Dominance of hole-boring radiation pressure acceleration regime with thin ribbon of ionized solid hydrogen

TL;DR

This study demonstrates that using a thick cryogenic hydrogen target with multiPW lasers enhances proton acceleration efficiency through hole-boring radiation pressure, outperforming thinner plastic foils, with detailed 3D PIC simulations supporting these findings.

Contribution

It introduces the use of thick cryogenic hydrogen targets for laser-driven proton acceleration and compares 2D and 3D simulation results, highlighting the dominance of the hole-boring regime.

Findings

Thick hydrogen targets yield higher proton energies than thin plastic foils.

3D PIC simulations show larger interior proton energies during hole boring.

Ultrashort pulses reduce the number of accelerated protons.

Abstract

Laser-driven proton acceleration from novel cryogenic hydrogen target of the thickness of tens of microns irradiated by multiPW laser pulse is investigated here for relevant laser parameters accessible in near future. It is demonstrated that the efficiency of proton acceleration from relatively thick hydrogen solid ribbon largely exceeds the acceleration efficiency for a thinner ionized plastic foil, which can be explained by enhanced hole boring driven by laser ponderomotive force in the case of light ions and lower target density. Three-dimensional (3D) particle-in-cell (PIC) simulations of laser pulse interaction with relatively thick hydrogen target show larger energies of protons accelerated in the target interior during the hole boring phase and reduced energies of protons accelerated from the rear side of the target by quasistatic electric field compared with the results obtained from two-dimensional (2D) PIC calculations. Linearly and circularly polarized multiPW laser pulses of duration exceeding 100 fs show similar performance in terms of proton acceleration from both the target interior as well as from the rear side of the target. When ultrashort pulse ($\sim$ 30 fs) is assumed, the number of accelerated protons from the target interior is substantially reduced.