Collisionless shocks in laboratory astrophysics experiments

TL;DR

This study investigates how plasma collisions affect laser-driven collisionless shock formation and ion acceleration in laboratory astrophysics, demonstrating that collisions can weaken shock effects and improve ion energy spectra.

Contribution

It compares two collisional algorithms in EPOCH and SMILEI codes, showing that collisions influence shock dynamics and ion acceleration, confirming the collisionless nature of shocks in experiments.

Findings

Collisions weaken space-charge effects in shock formation.

Ion energy spectra improve by at least 10% with collisions.

Results confirm the collisionless nature of shocks in laboratory settings.

Abstract

Influence of the plasma collisions on the laser-driven collisionless shock formation and subsequent ion acceleration is studied on the basis of two different collisional algorithms and their implementations in two well-known particle-in-cell codes EPOCH and SMILEI. In this setup, an ultra-intense incident laser pulse generates hot-electrons in a thick target, launching an electrostatic shock at the laser-plasma interface while also pushing the interface through the hole-boring effect. We observe, to varying degrees, the weakening of the space-charge effects due to collisions and improvements ($\ge 10\%$) in the energy spectra of quasi-monoenergetic ions in both PIC codes EPOCH and SMILEI. These results establish the `collisionlessness' of the collisionless shocks in laboratory astrophysics experiments.