Eur. Phys. J. Special Topics 223, 1069-1082 (2014)
https://doi.org/10.1140/epjst/e2014-02158-2

Regular Article

Near QED regime of laser interaction with overdense plasmas

¹ Institut für Theoretische Physik I, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
² Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
³ Institute of Applied Physics of the Russian Academy of Sciences, 603950 Nizhny Novgorod, Russia
⁴ Lobachevsky National Research University of Nizhni Novgorod, 603950 Nizhny Novgorod, Russia
⁵ The Ohio State University, Columbus, Ohio 43210, USA

Received: 13 March 2014
Revised: 24 March 2014
Published online: 4 June 2014

Abstract

Interaction of laser plulses with intensities up to 10²⁵ W/cm² with overdense plasma targets is investigated via three-dimensional particle-in-cell simulations. At these intensities, radiation of electrons in the laser field becomes important. Electrons transfer a significant fraction of their energy to γ-photons and obtain strong feedbacks due to radiation reaction (RR) force. The RR effect on the distribution of laser energies among three main species: electrons, ions and photons is studied. The RR and electron-positron pair creation are implemented by a QED model. As the laser intensity inreases, the ratio of laser energy coupled to electrons drops while the one for γ-photons reaches up to 35%. Two distinctive plasma density regimes of the high-density carbon target and low-density solid hydrogen target are identified from the laser energy partitions and angular distributions of photons. The power-laws of absorption efficiency versus laser intensity and the transition of photon divergence are revealed. These show enhanced generation of γ-photon beams with improved collimation in the relativistically transparent regime. A new effect of transverse trapping of electrons inside the laser field caused by the RR force is observed: electrons can be unexpectedly confined by the intense laser field when the RR force is comparable to the Lorentz force. Finally, the RR effect and different regions of photon emission in laser-foil interactions are clarified.