贝叶斯理论在脉冲裂变中子能谱诊断中的应用
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摘要
本文建立了以贝叶斯理论为基础的脉冲裂变中子能谱的数值迭代计算方法,解决了脉冲裂变中子能谱测量的技术难题。对脉冲裂变中子空间输运、物质衰减、探测器灵敏度等进行了分析,将脉冲裂变中子能谱在空间传输中的飞行展宽时间谱理解为出壳时间谱在不同测点的概率分布函数,脉冲中子在不同测点的信号强度分布是出壳时间谱和脉冲中子能谱飞行展宽时间谱的卷积信号,将物质衰减、探测器灵敏度响应等转换环节对中子能谱的影响因子进行了分别处理,消除了通道物质对中子能谱衰减和探测器非线性灵敏度等因素对脉冲裂变中子能谱解谱的影响。研究结果表明,对距辐射源5 m和10 m处的中子波形进行数值处理,均能获得理想的脉冲裂变中子能谱,当考虑传输系统响应函数对中子波形影响时,仍能获得较理想的中子能谱。
To figure out the problem of neutron energy spectrum measurement in pulsed fission,a numerical iteration method for neutron energy spectrum based on Bayesian theory was established in this paper. The spatial transport,material attenuation and detector sensitivity were analyzed. In the proposed method,the broadened time-of-flight spectrum was regarded as the probability distribution function of off-shell time spectrum at different measuring points. The signal intensity distribution of pulsed neutron at different measuring points is the convolution of off-shell time spectrum and the broadened time-of-flight spectrum. The impact factor of the conversion process,such as material attenuation and detector sensitivity,on neutron energy spectrum was disposed,respectively. The influences of several factors,including neutron energy spectrum attenuation by channel materials and non-linear detector sensitivity,on the unfolding of the neutron energy spectrum were eliminated. The result shows that the ideal pulsed fissionneutron spectrum can be obtained after the numerical treatment for the neutron waveforms with the distance of 5 m and 10 m from the radiation source,respectively. When taking into consideration of the effect of the response function for the transmission system to the neutron waveform,the relative ideal neutron spectrum can still be obtained.
To figure out the problem of neutron energy spectrum measurement in pulsed fission,a numerical iteration method for neutron energy spectrum based on Bayesian theory was established in this paper. The spatial transport,material attenuation and detector sensitivity were analyzed. In the proposed method,the broadened time-of-flight spectrum was regarded as the probability distribution function of off-shell time spectrum at different measuring points. The signal intensity distribution of pulsed neutron at different measuring points is the convolution of off-shell time spectrum and the broadened time-of-flight spectrum. The impact factor of the conversion process,such as material attenuation and detector sensitivity,on neutron energy spectrum was disposed,respectively. The influences of several factors,including neutron energy spectrum attenuation by channel materials and non-linear detector sensitivity,on the unfolding of the neutron energy spectrum were eliminated. The result shows that the ideal pulsed fissionneutron spectrum can be obtained after the numerical treatment for the neutron waveforms with the distance of 5 m and 10 m from the radiation source,respectively. When taking into consideration of the effect of the response function for the transmission system to the neutron waveform,the relative ideal neutron spectrum can still be obtained.
引文
[1]SIMMER G,MARES V,WEITZENEGGER E,et al.Iterative unfolding for Bonner sphere spectrometers using the MSANDB code—Sensitivity analysis and dose calculation[J].Radiation Measurements,2010,45(1):1-9.
[2]SUMAN V,SARKAR P K.Neutron spectrum unfolding using genetic algorithm in a Monte Carlo simulation[J].Nuclear Instruments and Methods in Physics Research A,2014,737(3):76-86.
[3]MUKHERJEE B.BONDI-97:A novel neutron energy spectrum unfolding tool using a genetic algorithm[J].Nuclear Instruments and Methods in Physics Research A,1999,432(2-3):305-312.
[4]杨洪琼,唐正元,潘文明,等.聚变脉冲中子源特性的近距离测量方法[J].核电子学与探测技术,2005,25(2):160-162.YANG Hongqiong,TANG Zhengyuan,PAN Wenming,et al.The method of short distance measurement for fusion pulse neutron source characteristic[J].Nuclear Electronics&Detection Technology,2005,25(2):160-162(in Chinese).
[5]IRANI M,PELEG S.Improving resolution by image registion[J].CVGIP:Graphical Models&Image Processing,1991,53(3):231-239.
[6]WEI B,HUI W.POCS embedded MAP method for image super resolution restoration[J].IEEE Conference on Industrial Electronics&Applications,2009:3 791-3 794.
[7]ZHU Hao.Super_resolution image restoration by maximum likelihood method and edge orient diffusion[J].Proc SPIE,2008,6625:66250Y-1-66250Y-8.
[8]AGOSTINI G D.A multidimensional unfolding method based on Bayes’therem[J].Nuclear Instruments and Methods in Physics Research A,1995,362(2-3):487-498.
[9]周林,蒋世伦,祁建敏,等.反冲质子磁分析技术用于氘氚中子能谱测量研究[J].物理学报,2012,61(7):072902.ZHOU Lin,JIANG Shilun,QI Jianmin,et al.Study of magnetic proton recoil technology for measurement of deuterium-tritium neutron spectrum[J].Acta Physica Sinica,2012,61(7):072902(in Chinese).
[10]张小东,张显鹏,李宏云,等.狭缝式裂变探测系统的中子灵敏度解析计算方法[J].强激光与粒子束,2011,23(2):559-562.ZHANG Xiaodong,ZHANG Xianpeng,LI Hongyun,et al.Analytical calculation of neutron sensitivity of fission detector system with slotcollimator[J].High Power Laser and Particle Beams,2011,23(2):559-562(in Chinese).
[11]马彦良,欧阳小平,王群书,等.裂变靶探测系统中子灵敏度的理论计算[J].核技术,2009,32(6):473-476.MA Yanliang,OUYANG Xiaoping,WANG Qunshu,et al.Neutron sensitivity calculation of a slotcollimated PIN fission chamber[J].Nuclear Techniques,2009,32(6):473-476(in Chinese).
[2]SUMAN V,SARKAR P K.Neutron spectrum unfolding using genetic algorithm in a Monte Carlo simulation[J].Nuclear Instruments and Methods in Physics Research A,2014,737(3):76-86.
[3]MUKHERJEE B.BONDI-97:A novel neutron energy spectrum unfolding tool using a genetic algorithm[J].Nuclear Instruments and Methods in Physics Research A,1999,432(2-3):305-312.
[4]杨洪琼,唐正元,潘文明,等.聚变脉冲中子源特性的近距离测量方法[J].核电子学与探测技术,2005,25(2):160-162.YANG Hongqiong,TANG Zhengyuan,PAN Wenming,et al.The method of short distance measurement for fusion pulse neutron source characteristic[J].Nuclear Electronics&Detection Technology,2005,25(2):160-162(in Chinese).
[5]IRANI M,PELEG S.Improving resolution by image registion[J].CVGIP:Graphical Models&Image Processing,1991,53(3):231-239.
[6]WEI B,HUI W.POCS embedded MAP method for image super resolution restoration[J].IEEE Conference on Industrial Electronics&Applications,2009:3 791-3 794.
[7]ZHU Hao.Super_resolution image restoration by maximum likelihood method and edge orient diffusion[J].Proc SPIE,2008,6625:66250Y-1-66250Y-8.
[8]AGOSTINI G D.A multidimensional unfolding method based on Bayes’therem[J].Nuclear Instruments and Methods in Physics Research A,1995,362(2-3):487-498.
[9]周林,蒋世伦,祁建敏,等.反冲质子磁分析技术用于氘氚中子能谱测量研究[J].物理学报,2012,61(7):072902.ZHOU Lin,JIANG Shilun,QI Jianmin,et al.Study of magnetic proton recoil technology for measurement of deuterium-tritium neutron spectrum[J].Acta Physica Sinica,2012,61(7):072902(in Chinese).
[10]张小东,张显鹏,李宏云,等.狭缝式裂变探测系统的中子灵敏度解析计算方法[J].强激光与粒子束,2011,23(2):559-562.ZHANG Xiaodong,ZHANG Xianpeng,LI Hongyun,et al.Analytical calculation of neutron sensitivity of fission detector system with slotcollimator[J].High Power Laser and Particle Beams,2011,23(2):559-562(in Chinese).
[11]马彦良,欧阳小平,王群书,等.裂变靶探测系统中子灵敏度的理论计算[J].核技术,2009,32(6):473-476.MA Yanliang,OUYANG Xiaoping,WANG Qunshu,et al.Neutron sensitivity calculation of a slotcollimated PIN fission chamber[J].Nuclear Techniques,2009,32(6):473-476(in Chinese).