14MeV中子照相中散射中子对成像影响的Monte Carlo模拟

依据实验参数，建立了14MeV快中子照相的物理模型，并利用Monte Carlo方法对照相过程进行了模拟. 分析了经聚乙烯样品散射的中子对快中子图像的影响随样品与探测器间距及样品参数的变化. 计算结果表明，样品与探测器的距离d<5cm时，样品中的散射中子对图像的影响强烈依赖于d，而当d>20cm时，样品散射中子对图像的影响可忽略；当样品密度为3—5g/cm³时散射中子对图像的影响相对最大；样品宽度越大，图像中的散射成分越多，当宽度在3cm以上时散射成分的强度趋于饱和. 关键词： 14MeV中子 快中子照相 散射中子 Monte Carlo模拟

Monte Carlo simulation of effect of neutron scattering on image information in 14MeV fast neutron radiography

Referring to the experimental parameters, the physical model of neutron radiography with 14-MeV neutrons is built and the process of radiography is simulated using the Monte Carlo method. Effect of neutron scattering by a polyethylene sample on radiography is analyzed as a function of d, the distance between the sample and the detector, and parameters of the sample. The calculated results indicates that for a d values smaller than 5-cm, intensity of scattered neutron component strongly depends on d, while when d is greater than 20-cm, the influence of scattered neutrons to the image is reduced to a negligible level. The results also indicates that the effect of neutron scattering is relatively large when density of the sample ranges from 3-g/cm3 to 5-g/cm3, and intensity of scattered neutron component increases with width of the sample and is almost saturated at width greater than 3-cm.