光子学报, 2006, 35 (12): 1827, 网络出版: 2010-06-03
飞秒电子衍射系统的设计
Design of an Ultra-fast Electron Diffraction System
超快电子衍射 微通道板 磁聚焦 时间分辩 Ultra-fast electron diffraction MCP Imaging Magnetic focusing Temporal resolution
摘要
研发的超快电子衍射系统由超快电子枪、样品室、超快读出系统、电源系统,以及真空系统等组成,该超快电子衍射系统具有较高的时间分辩能力和较强的探测能力.光电阴极是蒸镀于MgFB2窗上的35nm的银膜,该阴极对266nm的紫外光比较敏感,有较高的量子效率,又具有很好的化学稳定性.用短磁聚焦系统来实现对光电子的聚焦,有两对偏转板,其中的一对在测量时间脉宽时用作扫描板.用双MCP探测器来增强电子图像的强度,其增益在104以上,具有单电子探测能力.系统的总时间脉宽设计为358fs.
Abstract
The designed electron diffraction system consists of an ultra-fast electron gun,a sample chamber,a readout system,a power supply system,and a vacuum system,and it bears such unique characteristics as high energy,high temporal resolution,and high detection capacity.The photocathode is of a 35 nm Ag film deposited on an MgF2 glass disk,and it is sensitive to ultraviolet light with wavelength of 266 nm. A magnetic lens is used to focus the electrons. Two pairs of electric deflection plates are used in the X and Y directions respectively to control the movement of the electrons,and one pair of them will act as a scanning plate while measuring the pulse width of electrons. The sample chamber is made of stainless steel,and in the middle of the chamber there is a specimen holder,capable of shifting in three dimensions and turning around its axis. The diffraction pattern recording system has a very high detecting efficiency,and even a single electron could be detected. A cascade MCP detector is used to ensure an electron gain reached to 104. The electron gun is in a vacuum system of 10-4 Pa. The whole gun is shielded by a μ-metal sheath. The designed temporal resolution of the ultra-fast electron diffraction system(UED) is about 358fs.
吴建军, 田进寿, 王俊锋, 邹玮, 赛小锋, 赵宝升, 刘运全, 梁文锡, 张杰. 飞秒电子衍射系统的设计[J]. 光子学报, 2006, 35(12): 1827. Wu Jianjun, Tian Jinshou, Wang Junfeng, Zou Wei, Sai Xiaofeng, Zhao Baosheng, Liu Yunquan, Liang Wenxi, Zhang Jie. Design of an Ultra-fast Electron Diffraction System[J]. ACTA PHOTONICA SINICA, 2006, 35(12): 1827.