【作者】 蔡欣；

【导师】 肖沙里；

【作者基本信息】 重庆大学 ， 仪器科学与技术， 2011， 硕士

【摘要】 碲锌镉（CdZnTe,CZT）核辐射探测器是一种新型三元化合物半导体探测器,具有能量分辨率高、本征探测效率好、禁带宽度大、电阻率高、体积小、重量轻、可在室温下使用等优点,可广泛应用于X、γ射线成像装置中,在国防、天体物理研究、环境监测、医疗成像等领域有着广阔的应用前景。CZT探测器近年来倍受人们的关注,已成为世界各国研究的前沿热点。本文分析和总结了近年来国内外研究学者在CZT核辐射探测技术领域的最新进展,对CZT像素阵列核辐射探测成像系统进行了研究,主要研究工作如下:①以CZT像素阵列核辐射探测器为研究对象,分析了工作原理及其CZT晶体的特性,讨论了CZT像素阵列核辐射探测成像系统组成。②针对CZT像素阵列核辐射探测器输出信号特点设计读出电路。讨论了CZT像素阵列核探测器件用电荷灵敏前置放大器的参数指标,研究分析了电荷灵敏前置放大器对核脉冲信号的响应特性,确定了成像系统的电荷灵敏前置放大器。进一步根据电荷灵敏前置放大器输出信号的特性,完成了整形放大器电路的设计;其主要由放大电路、极零相消电路、直流偏置校正电路、Sallen-Key滤波电路、50Ω线性驱动电路和电源滤波电路构成,最后进行了电路的测试。结果表明,整形放大器能够使不规则脉冲信号变换成标准的准高斯脉冲信号,满足系统要求。③对CZT像素阵列核辐射探测成像系统进行了性能测试,实验在中国人民解放军第三军医大学辐射中心实验室进行,采用了662 keV Cs¹³⁷伽玛源测试了CZT探测器的能量分辨率及峰值效率。实验结果表明,探测器整体能量分辨率较高,各像素能量分辨率主要分布在6.25%～7.5%,各像素峰值效率主要分布在65%～72.5%,像素的峰值效率集中在67.5%左右。④采用Cs¹³⁷圆形放射源进行了探测系统的成像实验,并通过调制传递函数对成像系统进行了评估。实验结果表明,CZT像素阵列核辐射探测成像系统能够探测获得较好的Cs¹³⁷圆形放射源图像。由于噪声、系统影响,图像存在一定的扩散现象。⑤采用Lucy-Richardson算法对原始图像进行了复原,并对复原后的图像和原始图像进行了比较与分析。所采用图像复原算法较好地再现了各种边缘信息,图像中心细节得到一定提高,复原图像所得源尺寸最小误差0.5 mm。更多还原

【Abstract】 CdZnTe（CZT） is a new developing compound semiconductor, and has been regarded as leading materials for room temperature nuclear radiation detectors. CZT nuclear radiation detectors have been widely utilized as X-ray andγ-ray telescopes and imaging instruments due to its high energy resolution, high detection efficiency and little bulk. Therefore, it has been a choice for many applications in the field of national security, astrophysics, environmental monitoring and medicine imaging system. In recent years, there is a rapid rise of attention for the investigation of CZT pixel arrays detector. And then, the research of CZT pixel arrays detector becomes a very hot issue on the radiation detection field.This paper analyzes and summarizes the recent achievement of scholars in and abroad for the CZT nuclear detection. The CZT pixel arrays nuclear radiation detection is studied in detail and the main research work is summarized as follows: Firstly, it has been studied the CZT pixel arrays nuclear radiation detector and has analyzed the characteristic of CZT crystal and the principle of CZT detector. Then, the fabrications of various parts of the system are also discussed. Secondly, the readout circuit especially for the CZT pixel arrays detector is presented in detail. The charge sensitive preamplifier is determined based on the requirement of the system characteristic and detector parameters. The designment of the shaper amplifier is accomplished based on the analysis of the preamplifier signal characteristic. The shaper amplifier is comprised of the amplification, the pole-zero cancellation, the DC offset adjust, Sallen-Key filter, 50Ωline driver and power supply filtering. In order to meet the requirement of CZT detector system, experimental results show that the shaper amplifier is to turn irregular pulse signals to standard quasi-gauss pulse signals. The simulation result of this circuit is in good accordance with the experimental result.Thirdly, the performance of the detector imaging system which includes the energy resolution and the peak efficiency has been also tested by using 662 keV Cs¹³⁷ gamma source. Experimental results show that the energy resolution of the CZT pixel arrays detector system distributes in the range of 6.25% and 7.50% for Cs¹³⁷. The photon peak efficiency which centers at about 67.5% mainly distributes between 65.0% and 72.5%. The performance of the detector imaging system meets the imaging requirements.Fourthly, the imaging experiment with a circular Cs137gamma source has been accomplished, meanwhile in order to evaluate the imaging system, modulation transfer function has been tested. Experimental results indicate that the source image can be obtained accurately, although there is lateral spread distribution which reduces from the noise.Lastly, the Lucy-Richardson algorithm, which has been also compared and analyzed, is adopted to restore the image degraded. The algorithm can properly retrieve various kinds of edges. Inner area spatial resolution has been obviously. The estimated source diameter has an error of 0.5 mm.更多还原