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Towards jitter-free ultrafast electron diffraction technology

December 23, 2019

Stroboscopic visualization of nuclear or electron dynamics in atoms, molecules or solids requires ultrafast pump and probe pulses and a close to perfect synchronization between the two. We have developed a 3 MeV ultrafast electron diffraction (UED) probe technology that nominally reduces the electron bunch duration and the arrival time jitter to the sub-femtosecond level. This simple configuration uses a radiofrequency photogun and a 90° achromatic bend and is designed to provide effectively jitter-free conditions. Terahertz streaking measurements reveal an electron bunch duration of 25 fs, even for a charge as high as 0.6 pC, and an arrival time jitter of 7.8 fs, the latter limited by only the measurement accuracy. From pump–probe measurements of photoexcited bismuth films, the instrument response function was determined to be 31 fs. This pioneering jitter-free technique paves the way towards UED of attosecond phenomena in atomic, molecular and solid-state dynamics.




THz streaking experiment. a,b, The electron beam image on the P43 phosphor screen located 2.4 m away from the slit without (a) and with (b) the THz pulse. The red dashed box indicates the region of interest used to calculate the vertical beam profiles. c, The measured THz streaking deflectogram as a function of a time delay with 10 fs steps. The red line indicates linear fitting at the zero crossing. The slope is 4.8 μrad fs−1. d, 1200 successive measurements of the beam profile without a THz pulse (the first 200 shots) and with a THz pulse (the remaining 1000 shots).

Reference: Hyun Woo Kim, Nikolay A. Vinokurov, In Hyung Baek, Key Young Oang, Mi Hye Kim, Young Chan Kim, Kyu-Ha Jang, Kitae Lee, Seong Hee Park, Sunjeong Park, Junho Shin, Jungwon Kim, Fabian Rotermund, Sunglae Cho, Thomas Feurer and Young Uk Jeong, “Towards jitter-free ultrafast electron diffraction technology”, Nature Photonics,
(https://doi.org/10.1038/s41566-019-0566-4 )
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