Ion acceleration at two collisionless shocks in a multicomponent plasma

TL;DR

This study uses particle-in-cell simulations to demonstrate the formation of two distinct electrostatic collisionless shocks in a multicomponent plasma driven by intense laser interactions, revealing new insights into ion acceleration mechanisms.

Contribution

The paper presents the first detailed simulation of two separate collisionless shocks in a multicomponent plasma under laser driving, highlighting the role of ion charge-to-mass differences.

Findings

Two shocks form at different positions with distinct ion species.

Ion energies follow a power-law dependence on laser intensity.

Higher ion fluxes are observed compared to single-component plasmas.

Abstract

Intense laser-plasma interactions are an essential tool for the laboratory study of ion acceleration at a collisionless shock. With two-dimensional particle-in-cell calculations of a multicomponent plasma we observe two electrostatic collisionless shocks at two distinct longitudinal positions when driven with a linearly-polarized laser at normalized laser vector potential a0 that exceeds 10. Moreover, these shocks, associated with protons and carbon ions, show a power-law dependence on a0 and accelerate ions to different velocities in an expanding upstream with higher flux than in a single-component hydrogen or carbon plasma. This results from an electrostatic ion two-stream instability caused by differences in the charge-to-mass ratio of different ions. Particle acceleration in collisionless shocks in multicomponent plasma are ubiquitous in space and astrophysics, and these calculations identify the possibility for studying these complex processes in the laboratory.