ABSTRACT This paper is about the Gas Electron Multiplier (GEM), a gas detector that will be installed on the new Super BigBite Spectrometer (SBS), under construction at Jefferson Laboratory in Newport News, VA, USA; the main interest of JLAB physics is the study of the fundamental interactions and constituents of hadronic matter and in particular the study of the electromagnetic Form Factors of the nucleons. The Italian group, JLAB12, is engaged in the construction, characterization and commissioning of two of the detectors that will be implemented in SBS: the GEM front tracker and the hadron calorimeter HCAL-J. A Gas Electron Multiplier is a gas detector useful to track the charged particles. It is composed of 2 layers of copper and a layer of Kapton, a dielectric material; all the layers together are inside a box with a mixture of gas: of Argon an of CO. In each GEM foil there are a lot of biconical holes, and it is placed between a drift plane and a readout plane; when a charge particle crosses the gas, it loses energy creating couple ion-electron. If we apply a potential difference, the pairs are accelerated by the electric field, and they have enough energy to create an avalanche. The gain that we can reach with a single GEM foil is 1000. In JLAB's configuration for SBS, a TripleGEMs system will be used; a TripleGEM is composed of 3 GEM foil placed in cascade. The advantages of this technology are: the layers structure, so the primary ionization, the multiplication and the charge collection regions are separated, the high gain about 100,000, the flexibility of geometry, the good spatial resolution about 70 µm, low costs and small streamer or charging up phenomena. To verify GEMs performances and to optimize the digitalization model, we started simulations changing some physical and geometric parameters. In order to run the GEM's simulations, we used two different software: ANSYS Mechanical APDL to create the detector geometry, assign the materials, define the meshes in shape and size and the electric field, and Garfield++, a toolkit for detailed Monte Carlo simulation of a gaseous detector, to evaluate the distribution of the charged particles on the readout plane when we change some parameters like the type of the primary particle, its energy and its incident slope. In particular, we built two different models: a triple GEM model and a cascade model; we are comparing the simulations results with the real test that we did in Juelich (Germany) with a beam of 2.8 GeV protons.

中文翻译：

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在杰斐逊实验室模拟 Triple-GEM 跟踪器对实验的响应

摘要 本文是关于气体电子倍增器 (GEM)，这是一种气体探测器，将安装在美国弗吉尼亚州纽波特纽斯的杰斐逊实验室正在建造的新型 Super BigBite 光谱仪 (SBS) 上；JLAB 物理学的主要兴趣是研究强子物质的基本相互作用和成分，特别是研究核子的电磁形式因素。意大利小组 JLAB12 参与了将在 SBS 中实施的两个探测器的构建、表征和调试：GEM 前跟踪器和强子量热仪 HCAL-J。气体电子倍增器是一种用于跟踪带电粒子的气体探测器。它由2层铜和一层介电材料Kapton组成；所有层一起放在一个混合气体的盒子里：氩气和一氧化碳。每个GEM箔片上有很多双锥孔，位于漂移面和读出面之间；当带电粒子穿过气体时，它会失去能量，产生离子-电子耦合。如果我们施加一个电位差，电场对就会加速，并且它们有足够的能量来产生雪崩。我们可以使用单个 GEM 箔达到的增益为 1000。在 JLAB 的 SBS 配置中，将使用 TripleGEMs 系统；一个 TripleGEM 由 3 个 GEM 箔片级联放置。该技术的优点是：层状结构，初级电离区、倍增区和电荷收集区分开，增益高约100,000，几何形状灵活，70μm左右的良好空间分辨率，成本低，流光小或充电现象。为了验证 GEM 的性能并优化数字化模型，我们开始模拟更改一些物理和几何参数。为了运行 GEM 的模拟，我们使用了两种不同的软件：ANSYS Mechanical APDL 用于创建探测器几何结构、分配材料、定义形状和尺寸的网格以及电场，以及 Garfield++，一个用于详细蒙特卡罗模拟的工具包气体探测器，当我们改变一些参数（如初级粒子的类型、能量和入射斜率）时，评估带电粒子在读出平面上的分布。特别是，我们建立了两个不同的模型：三重 GEM 模型和级联模型；我们正在将模拟结果与我们在 Juelich（德国）用 2.8 GeV 质子束进行的真实测试进行比较。