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Modern Physics 2026
散射中子对241Am-Be中子能谱精度的影响研究
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Abstract:
在辐射场进行中子能谱测量实验时，实验室环境散射会对中子能谱精度造成影响。本文采用多球谱仪测量241Am-Be中子能谱。首先通过蒙特卡洛方法模拟并计算实验环境中空气和实验室大厅墙面对测量241Am-Be中子能谱的影响。仿真结果显示：空气散射率随着中子源与聚乙烯的距离增加而增加；地面散射是实验室大厅影响探测器计数的主要因素，并且聚乙烯球的尺寸越小，散射对其影响越大。其次本文分析了多个聚乙烯球同时测量时存在的球间散射所带来的影响。结果表明球间散射对较小尺寸和较大尺寸聚乙烯球造成的误差较大。最后本文完成了241Am-Be中子实验，并依据仿真得到的散射影响结果修正实验计数，求解了中子能谱。实验结果表明：扣除散射影响之后的241Am-Be中子能谱更接近标准能谱；相比于原始能谱，其均方根误差RMSE降低了3.75%。
In the experiment of neutron spectrum measurement in radiation field, the laboratory environment scattering will affect the accuracy of neutron spectrum. In this paper, the neutron spectrum of 241Am-Be is measured by a Bonner sphere spectrometer. Firstly, Monte Carlo method is used to simulate and calculate the influence of air and the wall of the neutron laboratory on the measurement of 241Am-Be neutron spectrum. The simulation results show that the air scattering rate increases with the increase of the distance between the neutron source and Bonner sphere. Floor scattering is the main factor affecting the detector count in the laboratory, and the smaller the size of the Bonner sphere, the greater the impact of scattering on it. Secondly, the influence of the inter-sphere scattering when Bonner spheres are measured at the same time is analyzed. The results show that the error caused by the inter-sphere scattering is larger for the smaller and larger Bonner spheres. Finally, we complete the 241Am-Be neutron experiment. The neutron experimental counts are modified according to the scattering effect results obtained by Geant4 simulation, and then the neutron energy spectrum is calculated. The experimental results show that the neutron energy spectrum of 241Am-Be is closer to the standard energy spectrum after deducting the scattering effect. Compared with the original energy spectrum, the root mean square error is reduced by 3.75%.
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