测量几何条件对外中子源激励铀产生的中子和γ飞行时间谱的影响分析

Influences of Measuring Geometry Conditions on Flight TimeSpectra of Neutron and Gamma Rays of UraniumMaterial Excited by External Neutron Source

为确定主动法外中子源激励铀材料时中子、γ飞行时间谱的实验测量条件,基于Geant4数值模拟平台建立了D-D外中子源激励铀材料后中子、γ飞行时间谱的计算模型,计算了探测器表面距铀材料中心不同距离下的中子、γ飞行时间透射谱及飞行时间关联符合谱,分析讨论了D-D外中子源激励铀材料时,探测距离、探测时间及探测器角度等因素对中子、γ飞行时间谱的影响。模拟结果表明,实验中样品与中子源之间的距离应小于10 cm,用于记录中子、γ飞行时间透射谱的探测器表面与铀样品几何中心间的距离应控制在80 cm左右,用于探测中子、γ飞行时间关联符合谱的探测器表面与铀样品几何中心间的距离应控制在30 cm左右,且探测器应置于与束流方向成53°夹角的方向上。

In this paper,the influences of the experimental measurement conditions on the flight time spectra of neutron and gamma rays of the uranium materials excited by external neutron source are studied.Based on the Geant4 toolkit,a model of calculating the flight time spectra of neutron and gamma rays of uranium sample excited by a D-D external neutron source is established,and the flight time transmission spectra and the correlation spectra of neutron and gamma rays are calculated at different distances from the surface of detector to the center of the uranium sample.Furthermore,the influences of detection distance,detection time,and detector layout of D-D external neutron source on the flight time spectra of neutron and gamma rays are also analyzed and discussed.To obtain a better statistical accuracy of the energy spectra,the distance between the sample and the neutron source should be less than 10 cm,the distance between the sample and the detector used to record the flight time transmission spectra of neutron and gamma rays should be about 80 cm,and the distance between the sample and the detector for recording the correlation spectra of the neutron and gamma rays should be controlled at about 30 cm.Meanwhile,the detector should be placed in the direction of 53 degrees from the incident beam.