Hafke B, Witte T, Brand C, Duden Th, Horn-von Hoegen M
Department of Physics and Center for Nanointegration CENIDE, University of Duisburg-Essen, Lotharstraße 1, 47057 Duisburg, Germany.
Th. Duden Konstruktionsbüro, Borgsen-Allee 35, 33649 Bielefeld, Germany.
Rev Sci Instrum. 2019 Apr;90(4):045119. doi: 10.1063/1.5086124.
We present a newly designed 30 kV pulsed electron gun for ultrafast electron diffraction suited for pump-probe setups driven by femtosecond laser pulses. The electron gun can be operated both in transmission and reflection geometry. A robust design with a back illuminated Au photocathode, extraction fields of 7.5 kV/mm, and a magnetic focus lens ensures reliable daily use. Magnetic deflectors allow for beam alignment and characterization. Focusing of the UV pulse on the photocathode results in a small source size of photoemitted electrons and thus a high transverse coherence length of more than 50 nm in diffraction. A low difference of ΔE = 0.1 eV between the work function of the 10 nm Au photocathode and photon energy of the frequency tripled UV laser pulses results in an instrumental temporal resolution of 330 fs full width at half maximum. This resolution is discussed with respect to the number of electrons per pulse.
我们展示了一种新设计的30 kV脉冲电子枪，用于超快电子衍射，适用于由飞秒激光脉冲驱动的泵浦-探测装置。该电子枪可在透射和反射几何结构中运行。其坚固的设计采用背照式金光阴极、7.5 kV/mm的提取场和磁聚焦透镜，确保了日常可靠使用。磁偏转器可实现束流对准和表征。紫外脉冲聚焦在光阴极上会导致光发射电子的源尺寸较小，从而在衍射中产生超过50 nm的高横向相干长度。10 nm金光阴极的功函数与三倍频紫外激光脉冲的光子能量之间的低差值ΔE = 0.1 eV，导致仪器的时间分辨率为半高宽330 fs。本文针对每个脉冲的电子数量对该分辨率进行了讨论。
