正电子致原子内壳层电离截面测量的厚靶实验方法研究

低能正电子致原子电离截面数据在理论研究和实际应用方面都具有重要的意义。然而由于正电子的特殊性质及实验的复杂性，目前国内外可获得的低能正电子截面实验数据仅限于Cu, Ag, In, Sn，且与理论值差异显著。在成功地将厚靶实验方法应用于电子致电离截面实验的基础上，本研究拟将该厚靶方法拓展至正电子截面实验，通过采用分辨率更高的实验装置，改进和优化实验方法，将厚靶方法应用于近阈能区低能正电子致原子K、L及M壳层电离截面的测量,以期获得一批有价值的低能正电子截面数据，来填补国际上这方面的空白；同时，数据处理方面，采用解析计算和Monte Carlo模拟相结合的方法，对影响正电子厚靶实验测量的各种可能因素，如正电子的散射及韧致辐射效应，正电子束流强度的确定，正电子束斑立体角对探测效率的影响等，进行细致的模拟分析和修正，最终通过实验数据与最新发展的理论值相对比，来进一步发展和完善正电子的厚靶实验方法。

The experimental data of atomic inner-shell ionization cross-sections by low-energy positron impact are significant both in theoretical researches and practical applications. As for the special characteristic of positrons and complicated experiments, the available experimental data in the literature only focus on the Cu, Ag, In and Sn, and the differences between the experiment and theory are obvious. In this study, the thick-target experimental method, which has been successfully employed in the measurements of the cross sections by electron impact, would be extended to the measurements of the cross sections by positron impact. The experimental setup with higher resolution would be adopted, and the experimental method will be improved and optimized, through which the K- L-, M- shell ionization cross sections by low-energy positron impact can be measured, and L-shell ionization cross sections of a few elements, for which significant discrepancies exist will also be remeasured, so as to obtain more available cross section data by low-energy positron impact to fill the gap. Meanwhile, in the data processing, the factors that may affect the experimental accuracy ,such as the scattering and bremsstrahlung effect, the calculation of positron beam intensity，the influence of the solid angle of positron beam spot and so on, are discussed with the combination of analytic calculation and Monte Carlo simulations. Finally, through the comparisons with predictions of the theoretical models, the thick-target method by positron impact will be further developed and improved.