Femtosecond Time‐Resolved Electron Microscopy

Abstract

SUMMARY The revealing and understanding of ultrafast structural‐change induced dynamics not only are essential in physics, chemistry, and biology, but also are indispensable for the development of new materials, new devices, and applications. A new radio‐frequency electron gun‐based ultrafast relativistic electron microscopy (UEM) is being developed at Osaka University to for direct probing structural changes at the atomic scale with sub‐100 fs temporal resolution in materials. The first prototype femtosecond time‐resolved relativistic‐energy UEM was constructed at end of October 2012. Both relativistic‐energy electron diffraction and image measurements have been successfully performed using a femtosecond electron beam. In this paper, the development of the UEM prototype and the first experiments on relativistic‐energy electron imaging are reported.

A Compact Ultrafast Electron Diffractometer with Relativistic Femtosecond Electron Pulses

“…The Ti:Sapphire laser oscillator was time-synchronized to an external rf signal of 79.3 MHz, which is produced by dividing the accelerating 2856-MHz rf signal by 1/36. The time jitter between the laser pulse and the 79.3-MHz rf phase was 61 fs RMS [16], being approximately equal to the time jitter between the pump laser pulse and the electron pulse.…”

“…In recent years, relativistic-energy UEDs were developed with an advanced particle accelerator technology of photocathode radio-frequency electron gun (rf gun) [8][9][10][11][12][13][14][15]. Recently, an ultrafast electron microscope (UEM) using the rf gun has been developed at Osaka University [16,17]. The rf gun was operated with a high peak rf electric field of 100 MV/m on the photocathode, which is ten times higher than that of the dc gun.…”

Femtosecond Electron Diffraction Using Relativistic Electron Pulses

“…Therefore, the electrons emitted from the photocathode can be quickly accelerated into the relativistic energy region to minimize the space-charge effects in the pulse, yielding a femtosecond or picosecond pulse with numerous electrons. Recently, Yang et al [28][29][30] developed the first prototype for relativistic ultrafast electron microscopy using the RF gun. They succeeded in generating high-brightness electron pulses with a pulse duration of 100 fs containing 10 7 electrons at an energy of 3 MeV.…”

Evaluation of photocathode emission properties in an electron gun: one-step photoemission from bulk band to vacuum states

“…Planar, pulsed laser-driven, solid-state photocathodes are the most commonly employed electron sources for of x-ray free electron lasers (XFELs) [1,2], ultrafast electron diffraction [3][4][5][6] systems, and current (and potential future ultrafast) dynamic transmission electron microscopes (DTEMs) [7][8][9]-cutting-edge research instruments designed to study the atomic-scale dynamic properties of matter on fast timescales. The space-time resolution performance of these instruments is known to be limited primarily by the emission properties of the cathode.…”