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SJTU Team & Collaborators Realise Terahertz Streaking of Femtosecond Relativistic Electron Beams 

June 11, 2018      Author: Xiang Dao

The research is conducted by Zhang Jie, Professor of the School of Physics and Astronomy, SJTU and Academician of Chinese Academy of Sciences (CAS), and a research group led by Prof. Xiang Dao, School of Physics and Academy, SJTU. Its collaborators also include research teams from East China Normal University (ECNU), Shanghai Institute of Optics and Fine Mechanics of CAS, Northwest Institute of Nuclear Technology, China Academy of Engineering Physics (CAEP), and Tsinghua University. They adapted the technique of photoelectrons streaking in the attosecond science field and expanded it to relativistic electron beam whose energy is four orders of magnitude higher than photoelectrons. Besides, with the time reference of terahertz (THz) pulses produced from lithium niobate crystals and the technology of metamaterial near-field enhancement, they kept an exact record of the terahertz streaking of relativistic electron beams at an ultrahigh resolution of 1.5 femtoseconds. Their work was recently published on the Physical Review X. 

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This work was mainly funded by the National Key Scientific Research Instruments Development Project (No. 11327902) of the National Natural Science Foundation of China (NSFC), the Innovation Group Project (No. 11721091) of the NSFC and the Youth 973 Project (No. 2015CB859700) of the Ministry of Science and Technology. The first author of the paper is Zhao Lingrong, a doctoral student.

Streaking of photoelectrons with optical lasers has been widely used for temporal characterization of attosecond extreme ultraviolet pulses. Recently, this technique has been adapted to characterize femtosecond x-ray pulses in free-electron lasers with the streaking imprinted by far-infrared and terahertz (THz) pulses. Here, we report successful implementation of THz streaking for time stamping of an ultrashort relativistic electron beam, whose energy is several orders of magnitude higher than photoelectrons. Such an ability is especially important for MeV ultrafast electron diffraction (UED) applications, where electron beams with a few femtosecond pulse width may be obtained with longitudinal compression, while the arrival time may fluctuate at a much larger timescale. Using this laser-driven THz streaking technique, the arrival time of an ultrashort electron beam with a 6-fs (rms) pulse width has been determined with 1.5-fs (rms) accuracy. Furthermore, we have proposed and demonstrated a noninvasive method for correction of the timing jitter with femtosecond accuracy through measurement of the compressed beam energy, which may allow one to advance UED towards a sub-10-fs frontier, far beyond the approximate 100-fs (rms) jitter.

 

Translated by Zhu Fengyan      Reviewed by Wang Bingyu