闪烁伽马能谱仪全谱数据的蒙特卡罗模拟
摘要
多道γ能谱测量在电离辐射环境评价或放射性污染检测中是高效准确的方法,自1986年切尔诺贝利核电站事故以来得到了广泛的应用。NaI(Tl)伽马能谱仪具有探测效率高、可在常温下使用等特点,在航空和现场能谱测量中应用广泛,但是其晶体能量分辨率不高,导致人工核素~(137)Cs的全能峰与~(238)U系~(214)Bi和~(232)Bi和~(232)Th系~(208)Tl的峰重叠,提取人工核素铯比较困难。因此,研究如何快速、准确地提取人工核素~(137)Cs的有用信息,对提高NaI(Tl)闪烁体探测器伽马能谱测量资料的定量解释精度具有重要意义。
本论文应用蒙特卡罗方法,利用MCNP程序对DigiDART碘化钠伽马能谱仪测量的土壤天然放射性核素~(238)U、~(232)Th、40K及人工放射性核素~(137)Cs进行了定量分析。
论文在前人基础上对仪器探测效率重新进行了计算,并得到了仪器探测效率的响应函数。在模拟过程中修改了探测器的几何构造以及物质组成,使模拟的仪器设备参数更符合真实仪器。
模拟了~(137)Cs点源的模拟谱线,通过增加模拟时间提高了模拟数据的精度。模拟谱线比实测谱线在低能端较低,两者主峰位吻合较好,两者峰面积的相对误差在30%以内。
体源模拟加入了更多核素的能量,提高了低能端的康普顿散射计数。同时,考虑了光电效应以及电子对效应,使得模拟结果能更接近真实测量值。通过学习研究模拟值归一方法,修改了扩展因子,使得模拟谱线更接近实测谱线。高于583keV的特征峰模拟数值与实测谱线的特征峰数值相近,误差在20%以内。低于583keV的几个特征峰的康普顿散射坪低于实测值,但主峰位对应较好。
Multi-channelγspectrum of ionizing radiation measurements in the environmental assessment or detection of radioactive contamination is highly efficient and accurate way, since the 1986 Chernobyl accident has been widely used. NaI (Tl) gamma-ray spectrometer with high efficiency, can be used at room temperature, and other characteristics, in the air and in-site measurements in the application of broad spectrum, but its crystal energy resolution is not high, leading to artificial radionuclide the ~(137)Cs And ~(238)U of ~(214)Bi and ~(232)Bi and ~(232)Th peak of ~(208)Tl overlap, artificial isotope cesium extraction more difficult. Therefore, how quickly and accurately extract of the radionuclide ~(137)Cs useful information to enhance NaI (Tl) scintillator detector gamma-ray spectrometry quantitative data to explain the importance of accuracy.
This paper applications Monte Carlo method, using MCNP procedures DigiDART sodium iodide gamma-ray spectrometer measurement of the soil natural radionuclides ~(238)U, ~(232)Th, 40K and artificial radionuclides ~(137)Cs for the quantitative analysis.
In previous papers on the basis of the efficiency of detection equipment were re-calculated, and with the efficiency of detection equipment response function. In the simulation process of amending the geometry of the probe and the material composition, laboratory equipment closer to the real equipment.
Simulation of the 137Cs point source from the detector 10 cm from the analog spectrum, by increasing the simulation time to improve the accuracy of the simulation data. Analog spectrum than measured in the low-low spectrum, the two main peak in good agreement, the two relative error of 30 %.
Yuen joined the simulation of the radionuclide more energy to raise the low end of the Compton scattering count. At the same time, consider the photoelectric effect and electronic effects, makes simulation results can be closer to the real measurement. Through the study on a method to the value of simulation, amended the expansion factor, makes analog spectrum close to the measured spectrum. More than 583keV numerical simulation of the characteristic peaks and measured the spectrum characteristic peak values similar error at 20%. 583keV below the peak of several features of Compton scattering Ping lower than the actual value, but peak corresponds better.
本论文应用蒙特卡罗方法,利用MCNP程序对DigiDART碘化钠伽马能谱仪测量的土壤天然放射性核素~(238)U、~(232)Th、40K及人工放射性核素~(137)Cs进行了定量分析。
论文在前人基础上对仪器探测效率重新进行了计算,并得到了仪器探测效率的响应函数。在模拟过程中修改了探测器的几何构造以及物质组成,使模拟的仪器设备参数更符合真实仪器。
模拟了~(137)Cs点源的模拟谱线,通过增加模拟时间提高了模拟数据的精度。模拟谱线比实测谱线在低能端较低,两者主峰位吻合较好,两者峰面积的相对误差在30%以内。
体源模拟加入了更多核素的能量,提高了低能端的康普顿散射计数。同时,考虑了光电效应以及电子对效应,使得模拟结果能更接近真实测量值。通过学习研究模拟值归一方法,修改了扩展因子,使得模拟谱线更接近实测谱线。高于583keV的特征峰模拟数值与实测谱线的特征峰数值相近,误差在20%以内。低于583keV的几个特征峰的康普顿散射坪低于实测值,但主峰位对应较好。
Multi-channelγspectrum of ionizing radiation measurements in the environmental assessment or detection of radioactive contamination is highly efficient and accurate way, since the 1986 Chernobyl accident has been widely used. NaI (Tl) gamma-ray spectrometer with high efficiency, can be used at room temperature, and other characteristics, in the air and in-site measurements in the application of broad spectrum, but its crystal energy resolution is not high, leading to artificial radionuclide the ~(137)Cs And ~(238)U of ~(214)Bi and ~(232)Bi and ~(232)Th peak of ~(208)Tl overlap, artificial isotope cesium extraction more difficult. Therefore, how quickly and accurately extract of the radionuclide ~(137)Cs useful information to enhance NaI (Tl) scintillator detector gamma-ray spectrometry quantitative data to explain the importance of accuracy.
This paper applications Monte Carlo method, using MCNP procedures DigiDART sodium iodide gamma-ray spectrometer measurement of the soil natural radionuclides ~(238)U, ~(232)Th, 40K and artificial radionuclides ~(137)Cs for the quantitative analysis.
In previous papers on the basis of the efficiency of detection equipment were re-calculated, and with the efficiency of detection equipment response function. In the simulation process of amending the geometry of the probe and the material composition, laboratory equipment closer to the real equipment.
Simulation of the 137Cs point source from the detector 10 cm from the analog spectrum, by increasing the simulation time to improve the accuracy of the simulation data. Analog spectrum than measured in the low-low spectrum, the two main peak in good agreement, the two relative error of 30 %.
Yuen joined the simulation of the radionuclide more energy to raise the low end of the Compton scattering count. At the same time, consider the photoelectric effect and electronic effects, makes simulation results can be closer to the real measurement. Through the study on a method to the value of simulation, amended the expansion factor, makes analog spectrum close to the measured spectrum. More than 583keV numerical simulation of the characteristic peaks and measured the spectrum characteristic peak values similar error at 20%. 583keV below the peak of several features of Compton scattering Ping lower than the actual value, but peak corresponds better.
引文
[1] 许淑艳,刘保杰,LI Qin.核技术应用研究中的蒙特卡罗计算问题.核技术,2007,30(7):597～600
[2] 向东,郭兰英.γ 能谱的蒙特卡罗模拟.数理医药学杂志,2006,19(3):229～231
[3] 李婧,张江,葛良全,等.蒙特卡罗模拟 NaI 探测天然γ能谱的软件设计方法及应用.核电子学与探测技术,2005,25(4):423～425
[4] 张富利,曲德成,杨国山.应用蒙特卡罗方法确定 NaI 探测器的点源效率函数及其参数.核技术,2007,30(3):231～235
[5] 马国学,王海鹏,梁勇,等.高纯锗 γ 谱仪对放射性标准土壤的探测效率刻度.原子能科学技术,2006,40(6):749～751
[6] 张积运,肖雪夫,管少斌.MC 模拟计算法在确定模型体源表面上方空气比释动能率的应用.研究与探讨,2004,(3):16～25
[7] 武祯,李君利.用于探测器校正因子计算的 MonteCarlo 方法.清华大学学报(自然科学版),2006,46(9):1585～1588
[8] 胡广春,龚建,刘晓亚,等.体源探测效率计算及修正方法研究.核电子学与探测技术,2005,25(6):798～802
[9] Hu-Xia Shi,B0-Xian Chen,Ti-Zhu Li,et al.Precise Monte Carlo simulation of gamma-ray response functions for an NaI(Tl) detector.Applied Radiation and Isotopes 57(2002) 517-524
[10]P.H.G.M. Hendriks,M.Mau?ec,R.J.de Meijer.MCNP modeling of scintillation-detector γ-ray spectra from natural radionuclides.Applied Radiation and Isotopes 57(2002) 449-457
[11]A.Likar,T.Vidmar,M.Lipoglavsěk,et al.Monte Carlo calculation of entire in situ gamma-ray spectra.Journal of Environmental Radioactivity 72 (2004) 163–168
[12]许淑艳.蒙特卡罗方法在实验核物理中的应用.北京:原子能出版社,1996
[13]金文绵,李素梅.MCNP3B 使用手册.中国原子能科学研究院计算机应用研究所,1998
[14]程业勋,王南萍,侯胜利.核辐射场与放射性勘查.北京:地质出版社,2005
[15]高宝龙.利用蒙特卡罗方法进行伽马能谱全谱重叠峰模拟分解初步研究:[硕士学位论文] .北京:中国地质大学(北京),2006
[16]H.L.Beck et al,In situ Ge(Li)and NaI(Tl)gamma-ray spectrometry.hasl-258,September 1972
[17]M. MauWec, R.J. de Meijer, C. Rigollet, et al.Detection of radioactive particles offshore by γ-ray spectrometry Part I: Monte Carlo assessment of detection depth limits. Nuclear Instruments and Methods in Physics Research A 525 (2004) 593–609
[2] 向东,郭兰英.γ 能谱的蒙特卡罗模拟.数理医药学杂志,2006,19(3):229～231
[3] 李婧,张江,葛良全,等.蒙特卡罗模拟 NaI 探测天然γ能谱的软件设计方法及应用.核电子学与探测技术,2005,25(4):423～425
[4] 张富利,曲德成,杨国山.应用蒙特卡罗方法确定 NaI 探测器的点源效率函数及其参数.核技术,2007,30(3):231～235
[5] 马国学,王海鹏,梁勇,等.高纯锗 γ 谱仪对放射性标准土壤的探测效率刻度.原子能科学技术,2006,40(6):749～751
[6] 张积运,肖雪夫,管少斌.MC 模拟计算法在确定模型体源表面上方空气比释动能率的应用.研究与探讨,2004,(3):16～25
[7] 武祯,李君利.用于探测器校正因子计算的 MonteCarlo 方法.清华大学学报(自然科学版),2006,46(9):1585～1588
[8] 胡广春,龚建,刘晓亚,等.体源探测效率计算及修正方法研究.核电子学与探测技术,2005,25(6):798～802
[9] Hu-Xia Shi,B0-Xian Chen,Ti-Zhu Li,et al.Precise Monte Carlo simulation of gamma-ray response functions for an NaI(Tl) detector.Applied Radiation and Isotopes 57(2002) 517-524
[10]P.H.G.M. Hendriks,M.Mau?ec,R.J.de Meijer.MCNP modeling of scintillation-detector γ-ray spectra from natural radionuclides.Applied Radiation and Isotopes 57(2002) 449-457
[11]A.Likar,T.Vidmar,M.Lipoglavsěk,et al.Monte Carlo calculation of entire in situ gamma-ray spectra.Journal of Environmental Radioactivity 72 (2004) 163–168
[12]许淑艳.蒙特卡罗方法在实验核物理中的应用.北京:原子能出版社,1996
[13]金文绵,李素梅.MCNP3B 使用手册.中国原子能科学研究院计算机应用研究所,1998
[14]程业勋,王南萍,侯胜利.核辐射场与放射性勘查.北京:地质出版社,2005
[15]高宝龙.利用蒙特卡罗方法进行伽马能谱全谱重叠峰模拟分解初步研究:[硕士学位论文] .北京:中国地质大学(北京),2006
[16]H.L.Beck et al,In situ Ge(Li)and NaI(Tl)gamma-ray spectrometry.hasl-258,September 1972
[17]M. MauWec, R.J. de Meijer, C. Rigollet, et al.Detection of radioactive particles offshore by γ-ray spectrometry Part I: Monte Carlo assessment of detection depth limits. Nuclear Instruments and Methods in Physics Research A 525 (2004) 593–609