成像电子光学系统空间和时间像差的均方根半径(RMS)研究

Study on the root mean square (RMS) radius of spatial-temporal aberrations in imaging electron-optical systems

在成像电子光学系统中,均方根半径不仅可以表示系统的时间和空间分辨率特性,而且可以作为计算调制传递函数的一个辅助评价指标,具有计算量小,直观方便等优点。研究和推导了成像电子光学系统中逸出光电子的初角度为朗伯分布,初能量分别为余弦分布、贝塔分布和麦克斯韦分布下的系统时间和横向像差的均方根半径表达式,求解了不同初能分布下的时间和横向像差的均方根半径的最小值及其对应的最佳像平面位置,并对其进行了比较分析。结果表明,该研究不仅对计算和评价成像系统空间和时间分辨率具有实际意义,而且为选择合适的光阴极以满足不同要求的像管和条纹管的设计提供了理论指导。

In imaging electron-optical systems, the root mean square（RMS）radius can not only express the characteristics of spatial-temporal resolutions, but also serve as a supplementary evaluation index of electron-optical modulation transfer function with the advantages of less calculation, more convenience and more visual. The expressions of RMS ra- dius of spatial-temporal aberrations are deduced and discussed with the assumptions that the initial emission angle of photoelectron obeys Lambert distribution and the initial energy obeys Cosine, Beta and Maxwell distributions respectively. The minimum values of RMS radius of spatial-temporal aberrations and their corresponding optimal positions of imaging plane are solved. This research not only has importance in spatial-temporal resolutions calculation and evaluation of imaging systems, but also provides theoretical guidance for selecting suitable photocathode in the design of image tubes and streak tubes.