Study on Relationship between Microinhomogeneity and Measurement Precision of γ-Ray Transmission Technique
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摘要: 本文研究了单能γ射线透射法测量精度与样品微观均匀性之间的关系。通过建立与γ射线透射方向平行、垂直的微观分布模型，并对不同模型展开理论分析得出，与γ射线透射平行方向的微观不均匀性会导致γ射线的透射率增大，进而导致质量厚度测量结果偏低；与γ射线透射垂直方向的微观不均匀性对测量结果无影响。同时还建立了不同质量厚度分布的微观不均匀性模型，并用这些模型进行了测量精度受微观不均匀性影响的规律分析，其中模型的不均匀性状态用变异系数进行描述。分析结果表明，相同实验条件下变异系数越大对γ射线透射强度的影响越大，且γ射线透射率的相对变化量与样品变异系数之间存在线性递增关系。Abstract: In this paper, the relationship between the measurement accuracy of monoenergetic γ-ray transmission method and the microscopic uniformity of the sample is studied. By establishing a microscopic distribution model parallel to and perpendicular to the transmission direction of γ-ray, and carrying out theoretical analysis of different models, it is concluded that the microscopic inhomogeneity in the direction parallel to the transmission of γ-ray will increase the transmittance of the γ-ray, which in turn leads to low mass thickness measurement results; the microscopic inhomogeneity in the direction perpendicular to the transmission of γ-ray has no effect on the measurement results. At the same time, the microscopic inhomogeneity models of different mass thickness distributions are established, and these models are used to analyze the law that the measurement accuracy is affected by the microscopic inhomogeneity. The inhomogeneity of the model is described by the coefficient of variation. The results show that under the same experimental conditions, the greater the coefficient of variation, the greater the influence on the transmission intensity of γ-ray, and there is a linear increasing relationship between the relative change of γ-ray transmittance and the coefficient of variation of the sample.
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图 2 不同微观分布状态的纵向微分模型
Figure 2. Longitudinal Differential Models with Different Microscopic Distributions
图 3 样品变异系数值与射线透射强度相对偏差的拟合结果
Figure 3. Fitting Results of the Relative Deviation between the Sample Coefficient of Variation and the Ray Transmission Intensity
表 1 不同变异系数值模型的计算结果
Table 1. Calculated Results of Models with Different Coefficients of Variation
变异系数 γ射线透射强度 射线透射强度相对偏差/% 0.514 0.463 I0 25.9 0.429 0.449 I0 22.1 0.337 0.433 I0 17.7 0.238 0.416 I0 13.1 0.109 0.388 I0 5.5 0.049 0.377 I0 2.5 0.000 0.368 I0 0 
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