【作者】 傅卓人；

【导师】 葛良全；

【作者基本信息】 成都理工大学 ， 辐射防护及环境保护， 2011， 硕士

【摘要】 对于地质样品而言,其基体主要由三大岩类（岩浆岩、变质岩和沉积岩）组成,它们的成分主要是硅、铝、氧、硫和钙等轻元素。在X荧光测量中,由于基体成分的变化引起待测样品的密度、有效原子序数的变化,进而引起散射和吸收情况的变化,直接影响待测元素特征X射线照射量率与其含量之间的线性关系。在国内外有很多学者做过相关由于基体成分变化所引起的有效原子序数变化的研究,通过测量相干散射与非相干散射计数率的比值来确定与试样有效原子序数的关系,进行物质成分分析,并在简单的无机物、有机物、玻璃和合金试样的实际分析工作所证实。在国内有学者做过用Si（Li）探测器,238Pu源对岩石标准样测定散射比与平均原子序关系的实验,但是用Si PIN探测器,238Pu源激发来确定地质样品有效原子序数的研究工作却不多。针对目前国内研究的不足,本文利用成都理工大学核技术与自动化工程学院研制的IED 2000P手提式多元素X射线荧光仪（Si PIN探测器,238Pu同位素源）对散射比与有效原子序数之间的关系进行研究。本课题来源于中国国土资源航空物探遥感中心项目“西天山航磁异常查证野外X荧光示范”和国家863计划资源环境技术领域重大项目“航空伽玛能谱勘查系统研发”。1、本文对电子壳层结合能的原子序数修正因子进行拟合,拟合范围为4到20号元素,得到K层修正系数与原子序数的一个曲线关系,其拟合相关系数达0.9999。同时又对部分元素较外层的L层、M层电子结合能的原子序数修正因子进行拟合。2、通过蒙特卡罗模拟方法,得到与地质样品有效原子序数十分接近的SiO₂和Al₂O₃分析纯样品密度与有效原子序数的关系。通过对固体压片样常用的硼酸试剂展开不同质量测试,得到样品压片前后的密度增量。结合蒙特卡罗模拟结果,分别算出SiO₂和Al₂O₃密度增量（压片样品和粉末样品的密度差）下的有效原子序数增量分别0.00115和0.00054,其结果对计算地质样品中有效原子序数的影响有限。3、对于同位素放射源便携式X荧光仪的测量来说,散射角是一个很重要的参数,不同的散射角会对结果造成很大的影响,而且用同位素源激发的X荧光仪散射角很难精确确定。本文通过与地质样品有效原子序数十分接近的SiO₂和Al₂O₃分析纯样品的大量实验,大致计算出IED 2000P手提式多元素X射线荧光仪的最佳散射角度为169°。4、深入的研究散射峰与有效原子序数之间的关系,得出一种计算样品有效原子序数的方法（谱线散射法）,并将其应用于红山嘴、蒙马拉和托逊等三个工区,与波长色散X荧光仪测量的有效原子序数（波长色散法）比较,具有较小的相对误差,取得了较好的效果。①对红山嘴工区,谱线散射法计算整个工区的有效原子序数为13.23,波长色散法计算整个工区的有效原子序数为13.45,其相对误差为1.67%。②对蒙马拉工区,谱线散射法计算整个工区的有效原子序数为12.93,波长色散法计算整个工区的有效原子序数为13.20,其相对误差为2.06%。③对托逊工区,谱线散射法计算整个工区的有效原子序数为13.14,波长色散法计算整个工区的有效原子序数为13.17,其相对误差为0.32%。更多还原

【Abstract】 For geological samples are concerned, the matrix consists mainly three rock types （magmatite, metamorphic and sedimentary rocks）, the composition mainly are silica, aluminum, oxygen, sulfur and calcium and the like. In X ray fluorescence measurement, the change of matrix’s composition brings the change of test sample’s density, effective atomic number, then causes the change of scattering and absorption conditions, and brings direct impact to test elements’X ray eminence and linear relationship between its content.There are many scholars at home and abroad who did some related experiments about the change of matrix’s composition which brings the change of test sample’s effective atomic number. By measuring scattering and incoherent coherent ratio of the scattering count and determine the relations with sample’s effective atomic number, Then to analysis the substance composition. This method was validated in actual analysis work of simple inorganics, organics, glass and alloy specimens. In China some scholars have used Si （Li） detectors, and use 238Pu source to test rock samples and determine relationship of scattering rate and average atomic number. But the research work of using Si PIN detector, 238Pu radioactive isotopes source excitation to determine the geological samples’effective atomic number is not much.In view of the present limitation of study in this field, this paper bases on usage of IED 2000P portable multi elements X ray fluorescence analyzer （Si PIN detector, 238Pu radioactive isotopes source）, developed by the college of nuclear technology and automation engineering institute of Chengdu University of Technology, to study the relationship between scattering rate and effective atomic number. This subject comes from China Aero Geophysical Survey & Remote Sensing Center for Land and Resources’s project“Application of X fluorescence analyzer in the West Tianshan of aeromagnetic anomaly verification”and national 863 high tech research project“Research of airborne gamma ray spectrometry exploration system”. 1. In this paper, electronic shells binding energy’s atomic number correction factor is fitted. The fitting scope is 4 to 20 elements. And get a curve relationship of K layer correction coefficient and atomic number. The correlation coefficient of fitting is 0.9999. And some elements relatively outer layers L layer, M layer electronic binding energy atomic number correction factors is also fitted.2. By Monte Carlo Simulation method, we get the relationship between density and effective atomic number of analysis pure samples SiO₂ and Al₂O₃ which have very close effective atomic number with geological samples. Through different quality test of boric acid reagents which are commonly used in solid presser sample, and get the density increment after the samples are pressed. And compare to Monte Carlo Simulation results, calculated the density increment of SiO₂ and Al₂O₃ （the increment of powder samples and powder presser samples）, and got the results of effective atomic number’s increment of SiO₂ and Al₂O₃ is only 0.00115and 0.00054, this influence for the calculation results of effective atomic number is limited.3. For the measurements of portable isotope radioactive sources X fluorescence analyzer, scattering Angle is a very important parameter. Different scattering Angle will have a big impact on results. And X fluorescence analyzer’s scattering Angle inspired by isotopic source is difficult to accurately determine. This paper roughly shows the calculated best scattering Angle of IED 2000P portable multi elements X ray fluorescence analyzer, by a lot of experiments of analysis pure samples SiO₂ and Al₂O₃ whose effective atomic number is very close to geological samples.4. In in depth researchof the relationship of scattering peak and effective atomic number. And get a method of calculating samples’effective atomic number （spectral lines scattering method）, and apply to xinjiang tianshan, Mengmala and Touxun these three work area. Comparing to effective atomic number measured by Wavelength dispersive X fluorescence spectrometer （wavelength dispersion Method）, it has a smaller relative error, and good results were obtained.1) In the whole work area of Hongshanzui, effective atomic number calculated by spectral lines scattering method is 13.23, and for wavelength dispersion Method, it’s 13.45. The relative error is 1.67%.2) In the whole work area of Mengmala, effective atomic number calculated by spectral lines scattering method is 12.93, and for wavelength dispersion Method, it’s 13.20. The relative error is 2.06%.3) In the whole work area of Tuoxun, effective atomic number calculated by spectral lines scattering method is 13.14, and for wavelength dispersion Method, it’s 13.17. The relative error is 0.32%.更多还原