A Particle-In-Cell Code Comparison for Ion Acceleration: EPOCH, LSP, and WarpX

TL;DR

This study compares three Particle-in-Cell codes—EPOCH, LSP, and WarpX—in simulating relativistic laser-driven ion acceleration, analyzing their accuracy, statistical variability, and computational efficiency.

Contribution

It provides the first direct comparison of these three PIC codes for laser-ion acceleration, including statistical analysis and performance benchmarking.

Findings

Strong agreement in plasma density and ion spectra across codes.

Statistical fluctuations are significant and consistent across simulations.

Performance varies with processor count, informing computational choices.

Abstract

There are now more Particle-in-Cell (PIC) codes than ever before that researchers use to simulate intense laser-plasma interactions. To date, there have been relatively few direct comparisons of these codes in the literature, especially for relativistic intensity lasers interacting with thin overdense targets. To address this we perform a code comparison of three PIC codes: EPOCH, LSP, and WarpX for the problem of laser-driven ion acceleration in a 2D(3v) geometry for a $10^{20}$ W cm$^{-2}$ intensity laser. We examine the plasma density, ion energy spectra, and laser-plasma coupling of the three codes and find strong agreement. We also run the same simulation 20 times with different random seeds to explore statistical fluctuations of the outputs. We then compare the execution times and memory usage of the codes (without "tuning" to improve performance) using between 1 and 48 processors on one node. We provide input files to encourage larger and more frequent code comparisons in this field.