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arXiv · 2508.10829

Energy Bunching from Sub-Cycle Ionization Injection in Laser Wakefield Acceleration

A. Angella·E. Löfquist·C. Gustafsson·V. Poulain·F. D'Souza·C. Guo·A. Persson·P. Eng-Johnsson·C. -G. Wahlström·O. Lundh
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Abstract

We report the first experimental observation of carrier-envelope phase-driven energy bunching in laser wakefield acceleration. Using a few-cycle (~9 fs), multi-terawatt laser pulse and ionization injection in a helium-nitrogen gas mixture, we observe electron spectra composed of multiple quasi-monoenergetic peaks with regular narrow energy spacing. This comb structure arises from intermittent injection from successive half-cycles of the laser field, enabled by the evolving carrier-envelope phase during propagation in the plasma. These findings establish sub-cycle ionization injection as a potential route to attosecond control in plasma acceleration, enabling injection and beam structuring synchronized to the optical waveform on sub-femtosecond timescales.

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A. Angella, E. Löfquist, C. Gustafsson, V. Poulain, F. D'Souza, C. Guo, A. Persson, P. Eng-Johnsson, C. -G. Wahlström, O. Lundh. 2025-08-14. Energy Bunching from Sub-Cycle Ionization Injection in Laser Wakefield Acceleration. https://arxiv.org/abs/2508.10829

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