Capturing relativistic wakefield structures in plasmas using ultrashort high-energy electrons as a probe

Abstract: A new method capable of capturing coherent electric field structures propagating at nearly the speed of light in plasma with a time resolution as small as a few femtoseconds is proposed. This method uses a few femtoseconds long relativistic electron bunch to probe the wake produced in a plasma by an intense laser pulse or an ultra-short relativistic charged particle beam. As the probe bunch traverses the wake, its momentum is modulated by the electric field of the wake, leading to a density variation of the probe after free-space propagation. This variation of probe density produces a snapshot of the wake that can directly give many useful information of the wake structure and its evolution. Furthermore, this snapshot allows detailed mapping of the longitudinal and transverse components of the wakefield. We develop a theoretical model for field reconstruction and verify it using 3-dimensional particle-in-cell (PIC) simulations. This model can accurately reconstruct the wakefield structure in the linear regime and it can also qualitatively map the major features of nonlinear wakes. The capturing of the injection in a nonlinear wake is demonstrated through 3D PIC simulations as an example of the application of this new method.

Impact: This work pioneered femtosecond relativistic electron probe (concept and theoretical framework), opening new avenues for plasma wakefield visualization.

Recommended citation: Chaojie Zhang, Jianfei Hua, Xinlu Xu, Fei Li, Chi-Hao Pai, Yang Wan, Yipeng Wu, Yuqiu Gu, Warren B. Mori, Chan Joshi, Wei Lu, "Capturing relativistic wakefield structures in plasmas using ultrashort high-energy electrons as a probe," Sci. Rep. 6, 29485 (2016).
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