处)。多丝正比室采用阳极丝逐丝读出法,位置读出精度2mm。谱仪配有自动数据记录系统。     

位敏型探测器数字法读出研究(英文)

中国散裂中子源( CSNS ) 的建造对中子探测器提出了非常高的要求,如更大的有效面积、二维位置灵敏、高计数率、高探测效率和低的 灵敏度等。与传统的模拟读出方法相比,数字法读出具有更高的计数率, 更小的数据传输量,更简单的电子学设计以及更高的信噪比。对数字法读出进行了理论计算,利用GEM探测器的原始数据分析了数字法读出的位置分辨率与读出条宽度的关系。结果表明,数字法读出对于位置分辨要求较低( 小于4 mm) 的大面积位置灵敏探测器是一种较好的选择,如CSNS 小角谱仪探测器。Efficient thermal neutron detectors with large area, two-dimensional position sensitive, high counting rate high detection efficiency and low gamma sensitivity are required to satisfy the demands for the China Spallation Neutron Source (CSNS). Compared with the traditional analog readout method, the digital readout method has the advantages of higher counting rate, smaller quantity of data transmission, simpler readout system and higher signal to noise ratio. The theoretical analysis of the digital readout method is reported in this paper. Used the raw data of GEM detector, the relationship between the position resolution and the width of the readout strip was studied. The results indicate that the digital readout method could be a good choice for the large area position sensitive detector where the requirement of position resolution is less than 4 mm, e.g. the detector of Small-Angle Neutron Scattering (SANS) diffractometer of CSNS.     

A stopping layer concept to improve the spatial resolution of gas-electron-multiplier neutron detector

In recent years, gas electron multiplier (GEM) neutron detectors have been developing towards high spatial resolution and high dynamic counting range. We propose a novel concept of an Al stopping layer to enable the detector to achieve sub-millimeter (sub-mm) spatial resolution. The neutron conversion layer is coated with the Al stopping layer to limit the emission angle of ions into the drift region. The short track projection of ions is obtained on the signal readout board, and the detector would get good spatial resolution. The spatial resolutions of the GEM neutron detector with the Al stopping layer are simulated and optimized based on Geant4GarfieldInterface. The spatial resolution of the detector is 0.76 mm and the thermal neutron detection efficiency is about 0.01% when the Al stopping layer is 3.0 μ m thick, the drift region is 2 mm thick, the strip pitch is 600 μ m, and the digital readout is employed. Thus, the GEM neutron detector with a simple detector structure and a fast readout mode is developed to obtain a high spatial resolution and high dynamic counting range. It could be used for the direct measurement of a high-flux neutron beam, such as Bragg transmission imaging, very small-angle scattering neutron detection and neutron beam diagnostic.     

An X-ray imaging device based on a GEM detector with delay-line readout

An X-ray imaging device based on a triple-GEM (Gas Electron Multiplier) detector, a fast delay-line circuit with 700 MHz cut-off frequency and two dimensional readout strips with 150 μm width on the top and 250 μm width on the bottom, is designed and tested. The localization information is derived from the propagation time of the induced signals on the readout strips. This device has a good spatial resolution of 150 μm and works stably at an intensity of 105 Hz/mm2 with 8 keV X-rays.     

Characterization of a triple-GEM position sensitive detector for X-ray fluorescence imaging

In this work, we characterized an X-ray position sensitive gaseous detector based in a triple stack of gas electron multipliers. The readout circuit is divided in 256 strips for each dimension and using a resistive chain interconnecting the strips, we are able to reconstruct the radiation interaction points by resistive charge division. The detector achieved gains above 10⁴, energy resolution of 15.28% (full width at half maximum) for 5.9 keV X-rays, and position resolution of 1.2 mm, while operating in Ar/CO₂(90/10) at atmospheric pressure.     

高通量下GEM探测器高压供电模式研究

GEM探测器的供电一般采用电阻链分压供电模式和多路分立供电模式,在低通量X射线下测量时区别不大,但是在高通量X射线时,电阻链分压供电模式会带来饱和效应引起工作电压的变化,造成探测器工作不稳定。本研究在高通量X 射线照射下,研究了有效面积为100 mm100 mm三层级联GEM探测器的有效增益(稳定性) 与不同高压供电模式的关系。通过测量不同分压电阻值(1, 2, 5 到30 MΩ)的实验研究,发现随着X 射线通量的增加,在电阻链分压供电模式下,出现了GEM探测器感应电极的读出电流饱和趋势,分析了可能导致饱和效应出现的原因。结果表明,当入射X射线在探测器上的有效吸收剂量不断增加时,电阻链供电模式需要调整分压单元电阻值,或者采用多路分立供电模式,从而避免因饱和效应引起的GEM探测器有效增益的变化,实现探测器稳定的工作状态。There are two methods of the HV power supply for the GEM detector. One is a HV channel divided by the resistive chain and the other is the several separate HV channels. In the smaller dose rate of X-ray, all of the methods are similar. When the dose rate increases, the resistive chain-dividing mode has more obvious saturation effect and the working voltage of the GEM detector is unstable. In the paper, a GEM detector with an effective area of 100 mm100 mm has been studied in the high dose rate using X-tube. The unit values in the divider resistance chain are set to 1, 2, 5 and 30 MΩ respectively in the test. With the resistive chain-dividing mode, the readout current of the GEM detector’s anode tends to saturate when the dose rate of X-ray increases,and the reasons of the saturation effect are analyzed. The results indicate that the effective absorbed dose of X-ray by the triple GEMs detector reaches to the pecific value and the divider resistance needs to re-select, even the several separate HV channels mode should be considered. It will keep the constant of the working voltage of the GEM detector without the saturation effect and gain variation and the performance of GEM detector is stable.     

CEE-TPC中GEM读出探测器传输性能实验研究

气体电子倍增器(GEM)因其具有较好的位置分辨以及各项同性的二维结构等优点，近年来受到了广泛的关注，在HIRFL-CSR上正在建设的低温高密核物质测量谱仪(CEE)也计划使用GEM作为TPC的读出探测器。不同电场条件下GEM探测器的传输特性对探测器的有效增益及能量分辨有较大影响。文中研究了单层GEM探测器中漂移区电场及感应区电场对探测器传输特性的影响；随后研究了双层GEM探测器的电压分配及传输区电场对探测器电荷传输性能的影响。结果表明，在单层及多层GEM探测器中，漂移区电场、传输区电场及感应区电场主要通过改变电子透过率和GEM雪崩电场强度及分布影响探测器的电荷传输性能，进而影响探测器的有效增益及能量分辨。以上实验结果表明GEM探测器是CEE-TPC读出探测器的理想选择，同时测试结果也为TPC中多层级联GEM工作点的选择提供了参考依据。     

新型涂硼热中子MWPC探测器的时间信号读出方法

基于10B薄膜的二维灵敏探测器是新近发展起来的热中子探测器,其灵敏面积大,时间和位置分辨好,n/抑制能力高,抗辐射能力强,可二维读出且具有良好的耐计数能力。针对新型的涂硼灵敏热中子多丝正比（MWPC）探测器,在延迟线时间差方法的基础上,提出一种中子击中位置数字信息的读出方法,并设计NIM读出插件用以验证该方法对于二维中子探测位置信息的读出能力。测试结果表明,本方法能完成4通道探测器信号的实时测量,其时间测量精度好于50 ps。结合FPGA片上系统实时数据控制和处理技术,单插件可支持最高1.3MHz的探测计数率。     

基于LC延迟电路的双层多丝正比室的研制

描述了为兰州放射性粒子束流线（RIBLL Ⅱ）上测量束流径迹而研制的一种基于LC延迟电路的双层多丝正比室（MWPC）。该探测器的探测灵敏面积为100 mm×80 mm,位置信号由阴极丝引出并通过LC延迟电路读出。探测器由两套完整的多丝正比室组成,每套的阳极丝夹在两层平行的阴极丝之间,阳极丝和阴极丝相互垂直。两套阴极丝相互垂直给出入射粒子的二维位置信息。为了增大感应信号以提高探测效率,将每套位置对应的阴极丝合并成一路接入LC延迟电路。用55Fe-5.9 keV X射线源均匀照射探测器的灵敏区域,测试表明其具有良好的位置灵敏一致性。用X射线源通过准直狭缝扫描整个探测器的灵敏区域,得到X,Y层的位置线性度均好于0.999;其位置分辨（σ）分别为199.9 μm和154.0 μm,目前,该探测器已成功用于RIBLL Ⅱ的实验中。A double-layer Multi-Wire Proportional Chamber (MWPC) with 100 mm×80 mm active area has been developed for Radioactive Ion Beam Line in Lanzhou(RIBLL Ⅱ). The position information has been obtained by a LC delay circuit readout method. Being called of double-layer MWPC, it is composed of two full MWPCs, each consists of an anode plane sandwiched between two parallel cathode planes, anode wires and cathode wires are perpendicular to each other. In order to improve the detection efficiency, the cathode wires of corresponding position are combined to enhance inductive signal. The cathode wires of two full MWPCs are orthogonally placed to give two coordinates of the incident particles. The sensitivity uniformity is also found to be relatively good and the position resolution of X, Y direction are measured to be 199.9 and 154.0 μm using a 55Fe-5.9 keV X ray, respectively. The position linearity of X, Y direction are as good as 0.999 for whole sensitive area of the detector. The detector has been used successfully on the experiment at RIBLL Ⅱ.