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采用质子激发X射线荧光法(PIXE)分析生物,医学及环境等样品时,都要涉及到厚靶的分析。通常,靶都制得很薄,即所谓的薄靶(对2.0MeV的质子束,靶厚小于1mg/cm~2),这可使对样品中各元素含量的计算简单,但其计数效率太低。为了提高效率而又节省用机时间,希望将靶制得稍厚一些,即所谓厚靶(靶厚大于1mg/cm~2),这时就必须考虑质子束通过靶层时能量损失所引起的特征X射线产生截面的变化,以及靶不同深度处产生的特征X射线穿出靶时因吸收而致的强度减弱。本文主要介绍从理论上对未考虑上述影响的薄靶计算公式的修正问题,并通过对标准桃叶的测量来验证这一计算方法的可靠性。
Proton Excited X-ray Fluorescence (PIXE) analysis of biological, medical and environmental samples, we must involve the thick target analysis. In general, the target is made very thin, the so-called thin target (for a 2.0 MeV proton beam with a target thickness of less than 1 mg / cm2) which makes the calculation of the content of each element in the sample simple but its counting efficiency too low. In order to improve the efficiency and save the machine time, the target is expected to be slightly thicker, that is, the so-called thick target (target thickness greater than 1mg / cm ~ 2), then we must consider the proton beam energy loss caused by the target layer Changes in the characteristic X-ray generation cross-section, as well as the weakening of the absorption due to absorption of the characteristic X-rays generated at different depths of the target. In this paper, we mainly introduce the theoretic correction of the thin target calculation formula without considering the above-mentioned impact, and verify the reliability of this method by measuring the standard peach leaf.