Photoemission sources and beam blankers for ultrafast electron microscopy

IF 2.3 2区物理与天体物理 Q3 CHEMISTRY, PHYSICAL

Structural Dynamics-Us Pub Date : 2019-09-01 DOI:10.1063/1.5117058

Lixin Zhang, J. Hoogenboom, B. Cook, P. Kruit

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引用次数: 25

Abstract

Observing atomic motions as they occur is the dream goal of ultrafast electron microscopy (UEM). Great progress has been made so far thanks to the efforts of many scientists in developing the photoemission sources and beam blankers needed to create short pulses of electrons for the UEM experiments. While details on these setups have typically been reported, a systematic overview of methods used to obtain a pulsed beam and a comparison of relevant source parameters have not yet been conducted. In this report, we outline the basic requirements and parameters that are important for UEM. Different types of imaging modes in UEM are analyzed and summarized. After reviewing and analyzing the different kinds of photoemission sources and beam blankers that have been reported in the literature, we estimate the reduced brightness for all the photoemission sources reviewed and compare this to the brightness in the continuous and blanked beams. As for the problem of pulse broadening caused by the repulsive forces between electrons, four main methods available to mitigate the dispersion are summarized. We anticipate that the analysis and conclusions provided in this manuscript will be instructive for designing an UEM setup and could thus push the further development of UEM.

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用于超快电子显微镜的光发射源和光束消光器

观察原子运动是超快电子显微镜（UEM）的梦想目标。到目前为止，由于许多科学家在开发用于UEM实验的短电子脉冲所需的光电发射源和光束阻断器方面的努力，已经取得了巨大进展。虽然通常已经报道了这些设置的细节，但尚未对用于获得脉冲束的方法进行系统概述，并对相关源参数进行比较。在本报告中，我们概述了UEM的基本要求和重要参数。对UEM中不同类型的成像模式进行了分析和总结。在回顾和分析了文献中报道的不同类型的光发射源和光束消隐器后，我们估计了所回顾的所有光发射源的降低亮度，并将其与连续光束和消隐光束中的亮度进行了比较。针对电子间排斥力引起的脉冲增宽问题，总结了四种主要的缓解色散的方法。我们预计，本文中提供的分析和结论将对设计UEM设置具有指导意义，从而推动UEM的进一步发展。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Structural Dynamics-Us CHEMISTRY, PHYSICALPHYSICS, ATOMIC, MOLECU-PHYSICS, ATOMIC, MOLECULAR & CHEMICAL

CiteScore

5.50

自引率

3.60%

发文量

审稿时长

16 weeks

期刊介绍： Structural Dynamics focuses on the recent developments in experimental and theoretical methods and techniques that allow a visualization of the electronic and geometric structural changes in real time of chemical, biological, and condensed-matter systems. The community of scientists and engineers working on structural dynamics in such diverse systems often use similar instrumentation and methods. The journal welcomes articles dealing with fundamental problems of electronic and structural dynamics that are tackled by new methods, such as: Time-resolved X-ray and electron diffraction and scattering, Coherent diffractive imaging, Time-resolved X-ray spectroscopies (absorption, emission, resonant inelastic scattering, etc.), Time-resolved electron energy loss spectroscopy (EELS) and electron microscopy, Time-resolved photoelectron spectroscopies (UPS, XPS, ARPES, etc.), Multidimensional spectroscopies in the infrared, the visible and the ultraviolet, Nonlinear spectroscopies in the VUV, the soft and the hard X-ray domains, Theory and computational methods and algorithms for the analysis and description of structuraldynamics and their associated experimental signals. These new methods are enabled by new instrumentation, such as: X-ray free electron lasers, which provide flux, coherence, and time resolution, New sources of ultrashort electron pulses, New sources of ultrashort vacuum ultraviolet (VUV) to hard X-ray pulses, such as high-harmonic generation (HHG) sources or plasma-based sources, New sources of ultrashort infrared and terahertz (THz) radiation, New detectors for X-rays and electrons, New sample handling and delivery schemes, New computational capabilities.