求解航空γ 能谱模拟中的深穿透问题
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摘要
蒙特卡罗(Monte Carlo,MC)模拟方法被广泛应用于γ能谱分析参数的获取,但因探测高度较高带来的深穿透问题限制了其在航空γ能谱中的应用。研究发现,探测器距离地层边界大于可探测半径时,MC模拟得到地层上空相同高度所有航空γ能谱仪响应规律均相同。根据这一规律,本文提出一种球壳型地层、航空γ探测器的MC模拟模型,通过对4个航空γ能谱仪刻度模型的模拟发现,MC模拟谱与多次实测平均谱吻合较好。同时利用该模型模拟了芬兰Vesivehmaa地区4种典型核素于100 m高空的刻度系数,结果显示模拟值与取样实测值及Allyson自编软件模拟值在±20%内符合,证明该模型能很好地应用于航空γ能谱仪地层信息反演计算参数的快速获取。
Background: Monte Carlo(MC) simulation method is often used to estimate various parameters for analyzing gamma-ray spectrum, but the deep penetration constrains its application in airborne detection. Purpose: This study aims to find a solution for the deep penetration problem in MC simulation of airborne gamma-ray spectrum. Methods: When many of same-sized airborne gamma-ray spectrometry(AGS) are placed in the same height and the distances between the center of each AGS and the boundary of stratum are greater than the detectable radius, the response laws of these AGSs are the same under infinite source particles. Based on the principle, a spherical shell model of MC simulation for an airborne gamma-ray spectrum is proposed to solve the above problem. Results: Airborne gamma-ray spectrums of four calibration models are simulated by this spherical shell model on the MCNP(Monte Carlo N Particle) platform, which are in agreement with their respective observational average spectrums. Moreover, the estimated calibration factors of four radionuclides at 100-m altitude in the Vesivehmaa region of Finland are calculated by this method, which show an agreement within 20% error in comparison with the sampling methodology and simulation values of Allyson et al. Conclusion: The results verify that the spherical shell model has high simulation efficiency and can provide reliable parameters for inversing stratum information by airborne gamma-ray spectrum.
Background: Monte Carlo(MC) simulation method is often used to estimate various parameters for analyzing gamma-ray spectrum, but the deep penetration constrains its application in airborne detection. Purpose: This study aims to find a solution for the deep penetration problem in MC simulation of airborne gamma-ray spectrum. Methods: When many of same-sized airborne gamma-ray spectrometry(AGS) are placed in the same height and the distances between the center of each AGS and the boundary of stratum are greater than the detectable radius, the response laws of these AGSs are the same under infinite source particles. Based on the principle, a spherical shell model of MC simulation for an airborne gamma-ray spectrum is proposed to solve the above problem. Results: Airborne gamma-ray spectrums of four calibration models are simulated by this spherical shell model on the MCNP(Monte Carlo N Particle) platform, which are in agreement with their respective observational average spectrums. Moreover, the estimated calibration factors of four radionuclides at 100-m altitude in the Vesivehmaa region of Finland are calculated by this method, which show an agreement within 20% error in comparison with the sampling methodology and simulation values of Allyson et al. Conclusion: The results verify that the spherical shell model has high simulation efficiency and can provide reliable parameters for inversing stratum information by airborne gamma-ray spectrum.
引文
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13航空伽玛能谱测量规范:EJ/T 1032-2005[S].中华人民共和国核行业标准,2005:1-25Specification for air borne gamma-ray spectrometry:EJ/T1032-2005[S].The People’s Republic of China Nuclear Trade Standards,2005:1-25
14 Wu H X,Zhang H Q,Liu Q C,et al.Information retrieval methods for high resolutionγ-ray spectra[J].Nuclear Science and Techniques,2012,23(6):332-336
15 Sanderson D C W,Allyson J D,Toivonen H,et al.Gamma ray spectrometry results from core samples collected for RéSUME 95[OL].1996.https://www.etde.org/etdeweb/servlets/purl/587788-Zxef Dt/webviewable/587788.pdf
2 Liu L P,Liu Y B,Wang J,et al.The influence of reactor core parameters on effective breading coefficient keff[J].Chinese Physics B,2008,17(3):996-1000.DOI:10.1088/1674-1056/17/3/026
3魏强林,杨波,王毅,等.含硼钢对慢中子衰减性能的蒙特卡罗模拟[J].核技术,2010,33(5):367-369WEI Qianglin,YANG Bo,WANG Yi,et al.M-Csimulation of slow neutron attenuation in boroncontaining stainless steel[J].Nuclear Techniques,2010,33(5):367-369
4刘合凡,葛良全,谢希成,等.基于蒙特卡罗方法的XRF探测器立体角分析[J].核技术,2015,38(6):060502.DOI:10.11889/j.0253-3219.2015.hjs.38.060502LIU Hefan,GE Liangquan,XIE Xicheng,et al.Calculation of desired X-ray collection angle on XRFanalyzer designed by Monte Carlo method[J].Nuclear Techniques,2015,38(6):060502.DOI:10.11889/j.0253-3219.2015.hjs.38.060502
5张庆贤.航空γ能谱特征和仪器谱解析方法研究[D].成都:成都理工大学,2010ZHANG Qingxian.The character of airborne gamma-ray spectrometry and the method for spectrum analysis[D].Chengdu:Chengdu University of Technology,2010
6 Gerward L,Guilbert N,Jensen K B,et al.WinX Com-a program for calculating X-ray attenuation coefficients[J].Radiation Physics and Chemistry,2004,71(1):653-654.DOI:10.1016/j.radphyschem.2004.04.040
7谷懿,葛良全,熊盛青,等.基于康普顿散射本底扣除的航空γ能谱测量谱线比大气氡校正方法[J].原子能科学技术,2014,48(1):147-151.DOI:10.7538/yzk.201448.01.0147GU Yi,GE Liangquan,XIONG Shengqing,et al.Spectral-ratio radon background correction method in airborneγ-ray spectrometry based on Compton scattering deduction[J].Atomic Energy Science and Technology,2014,48(1):147-151.DOI:10.7538/yzk.2014.48.01.0147
8 Allyson J D,Sanderson D C.Monte Carlo simulation of environmental airborne gamma-spectrometry[J].Journal of Environmental Radioactivity,1998,38(3):259-282.DOI:10.1016/S0265-931X(97)00040-4
9李德华,梁锦华.航空γ测量的Monte Carlo模拟[J].成都地质学院学报,1992,19(1):115-120LI Dehua,LIANG Jinghua.On the Monte Carlo simulation of airborneγ-ray survey[J].Journal of Chengdu College of Geology,1992,19(1):115-120
10朱迪.航空γ能谱测量仪器谱蒙特卡罗模拟[D].成都:成都理工大学,2009ZHU Di.Equipment spectrum simulation in airborne gamma-ray spectrometry by Monte Carlo method[D].Chengdu:Chengdu University of Technology,2009
11方晟,曾志,吴其反,等.航空γ谱探测地层中放射性同位素的Monte Carlo模拟计算[J].清华大学学报(自然科学版),2007,47(S1):1018-1021.DOI:1000-0054(2007)S1-1018-04FANG Sheng,ZENG Zhi,WU Qifan,et al.Monte Carlo simulations of airborne gamma spectrometry of radionuclide in earth[J].Journal of Tsinghua University(Science and Technology),2007,47(S1):1018-1021.DOI:1000-0054(2007)S1-1018-04
12章晔,陈天友.航空伽玛测量作用带的理论研究及其应用[J].现代地质,1994,8(4):497-502ZHANG Ye,CHEN Tianyou.Theoretical study and application of investigation strips in airborneγ-ray surveying-a practical model[J].Geoscience,1994,8(4):497-502
13航空伽玛能谱测量规范:EJ/T 1032-2005[S].中华人民共和国核行业标准,2005:1-25Specification for air borne gamma-ray spectrometry:EJ/T1032-2005[S].The People’s Republic of China Nuclear Trade Standards,2005:1-25
14 Wu H X,Zhang H Q,Liu Q C,et al.Information retrieval methods for high resolutionγ-ray spectra[J].Nuclear Science and Techniques,2012,23(6):332-336
15 Sanderson D C W,Allyson J D,Toivonen H,et al.Gamma ray spectrometry results from core samples collected for RéSUME 95[OL].1996.https://www.etde.org/etdeweb/servlets/purl/587788-Zxef Dt/webviewable/587788.pdf