Towards Dephasingless LWFA | Aaron Liberman

Speaker: Aaron Rafael Liberman, Researcher at the Weizmann Institute of Science Laser-wakefield accelerators (LWFAs) have demonstrated the ability to generate high-quality, monoenergetic electron beams. Yet, efforts to achieve higher electron energies and improved accelerator efficiency remain limited by several fundamental constraints, most notably electron dephasing and beam diffraction. One promising approach to mitigating these limitations is the use of structured light to control the on-axis propagation velocity within LWFAs. By combining the diffraction-resistant characteristics of Bessel beams with spatiotemporal pulse shaping, this method promises an improved balance of extended acceleration distances and strong accelerating gradients. In this seminar, we report the first experimental observation of wakefields driven by such structured-light beams as well as the first experimental evidence of the mitigation of dephasing in electron acceleration. Spatiotemporally engineered laser pulses are focused using a specialized mirror to produce a quasi-Bessel beam, and the resulting wakefields are directly measured using femtosecond relativistic electron microscopy. Numerical simulations support the experimental observations and provide new insight into this largely unexplored regime. We experimentally demonstrate control over the on-axis propagation velocity of the wakefield and follow its evolution throughout the focal region. Furthermore, we investigate how targeted spatiotemporal modifications affect both the wakefield structure and its propagation velocity. Finally, we present the first successful acceleration of electrons using these wakefields. We compare the electron profiles obtained by wakefields traveling at different velocities, demonstrating that the faster wakefield is able to achieve a higher electron cutoff energy. By combing our data with insights from simulations, we suggest the first successful partial mitigation of dephasing with such techniques. Together, these results lay the groundwork for leveraging structured-light-based techniques to overcome dephasing limitations in LWFA systems. This seminar is part of the EuPRAXIA Virtual Seminar Series https://agenda.infn.it/e/eupraxia-vir...