QED cascade initiation via reflection of a multipetawatt laser pulse from a self-organized parabolic plasma mirror

TL;DR

This paper demonstrates that a single high-power laser pulse reflecting off a self-organized plasma mirror can initiate an avalanche-type QED cascade, producing gamma photons and electron-positron pairs, simplifying experimental requirements.

Contribution

It introduces a novel setup using a multipetawatt laser and a self-organized plasma mirror to trigger QED cascades without multiple synchronized laser channels.

Findings

QED cascade threshold around 7 PW laser power

Clear avalanche signatures with a 27 PW pulse

Over 15 positron generations observed

Abstract

The self-sustained or avalanche-type cascade is an intriguing prediction of strong-field quantum electrodynamics (QED) that has yet to be observed in laboratories. It is accompanied by the conversion of electromagnetic energy into gamma photons and electron-positron ($e^-e^+$) pairs, whose number increases exponentially over time. We investigate a simple configuration to initiate a QED cascades: it is based on the superposition of an incident multipetawatt laser pulse and its reflection from a solid target. The incident laser pulse <<deforms>> the initially flat target surface, creating a parabolic mirror that focuses the reflected radiation. For the considered setup the threshold laser power is about $7\,\text{PW}$. With a $27\,\text{PW}$ laser pulse, positron production exhibits clear signatures of an avalanche-type cascade, including exponential growth and more than 15 positron generations with similar energy spectra. Therefore, observing an avalanche-type QED cascade does not require the use of multiple laser channels with precise spatio-temporal synchronization, as previously supposed.