Micro-pillar surface orientation and its effect on laser-accelerated proton beam quality

Abstract

Implementing micro-pillar protrusions on a micro-target surface can potentially enhance laser-to-ion energy conversion and proton beam collimation during laser-driven ion acceleration. Using the particle-in-cell (PIC) simulation code EPOCH, a singular pulse of a 1 μm relativistic Gaussian laser beam irradiated the front surface of a 2 μm thick Al substrate with micro-pillars, heating the target and producing plasma. The laser-plasma interaction produced a strong electric field (10¹³ V/m) and proton beams with energies tens of MeV high. The target with rear surface micro-pillars emitted stronger electric fields, while the target with front surface micro-pillars produced proton beams of higher energy and lower divergence. However, the implementation of micro-pillars appeared to have lowered the proton beam density.