X射线束斑强度分布对EDXRF分析精度影响研究

Study on Influence of X-Ray Beam Spot Intensity on EDXRF Analytical Precision

能量色散X射线荧光（EDXRF）光谱法分析复杂背景样品中的低含量元素时,X射线散射产生的干扰会影响系统检测精度,而X射线散射与X射线束斑强度密切相关。利用微光像增强器采集了不同工作电流下X射线束斑的投影图像,用投影光斑外围杂散射线强度表征X射线散射强度,分析得到了减小X射线束斑强度的两种方式,即降低X射线管工作电流和减小准直器孔径。通过实验对比发现,利用EDXRF法分析样品中低组分元素时,用减小准直器孔径的方法来降低X射线散射,要比降低X射线管电流的方式更加有效,且减小准直器孔径的同时增大X射线管工作电流能够提高系统检测精度。实验结果表明,该方法检测土壤中微量元素Cr时,实际相对误差为0.9%~6.6%,相对标准偏差为0.7%~1.5%,经过t检验,p〉0.05,测试结果在统计学上与标准样品结果无显著差异。

When energy dispersive X-ray fluorescence （EDXRF） spectroscopy is used to analyze low-content element in samples with complicated background, interference from X-ray scattering will affect system detection precision, and X-ray scattering is closely related to X-ray beam spot intensity. A shimmer image intensifier is utilized to collect projection image of X-ray beam spot under different working current and the intensity of mixed and scattered ray around the projection flare is used to characterize X-ray scattering intensity, two methods to reduce X-ray beam spot intensity, i.e. reducing X-ray tube current and collimator diameter, are obtained so as to reduce the impact of the mixed and scattered ray on X-ray. It is found that when the EDXRF method is used to analyze low-content element in samples, the method of reducing collimator diameter is more effective than the method of reducing X-ray tube current for decrease of X-ray scattering, and the system detection precision can be improved when the collimator diameter is reduced and the X-ray tube current is increased meanwhile. The experimental results show that for detecting microelement Cr in the soil, actual relative error of this method is 0.9%- 6.6%, and relative standard deviation is 0.7%-1.5%. p is higher than 0.05 in t test, and the test result has no significant difference with standard samples statistically.