Pair plasma cushions in the hole-boring scenario

TL;DR

This paper investigates how a pair plasma cushion formed in front of a target during high-power laser interactions can reduce reflectivity and enhance gamma-ray production, affecting the efficiency of laser-driven pair cascades.

Contribution

It provides a theoretical analysis of pair plasma effects in the hole-boring scenario using stationary two-fluid and Maxwell equations including radiation reaction.

Findings

Pair plasma cushions significantly reduce reflectivity.

The cushion converts absorbed flux into gamma-rays.

A modest increase in laser intensity is needed for pair cascade threshold.

Abstract

Pulses from a 10 PW laser are predicted to produce large numbers of gamma-rays and electron-positron pairs on hitting a solid target. However, a pair plasma, if it accumulates in front of the target, may partially shield it from the pulse. Using stationary, one-dimensional solutions of the two-fluid (electron-positron) and Maxwell equations, including a classical radiation reaction term, we examine this effect in the hole-boring scenario. We find the collective effects of a pair plasma "cushion" substantially reduce the reflectivity, converting the absorbed flux into high-energy gamma-rays. There is also a modest increase in the laser intensity needed to achieve threshold for a non-linear pair cascade.