Coherent femtosecond low-energy single-electron pulses for time-resolved diffraction and imaging: A numerical study
Coherent femtosecond low-energy single-electron pulses for time-resolved diffraction and imaging: A numerical study
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DOI：
10.1063/1.4768204
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发表时间：
2012-12-01
影响因子：
3.2
通讯作者：
Ernstorfer, R.
中科院分区：
文献类型：
--
作者：
Paarmann, A.;Gulde, M.;Ernstorfer, R.
为了在超快电子衍射和低能电子无损成像领域的应用，对纳米针尖光发射的相干飞秒单电子波包的性质进行了数值研究。对于两种不同的几何形状，我们分析了从针状发射极到阳极传播过程中的时间和空间展宽，确定了实现飞秒时间分辨率的实验参数和挑战。简单的尖端阳极几何结构是最通用的，并且允许使用非常紧凑的实验设计进行几十飞秒持续时间的电子脉冲，然而，对电子束准直的控制非常有限。还研究了一个更复杂的几何结构，包括一个抑制-提取静电单元和一个透镜，类似于典型的场发射电子显微镜光学，允许完全控制光束参数。使用这样的设计，我们发现在聚焦电子束中类似于230 fs的脉冲是可行的。实现低于百飞秒时间分辨率的主要限制是这种设备的典型尺寸，我们建议实现更紧凑的电子光学器件以获得最佳性能。(C) 2012年美国物理研究所。[http://dx.doi.org/10.1063/1.4768204]
We numerically investigate the properties of coherent femtosecond single electron wave packets photoemitted from nanotips in view of their application in ultrafast electron diffraction and non-destructive imaging with low-energy electrons. For two different geometries, we analyze the temporal and spatial broadening during propagation from the needle emitter to an anode, identifying the experimental parameters and challenges for realizing femtosecond time resolution. The simple tip-anode geometry is most versatile and allows for electron pulses of several ten of femtosecond duration using a very compact experimental design, however, providing very limited control over the electron beam collimation. A more sophisticated geometry comprising a suppressor-extractor electrostatic unit and a lens, similar to typical field emission electron microscope optics, is also investigated, allowing full control over the beam parameters. Using such a design, we find similar to 230 fs pulses feasible in a focused electron beam. The main limitation to achieve sub-hundred femtosecond time resolution is the typical size of such a device, and we suggest the implementation of more compact electron optics for optimal performance. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4768204]