High-density electron–ion bunch formation and multi-GeV positron production via radiative trapping in extreme-intensity laser–plasma interactions

Abstract

Multi-petawatt laser systems will open up a novel interaction regime mixing collective plasma and quantum electrodynamic processes, giving rise to prolific generation of gamma-ray photons and electron–positron pairs. Here, using particle-in-cell simulations, we investigate the physics of the interaction of a 1024 W cm−2 intensity, 30 fs duration, circularly polarized laser pulse with a long deuterium plasma at classically overcritical electron density (1022 cm−3). We show that radiative trapping of the plasma electrons causes a high-density (∼5 × 1023 cm−3), quasineutral electron–ion bunch to form inside the laser pulse. This phenomenon is accompanied by up to ∼40% energy conversion efficiency of the laser into gamma rays. Moreover, we find that both the radiation-modified Laplace force and the longitudinal electric field exerted on the positrons created by the multiphoton Breit–Wheeler process can accelerate them to GeV-range energies. We develop a theoretical model, the predictions of which provide a good match to the simulation results. Finally, we address the influence of the ion mass, showing that the laser absorption and positron acceleration is enhanced with deuterons compared to protons.

Opacity of relativistically underdense plasmas for extremely intense laser pulses

“…This regime differs significantly from the quasi one-dimensional hole boring or light sail regimes which occur at higher densities, and where QED processes have been studied recently [15,17]. The previous simulations of the channelling regime performed for a 0 10 3 revealed that the laser pulse can trap plasma electron which field drags ions, hence dense electron-ion bunch is formed right in the laser pulse [19,20,21]. Radiation reaction plays a crucial role in this electron trapping and plasma transparency [20,21], however, the laser pulse still can travel a long distance despite of the electron trapping and "snow plough" effects.…”

“…The previous simulations of the channelling regime performed for a 0 10 3 revealed that the laser pulse can trap plasma electron which field drags ions, hence dense electron-ion bunch is formed right in the laser pulse [19,20,21]. Radiation reaction plays a crucial role in this electron trapping and plasma transparency [20,21], however, the laser pulse still can travel a long distance despite of the electron trapping and "snow plough" effects. Also, pair photoproduction for such field strength lead to a small number of positrons whose field is not enough to influence the laser pulse propagation.…”

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

“…The most important effects are high-frequency radiation emission by electrons pushed in the laser-field (with a consequent back reaction on individual electrons, the radiation reaction (RR)) and the multi-photon Breit-Wheeler (BW) process leading to the generation of electron-positron pairs [37] . These QED effects, usually expected to deplete energy from a physical system [38][39][40][41][42] , may though significantly modify the collective plasma dynamics [43] with yet unexplored indirect effects on the ion energy.…”

Collective plasma effects of electron-positron pairs in beam-driven QED cascades

“…Tremendous effects have been made to understand the QED plasma dynamics [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] and to explore possibilities of their preparation in laboratories [48][49][50][51][52][53][54][55][56][57][58][59][60] . The QED plasma dynamics 9,[60][61][62] is characterized by strong field QED and collective plasma effects.…”