基于GEM探测器的阻性阳极二维插值读出方法研究

For the traditional strip readout of micro-pattern gaseous detector, a large number electronic readout channels are required to improve the position resolution, which leads to an enormous increase in the cost of detector construction. So the two-dimensional interpolating readout method with resistive anode based on gas electron multiplier (GEM) and its corresponding two dimensional position reconstruction method will be studied in this project for the demand of two dimensional position sensitive detectors to Beijing synchrotron radiation facility (BSRF). We will develop a resistive anode readout structure with large area pad, whose dimension is as large as square cm. Measure and analyze the distribution and diffusion of the electron bunch in the resistive readout pads, in different conditions of working gas, electric field. Study the relationship between the position resolution and count rate capability of the detector and the parameters of the resistive readout structure. Optimize the design of the resistive structure to improve the performance of the detector. Finally develop a GEM prototype with the two-dimensional interpolating resistive readout structure, which should be used for the synchrotron radiation measurement in the energy range of 10keV. The realization of this two dimensional interpolating readout method with resistive anode for GEM detector will not only meet the BSRF application demanding high count rate capability (>100kHz) and high position resolution (<200μm), but also reduce the number of readout electronics efficiently, and save the cost of the detector construction. In addition, the resistive anode readout structure can relieve the discharge of GEM detector, and make the detector robust and stable working at the high count rate, which will promote the application of the two dimensional position sensitive GEM detector in BSRF.

鉴于北京同步辐射装置对二维位置灵敏探测器的实际需求，本项目针对微结构气体探测器传统的读出条读出方法，提高位置分辨需要匹配大量读出电子学通道而造成建造成本剧增的问题，研究基于GEM探测器的阻性阳极插值读出方法及其二维位置重建算法。研制较大面积Pad（cm量级）的阻性阳极读出结构，分析不同工作气体、不同电场下，阻性读出Pad上电子束团扩散、收集过程，研究探测器的位置分辨、计数能力等性能与阻性读出结构参数之间的关系。优化设计阻性结构，提高探测器性能，研制可用于同步辐射10keV能量范围内的阻性阳极插值读出GEM探测器。该读出方法的实现在保证探测器满足同步辐射测量高计数率（>100kHz）和高位置分辨率（<200μm）的条件下，能够有效减少读出电子学通道，降低探测器的研制成本，提高GEM探测器在高计数率下的工作稳定性，推动GEM探测器在同步辐射上的应用。

鉴于北京同步辐射装置对二维位置灵敏探测器的实际需求，本项目针对微结构气体探测器传统的读出条读出方法，提高位置分辨需要匹配大量读出电子学通道而造成建造成本剧增的问题，研究基于GEM探测器的阻性阳极插值读出方法及其二维位置重建算法。开发了一套模拟算法研究分析阻性读出pad上电子束团扩散、收集过程，研究了阻性阳极读出板各参数对探测器性能的影响，完成了阻性读出阵列结构的优化设计及研制。开发了多种二维位置重建算法，尤其是346节点加权重建算法可以实现很好的二维位置重建，最大限度地减小了成像畸变。研制出了灵敏面积为100mm×100mm的阻性阳极读出GEM探测器样机，并利用8 keV X射线对其性能进行了细致的测试研究，测试结果表明，探测器具有很好的位置分辨率（107μm @ 8 mm cell size）、较高的计数能力（130kHz/cm2），并具有良好的二维成像能力。同时，由于采用了cm量级pad的阻性阳极读出阵列结构，该探测器相较二维条读出结构，节省了约一半的读出电子学通道，相较pad读出结构，读出通道数更是实现了数量级规模的节省。阻性阳极读出方法的深入研究，特别是它在GEM探测器上的成功应用，为气体探测器，尤其是二维射线成像探测器的读出方法提供了新的备选方案，其节省电子学的能力将促进微结构气体探测器在X射线成像和中子成像等领域的应用。同时，该研究也对采用类似读出结构的固体探测器等具有重要的借鉴意义。