Images of triple gas electron multiplier with pixel-pads

Testing of a triple gas electron multiplier （GEM） with pixel-pads is described. Images by scanning and suspending radioactive sources were obtained by using 96 channels digital data acquisition （DAQ） system which was composed of 96 8×8 mm2 pads and associated electronics channels.

Recent Achievement of Gas Electron Multiplier

Gas electron multiplier (GEM) as a novel gas detector,due to it’s simple structure,high performance,well compatibility etc.,is widely used in high-energy physics,nuclear physics and other fields.In this review,the principle,recent achievements,developments and applications of GEM are mainly described.

GEM探测器延迟线读出方法的模拟研究

采用MATLAB-Simulink环境下的SimPowerSystem程序,对GEM探测器的延迟线读出方法进行了模拟和计算。介绍了延迟线读出电路模型的建立方法,给出了相关的模拟和测试结果。

Experimental study on the performance of a single-THGEM gas detector

A kind of thick GEM-like gaseous electron multiplier （THGEM）, which is mechanically an expansion of the GEM with its various dimensions being enlarged, is studied. The leak current of THGEM plates is measured. The effective gain and energy resolution of a single THGEM are studied with a source of 55Fe, and the effective gain of the single THGEM versus the electric field strength in the induction region is investigated. The results show that the leak current of THGEM plates is less than 200 pA. In an atmospheric-pressure standard gas mixture, 8×103 effective gain and about 32% energy resolution can be reached for the single-THGEM detector.

应用于厚型气体电子倍增器的高耐压PCB研究

厚型气体电子倍增器（Thick Gaseous Electron Multiplier，THGEM／TGEM）在高能物理实验中有广泛应用，如X射线、带电粒子及中子的探测和成像等领域。THGEM的制作通过印制电路的钻孔、蚀刻和外形等工艺来实现，并要求具有高耐压、强电场、小孔间距和高孔位精度等特点。本文将根据THGEM的以上特点，分析其对PCB在材料选择、设计和工艺制程等方面的特殊要求，并通过对比各条件的产品性能数据给出应用于高性能THGEM制作的PCB解决方莱。

基于厚GEM的宽量程γ剂量率探测器研究

厚型气体电子倍增器是一种近10年迅速发展并逐步在多个领域得到应用的气体探测器,具有死时间小、动态范围大、n/γ排斥比高等优点。除了在高能粒子探测、辐射成像等方面的应用外,厚GEM在辐射防护领域也表现出较好的应用潜力。该研究对厚GEM进行建模,仿真计算不同结构、不同灵敏区尺寸以及不同GEM膜厚度时,厚GEM探测器对γ射线的探测效率,在此基础上采用新型基底材料和自主印制电路板技术设计并制作了具有良好稳定性的厚GEM膜,其单层增益可达2×10^(4),工作电压范围超过150 V,探测效率满足辐射监测的需求。利用新研制的GEM膜制作了探测器,设计并搭建了计数模式和电流模式两种信号读出电路。经测试,该探测器对^(137)Cs和^(60)Co的γ射线实现了0.3×10^(−6) Gy/h~8 Gy/h宽量程范围的γ剂量率监测。

新型M-THGEM结构探测器的蒙特卡罗模拟研究

新型多层厚型气体电子倍增器(Multi-layers THick Gas Electron Multiplier,M-THGEM)和传统THGEM(厚型气体电子倍增器)相比,具有连续的雪崩区,能够在低气压和低电压下都有较高增益,结构更紧凑,易于大面积制作等优势。对M-THGEM探测器的工作原理及性能进行了模拟研究,首先通过有限元(ANSYS)软件对二层与三层结构的M-THGEM进行了建模,对电场和电势分布分别进行了模拟计算;再利用Garfield++程序包对M-THGEM探测器在不同低气压和不同工作电压下的增益、感生信号、正离子反馈率等性能进行了研究。模拟结果表明,三层结构M-THGEM在低气压(200 Torr)、纯He气体条件下,能够获得较稳定的增益(10~5),输出信号的宽度在12 ns左右;同时,为降低正离子反馈率,本工作提出并研究了一种非对称的电压施加方式,结果表明,这种施加方式能有效降低正离子的反馈率。

Spatial resolution optimization in a THGEM-based UV photon detector

Introduction THick Gas Electron Multiplier(THGEM)is considered in many UV photon detector applications.It has the capability of detecting single photon and imaging with high sensitivity.Operating parameters such as choice of gas mixture,pressure,drift field,drift gap,multiplication voltage,induction field and induction gap play an important role in deciding the spatial resolution of the detector.Detailed simulation study enables to optimize the above-mentioned parameters for a given THGEM-based imaging detector and hence to achieve improved performance for the same.Materials and methods Simulation,using ANSYS and Garfield++,starts with the release of primary electrons at random coordinates on the photocathode plane.They are tracked as they pass through the drift gap and THGEM hole till the electron cloud reaches anode plane.Distribution of electron cloud on the anode plane along X and Y axis is plotted in histogram and fitted with Gaussian function to determine spatial resolution.Ar/CO_(2)(70:30)mixture,which shows higher ETE and lower transverse diffusion,is chosen for this simulation study.Conclusion Transverse diffusion has a major impact on both ETE and the spatial resolution.Lower transverse diffusion coefficient is always desired for having better resolution as well as for ETE.It is found from the simulation study that higher gas pressure,lower drift field and induction field,smaller drift and induction gap can provide optimum detection efficiency with the best spatial resolution.The simulation method proposed here can also be extended to X-ray imaging detectors.

Monte Carlo simulation of GEM-based for 14 MeV neutron detector

A new concept of neutron detector based on Gas Electron Multiplier(GEM) technology is presented in this paper,in which a novel multi-layer high density polyethylene(HDPE) as neutron-to-proton converter is proposed and studied with Geant4 toolkit for fast 14 MeV neutron.Our preliminary results show that the detection efficiency of the detector with 400 converter units is higher than 2.3% and reconstruction accuracy of the incident neutron position is higher than 2.6%.

Design and construction of a TPC prototype based on GEM detector readout

A time projection chamber （TPC） readout by gas electron multipliers （GEM） detector is a very promising candidate for the central tracking system of ILC （International Linear Collider）. A prototype is designed and set up in our lab and introduced here. The tests during and after the assembly prove that the prototype TPC has been constructed successfully. It is ready for further study.

Study on the novel neutron-to-proton convertor for improving the detection efficiency of a triple GEM based fast neutron detector

A high-efficiency fast neutron detector prototype based on a triple Gas Electron Multiplier（GEM） detector, which, coupled with a novel multi-layered high-density polyethylene（HDPE） as a neutron-to-proton converter for improving the neutron detection efficiency, is introduced and tested with the Am-Be neutron source in the Institute of Modern Physics（IMP） at Lanzhou in the present work. First, the developed triple GEM detector is tested by measuring its effective gain and energy resolution with55 Fe X-ray source to ensure that it has a good performance.The effective gain and obtained energy resolution is 5.0×104and around 19.2%, respectively. Secondly, the novel multi-layered HDPE converter is coupled with the cathode of the triple GEM detector making it a high-efficiency fast neutron detector. Its effective neutron response is four times higher than that of the traditional single-layered conversion technique when the converter layer number is 38.

Discriminating cosmic muons and X-rays based on rise time using a GEM detector

Gas electron multiplier （GEM） detectors have been used in cosmic muon scattering tomography and neutron imaging over the last decade. In this work, a triple GEM device with an effective readout area of 10 cm × 10 cm is developed, and a method of discriminating between cosmic muons and X-rays based on rise time is tested. The energy resolution of the GEM detector is tested by 55Fe ray source to prove the GEM detector has a good performance. Analysis of the complete signal-cycles allows us to get the rise time and pulse heights. The experiment result indicates that cosmic muons and X-rays can be discriminated with an appropriate rise time threshold.

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.