Energy enhancement of laser-driven ions by radiation reaction and Breit-Wheeler pair production in the ultra-relativistic transparency regime

TL;DR

This paper demonstrates that radiation reaction and Breit-Wheeler pair production can unexpectedly enhance the energy of laser-driven Carbon ions in the ultra-relativistic transparency regime, revealing new mechanisms for ion acceleration.

Contribution

It uncovers the counterintuitive role of quantum electrodynamics effects in boosting ion energies during laser acceleration in the transparency regime.

Findings

Radiation reaction and pair production increase ion energy.

Pair plasma streams forward, reducing transverse electron momentum.

Non-classical effects improve maximum Carbon ion energies.

Abstract

The impact of radiation reaction and Breit-Wheeler pair production on acceleration of fully ionized Carbon ions driven by an intense linearly-polarized laser pulse has been investigated in the ultra-relativistic transparency regime. Against initial expectations radiation reaction and pair production at ultra-high laser intensities is found to enhance the energy gained by the ions. The electrons lose most of their transverse momentum and the additionally produced pair plasma of Breit-Wheeler electrons and positrons co-stream in the forward direction as opposed to the existing electrons streaming at an angle above zero. We discuss how these observations could be explained by the changes in the phase velocity of the Buneman instability, that is known to aid ion acceleration in the Breakout-Afterburner regime, by tapping the free energy in the relative electron and ion streams. We present evidence that these non-classical effects can further improve the highest Carbon ion energies in this transparency regime.