Self-absorption of synchrotron radiation in a laser-irradiated plasma

Abstract

Electrons at the surface of a plasma that is irradiated by a laser with intensity in excess of 1023 W cm−2 are accelerated so strongly that they emit bursts of synchrotron radiation. Although the combination of high photon and electron density and electromagnetic field strength at the plasma surface makes particle–particle interactions possible, these interactions are usually neglected in simulations of the high-intensity regime. Here we demonstrate an implementation of two such processes: photon absorption and stimulated emission. We show that, for plasmas that are opaque to the laser light, photon absorption would cause complete depletion of the multi-keV region of the synchrotron photon spectrum, unless compensated by stimulated emission. Our results motivate further study of the density dependence of quantum electrodynamics phenomena in strong electromagnetic fields.