超快电子脉冲的时域压缩

摘要

实现电子脉冲在时域上的压缩是提高条纹相机以及超快电子衍射仪等超快诊断仪器时间分辨能力的关键,本文提出用时间聚焦的方法来改善超快诊断技术的时间分辨能力.通过在时间聚焦电极上加随时间线性增加的电场来补偿光电子在光电阴极和阳极之间的时间弥散,从而使快电子相对变慢,慢电子相对变快,达到在时域压缩电子脉冲的目的.用Monte Carlo方法和有限差分法对大量光电子的追踪模拟显示,这种利用随时间变化的电场对电子脉冲速度进行调制的方法可以将初始时间宽度为300 fs的电子脉冲压缩到50 fs,为研制时间分辨能力高于100 fs的条纹相机和超快电子衍射仪等超快诊断技术提供了一种思路.%The compression of electron pulses in the temporal domain is a core technique to improve the temporal resolution of ultrafast diagnosis instruments, such as streak cameras and ultrafast electron diffraction systems. In this paper, a time focusing technique is adopted to potentially improve the physical temporal resolutions of streak cameras and ultrafast electron diffraction systems. This method uses a time-dependent acceleration field to greatly compensate the temporal dispersion between pho-tocathode and anode to accelerate the slow electrons and decelerate the fast electrons, relatively. As a result, the temperal dispersion due to an initial energy spread can be compensated to a large extent at the output of time focusing region. Tracing and simulating a large number of photoelectrons through. Monte-Carlo and finite difference methods shows that the electron pulse with a 300 fs can be compressed to 50 fs, which lays a powerful foundation for developing the streak cameras and ultrafast e-lectron diffraction systems with better than 100 fs temporal resolution.