Energy absorption in the laser-QED regime

Alex F Savin,Aimee J Ross,Robin H.-W Wang,Ramy Aboushelbaya,Ben Spiers,Marko W Mayr,Peter A Norreys

doi:10.1038/s41598-019-45536-x

Alex F Savin, Aimee J Ross + Show 5 more

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https://doi.org/10.1038/s41598-019-45536-x

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Abstract

A theoretical and numerical investigation of non-ponderomotive absorption at laser intensities relevant to quantum electrodynamics is presented. It is predicted that there is a regime change in the dependence of fast electron energy on incident laser energy that coincides with the onset of pair production via the Breit-Wheeler process. This prediction is numerically verified via an extensive campaign of QED-inclusive particle-in-cell simulations. The dramatic nature of the power law shift leads to the conclusion that this process is a candidate for an unambiguous signature that future experiments on multi-petawatt laser facilities have truly entered the QED regime.

Highlights

With the impending completion and commissioning of the Extreme Light Infrastructure - in particular ELI Beamlines[1], and the Apollon laser facility[2] amongst other multi-petawatt laser systems, it will soon be possible to investigate an entirely new regime of plasma physics in the laboratory
We propose an alteration to the ZVP model devised by Baeva et al.[33] that accounts for the possibility of generating electron-positron pairs and model how such pair production would affect the scaling of “hot” electron energy with a0
We have predicted and numerically verified that there is a distinct regime change for the electronic absorption of incident laser energy that is coincident with the onset of quantum electrodynamics effects

Summary

Introduction

With the impending completion and commissioning of the Extreme Light Infrastructure - in particular ELI Beamlines[1], and the Apollon laser facility[2] amongst other multi-petawatt laser systems, it will soon be possible to investigate an entirely new regime of plasma physics in the laboratory. Theoretical and numerical work in recent years has predicted that when moving into the regime of “ultra-relativistic” lasers incident on relativistically over-dense targets, absorption processes are dominated by non-ponderomotive mechanisms such as the zero-vector-potential (ZVP) absorption mechanism[27,33]. This regime is identified by a0 ≥ 5, and ne nc where nc is the critical density of the plasma, above which the plasma is opaque to light of wavelengths less than or equal to λ0: www.nature.com/scientificreports/. These high-momentum bunches of electrons, such as those shown in Fig. 1 are seen to co-propagate with the zeroes in the vector potential, the nomenclature ZVP absorption[27,33]

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