Ion energy scaling under optimum conditions of laser plasma acceleration

TL;DR

This paper derives a new scaling law for proton energy in laser plasma acceleration, showing how maximum proton energy depends on laser pulse energy through 3D PIC simulations, with implications for optimizing ion acceleration.

Contribution

The paper introduces a novel scaling law $e \,\sim\ E_L^{0.7}$ for proton energy based on extensive 3D PIC simulations and analytical modeling, advancing understanding of laser-driven ion acceleration.

Findings

Protons are accelerated during femtosecond laser interactions with semi-transparent targets.

Maximum proton energy scales as $E_L^{0.7}$ across various laser parameters.

Optimal target thickness enhances ion energy even below the radiation pressure regime.

Abstract

A new, maximum proton energy, $e$, scaling law with the laser pulse energy, $E_L$ has been derived from the results of 3D particle-in-cell (PIC) simulations. Utilizing numerical modelling, protons are accelerated during interactions of the femtosecond relativistic laser pulses with the plain semi-transparent targets of optimum thickness [Esirkepov {\it et al.} Phys. Rev. Lett. {\bf 96}, 105001 (2206)]. The scaling, $e \sim E_L^{0.7}$, has been obtained for the wide range of laser energies, different spot sizes, and laser pulse durations. Our results show that the proper selection of foil target optimum thicknesses, results in a very promising increase of the ion energy with the laser intensity even in the range of parameters below the radiation pressure (light sail) regime. The proposed analytical model is consistent with numerical simulations.