Thermal fluid closures and pressure anisotropies in numerical simulations of plasma wakefield acceleration

TL;DR

This paper evaluates the effectiveness of various thermal fluid closure models in simulating plasma wakefield acceleration, comparing them with particle-in-cell simulations to determine their accuracy in capturing pressure anisotropies and thermal effects.

Contribution

It introduces a systematic comparison of thermal fluid closures against PIC simulations for plasma wakefield acceleration, highlighting the importance of closure choice in modeling pressure anisotropies.

Findings

Fluid models with appropriate closures can accurately reproduce PIC results.

Pressure anisotropies depend strongly on the chosen closure scheme.

Thermal effects significantly influence plasma dynamics in wakefield acceleration.

Abstract

We investigate the dynamics of plasma-based acceleration processes with collisionless particle dynamics and non negligible thermal effects. We aim at assessing the applicability of fluid-like models, obtained by suitable closure assumptions applied to the relativistic kinetic equations, thus not suffering of statistical noise, even in presence of a finite temperature. The work here presented focuses on the characterization of pressure anisotropies, which crucially depend on the adopted closure scheme, and hence are useful to discern the appropriate thermal fluid model. To this aim, simulation results of spatially resolved fluid models with different thermal closure assumptions are compared with the results of particle-in-cell (PIC) simulations at changing temperature and amplitude of plasma oscillations.