Low divergence multi-10-MeV protons driven by a twisted driver

The study of compact high-intensity laser-driven proton sources is motivated due to a wide range of potential applications, from high brightness injectors for accelerators to inertial fusion and medical applications [1]. A crucial task to fully realize their potential is to reduce the proton bunch divergence while maintaining energy gain.

We demonstrate that a twisted laser [2] in combination with a double-layer target (for enhanced proton energies [3]) has the potential to reduce the proton bunch divergence by almost an order of magnitude while accelerating to similar energies (multi-10-MeV) when compared to a Gaussian driver. We find that a less pronounced self-focusing of the twisted laser [4] plays a critical role in our findings and identify a regime that allows for consistent acceleration of highly collimated proton bunches for a broad range of moderate laser energies. The self-consistent laser–plasma dynamics is investigated analytically and by relying on three-dimensional particle-in-cell simulations in OSIRIS.

[1] A. Macchi et al., Rev. Modern Phys. 85, 715 (2013)., [2] L. Allen et al., Phys. Rev. A 45, 8185 (1992). [3] M. J. Ma et al., Phys. Rev. Lett. 122, 014803 (2019), [4] L. Sa and J. Vieira, Phys. Rev. A 100, 013836 (2019).