基于μ子动量谱的多群模型测量平板材料的厚度

Muon momentum spectra analysis by multi-group model for thickness measurement of slabs

在基于μ子多重库仑散射的断层成像技术中,天然宇宙射线中不同动量的μ子在同一目标对象中的散射特性存在明显的差异,这在一定程度上影响了成像分辨率。为了减少或消除这种不利影响,建立了一套基于天然宇宙射线μ子动量谱的多群模型,并检验其用于铅板厚度测量及平板材料识别中的性能和特征。结果表明,采用基于μ子动量谱的多群模型能够实现1~16cm范围内铅板厚度的准确测量,相对误差小于5%。此外,该多群模型还可以通过计算辐射长度来识别未知平板的材料组成,尤其是对于高原子序数材料组成的平板,其辐射长度相对误差小于4%。

In muon tomography based on multiple Coulomb scattering,the scattering properties of cosmic-ray muons are distinctive even for the same target due to their different momentum distribution,which,to some extent,cast down the imaging resolution.For the purpose of suppressing or eliminating this effect,a multi-group model （MGM）of the momentum spectra of cosmic-ray muons was set up and validated by measuring the thicknesses of Pb slabs and by identifying the materials of unknown slabs.The results show that MGM can give a precise calculation of Pb slab thickness in the range of 1-1 6 cm,within an error of 5%.Moreover,MGM can also identify the materials of slabs by calculating the corresponding radiation lengths,which is espe-cially effective for high-Z materials with an calculation error below 4%.