高能X射线能谱测量中衰减材料特性影响北大核心CSCD

基于衰减透射原理的高能X射线能谱测量,采用蒙特卡罗成像模拟的方法研究衰减材料选择对能谱准确稳定重建的影响。设计多孔准直模型模拟X射线穿过不同衰减材料的透射过程,并在单次成像中获得完整的衰减透射率曲线。由衰减透射率求解能谱是一种病态条件问题,采用改进的迭代扰动法进行解谱,计算时考虑透射率计算值与真实值的差异最小化要求以及高能能谱分布曲线的平滑性特点。通过计算分析了材料在能谱范围内的衰减特性变化趋势与能谱准确稳定重建的内在联系。结果表明,选用材料的质量衰减系数需满足在整个能谱分布范围内单调递减的要求。

Impact of filter material properties in high-energy X-ray spectrum estimation

Monte Carlo imaging simulation is applied to investigate the impact of filter material properties on accurate and robust reconstruction of the high-energy X-ray spectrum based on the attenuated transmission principle. A model of multi-collimating apertures is designed to simulate the process of X-ray passing through filter materials, and an entire attenuation transmission curve is obtained in a single imaging simulation. It is an ill-conditioned problem to obtain the X-ray spectrum from the transmission data. An improved iterative perturbation method is used to reconstruct the spectrum, which considers minimization of the difference between the calculated and the true transmission curves and smoothness of the high-energy spectrum function. The inherent relation between the attenuation characteristic of the filter material and the accurate-and-robust reconstruction of the spectrum is also verified. The results show that the mass attenuation coefficient of the filter material should be monotonically decreasing over the spectrum.