碲锌镉像素阵列核探测器及其电子学设计
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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 Cs~(137)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Cs~(137)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Cs~(137)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。
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 Cs~(137) 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 Cs~(137). 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.
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 Cs~(137)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Cs~(137)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Cs~(137)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。
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 Cs~(137) 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 Cs~(137). 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.
引文
[1] T.Asahl, A. Oda, Y. Taniguchi, et a1. Growth and characterization of 100 mm diameter CdZnTe single crystals by the vertical gradient freezing method[J]. Crystal Growth, 1996, 161(4): 20-27.
[2] M. Richter, P. Siffert. High resolution gamma ray spectroscopy wjm CdTe detector Systems[J]. Nucl. Instr. and Meth A, 1992, 32(2): 529-537.
[3]吴治华等.原子核物理实验方法[M].北京:原子能出版社, 1997: 201-206.
[4] D. S. McGregor, H. Hermon[J]. Nucl. Instr. Meth A. 1997,395(1): 101-134.
[5] C. Matsumoto, T. Takahashi and K. Takizawa et al. Performance of a new Schottky CdTe detector for hard X-ray spectroscopy[J]. IEEE Trans. Nucl. Sci. 1998, 45(3): 428-432.
[6] SchieberM, CarlsconR, SchneppleW. Preliminary Studies of Charge Carrier Transport in .Mercuric Iodide Radiation Detectors[J]. IEEE Trans. Nucl. Sci. 1974, 21: 305-314.
[7]丁洪林.核辐射探测器[M].哈尔滨:哈尔滨工业大学出版社, 2009: 371-372.
[8] J. J. Kennedy, et al.红外[M]. 1989(3): 13-8.
[9]李奇峰等.碲锌镉单晶成长的研究[J].广西师范大学学报.2000, 2: 7-9.
[10]韦永林.碲锌镉探测器的制备及性能研究[D].成都:四川大学,2005: 16.
[11] T.E.Schlesinger, J. E. Toney, H.Yoon et al. Cadmium zinc telluride and its use as a nuclear radiation detector material[J]. Materials Science and Engineering R. 2001, 32: 103-189.
[12] Eisen Y. Current State-of-the-art Industrial and Research Applications Using Room Temperature CdTe and CdZnTe Solid State Detectors[J]. Nucl. Instr. And Meth, 1996, A380: 431-439.
[13]张冬敏. CZT核辐射探测器的电极研究[D].成都:四川大学, 2007: 7-18.
[14]王孝忠.核辐射物理学[M].北京:原子能出版社, 1981: 135-142.
[15] M. M. Sechieber. Capabilities of mercuric iodide as a room temperature x-ray detector[J]. IEEE Trans. Nucl. Sci, 1976, NS23: 102-111.
[16] G.D. Geronimo, P. O Connor, et a1. A Generation of CMOS Readout ASICs for CZT detectors[J]. IEEE Trans. Nucl. Sci, 2000, 47(6): 642-647.
[17] T. H. Lee, S. B. Hong. An 8-Channel CMOS Low-Noise Fast Readout IC for CZT X-Ray Detectors Designed by Time-Domain Hspice Noise Simulation[J]. IEEE Trans. Nucl. Sci, 2003, 46(6): 892-895.
[18] http://www.cremat.com[EB/OL].
[19] N.Bingefors, S. Bouvier,S.Giodmski, et al. A novel technique for fast pulse-shaping using aslow amplifier at LHC[J]. IEEE Trans. Nucl. Sci. 1993, A326: 112-119.
[20] J. Lu, P. Figuera, F.Amorini.Pulse shape discrimination of charged particles with a silicon strip detector[J]. IEEE Trans. Nucl. Sci, 2001, A471(3): 374-379.
[21]李小刚,苏弘,张殿胜等.线性脉冲放大器[J].核电子学与探测技术, 1999, 119(13): 224-226.
[22]蔡欣,肖沙里等.基于碲锌镉探测器脉冲整形电路设计[J].光电子技术,2010,30(1): 64-67.
[23] E.Liptac Jr. Lower Hybrid Modeling and Experiments on Alcator C-Mod[J]. MASSACHUSETTS INSTITUTE OF TECHNOLOGY, 2006, 5(5): 115-116.
[24] Huelsman L. P. and P. E. Allen. Electronic Circuit Analysis and Design [M]. New-York: Mc Graw-Hill Book Company, 2000.
[25] Puncochar J. Analysis of Sallen and Key low-pass filters with real operational amplifiers[J]. TRANSACTIONS of the VSB - Technical University Ostrava, 1999,5(1).
[26] Alexei V. N, Ruslan L. D, Thoms P. A. Analog multivariate counting analyze[J]. Nuclear Instruments and Methods in Physics Research, 2003, 496(2-3): 465-480.
[27]邵建辉,李坚.谱仪放大器中滤波成形电路的一种改进设计[J].核电子学与探测技术, 2006, 26(5): 646-648.
[28]贾新章等. OrCAD/PSpice实用教程[M].西安:西安电子科技大学出版社, 1999.
[29] http://www.national.com[EB/OL].
[30] http://www.ti.com[EB/OL].
[31]席德明.常用核电子技术[M].北京:科学出版社, 1982.
[32] G.Bertucci,C. Canali and F. Nava,The influence of the charge trapping in gallium arsenide radiation detectors[J]. SPIE, 3446: 10-16.
[33]夏军. CdZnTe电容性Frisch栅探测器的电极设计及制备工艺研究[D].上海:上海大学, 2007: 52.
[34] Barrett H H, Eskin J D, Barber H B. Charge transport in arrays of semiconductor gamma ray detectors[J]. Phys. Rev. Lett., 1995, 75(5): 156-159.
[35] Narita T, Bloser P, Grindlay J E, et al. Development of gold contacted flip chip detectors with IMARAD CZT[J]. Proc. SPIE, 2000, 89: 4141.
[36]秦克诚,刘培森等.傅里叶光学导论[M].北京:电子工业出版社, 2006: 7.
[37]吴海平.点源法MTF测试技术研究[D].南京:南京理工大学, 2007: 7-9;
[38] Dainty J C, Shaw R. Image science[M]. New York :Academic Press, 1974: 214,152-161.
[39] Accorsi R, Metezler S D. Analytic determination of the resolution equivalent effective diameter of a pinhole collimator[J]. IEEE Transa on Medical Imaging, 2004,23(6): 750-763.
[40]朱宏权.γ射线针孔照相系统的图像复原研究[D].北京:清华大学, 2008: 94-97.
[41] Sudhakar Prasad. Statistical information based performance criteria for Richardson-Lucy image deblurring[J]. Journal of Optical Society of America A, 2002, 19(7): 1286-1296.
[2] M. Richter, P. Siffert. High resolution gamma ray spectroscopy wjm CdTe detector Systems[J]. Nucl. Instr. and Meth A, 1992, 32(2): 529-537.
[3]吴治华等.原子核物理实验方法[M].北京:原子能出版社, 1997: 201-206.
[4] D. S. McGregor, H. Hermon[J]. Nucl. Instr. Meth A. 1997,395(1): 101-134.
[5] C. Matsumoto, T. Takahashi and K. Takizawa et al. Performance of a new Schottky CdTe detector for hard X-ray spectroscopy[J]. IEEE Trans. Nucl. Sci. 1998, 45(3): 428-432.
[6] SchieberM, CarlsconR, SchneppleW. Preliminary Studies of Charge Carrier Transport in .Mercuric Iodide Radiation Detectors[J]. IEEE Trans. Nucl. Sci. 1974, 21: 305-314.
[7]丁洪林.核辐射探测器[M].哈尔滨:哈尔滨工业大学出版社, 2009: 371-372.
[8] J. J. Kennedy, et al.红外[M]. 1989(3): 13-8.
[9]李奇峰等.碲锌镉单晶成长的研究[J].广西师范大学学报.2000, 2: 7-9.
[10]韦永林.碲锌镉探测器的制备及性能研究[D].成都:四川大学,2005: 16.
[11] T.E.Schlesinger, J. E. Toney, H.Yoon et al. Cadmium zinc telluride and its use as a nuclear radiation detector material[J]. Materials Science and Engineering R. 2001, 32: 103-189.
[12] Eisen Y. Current State-of-the-art Industrial and Research Applications Using Room Temperature CdTe and CdZnTe Solid State Detectors[J]. Nucl. Instr. And Meth, 1996, A380: 431-439.
[13]张冬敏. CZT核辐射探测器的电极研究[D].成都:四川大学, 2007: 7-18.
[14]王孝忠.核辐射物理学[M].北京:原子能出版社, 1981: 135-142.
[15] M. M. Sechieber. Capabilities of mercuric iodide as a room temperature x-ray detector[J]. IEEE Trans. Nucl. Sci, 1976, NS23: 102-111.
[16] G.D. Geronimo, P. O Connor, et a1. A Generation of CMOS Readout ASICs for CZT detectors[J]. IEEE Trans. Nucl. Sci, 2000, 47(6): 642-647.
[17] T. H. Lee, S. B. Hong. An 8-Channel CMOS Low-Noise Fast Readout IC for CZT X-Ray Detectors Designed by Time-Domain Hspice Noise Simulation[J]. IEEE Trans. Nucl. Sci, 2003, 46(6): 892-895.
[18] http://www.cremat.com[EB/OL].
[19] N.Bingefors, S. Bouvier,S.Giodmski, et al. A novel technique for fast pulse-shaping using aslow amplifier at LHC[J]. IEEE Trans. Nucl. Sci. 1993, A326: 112-119.
[20] J. Lu, P. Figuera, F.Amorini.Pulse shape discrimination of charged particles with a silicon strip detector[J]. IEEE Trans. Nucl. Sci, 2001, A471(3): 374-379.
[21]李小刚,苏弘,张殿胜等.线性脉冲放大器[J].核电子学与探测技术, 1999, 119(13): 224-226.
[22]蔡欣,肖沙里等.基于碲锌镉探测器脉冲整形电路设计[J].光电子技术,2010,30(1): 64-67.
[23] E.Liptac Jr. Lower Hybrid Modeling and Experiments on Alcator C-Mod[J]. MASSACHUSETTS INSTITUTE OF TECHNOLOGY, 2006, 5(5): 115-116.
[24] Huelsman L. P. and P. E. Allen. Electronic Circuit Analysis and Design [M]. New-York: Mc Graw-Hill Book Company, 2000.
[25] Puncochar J. Analysis of Sallen and Key low-pass filters with real operational amplifiers[J]. TRANSACTIONS of the VSB - Technical University Ostrava, 1999,5(1).
[26] Alexei V. N, Ruslan L. D, Thoms P. A. Analog multivariate counting analyze[J]. Nuclear Instruments and Methods in Physics Research, 2003, 496(2-3): 465-480.
[27]邵建辉,李坚.谱仪放大器中滤波成形电路的一种改进设计[J].核电子学与探测技术, 2006, 26(5): 646-648.
[28]贾新章等. OrCAD/PSpice实用教程[M].西安:西安电子科技大学出版社, 1999.
[29] http://www.national.com[EB/OL].
[30] http://www.ti.com[EB/OL].
[31]席德明.常用核电子技术[M].北京:科学出版社, 1982.
[32] G.Bertucci,C. Canali and F. Nava,The influence of the charge trapping in gallium arsenide radiation detectors[J]. SPIE, 3446: 10-16.
[33]夏军. CdZnTe电容性Frisch栅探测器的电极设计及制备工艺研究[D].上海:上海大学, 2007: 52.
[34] Barrett H H, Eskin J D, Barber H B. Charge transport in arrays of semiconductor gamma ray detectors[J]. Phys. Rev. Lett., 1995, 75(5): 156-159.
[35] Narita T, Bloser P, Grindlay J E, et al. Development of gold contacted flip chip detectors with IMARAD CZT[J]. Proc. SPIE, 2000, 89: 4141.
[36]秦克诚,刘培森等.傅里叶光学导论[M].北京:电子工业出版社, 2006: 7.
[37]吴海平.点源法MTF测试技术研究[D].南京:南京理工大学, 2007: 7-9;
[38] Dainty J C, Shaw R. Image science[M]. New York :Academic Press, 1974: 214,152-161.
[39] Accorsi R, Metezler S D. Analytic determination of the resolution equivalent effective diameter of a pinhole collimator[J]. IEEE Transa on Medical Imaging, 2004,23(6): 750-763.
[40]朱宏权.γ射线针孔照相系统的图像复原研究[D].北京:清华大学, 2008: 94-97.
[41] Sudhakar Prasad. Statistical information based performance criteria for Richardson-Lucy image deblurring[J]. Journal of Optical Society of America A, 2002, 19(7): 1286-1296.