远紫外光子计数成像读出系统算法设计

发布时间：2018-07-23 14:08

【摘要】：气辉和极光是发生在地球电离层的重要的自然发光现象,它们的产生与太阳活动强度和地磁活动强度息息相关。通过对气辉和极光的远紫外波段探测可以确定电离层的离子和中性粒子的密度、温度、及其随环境的变化情况,为研究磁层-电离层-热层之间能量传输和转换提供依据。远紫外辐射信息几乎不受地球辐射背景的影响,已经成为电离层参量日常监测的理想手段。气辉极光的远紫外辐射属于微弱光信号,利用光子计数技术对微弱光信号进行探测具有和其他模拟探测方法相比的诸多优势,比如有好的抗漂移性、高的灵敏度、高的信噪比、较好的时间稳定性等。基于微通道板的二维探测器是实现微弱气辉探测的理想单光子成像探测器,探测器采用碘化铯的光阴极将入射光子转化为光电子,通过微通道板对光电子进行倍增形成电子云。微通道板出射的电子云保留了原来的光子位置信息,通过阳极收集电荷,并在电子读出电路中计算可以得到光子位置,从而实现对二维图像信号的探测。本课题立足国内外研究现状,以探测气辉极光为目标,围绕远紫外光子计数成像探测器展开研究,主要完成以下工作:(1)使用LabVIEW编写上位机软件,通过控制FPGA完成数据的采集、传输和成像,并对探测器的暗计数、最大计数率等性能指标进行了测试和分析。(2)针对探测器的成像畸变原因,设计了多项式校正算法,使用C语言编写动态链接库实现了校正算法以便上位机软件调用,并通过实验验证了算法的可行性。(3)基于数字化仪NI5105搭建了探测器的高速信号采集系统,对前端电子读出电路的模拟电压信号进行采集并对采集数据进行了波形甄别、位置解码和计数成像,最后对探测器的最大计数率进行了测试,分析了限制探测器最大计数率的原因。
[Abstract]:Gas glow and aurora are important natural luminescence phenomena occurring in the earth's ionosphere. Their generation is closely related to the intensity of solar activity and geomagnetic activity. The density, temperature and variation of ionospheric ions and neutral particles in the ionosphere can be determined by detecting the far ultraviolet band of the gas and aurora, which provides a basis for the study of energy transfer and conversion between the magnetosphere and the ionospheric thermosphere. The information of far ultraviolet radiation is almost independent of the earth's radiation background and has become an ideal method for the daily monitoring of ionospheric parameters. The far ultraviolet radiation of aurora is a weak light signal. The use of photon counting technology to detect weak optical signals has many advantages over other analog detection methods, such as good anti-drift, high sensitivity, high signal-to-noise ratio. Better time stability, etc. Two-dimensional detector based on microchannel plate is an ideal single-photon imaging detector for weak gas luminescence detection. The detector converts incident photon into photoelectron by photocathode of cesium iodide, and multiplies the photoelectron to form electron cloud through microchannel plate. The electron cloud emitted from the microchannel plate retains the original photon position information and collects the charge through the anode and calculates the photon position in the electronic readout circuit so as to realize the detection of the two-dimensional image signal. Based on the current research situation at home and abroad, the research is carried out around the far ultraviolet light counting imaging detector. The main work is as follows: (1) using LabVIEW to write the software of host computer, the acquisition of data is accomplished by controlling FPGA. Transmission and imaging, and the detector's dark count, the maximum counting rate and other performance indicators are tested and analyzed. (2) for the imaging distortion of the detector, a polynomial correction algorithm is designed. Using C language to write dynamic link library to realize the correction algorithm for the host computer software call, and through the experiment to verify the feasibility of the algorithm. (3) based on the digital instrument NI5105 to build the detector high-speed signal acquisition system, The analog voltage signal of the front-end electronic readout circuit is collected, and the collected data are detected by waveform identification, position decoding and counting imaging. Finally, the maximum counting rate of the detector is tested. The reason of limiting the maximum counting rate of the detector is analyzed.
【学位授予单位】：中国科学院大学(中国科学院国家空间科学中心)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P352.7

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