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arXiv · 2508.20685

Terahertz control of relativistic electron beams for femtosecond bunching and laser-synchronized temporal locking

Morgan T. Hibberd·Christopher T. Shaw·Joseph T. Bradbury·Daniel S. Lake·Connor D. W. Mosley·Sergey S. Siaber·Laurence J. R. Nix·Beatriz Higuera-González·Thomas H. Pacey·James K. Jones·David A. Walsh·Robert B. Appleby·Graeme Burt·Darren M. Graham·Steven P. Jamison
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Abstract

Femtosecond relativistic electron bunches and micro-bunch trains synchronised with femtosecond precision to external laser sources are widely sought for next-generation accelerator and photonic technologies, from extreme UV and X-ray light sources for materials science, to ultrafast electron diffraction and future high-energy physics colliders. While few-femtosecond bunches have been demonstrated, achieving the control, stability and femtosecond-level laser synchronisation remains critically out of reach. Here we demonstrate a concept for laser-driven compression of high-energy (35.5 MeV) electron bunches with temporal synchronisation to a high-power (few-TW) laser system. Laser-generated multi-cycle terahertz (THz) pulses drive periodic electron energy modulation, enabling subsequent magnetic compression capable of generating tuneable picosecond-spaced bunch trains with 30 pC total charge and 50 A peak currents, or to compress a single bunch by a factor of 27 down to 15 fs duration. The THz-driven compression simultaneously drives temporal-locking of the bunch to the THz drive laser, providing a route to femtosecond-level synchronisation, overcoming the timing jitter inherent to radio-frequency accelerators and high-power laser systems. This THz technique offers compact and flexible bunch control with unprecedented temporal synchronisation, opening a pathway to unlock new capabilities for free electron lasers, ultrafast electron diffraction and novel plasma accelerators.

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Morgan T. Hibberd, Christopher T. Shaw, Joseph T. Bradbury, Daniel S. Lake, Connor D. W. Mosley, Sergey S. Siaber, Laurence J. R. Nix, Beatriz Higuera-González, Thomas H. Pacey, James K. Jones, David A. Walsh, Robert B. Appleby, Graeme Burt, Darren M. Graham, Steven P. Jamison. 2025-08-28. Terahertz control of relativistic electron beams for femtosecond bunching and laser-synchronized temporal locking. https://arxiv.org/abs/2508.20685

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