Probing the radiation-dominated regime of laser-plasma interaction in multibeam configurations of petawatt lasers.

Abstract

We numerically model the ultrarelativistic dynamics of a dense plasma microtarget, in a focus of several intersecting femtosecond laser pulses of multipetawatt power each. The aim is to examine prospective experimental approaches to the search for the Inverse Faraday Effect induced by radiation friction. We show that multibeam configurations allow lowering the single beam peak laser power required to generate a detectable quasistatic longitudinal magnetic field excited due to the radiation reaction force. The effect is significant at angles around 10^{o} between the beam propagation axes, almost vanishes when the angle exceeds 20^{o}, and remains rather stable with respect to the variations of relative phases and amplitudes of the beams. Quantum recoil, accounted for semiclassically, is shown to considerably suppress the longitudinal magnetic field, which, however, remains sizable. We conclude that, by using four infrared femtosecond linearly polarized pulses of 15 petawatt power each, crossing at angles of ≈10^{o}, the radiation-dominated regime of laser-plasma interaction can be experimentally demonstrated.