EDXRF仪靶源及自动控制系统的研制

【作者】 马永红；

【导师】 葛良全； 赖万昌；

【作者基本信息】 成都理工大学 ， 测试计量技术及仪器， 2006， 硕士

【摘要】 EDXRF(能量色散X荧光分析，Energy-dispersive X-Ray Fluorescence spectrometer)分析技术已被广泛应用于地质矿产资源勘查、工业过程分析和环境调查。为了提高X射线荧光分析仪的准确度、精确度与降低分析检出限，有效地提高目标元素特征X射线的激发效率是关键性措施之一。当激发源发出的初级射线的光子能量与目标元素的吸收限越接近时，特征X射线的激发效率越高。尤其是当以低功率X射线管作为X射线荧光仪的激发源时，由于轫致辐射的影响，其发射的是连续的X射线能谱，不利于能量色散X射线荧光分析，采用二次转换靶将它变成单能X射线，激发样品中的单一元素，从而对每种元素的谱线进行测量。为了对样品中的各种元素进行测量，往往需要用多种靶，通过更换不同的靶物质，改变激发源的X射线能量，使之与目标元素的吸收限相近。 本论文来源于：①国家自然资金项目“核地球物理学现场X荧光技术研究”(项目编号：40274048)；②中国地质调查局地质调查项目“手提式X荧光仪的开发和实用化研究”(项目编号：200320120002)。本文设计了采用低功率X射线管作为发射源，通过采用纯元素做靶来进行选择激发，从而将X射线管发出的初级X射线变成单能X射线，利用单能X射线来激发样品，最终达到降低元素分析检出限，提高分析准确度的目的。并且讨论了选择激发方式下X光管、二次靶、样品以及探测器之间的最佳几何布置，包括四者之间的角度、距离等关系，对二次靶与样品之间的最佳激发也进行了讨论。 本文设计出了基于单片机和光学编码器控制的闭环控制系统，实现整个换靶系统的自动化，以及对整个系统的实时监控。 最终的实验结果表明，通过选择激发，能提高待测元素的峰背比，降低待测元素的检出限。更多还原

【Abstract】 EDXRF (Energy-dispersive X-Ray Fluorescence spectrometer) has be widely used in the fields of geology, metallurgy, architectural material and environment. Born from the EDXRF so far, people have been studying how to solve their bottleneck of problems: high detection.To raise the accuracy and precision of EDXRF and reduce detection, it is one of key measure that rising source power of spectral X-ray. When energy of photon in source ray approach detection, efficiency of source power of spectral X-ray is very high. Especially when using low-power X-ray pipe as source of EDXRF, because of bremsstrahlung, X-ray spectroscopy which emitted by it is consecutive, go against EDXRF, and convert it to single-energy X-ray with second target, excitated singleness element, so measure spectrum of each element. To measure diversified elements in sample, it need diversified target to change X-ray energy of source, make it approach element detection.This text adopt low power X-ray pipe as source, selective-excitated with pure-element target, so convert orient X-ray to single-energy X-ray, use single-energy X-ray to excitated sample for the final aim that falling element detection and raising precision. Discuss something about optimal geometry location of X-ray pipe, second target, target and detector under selective-excitated situation, include angle and distance relationship between them, and discuss optimal excitated between second target and sample.Design closed-loop command system which control by single chip and optical coder, realize automation of the whole change-target system, monitor and control the whole system real time. The result of experiment show that it could raise P/B Ratio of element to be measured, and fall detection of it, by selective-excitated.更多还原