TNSA using twisted laser pulses and shaped targets

Multi-MeV proton beams find various applications such as proton beam therapy or "fast ignition" of inertial confinement fusion targets. Target normal~sheath acceleration (TNSA) driven by short intense laser pulses is, in this context, a well-established proton acceleration model. The generation of multi-MeV proton beams with ultrashort duration (ps) and a high number of protons in a bunch (10$^{\mathrm{11}}$~-- 10$^{\mathrm{13}})$~has been successfully demonstrated in~experiments, but beam properties still need improvement for applications. Improving the properties of TNSA schemes is thus very important for future~progress. Here, we explore the phase-space properties of protons accelerated from shaped targets by intense lasers with orbital angular momentum~(OAM) and discuss how these lasers could be used to address key issues in proton acceleration in plasma, such as their divergence and energy. The self-consistent laser---plasma dynamics is investigated analytically and by relying on three-dimensional particle-in-cell simulations in OSIRIS.