光学渡越辐射电子束发散角二维拟合数值分析

光学渡越辐射具有良好的方向性,通过对光学渡越辐射空间分布曲线进行拟合可以对束流发散角进行计算。采用理论计算的方法,分析了电子入射到金属-介质界面时,入射角变化对光学渡越辐射二维空间分布的影响。计算分析表明,光学渡越辐射在特定偏振方向上的分布并不仅仅由电子束在该方向的发散角分量决定,同时还受到其他方向发散角分量的影响。计算对比了电子束散角一维分布和二维分布模型下光学渡越辐射空间分布的差异。结果表明,采用一维分布模型拟合计算的电子束均方根发散角存在偏差,较二维分布拟合结果偏小。

Numerical analysis of two-dimensional fitting of the electron beam divergence angle in optical transition radiation

The optical transition radiation (OTR) shows a distinct directional property with respect to the incident charged particle. The beam divergence angle can be measured by curve fitting of the OTR spatial distribution. The method of theoretical calculation is used to analyze the impact of the variation of the incident angle on the two-dimensional spatial distribution of the OTR when the electron incidents at the metal-dielectric boundary. Theoretical calculations indicate that the OTR distribution in a specific polarization is determined not only by the divergence angle component in the polarization direction but also by that in the perpendicular direction. The difference between the OTR distributions based on one-dimensional modeling and two-dimensional modeling of the divergence angle of the electron beam is calculated. It is demonstrated that the RMS divergence angle of the electron beam based on one-dimensional modeling is generally smaller than that based on two-dimensional modeling.