蒙特卡罗模拟-高斯重建相结合解析γ能谱

Analysis of the Gamma spectrum using Monte Carlo simulation and Gaussian reconstruction

为了解决常规γ能谱解析中康普顿坪影响较大、峰面积计算不准确的问题,提高γ核素活度测量结果的准确度,本文基于蒙特卡洛方法建立了NaI(Tl)探测器物理模型,同时针对模拟谱与实测谱在康普顿坪区的差异,根据γ谱形成机理,提出比值法以修正模拟谱,并生成标准γ核素谱。再以标准γ能谱为基础,通过从高能到低能的顺序进行剥谱和确定全能峰区,以解析^(137)Cs和^(60)Co相叠加的γ实测谱,所得活度测量结果的相对误差在±3.5%以内,明显优于常规解谱方法。结果表明:采用蒙特卡罗模拟标准谱与实测谱特征峰高斯重建相结合而解析γ能谱,既能大幅降低实测谱中康普顿坪对较低能量γ射线特征峰的影响,也能较准确地确定特征峰面积,为γ能谱分析提供了一种能显著提高γ核素活度测量准确度的方法。

In this study,to solve the problem of the large influence of the Compton plateau and inaccurate calcula-tion of the peak area in conventionalγspectrum analysis and improve the accuracy ofγnuclide activity measure-ment,a physical model of NaI(Tl)detector was established using the Monte Carlo(MC)method.Considering the difference between the simulated and measured spectra at the Compton plateau,the ratio method was established to modify the simulated spectrum according to the formation mechanism ofγspectrum,thereby generating a standardγnuclide spectrum.Based on the standardγspectrum,the spectrum was stripped from high to low energy,and the all-around peak regions were determined.Additionally,the measuredγspectrum of^(137)Cs and^(60)Co phase superpo-sition was analyzed.The result reveals that the relative error of 137Cs and 60Co activities is less than 3.5%,which is obviously better than conventional spectral-solving methods.This also indicates that combining the MC simulated standard spectrum and Gaussian reconstruction of the characteristic peak of the measured spectrum can significantly reduce the influence of Compton plateau to low energyγ-ray characteristic peak and accurately determine the area of the characteristic peak.Moreover,this study provides a promising method forγspectrum analysis,which can significantly improve the accuracy ofγnuclide activity measurements.