兆伏特超快电子成像系统为微观物质机理的探索提供了一种有效的研究手段，而电子聚焦系统是其核心组成部分。目前电子聚焦系统大多采用常温或超导螺线管磁铁，体积大，结构复杂,需要高稳定性的电源、冷却水等附属设施。永磁四极磁铁是一个值得考虑的选择，其在超快电子成像领域的尝试刚刚开展。永磁聚焦元件磁场强度高，体积小，没有散热问题，不需要冷却系统，且可以长时间提供稳定的磁场。本项目计划为超快电子成像系统研制一套由永磁四极磁铁组成并采用Russian quatruplet结构的电子聚焦系统。这种反对称结构的电子聚焦系统相比于前人的工作有很大改进，能够实现在水平和垂直两个横向方向上同时成像，且放大率相同，从而满足实用的要求。本项目的研究工作将为永磁聚焦元件在成像设备小型化方向的应用储备技术。

MeV ultrafast electron microscope has been proposed as a promising tool to study structural dynamics at the nanometer spatial scale and picosecond temporal scale. Electronic focusing system, which is the key component of the ultrafast electron microscope, mostly employs solenoids. Solenoids with large size and complicated structure require stable power supply and cooling system. The attempt using permanent magnetic quadrupole just began. Permanent magnet can provide stable and strong magnetic field in small volume without cooling problem. This project will develop a focusing system called Russian quatruplet with four permanent magnetic quadrupoles and antisymmetric structure. Compared to former work, this system can provide equal magnification in both horizontal and vertical direction. And the image planes for the two direction match at the same location. These advantages of the new system meet the requirement of electron microscope. This project will develop the permanent focusing device for miniaturization of electron microscope.