α能谱峰形函数及其拟合参数初始值获取

摘要

The weighted nonlinear least squares iterative fitting method is an important method to solve the α-particle spectra.The appropriate spectrum peak shape function model and the initial values of the parameters are the key to the nonlinear least squares iterative fitting.Based on the shaping mechanism of α-ray spectrum,a kind of α-ray spectrum peak shape function was established,and the method of determining the initial values of the peak shape function based on the moment estimation was proposed.The mathematical statistics,the mean,variance and third-order central moments of the peak shape function and the discrete spectral peak data were calculated respectively.The initial values of the parameters were obtained by the established equations.The radon daughters' alpha spectra detected by a continuous aerosol detector and 238 Pu surface-source α-energy spectra detected by a low-background α-ray spectrometer were used to test the peak shape function model and the initial values acquisition method.The results show that the peak shape function model can be well applied from high-degree overlapping to low-degree overlapping.The initial values of the parameters of the peak shape function obtained by the moment estimation method can make the peak shape function well fit the alpha spectrum data.The method has strong practicability in the computer automatic analysis of alpha spectrum.%根据α能谱的形成机理,建立了一种a能谱峰形函数,提出基于矩估计法确定该峰形函数的拟合参数初始值的方法.以数理统计为基础,分别通过峰形函数和离散谱峰数据计算均值、方差和三阶中心矩建立方程组求解获取拟合参数的初始值.通过连续气溶胶检测仪探测的氡子体α能谱和低本底α能谱仪探测的238Pu面源a能谱对该峰形函数模型和初始值获取方法进行了测试.结果表明:从低重合度到高重合度,该峰形函数模型都能得到较好的应用;基于矩估计法确定该峰形函数的参数初始值能够使该峰形函数较好地拟合α能谱数据.该方法在采用计算机自动α能谱拟合分析中具有较强的实用性.