基于最小二乘法的航空?能谱解析

Analyzing airborne gamma-ray spectrum by the least square method

在天然辐射环境下,无法找到仅含单一天然放射性系列的近似无限大地层用于获取航空γ谱仪的响应谱,这是导致无法利用最小二乘法解析航空γ能谱的关键问题所在。本文基于介质互换原理、地层模块化与分能区多次模拟的思想,通过构建Monte Carlo组合模型,从而获得了含不同放射性物质的任意形状地层上空航空γ谱仪的响应谱。依据航空γ能谱测点上γ辐射来源与石家庄动态带分析,建立了一套可靠的最小二乘法航空γ能谱解析模型。通过对野外10 km测线分析发现,当地层含量大于4×10^(-6)时,该方法与标准方法分析结果相当。同时该方法为人工放射性核素响应谱的剥离提供参考。

Background： It is difficult to establish the least square method for parsing airborne gamma-ray spectrum because the approximately infinite stratum does not exist when it contains only 235U and 238U series, 232Th series or 40K. Purpose： This study aims to acquire the response spectrum of airborne gamma-ray spectrometry （AGS） by Monte Carlo simulation and establish the above-described method. Methods： Based on the principle of media interchange, the basic thought of modular stratum and energy partitioning for characteristic gamma-ray, the combination model is used to obtain the AGS＇ response spectrum of any shape of stratum by Monte Carlo simulation. And the least square model for solving airborne gamma-ray spectrum is established by the above response spectrum. Results： The corrected model of eU, eTh and 40K content in stratum is acquired by analyzing the eight airborne gamma-ray spectra from the dynamic scale model in Shijiazhuang City. The calculation values of 10 km survey lines coincide with the specification for AGS when the content of natural radioactivity nuclide is larger than 4×10-6. Conclusion： The results verify that the calculation model is a valid analytical technique of AGS for natural radioactivity nuclide in stratum. And it provides a valid method to acquire the AGS＇ response spectrum of artificial radioactivity nuclide.