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Description
A laser beam carrying orbital angular momentum (OAM) is characterized by a helical wavefront, with an optical vortex in the center. Most applications of OAM laser beams, including optical prob-ing, particle manipulation, and communications, operate at relatively low intensities. Recently, high-intensity OAM beams have been generated using spiral phase mirrors, expanding their applicability in high-power laser-plasma experiments. Here, we present laser wakefield acceleration (LWFA) driven by relativistic optical vortex beams performed at the ZEUS Laser Facility. We observe high-energy electron beams with broadband spectra exhibiting distinct energy branches and correlated angular dispersion. Quasi-3D particle-in-cell simulations show agreement with the observed spec-tra, and further reveal helical electron trajectories within the ring-shaped wakefield. The results demonstrate the correlation between the helical phase structure of the driven laser pulse and the phase-space structure of the accelerated electron beam, and are consistent with angular momentum transfer between the laser driver and the accelerated electrons. This work demonstrates that OAM offers a new degree of freedom for structuring relativistic electron beams in LWFA.
| Working group | WG1 |
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