3D PIC simulations of electron beams created via reflection of intense laser light from a water target

TL;DR

This paper presents pioneering 3D PIC simulations of ultra-intense laser interactions with water targets, revealing insights into electron ejection and energy conversion efficiencies, with implications for future experimental designs.

Contribution

First 3D PIC simulations of laser-water interactions at AFRL, comparing results with 2D simulations and exploring polarization effects on electron acceleration.

Findings

3D simulations show similar energy conversion efficiencies as 2D.

Angular electron distributions differ qualitatively at higher intensities.

Circular polarization increases electron energy and conversion efficiency.

Abstract

We present 3D Particle-in-Cell (PIC) modeling of an ultra-intense laser experiment by the Extreme Light group at the Air Force Research Laboratory (AFRL) using the PIC code LSP. This is the first time PIC simulations have been performed in 3D for this experiment which involves an ultra-intense, short-pulse (30 fs) laser interacting with a water jet target at normal incidence. These 3D PIC simulation results are compared to results from 2D(3$v$) PIC simulations for both $5.4~\cdot~10^{17}$ W cm$^{-2}$ and $3~\cdot~10^{17}$ W cm$^{-2}$ intensities. Comparing the 2D(3$v$) and 3D simulation results, the laser-energy-to-ejected-electron-energy conversion efficiencies were comparable, but the angular distribution of ejected electrons show interesting differences with qualitative differences at higher intensity. An analytic plane-wave model is discussed which provides some explanation for the angular distribution and energies of ejected electrons in the 2D(3$v$) simulations. We also performed a 3D simulation with circularly polarized light and found a significantly higher conversion efficiency and peak electron energy, which is promising for future experiments.