Russian quadruplet quadrupole based electron beam optics for ultrafast electron microscopy

Abstract

Mega-electron-Volt Ultrafast Electron Microscope (MeV UEM) has become a promising tool to real-time observe ultrafast dynamics at the atomic scale, where a magnetic objective lens system is critical to manipulating the high-energy beam to achieve point-to-point imaging. However, the upper limit of spatial resolution is mainly determined by the high-order chromatic aberration resulting from the electron energy spread and the imaging lens system. A magnetic lens system based on the Russian Quadruplet (RQ) is being studied to improve the degree of symmetry and further reduce the aberration. The beam optics design and multi-target optimization are finished to achieve a good spatial resolution of point-to-point imaging. This paper will introduce the theoretical deviation and design results of our first-stage imaging lens system, and second-order beam optics is optimized further to improve the resolution.