论文标题
用于量化放射线沉积量的Compton-Peak方法的仿真分析
Simulation analysis of the Compton-to-peak method for quantifying radiocesium deposition quantities
论文作者
论文摘要
Compton-to-peak分析是一种用于选择用于通过原位伽玛射线光谱测量计数率的系数，以$^{134} $ CS和$^{137} $ CS的放射性浓度。 Compton-to-peak分析基于包含散射伽玛射线与主要$^{134} $ CS和$^{137} $ cs photopopeaks（称为Compton to-Peak-pak-pak to-patio-rcp）的光谱区域之间的计数率比。 RCP随$^{134} $ cs和$^{137} $ cs的垂直分布而变化。推断此分布可以选择适当的计数速率来进行活动浓度转换系数。在这里，PHIT用于模拟RCP对$^{134} $ cs和$^{137} $ cs的不同垂直分布的依赖性。创建了一个模型，该模型是在福岛县的无人机直升机空中调查中使用的LABR $ _3 $（CE）检测器。通过将模拟的伽马射线光谱与测试源的测量进行比较，可以验证该模型。对无限半空间几何形状进行了模拟，以计算RCP对$^{134} $ CS的质量深度分布（指数或统一）的依赖性，以及地面内以及地面检测器的高度。计算表明，当$^{134} $ cs和$^{137} $ CS位于地面附近，对于在低海拔高度进行的空中调查时，核辐射后的初始阶段的敏感性最高。这是因为在这两种情况下，RCP在质量深度分布的变化方面计算出的相对差异最大。关于应用$^{134} $ cs至$^{137} $ cs活动比的数据的数据对于应用Compton-Peak方法确定$^{134} $ CS和$^{137} $ CS的分布和放射性浓度是必要的。
Compton-to-peak analysis is a method for selecting coefficients for converting count rates measured with in situ gamma ray spectrometry to radioactivity concentrations of $^{134}$Cs and $^{137}$Cs in the environment. Compton-to-peak analysis is based on the count rate ratio between the spectral regions containing scattered gamma rays to the primary $^{134}$Cs and $^{137}$Cs photopeaks (known as the Compton-to-peak ratio - RCP). RCP changes with the vertical distribution of $^{134}$Cs and $^{137}$Cs within the ground. Inferring this distribution enables the selection of appropriate count rate to activity concentration conversion coefficients. Here PHITS was used to simulate the dependency of RCP on different vertical distributions of $^{134}$Cs and $^{137}$Cs within the ground. A model was created of a LaBr$_3$(Ce) detector used in drone helicopter aerial surveys in Fukushima Prefecture. The model was verified by comparing simulated gamma ray spectra to measurements from test sources. Simulations were performed for the infinite half-space geometry to calculate the dependency of RCP on the mass depth distribution (exponential or uniform) of $^{134}$Cs and $^{137}$Cs within the ground, and on the altitude of the detector above the ground. The calculations suggest that the sensitivity of the Compton-to-peak method is greatest for the initial period following nuclear fallout when $^{134}$Cs and $^{137}$Cs are located close to the ground surface, and for aerial surveys conducted at low altitudes. This is because the relative differences calculated between RCP with respect to changes in the mass depth distribution were largest for these two cases. Data on the measurement height above and on the $^{134}$Cs to $^{137}$Cs activity ratio is necessary for applying the Compton-to-peak method to determine the distribution and radioactivity concentration of $^{134}$Cs and $^{137}$Cs within the ground.
