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…     

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.     

A study of gas electron multiplier

A new kind of gas detector based on gas electron multiplier (GEM) is studied for X-ray imaging of high luminosity. A single-GEM device is designed to test the prnperty of GEM foil ,The effective gain and counting capability of a double-GEM detector are measured by an X-ray tube with Cu target. An initial X-ray imaging experiment is carried out using a triple-GEM detcctor and the position iesolution of less than 0.1mm is achieved. The 3D distribution of electrostatic field of GEM mesh is also presented.     

一种新的气体电子倍增模式的研究

介绍了一种新的气体放大器件--GEM,制作了一个有效面积为100mm×100mm的GEM+MWPC的模型.用5.9 keV的X射线源测量它的气体倍增系数,并研究了不同气体比例(Ar/CO2)下GEM的放大的性能.GEM的放大倍数可达到94倍.     

Pressure Dependence of the Relativistic Rise in Neon and Highest Attainable Ionization Sampling Resolution in Neon, Argon, Ethylene and Propane

A full-scale detector segment with 128 samples of 2 cm and a 50 cm drift space was used to measure precisely the relativistic rise of ionization from 5 to 70 GeV/c in Ne at 1, 2 and 4 atm. The pressure dependence of dE/dx resolution and of particle separation efficiency was determined at 15 GeV/c in several Ne/CnHm mixtures, in Ar/CH4, pure C2H4 and pure C3H8. The results are used for optimization of parameters of a compact colliding beam detector suitable for particle identification up to the 30-50 GeV/c momentum range. The ?/K/p separation is found to be better in Ne, but extends to higher momenta in Ar. Ar is more efficient for e/? separation. The gain in resolution at higher pressures is to certain extent compensated by reduction of the relativistic rise slope, so that the separation efficiency is reduced when the detector dimensions are scaled down with pressure. At 4-5 atm. we obtained slightly better resolution than the 6.0% FWHM (? = 2.5%) record performance of the EPI. In pure C3H8 a resolution below ? = 2.0% was reached. Measurements of drift velocities in various Ne mixtures are presented, showing saturated behaviour already at low E/p values.     

基于峰值保持电路的GEM探测器前端读出ASIC设计

介绍了一种用于多层GEM探测器的低噪声前端读出ASIC芯片.针对GEM探测器输出信号特点,设计了电荷灵敏放大器、整形电路和峰值保持电路,并对其噪声、成形时间等设计指标参数进行了分析.     

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.     

基于APV25读出电子学系统的GEM探测器的位置分辨与X射线成像研究

采用3层GEM膜制作了有效面积为10 cm×10 cm的GEM探测器,该探测器采用二维条读出方式,条间距为400 μm,每个维度有256个读出通道。探测器的读出采用APV25读出电子学系统,根据GEM探测器的需要,设计并改进了电子学系统使用的背板连接器。实验测得GEM探测器空间分辨为76 μm。进行了X射线二维成像研究,获得了清晰的二维图像,探测器与电子学运行稳定可靠。     

TOF-PET探测器定时性能初步研究

本工作采用LYSO晶体阵列和平板型位置灵敏光电倍增管H8500对TOF-PET探测器进行了初步设计,能分辨3.2mm×3.2mm的晶体阵列。与BaF₂探测器组成时间谱仪,测量正电子湮没射线的瞬发时间谱,得到379ps的符合时间分辨率。根据已测量的BaF₂探测器时间分辨率（159ps）,可计算得到所设计的TOF-PET探测器时间分辨率为344ps。预计与此相同的两个TOF-PET探测器对正电子湮没射线的符合时间分辨率可达486ps左右,为新型PET的研究提供了有利条件。     

Use of Cramer-Rao Lower Bound for Performance Evaluation of Different Monolithic Crystal PET Detector Designs

We have previously reported on continuous miniature crystal element (cMiCE) PET detectors that provide depth of interaction (DOI) positioning capability. A key component of the design is the use of a statistics-based positioning (SBP) method for 3D event positioning. The Cramer-Rao lower bound (CRLB) expresses limits on the estimate variances for a set of deterministic parameters. We examine the CRLB as a useful metric to evaluate the performance of our SBP algorithm and to quickly compare the best possible resolution when investigating new detector designs.In this work, the CRLB is first reported based upon experimental results from a cMiCE detector using a 50×50×15-mm(3) LYSO crystal readout by a 64-channel PMT (Hamamatsu H8500) on the exit surface of the crystal. The X/Y resolution is relatively close to the CRLB, while the DOI resolution is more than double the CRLB even after correcting for beam diameter and finite X (i.e., reference DOI position) resolution of the detector. The positioning performance of the cMiCE detector with the same design was also evaluated through simulation. Similar with the experimental results, the difference between the CRLB and measured spatial resolution is bigger in DOI direction than in X/Y direction.Another simulation study was conducted to investigate what causes the difference between the measured spatial resolution and the CRLB. The cMiCE detector with novel sensor-on-entrance-surface (SES) design was modeled as a 49.2×49.2×15-mm(3) LYSO crystal readout by a 12×12 array of 3.8×3.8-mm(2) silicon photomultiplier (SiPM) elements with 4.1-mm center-to-center spacing on the entrance surface of the crystal. The results show that there are two main causes to account for the differences between the spatial resolution and the CRLB. First, Compton scatter in the crystal degrades the spatial resolution. The DOI resolution is degraded more than the X/Y resolution since small angle scatter is preferred. Second, our maximum likelihood (ML) clustering algorithm also has limitations when developing 3D look up tables during detector calibration.     

用于HL-2A装置的新型硬X射线探测器

介绍了一种应用于托卡马克等离子诊断领域的新型硬X射线探测器,该探测器主要由硅酸钇镥(Lutetium-yttrium Oxyorthosilicate,LYSO)闪烁体和硅光电倍增管(Silicon Photomultiplier,Si PM)组成。基于项目应用需求,对探测器的选型和基于粒子输运蒙特卡罗仿真软件GEANT4的探测器设计加以阐述,并搭建了前端的探测系统,在HL-2A托卡马克装置上进行了现场诊断实验。实现了硬X射线空间能谱和辐射强度分布的诊断测量。实验表明该探测器阵列具有10 ms的时间分辨率,同时具有结构紧凑、使用方便等特点,能够满足等离子体诊断中硬X射线动态能谱和强度分布测量的诊断需求。     

应用于气体电子倍增器的电子学板研制

气体电子倍增器（GEM）电子学板（GEB）在大面积GEM探测器系统中起重要作用。为满足大面积GEM探测器系统中高速电子学信号的传输、实现电磁屏蔽及为前端电子学提供电源等需求,本文设计了8层结构的GEB,并对该GEB原型进行了电气性能、机械兼容性、信号传输和噪声测试。测试结果显示,本文所设计的GEB在320 Mb/s信号传输速度下的误码率小于10^-13,在保证信号高速性和完整性的基础上能成功传输前端电子学信号;通过采用叠层对称式设计克服了大面积GEB生产时弯曲程度高的困难,生产的GEB原型弯曲高度降低了2/3,平均弯曲高度为1 mm,增强了前端电子学在探测器系统中的运行稳定性。     

Amplification process of a gas electron multiplier simulated by PIC-MCC model

The performance of a single gas electron multiplier(GEM) in pure Xe at an atmospheric pressure is investigated by Particle in Cell-Monte Carlo Collision(PIC-MCC) model.The micro development processes with electrons and ions distributions in space have been revealed.Based on the micro development processes,the macroscopic parameters such as GEM gain and the effective efficiency have also been obtained.The simulation results indicate that after tens of nanoseconds,electrons are collected by the readout electrode while the ions still exist in the gas space for several microseconds.The main signal current is formed by the electrons arriving at the readout electrode,but electrons and ions are also collected by the copper electrodes near the GEM hole and the thin Kapton film boundary.The simulated gain of GEM exponentially increases with the applied GEM voltage.With the PIC-MCC simulations,both the physical amplification and charging mechanisms in the GEM device can be well understood,which is beneficial to the device design.     

Study of 18-cm long single-sided AC-coupled silicon microstripdetectors

The SSC GEM silicon Central Tracker design incorporated 18-cm long single-sided AC-coupled silicon microstrip ladders. Compared to the 12-cm long ladders considered in the preliminary stages of the tracker design, the 18-cm long ladders have the advantage of reduced cost, channel count and overall power consumption, and led to a simplified tracker assembly. However, such long ships also present the challenge of maintaining satisfactory performance. The increased capacitance and series resistance contribute to lower signal-to-noise ratios, longer time walk, higher power consumption per channel and increased probability of crosstalk to neighboring channels. In this paper, an accurate method to calculate the geometric capacitance of the AC-coupled microstrips is presented and the calculated results are compared with measurements, SPICE simulations are performed to predict the noise, the extent of interstrip capacitive coupling and the dispersion of the detector signal due to the finite series resistance of the metal strips and the long length of the detector. The influence of the preamplifier current and the shaping time on the signal and noise levels is also presented. The study concludes that the 18-cm long ladders can successfully satisfy the performance goals of the GEM silicon Central Tracker     

蓬勃发展的位置灵敏气体探测器

介绍了近年来气体位置灵敏探测器的发展,简要描述了几种新型的高位置分辨、高计数率的探测器：MSGC、MGC、MICROMEGAS、GEM等。     

GEM探测器基线值获取和数据零压缩阈值的设定

针对X射线成像GEM探测器,分析了3种基线值获取方法,给出零压缩阈值的最佳设定方法。测试结果表明,采用文中方法给出的零压缩阈值对数据进行零压缩可有效提高数据的有效利用率,从而提高探测器的计数率。在相同时间内,统计量大大提高,也有效改善了探测器的二维成像质量。     

高分辨X射线成像器件——微间隙室(MGC)的研究

详细讨论了微间隙室的基本结构、特性及其主要研究内容;并在此基础上,探讨了微间隙室采用金刚石薄膜作为阳极电极微条和阴极电极微条之间的极间绝缘材料的可能性和有效性。为在第三代同步光源上实现具有良好时间和空间分辨的成像实验或衍射实验,提供了一种潜在的辐射成像探测器。     

应用于PandaX-Ⅲ实验探测器测试平台的Bulk Micromegas性能研究

探测无中微子双贝塔衰变的PandaX-Ⅲ实验需要一个能同时对多个Micromegas探测器的增益、能量分辨、坏道分布、位置分辨等性能参数进行测试的平台,为此中国原子能科学研究院建立了PandaX-Ⅲ实验探测器测试平台。本文采用由光蚀刻技术制作的Bulk Micromegas对该测试平台进行研究：利用⁵⁵Fe放射源在Ar+10%CO₂的流气情况下,使用基于AGET读出芯片制作的通用读出电子学进行数据采集;运用C++与ROOT软件库编写相应的后端数据分析软件,并对数据进行了分析。测试结果表明,PandaX-Ⅲ实验探测器测试平台各系统工作状态良好,应用于测试平台的Bulk Micromegas探测器具有良好的信噪比,X射线成像效果清晰,对5.9 keV X射线的能量分辨率为19.7%。     

薄型较大面积THGEM气体探测器的研制

为满足环形正负电子对撞机项目配置的需要,研制了薄型较大面积THGEM气体探测器。该探测器工作时不需要额外的腔室,并且其厚度能达到8 mm,较原来的11 mm有明显减少。其有效面积为20 cm×20 cm,其增益在Ar/iC_4H_(10)(97/3)工作气体中能达到10~4倍,最好能量分辨为30%,增益均匀性能达到88.5%,探测器增益也呈现出较好的长期稳定性。     

Validation of a NaI(Tl) detector's model developed with MCNP-X code

The Monte Carlo method was used to calculate the photon detection efficiency and energy resolution curves for a 1.5″ × 1″ NaI(Tl) scintillator detector (crystal + housing + photomultiplier tube material equivalent) exposed to gamma rays in the energy range from 20 keV to 662 keV. This work aims to design a precise computational model, based in Monte Carlo simulation, which can be used in practical application. The energy resolution curve was used to improve the response of the mathematical simulation of the detector. The detector was modeled with the MCNP-X code and the results were compared to experimental photopeak efficiency measurements of radiation sources. The results showed good agreement with the experimental data.